WO2011076416A1

WO2011076416A1 - Method and system for producing rectified x-ray images for dental or orthodontic diagnostics

Info

Publication number: WO2011076416A1
Application number: PCT/EP2010/007904
Authority: WO
Inventors: Herbert Häntsch; Martin DÜRRSTEIN; Herbert Gebhardt; Walter Bauer; Frank Hatzfeld
Original assignee: DüRR DENTAL AG
Priority date: 2009-12-24
Filing date: 2010-12-23
Publication date: 2011-06-30
Also published as: RU2012131268A; FI20125813A; DE102009060390A1

Abstract

In a method for producing rectified x-ray images for dental or orthodontic diagnostics, a x-ray source (28) is introduced into the oral cavity (34) of a patient (36). A x-ray detector (32) is arranged such that it extends at least about a part of the mandibular arch of the patient (36) from the outside. Subsequently, the teeth of the patient (36) are x-rayed, wherein the x-rays impinging on the x-ray detector (32) are detected. On the basis of the x-rays detected by the x-ray detector, a digital x-ray image is generated. According to the invention, the coordinates of a plurality of measuring points located on the teeth (38) are measured by means of a measuring device (50; 64; 73; 50a to 50d; 106a, 106b, 66a, 66b; 110a, 110b; 130). Finally, the digital x-ray image is rectified using said coordinates.

Description

METHOD AND SYSTEM FOR THE PRODUCTION OF

RESISTANT X-RAY IMAGES FOR DENTAL OR ORTHODONTIC DIAGNOSTICS

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention relates to a method and a system for producing rectified X-ray panorama magnification images for dental or orthodontic diagnostics.

2. Description of the Related Art

For diagnostic purposes, in dentistry and orthodontics, it is often desirable to have panoramic images that show the entire dentition and the entire periodontium of a patient. With such panoramic images, almost exclusively the technology of panoramic tomography (PSA) is used. The exposure of the image carrier, for example an X-ray film or a storage film, takes place from behind through the skull of the patient. It is ensured by the imaging geometry that only the areas of interest of the skull, namely the teeth with the periodontium apparatus, are sharply imaged. In most cases, the image carrier is exposed through a slit diaphragm which moves around the patient's jaw from outside. The X-ray source is simultaneously pivoted around the back of the patient's head. In this way, the respectively illuminated areas of the dentition are projected approximately parallel to the image carrier. The dentition appears on the radiograph as a development of the dentition, which greatly facilitates the diagnosis of a doctor.

CONFIRMATION COPY A disadvantage of this type of panoramic shots, however, is that the X-rays traverse the entire skull of the patient, and this in places even several times as a result of the scanner-like recording technique. Occasionally, it can not be avoided that even as sensitive to radiation sensitive organs, such as

Thyroid or eye lenses exposed to X-rays. In addition, the spatial resolution is usually between 2 and 4 line pairs per millimeter and the thickness of the layer shown is low, so that, for example, obliquely grown teeth are often difficult to see.

In addition, it often causes problems that the patient may not move during the relatively long recording time of usually 10 to 15 seconds. For this reason, panoramic shots of the mandibular arch of children, alcoholics or Parkinson's patients often fail, which increases the radiation dose in the event of recurrence. Therefore, there were early considerations to introduce an X-ray source into the oral cavity of the patient to be able to illuminate the dentition from the inside out with X-rays. The image carrier is arranged so that it extends from the outside around the mandibular arch of the patient around. Of the. The advantage of this method is, above all, that a single image can be used to obtain a panoramic image of the upper or lower row of teeth or even of the entire dentition. In addition, the X-ray light does not pass through the entire skull of the patient, but only those parts that limit the oral cavity to the front and to the side. For this type of intraoral radiograph, the term panoramic magnification image (PVA) is usually used. However, according to the PVA principle, operating X-ray devices are no longer in use. The main reason for this is that the x-ray tubes introduced into the mouth had an operating voltage of only about 55 kV, the electron beam current being at 5 mA and

Beam filters made of copper were used. Under such operating conditions, a greater portion of the radiation is emitted at relatively long wavelengths, which are very much absorbed by the soft tissue of the oral cavity and therefore result in a high local radiation dose.

Meanwhile, x-ray sources that can be inserted in the mouth have been developed that can be used in the range of 50 to 85 kV with currents of 0.1 mA and smaller. Also, the filters made of copper can be replaced by more suitable materials. In such X-ray tubes, the proportion of long-wave radiation is smaller, which also reduces the radiation dose. The diameter of the focal spot is less than 0.1 mm, and the typical exposure times are between 0.1 and 5 seconds. This enables a resolution of 5 line pairs per millimeter, with which caries can be detected by X-ray examination.

However, a problem of the PVA technique remains that the X-ray images are heavily distorted. The reason for this is that the teeth and the periodontal ligaments are not arranged on a spherical shell around the X-ray source. Because of this, many teeth are projected from awkward angles and appear distorted on the X-ray image in a manner that makes diagnosis difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and a system with which equalized X-ray generate images with an intraorally arranged X-ray source.

With regard to the method, this object is achieved by a method comprising the following steps: a) placing an X-ray source in the oral cavity of a

patients; b) arranging an X-ray detector such that it extends from outside at least around a part of the patient's dental arch; c) examining the patient's teeth with X-radiation; d) detecting the incident on the X-ray detector

X-rays; e) generating a digital x-ray image on the

Basis of the X-radiation detected by the X-ray detector; f) measuring coordinates of a plurality of measuring points located on the teeth by means of a measuring device; g) equalizing the digital X-ray image using the coordinates measured in step f).

The invention is based on the finding that, if one knows the position of the X-ray source and the X-ray detector and makes certain typifying assumptions with respect to the position of the teeth to be examined, it is possible to carry out a computational equalization of the X-ray image within certain limits. However, since the position of the teeth relative to the X-ray source and the detector device in such By specifying assumptions is estimated only, can be obtained with such an equalization no X-ray images from which, for example, size ratios can be read correctly, as is required for many diagnostic tasks.

Only then, when determining coordinates of a plurality of measuring points lying on the teeth in the manner according to the invention with the aid of a measuring device, the equalization can be carried out so that the proportions of the transilluminated structures are reproduced correctly on the rectified X-ray image.

The X-ray detector used according to the invention can be a digital X-ray detector which contains, for example, a CCD sensor or a CMOS sensor. As an X-ray detector, however, everyone else is here

Image carrier, for example, a classic X-ray film or a storage film called. Since the rectification is computer-aided and therefore a digital X-ray image is needed, X-ray images generated on classical X-ray films must first undergo digitization.

If a panoramic photograph of an entire mandibular arch is to be made with the aid of the method according to the invention, the x-ray detector must extend around the entire mandibular arch of the patient from the outside. In general, the x-ray detector will be adapted to the approximately parabolic shape of the mandibular arch. However, the X-ray detector can also follow a different course, for example the path of a circle or an ellipse. Especially if the X-ray detector has an exchangeable image carrier, for. B. a storage film or an X-ray film, it may be advantageous if the Röntgendetek- tor is composed of a plurality of plate-shaped elements which enclose an angle at their joints. Also, a subdivision of the X-ray detector into individual curved segments for the upper or lower mandibular arch and / or the right or left half of the dentition can be useful in many cases. Particularly advantageous is an arrangement in which a segment is provided for each row of teeth and the two segments in an vertical plane an angle, z. B. of about 160 ° include. The only prerequisite is that the position and shape of the X-ray detector is known with sufficient accuracy, since this information is required for the equalization in step g).

The same applies to the case where it is not the entire mandibular arch in the manner of a panoramic exposure but only a part of the dentition or even only a single tooth that is to be recorded on the X-ray image.

The measuring points whose coordinates are measured by means of the measuring device can be distributed in different ways on the teeth. The distribution of the measuring points can be regular or irregular, loose or dense. The measurement points may also be limited to parts of the denture, which experience has shown that the distortion is particularly large or in which a measurement is easier to perform. Furthermore, the measuring points can be arranged linearly and in particular form a line grid. It may even be sufficient to measure the coordinates of only a few measuring points on a few teeth, eg. B. from measuring points on the cutting edges of the incisors. If the coordinates of the measuring points are measured with a measuring device, this is itself a reference system for the coordinates. If the position of the measuring device to the X-ray detector and the X-ray source is known, the equalization can be performed relatively easily. As a reference point relative to which the coordinates of the teeth can be determined in step f), for example, a bite point of the patient can be determined. This is understood to mean a specific point, usually located on the incisors, relative to which both the X-ray source and the X-ray detector as well as the measuring device can be aligned. For this purpose, it is generally sufficient to attach a bite bar to the corresponding components, which is provided with a notch into which the respective incisors can engage in a defined position.

If the coordinates of the teeth relative to the X-ray detector and the X-ray source are known, then in step g) it is possible to determine from the measured coordinates of the teeth an object surface arranged between the X-ray source and the X-ray detector, in which the teeth are arranged. The rectified X-ray image is then determined by back-projection of the X-ray image onto the object surface. This procedure is particularly simple and leads to an equalized X-ray image, which appears similar to a processed under parallel projection processing. It is exploited that the X-ray radiation in the PVA technique, the teeth pass through more perpendicularly due to the arrangement of the X-ray source in the oral cavity and the inclination of the teeth, as is the case with the PSA technique.

Since it is not always easy to perform a measurement of the teeth according to step f) from the oral cavity and thereby to maintain a precisely defined position relative to the x-ray source and the x-ray detector, methods can also be used in which such an absolute reference is not required , These procedures In addition, they set the target perspective freely within certain limits.

In such a method, in which the coordinates of the teeth (only) relative to each other must be determined, the step g) comprises the following steps: ga) determining a desired perspective for the equalized

X-ray image; gb) equalizing the X-ray image in such a way that the X-ray image appears from the desired perspective determined in step ga).

In image processing, various algorithms are known with which optically recorded images can be compared with three-dimensional surface reliefs. Particularly suitable for the equalization desired here is a method in which step gb) comprises the following steps: gba) generating an edge image of the x-ray image using an edge detection algorithm; gbb) deriving a three-dimensional surface relief of the teeth from the coordinates obtained at the measurement points; gbc) representation of the surface relief from the desired perspective determined in step ga); gbd) selection of vertices on the surface relief depicted in step gbc) and assignment of the vertices to corresponding points on the edge image generated in step gba); gbe) deriving a transformation rule which converts the corresponding points on the edge image into the vertices selected in step (bbd); gbf) Apply the transformation rule to the in

Step e) recorded digital X-ray image.

The desired perspective, in which the three-dimensional surface relief of the teeth derived from the measuring points is represented in step gbc), can be fixed unchangeably by the programming, but can also be freely selected by a user within certain limits. In addition, different target perspectives can be defined for individual parts of the surface relief, so that, for example, each individual tooth is represented centrally in perspective. In addition, the escape point can be freely selected, for example at the height of the tooth crown or tooth root. The desired perspective can also be individual parallel perspective for each tooth, resulting in a developed representation as in conventional panoramic images. Depending on the task in diagnostics, one or the other perspective may be more favorable, so that a choice opens up improved diagnostic options.

Since the geometric conditions in the examination of the dentition change from tooth to tooth with an intraorally arranged X-ray tube, it may be expedient if the transformation instruction contains several partial instructions which convert partial areas of the X-ray image. Thus, possibly more distorted molars may require a different transformation than cutting teeth, which are penetrated approximately perpendicularly by the X-ray radiation. In particular, on each subarea of the X-ray image which, with the aid of a separate sub-rule, can be is torn, exactly one tooth or a certain number of teeth to be represented.

The embodiment described above, in which transformation instructions are derived using support points, requires an assignment of the support points to corresponding points on the edge image generated in step gba). In principle, this assignment can be carried out manually for one or more interpolation points, especially if ambiguities can not be ruled out. Preferably, however, this assignment is carried out automatically, wherein an edge image of the surface relief is generated from the surface relief shown in step gbc) by means of edge detection and corners or other characteristic support points are automatically selected according to predefinable selection criteria on the basis of the edge image.

As a measuring device for measuring the coordinates of the measuring points lying on the teeth can be made of a variety of distance sensors, which are known per se in the prior art. Triangulation sensors or ultrasound sensors with one or more ultrasound sources (so-called phased array ultrasound sensors) are also well suited for intraoral measurement.

Alternatively, in step f) a plurality of overlapping camera images can be taken from different intraoral positions and the coordinates of the measuring points derived therefrom. This can be done, for example, using a 3D camera having two mutually offset image pickup. However, the different camera images can also be recorded by one and the same camera if they are taken by different locations at different times. Also with a camera and a light mouse projected onto the teeth. ter, z. As a light grid, coordinates of measuring points can be determined. The use of cameras additionally has the advantage that additional intraoral images are available for the diagnosis, which can provide additional information on the status of the teeth.

The cameras may be configured as endoscopes, ^'which transmit the image information optically through a fiber bundle on an imager. Of course, so-called video endoscopes, in which the image recorder is located in the recording head and the data transmission is electrical, are also possible.

To determine the coordinates of the measuring points in step f), a light pattern, for. As a dot or stripe pattern, generated on the teeth and detected by directional optical sensors. In contrast to the use of a triangulation sensor whose light beam passes over the teeth like a scanner, in this way the coordinates of the measuring points lying on the light pattern can be detected in a single measurement process. In one embodiment of the invention, a calibration step is provided in which an X-ray image without patients is initially recorded. Then, pixel-wise or uniformly for areas of pixels is determined by which correction amounts the intensity must be changed to obtain a constant intensity across the X-ray image. Later generated X-ray images of teeth are then corrected for their intensity taking into account the correction amounts. In this way, it is ensured that any parts of the measuring device which are located in the beam path of the x-ray radiation and which cause the

X-rays (even if only slightly) absorb, are not visible on the later X-ray images. A sol- rather a calibration step further prevents other influences from leading to unwanted brightness differences in the X-ray images. These influences include, for example, the generally non-spherical shell shape of the X-ray detector, which lead to different distances between locations on the X-ray detector and the X-ray source, but also spatially inhomogeneous radiation of the X-ray source and local fluctuations in the sensitivity of the X-ray detector.

Such a calibration step can advantageously also be carried out inde pendent of the ^' steps f) and g). The Applicant therefore reserves the right to claim protection in a divisional application for a method for the production of X-ray images for dental or orthodontic diagnosis, which comprises the following steps: a) placing an X-ray source in the oral cavity of a patient; b) arranging an X-ray detector such that it extends from the outside at least around a part of the mandibular arch of the patient; c) examining the patient's teeth with X-radiation; d) detecting the incident on the X-ray detector X-ray radiation; e) generating a digital X-ray image on the basis of the X-ray radiation detected by the X-ray detector; f) taking an X-ray image without patients; g) image or area determination to which

Correction amounts, the intensity must be changed to obtain a constant intensity across the X-ray image; h) correction later generated by the patient's teeth

X-ray images with respect to their intensity taking into account the correction amounts.

If the x-ray detector has an exchangeable image carrier, in particular a storage film or an x-ray film, then a marking object can be arranged in the beam path of the x-ray radiation which is imaged on the image carrier. The position of the image carrier relative to the X-ray source can then be determined from the position of the image of the marking object on the image carrier. This measure is particularly advantageous if there is a risk that the interchangeable image carrier is not exactly aligned in a recording provided for him. Such an exact alignment is often not guaranteed because the image carrier with sufficient play must be inserted into the recording, so that no exact target position of the image carrier is guaranteed. The marking object according to the invention, the position of which is fixed relative to the X-ray source, then makes it possible to detect such deviations of the actual position of the image carrier from its nominal position and, if appropriate, to correct the remaining image accordingly.

Such a marking object can advantageously also be introduced into the beam path of the X-radiation independently of a measurement of the teeth according to steps f) and g). The Applicant therefore reserves the right

Protection in this application or a divisional application for a method of producing X-ray images for the dental medical or orthodontic diagnostics, comprising the steps of: a) placing an X-ray source in the oral cavity of a patient; b) arranging an X-ray detector such that it extends from the outside at least around a part of the patient's dental arch, the X-ray detector having an exchangeable image carrier, in particular a storage film or an X-ray film; c) arranging a marking object in the beam path of the X-ray radiation which is imaged on the image carrier; d) X-raying the patient's teeth; e) detecting the incident on the X-ray detector

X-rays; f) generating a digital X-ray image on the basis of the X-ray radiation detected by the X-ray detector; g) determining the position of the image carrier relative to the x-ray source from the position of the image of the marking object on the image carrier; h) equalizing the digital X-ray image using the position determined in step g).

If the x-ray detector has an exchangeable image carrier, in particular a storage film or an x-ray film, then this image carrier can carry a plurality of markings which, when the image carrier is read out onto the digital image carrier X-ray image to be transmitted. It can then be seen from the location of the markings on the digital X-ray images inhomogeneities of the image carrier and correct mathematically in the equalization.

Also, this measure is independent of a measurement de teeth in steps f) and g) applicable, so that the applicant reserves the right to seek protection for a method for the production of X-ray images for dental or orthodontic diagnostics in a divisional application, the the steps of: a) placing an X-ray source in the oral cavity of a patient; b) arranging an X-ray detector such that it extends from the outside at least around a part of the mandibular arch of the patient, wherein the X-ray detector has an exchangeable image carrier, in particular a storage film or an X-ray film, which carries a plurality of markings which are present when the image carrier is read the digital X-ray image is transmitted; c) examining the patient's teeth with X-radiation; d) detecting the incident on the X-ray detector X-ray radiation; e) generating a digital X-ray image on the basis of the X-ray radiation detected by the X-ray detector; f) equalizing the digital X-ray image, wherein the position of the markings on the digital X-ray image Inhomogeneities of the image carrier can be detected and corrected by calculation.

The object mentioned in the introduction is achieved with regard to the system by a system which comprises: a) an x-ray source which can be arranged in an oral cavity of a patient; b) an X-ray detector which can be arranged such that it extends from the outside at least around a part of the patient's dental arch, and with which X-radiation impinging on the X-ray detector can be detected; c) a digital memory for storing an X-ray

, image that has been taken by the X-ray detector after examining teeth of the patient; d) a measuring device for measuring coordinates of a plurality of measuring points located on the teeth; e) an equalization device adapted for computer-aided equalization of an X-ray image using the measured coordinates.

The measuring device may comprise an optical triangulation sensor and / or an ultrasound sensor and / or an SD camera.

In one embodiment, the measuring device comprises a light source, with which a light pattern can be projected onto the inner or outer surface of the teeth, and an (possibly direction-resolving) optical sensor for detecting the light pattern. With such a measuring device, the coordinates of the measuring points on the teeth can be measured without contact and with high accuracy. In some embodiments, the measuring device is configured for an intraoral arrangement. This has the advantage that even the molars can be surveyed well, which appear particularly distorted in panoramic magnification shots. As far as "set up" is mentioned here, this means that the measuring device will often not be permanently located at the relevant location (in the oral cavity of the patient), but only during the measuring process. At other times, the relevant parts of the measuring device can be dismantled, weggesehwenkt or otherwise removed.

In contrast, in other embodiments, the measuring device is set up for an extraoral arrangement. This has the advantage that not in addition to the X-ray source other devices must be introduced into the oral cavity of the patient, which can cause a malaise or even a choking reflex in this. Considered, for example, to use a mechanical roller switch, which can be firmly connected to the X-ray machine and before or after the fluoroscopy, the series of teeth of the patient descends and detects the coordinates of the worn teeth.

With an extra-oral arrangement of the measuring device, different variants can be distinguished. If the measurement of the teeth does not take place simultaneously with the fluoroscopy of the teeth, but before or after, the measuring device can be arranged during the measurement process so that parts which are impermeable to X-radiation are arranged at locations which pass through such X-rays during fluoroscopy which also penetrate teeth and other structures of interest. In this case it is necessary that these parts of the measuring device can be swung out of the beam path of the X-ray radiation or removed in any other way. In this context, parts which absorb more than 50% of the incident X-ray radiation are considered to be opaque to X-ray radiation.

Ideally, however, the measurement of the teeth takes place simultaneously with their fluoroscopy. In this way, it is ensured that the patient does not move between the measurement of the teeth and their fluoroscopy and thus possibly distorts the equalization of the X-ray images. In this case, however, it must be ensured that the measuring device does not affect the X-ray image.

This can be done, for example, by arranging the measuring device for an arrangement in which parts of the measuring device which are impermeable to X-radiation are not penetrated by X-rays which have previously been through-toothed. In this way it is ensured that the images of these parts on the X-ray image do not cover the teeth or other structures of interest.

As a location for an arrangement of these parts is, for example, the area above the upper mandibular arch and under the lower mandibular arch into consideration. However, from there, the teeth can only be poorly achieved for a measurement.

Therefore, parts of the measuring device which are impermeable to X-radiation can preferably be arranged in a plane which, with the patient's mouth open, extends between its upper and lower rows of teeth. Since the patient must have opened his mouth slightly anyway because of the introduction of the X-ray source, a relatively large gap remains between the rows of teeth, which ne arrangement of radiopaque parts of the measuring device is available.

The measuring device can generally be set up, at least in part, for an arrangement between the patient and the X-ray detector. Such an arrangement has the advantage that the X-ray detector does not interfere with the measurement of the teeth. Such a measuring device can, for. B. comprise a contour measuring arc, which extends in a measuring plane and has contact surfaces for engagement with a row of teeth up. The shape of the contour measuring arc is adjustable in the measuring plane in order to bring the contact surfaces into contact with the row of teeth. The measuring device further comprises means for determining the shape of the contour measuring arc. The contour measuring arc is preferably permeable to X-ray radiation so that the contour measuring arc can remain in place during transillumination.

Such a contour measuring arc is also advantageous insofar as it can be pushed under the lips of the patient with an appropriate design, so that some back teeth can be measured, which are otherwise not accessible or at least not readily accessible to an extraorally arranged measuring device.

The means for determining the shape of the contour measuring arc may be sensors that are integrated in the contour measuring arc. If, for example, the contour measuring arc has a plurality of contact members which are connected to one another by joints, then the sensors integrated in the contour measuring arc can be provided to determine the deflections of the joints. The shape of the contour measuring arc can then be derived from the deflections of the joints.

However, the means for determining the shape of the contour measuring arc can also be used with the contour measuring arc associated absorption. include bodies that are impermeable to X-rays. The absorption bodies are arranged in such a way that X-ray radiation, which is absorbed by the absorption bodies, has not previously illuminated through teeth. The position of the absorption bodies can then be determined by the equalization device, which allows an immediate conclusion to the shape of the contour measurement arc. In such an embodiment, the expense of a sensor that is integrated into the contour measuring arc is eliminated. Especially when a sensor integrated into the contour measuring arc is not required, the contour measuring arc can comprise a plastically deformable carrier. This is then simply applied to the patient's row of teeth for measurement and deformed in such a way that the largest possible area is achieved over the entire length of the contour measurement arc.

In other embodiments, the measuring device is at least partially set up for an arrangement on a rear side facing away from the patient of the X-ray detector. Such an arrangement has the advantage that comparatively much space is available for the arrangement of the measuring device. The X-ray detector should, however, if possible only have a detection surface there where teeth and other structures of interest can be imaged. In the already mentioned space between the two rows of teeth of the patient, an X-ray detector is not needed, so that there may be arranged advantageously the measuring device.

In particular, the X-ray detector can have an opening which is arranged in such a way that X-ray radiation which has passed through the opening has not previously illuminated through teeth. The measuring device is then behind the X-ray arranged detector in the region of the opening, that the opening allows a visual connection between the measuring device and the teeth.

It is also possible to arrange some parts of the measuring device in the area between the X-ray detector and the patient and other parts outside this area. For example, the measuring device can have a reflector which is set up for an arrangement between the patient and the X-ray detector and is reflective for light or sound waves and transparent for X-ray radiation. Since the reflector can be arranged in an optimal position relative to the measuring teeth, so that the teeth can optically or by means of ultrasonic waves u. U. even better measured, as if the corresponding sensors of the measuring device between the rows of teeth of the patient are arranged.

In another group of embodiments, the measuring device comprises a spatially resolving upbeat sensor by means of which the coordinates of a contact surface of a tooth and / or the lip of the patient can be measured at least along one direction. The contact surface of a tooth will most often be the cutting edge of the incisors; in principle, however, a detection of the adjacent canines is also considered if the Aufbisssensor has a sufficient width. Although only a few teeth can be measured with such a spatially resolving Aufbisssensor and also for this only measuring points that lie on the contact surface, but at least the important information is obtained as far as the incisors of the X-ray source is removed. The

The position of the remaining teeth must then be extrapolated. In general, at least the sex and the age of the patient will be taken into account, to a typical shape of the mandibular arch. This typical form can be obtained, for example, by averaging measured values obtained during the measurement of the mandibular arches of a large number of comparable patients. In one embodiment, the bite sensor has a bite element that is displaceable along an adjustment direction and provided with a bite notch. Furthermore, the bead sensor comprises a position sensor with which the position of the bite element along the adjustment direction can be measured. The provision of a bite-on notch in the bite sensor reduces the risk of the patient unintentionally leaving a position relative to the x-ray source due to minor jaw movements, which has previously been adjusted and provides the basis for the subsequent equalization of the x-ray image.

The bite sensor may include a motor for displacing the bite element. In this way, a desired distance between the incisors of the patient and the X-ray source can be input via an input device. The X-ray system will then stand on its own

Help the motor the desired distance. If the bite element has exactly one bite notch on each side, there is no danger of the patient accidentally placing their incisors in the wrong bite-kerf or changing them shortly before candling through smaller jaw movements.

If the motor is designed as a servomotor, this can also serve as a position sensor.

The bite element can have a sleeve-shaped base body which is displaceably arranged along an insertion axis of the insertion device on an insertion part of the x-ray device which contains the x-ray source. The insertion part at the same time serves as a guide for the bite element, which simplifies the construction of the Aufbisssensors. Alternatively, however, it is also possible to provide on a sleeve-shaped base body at the top and bottom each have a receiving shaft in which a strip-shaped bite element is arranged linearly movable.

The bite sensor may comprise at least one sensor element and a carrier which carries the at least one sensor element and is partially insertable into the oral cavity of the patient. At least the coordinates of the contact surface along a reference direction can be determined by the at least one sensor element. In this case, the attack

The patient's incisors are not inserted in a bite-off notch, but are resting against the bite sensor at any location with their cutting edge. This location is detected by the at least one sensor element. Such an embodiment is particularly advantageous if the measurement of the coordinates of the incisors is performed simultaneously with the fluoroscopy. In this case, there is no danger that the patient accidentally changes a previously set position of the incisors on the up to the moment of the X-ray.

The at least one sensor element may comprise a plurality of pressure or proximity sensors successively arranged along the reference direction, the size and arrangement of which determines the spatial resolution with which the coordinates of the contact surface can be measured. For example, piezo elements are particularly suitable as pressure sensors. As proximity sensors in particular capacitive sensors come into consideration, which can be specifically designed so that they respond only to teeth, only on lips or on the lips and teeth. In another embodiment, the at least one sensor element is designed as a linear potentiometer, which has a resistance surface and an elastic electrode. A movable tapping point of the linear potentiometer can be produced where the elastic electrode is deflected by a tooth and / or the lip of the patient so far that the electrode rests against the resistance surface. Such a linear potentiometer has a simple structure and requires fewer electrical leads than a plurality of successively arranged pressure or proximity sensors.

The carrier for the at least one sensor element is preferably fastened on an insertion part, which contains the X-ray source, and may for example be designed as a sleeve, which is pushed onto the insertion part.

For further advantages and developments with respect to the system, reference is made to the above explanations of the method.

BRIEF DESCRIPTION OF THE DRAWINGS Further features and advantages of the invention will become apparent from the following description of an embodiment with reference to the drawings. Show:

Figure 1 is a vertical section through an inventive X-ray examination system in use; Figure 2 is a horizontal section through that in the figure

1 X-ray examination system shown;

FIG. 3 shows a schematic illustration for illustrating a distortion arising on an X-ray image; Figure 4 is a schematic representation similar to Figure 3, but with undistorted image;

Figure 5 is a schematic representation similar to that in the

Figure 3 but with another projected body;

Figure 6 is a schematic representation similar to that in the

FIG. 3, but with emphasis on an object plane;

FIG. 7 shows an enlarged illustration of the geometric relationships that are present in the projection of teeth on the sensor surface of an X-ray detector of the X-ray examination system shown in FIGS. 1 and 2 for explaining a first exemplary embodiment of a method according to the invention;

Figure 8 is a vertical section through a triangulation sensor used as a measuring device, which is inserted into the oral cavity of a patient;

FIG. 9 is a front view of that shown in FIG

triangulation;

Figure 10 is a vertical section through a 3D stereoscopic camera inserted into the oral cavity of a patient;

FIG. 11 is a front view of that shown in FIG

3D camera;

Figure 12 is a generated by a light source regular

Light grid; FIG. 13 shows the light grid according to FIG. 12 when projected onto teeth;

FIG. 14 shows one for the implementation of the invention

Method suitable measuring device, which has to carry out a triangulation of multiple light sources and a plurality of detectors;

Figure 15 is a schematic representation of essential

Steps of the inventive method according to a second embodiment, in which the X-ray image can be equalized so that it appears taken from a desired target perspective;

FIG. 16 is a flowchart showing essential steps of the method according to the invention;

17 shows a vertical section through an inventive X-ray examination system according to an embodiment, in which a measuring device is attached to a distal end of an insertion part;

Figure 18 is a horizontal section through an inventive X-ray device according to an embodiment in which the measuring device is arranged between the patient and the X-ray detector; FIG. 19 is a front view of that shown in FIG

Measuring device at the height of the line XIX-XIX, wherein the X-ray detector and a holder connected thereto are not shown;

FIG. 20 shows a horizontal section through an inventive X-ray apparatus in which a measuring device is shown. is arranged on a side facing away from the patient side of the X-ray detector;

FIG. 21 is a front view of that shown in FIG

Measuring device at the height of the line XXI-XXI, wherein the X-ray detector and a holder associated therewith are not shown;

FIG. 22 shows a vertical section through an inventive X-ray device according to an embodiment, in which reflectors are arranged between the patient and the X-ray detector;

Figure 23 is a horizontal section through a fiction, according ^¬ X-ray apparatus according to an embodiment, in which the measuring means comprises a hingedly formed contour measuring sheet with integrated sensors;

FIG. 24 is a front view of that shown in FIG

Measuring device at the level of line XXIX-XXIX, wherein the X-ray detector and a holder associated therewith are not shown; FIG. 25 shows a horizontal section through an inventive X-ray device according to an exemplary embodiment, in which the measuring device comprises a plastically deformable contour measuring arc with absorption bodies carried therefrom; FIG. 26 is a front view of that shown in FIG

Measuring device at the height of the line XXVI-XXVI, wherein the X-ray detector and a holder connected thereto are not shown;

FIG. 27 shows a vertical section through an inventive X-ray apparatus according to an embodiment. game, wherein the measuring device comprises a Aufbisssensor with a plurality of successively arranged pressure sensors;

FIG. 28 an enlarged detail from FIG. 27, in which the arrangement of the pressure sensors designed as piezo elements can be recognized;

FIG. 29 is a fragmentary view of the figure 28

A sectional view of a Aufbsssssors according to an embodiment in which the sensors are capacitive proximity sensors;

FIG. 30 is a fragmentary view of the figure 28

A sectional view of a Aufbsssssorsors according to an embodiment, in which the Aufbsssensor comprises a linear potentiometer; 31 shows a vertical section through an inventive X-ray device according to an embodiment, in which the Aufbisssensor has a motor-displaceable sleeve.

DESCRIPTION OF PREFERRED EMBODIMENTS 1. Basic Structure of the X-ray Examination System

Figures 1 and 2 show an inventive and generally designated 10 X-ray examination system for dental and orthodontic diagnostics in a vertical or horizontal section. The x-ray examination system 10 has an x-ray device 12, which is connected to a computer 16 via a data line 14. Instead of the computer 16 may also be a specially developed for the X-ray examination system 10 Evaluation unit may be provided which has a data memory and a computing unit.

The X-ray device 12 has a protective housing 18, which consists of an electrically and thermally insulating material and is divided into a cuboid main part 20 and a tubular insertion part 22. The insertion part 22 is detachably fastened to the main part 20 via a fastening device, not shown, and receives an x-ray tube which, for the sake of clarity, is not shown in greater detail in FIGS. 1 and 2.

In the main part 20 of the protective housing 18, an electron beam source 24 is arranged, with which an electron beam can be generated. The electron beam source 24 has for this purpose in a conventional manner a cathode and an anode, which are connected to a high voltage source, which is also accommodated in the main part 20 of the protective housing 18. During operation of the X-ray apparatus 12, electrons are emitted from the cathode and accelerated in the electric field that forms between the cathode and the anode. The electrons leave the electron beam source 24 through a hole provided in the anode and form an electron beam 26 in the x-ray tube. At the rear end of the x-ray tube, this impinges on a target 27, which has the form of a truncated cone in the exemplary embodiment shown. Upon impact with the target 27, the electrons are decelerated and set free X-rays, which is indicated in Figures 1 and 2 with dashed lines 30. The tip of the target 27, on which the electron beam 26 impinges, thus constitutes a point-shaped X-ray source designated below by 28. The X-ray device 12 further has an X-ray detector 32, which is formed in the illustrated embodiment as a digital X-ray detector and is attached by means of a holder 31 to the main part 20 of the protective housing 18. For this purpose, the x-ray detector 32 has a CCD or a CMOS sensor whose pixels are arranged on a sensor surface 33 which is curved both in the sectional plane according to FIG. 1 and in the sectional plane according to FIG. The curvature in the horizontal sectional plane according to FIG. 2 is chosen such that it approximately follows the typical course of a human dental arch. Describe the detector surface of the X-ray detector 32 by moving a circular arc along an approximately parabolic path. Behind the X-ray detector 32, a shield may be arranged (not shown), which prevents that not absorbed by the X-ray detector X-ray propagates in the examination room.

The signals generated by the pixels of the sensor surface 33 are transmitted by the X-ray device 12 via the data line 14 to the computer 16 and there processed to form an X-ray image, which is stored in a memory, which is indicated at 39. Equalization of the X-ray image also takes place in the computer, which is explained in more detail below in sections 2 and 3.

When the tubular insertion part 22 of the x-ray device 12 is inserted into the oral cavity 34 of a patient 36, as can be seen in particular in FIG. 1, the x-rays 30 generated when the electrons are decelerated at the point of impact of the target 28 pass through

Teeth and the adjacent periodontal apparatus and meet the X-ray detector 32. The sensitivity of the X-ray detected by the pixels of the X-ray detector 32 depends thereby on the amount and the nature, in particular the density, the Ge ^¬ tissue disorders from which they pass on their way from the x-ray source 28 to the X-ray detector 32, the X-rays.

By suitable design of the X-ray source 28, it is ensured that the X-rays 30 cover both in the vertical direction (sectional plane of FIG. 1) and in the horizontal direction (sectional plane of FIG. 2) an angle which ensures the complete fluoroscopy of all the teeth 38 and the associated ones Ensuring dental restraints of the patient. On the sensor surface 33 of the X-ray detector 32, a panorama-like image of the tissue penetrated by the X-rays 30 thus results. Since the X-ray source 28 is approximately point-shaped and relatively close to the tissue to be screened, the image formed on the sensor surface 33 during fluoroscopy obeys the rules of central projection.

This will be explained in more detail below with reference to FIGS. 3 to 6.

2. General information on image formation FIG. 3 shows a cube-shaped grid 39 which is illuminated by a radiation source 40 assumed to be punctiform. On an image plane 42 emerges from the shadow of the grid 39 an image 139 according to the rules of central projection. Thus, for example, the parallelism of lines which, as assumed here, are arranged in planes which run parallel to the image plane 42 remains in the image 139. For three of the front corners of the grating 39 projection beams are indicated by dashed lines and for the three corners behind them by dotted lines. As can be seen in the rear view on the right side of Figure 3, the radiation source 40 is not centered with respect to the grid 39, but slightly offset to the bottom left. As a result of this staggered arrangement, the image 139 produced on the image plane 42 is distorted. For a viewer of the image 139, it is due to this distortion z. B. difficult to judge whether the grid 39 has the shape of a cube or not. Such an evaluation is only possible if the image 139 arises from a perspective known to the viewer and particularly suitable for an assessment.

Such a known perspective is shown in FIG. Here, it is assumed that the radiation source 40 'is located exactly on a central axis of the grating 39, ie on a line which passes through the centers of two opposite faces of the grating 39 (see rear view on the right-hand edge of FIG. The image 139 'now appears undistorted to the viewer because it reflects the regularity of the grid 39. As can readily be seen in FIGS. 1 and 2, the image formed on the sensor surface 33 of the X-ray detector 32 when the teeth 38 are illuminated will also generally be distorted. This is mainly because, as can be seen in Figure 2, the teeth 38 are not arranged on a circular arc around the X-ray source 28 around, but on a curve that can be approximated poorly by a circular arc. Therefore, the projection ratios are different for all the teeth 38 on one half of a row of teeth. Accordingly, the image formed on the sensor surface 33 of the X-ray detector 32 is also distorted, with the distortion continuously changing over the area of the image. For the doctor, who is to make a dental or orthodontic diagnosis on the basis of such a distorted image, it is difficult to reverse this distortion when looking at the obtained X-ray image. It is particularly difficult or even impossible to correctly assess the proportions of the structures shown on such a distorted X-ray image.

It would be ideal for the doctor if for each tooth 38 his picture would appear under the same perspective. This may, for example, be a central perspective, as shown in FIG. However, consideration is also given to a parallel perspective as it arises when the radiation source 40 is far (ideally infinitely far) away from the grating 39 or any other object. If the front surface of the grating 39 is, for example, perpendicular to the propagation direction of the rays, the images of the front and the rear edges of the grating 39 are superposed on one another in parallel projection. The doctor knows such a parallel perspective, for example, from conventional panoramic images in which the X-ray source is moved around the patient behind the head (and thus relatively far away from the teeth) and an X-ray film or other X-ray detector is exposed through a wandering slit diaphragm. If the image 139 of the grating 39 shown in FIG. 3 and the relative position of the image plane 42 to the radiation source 40 are known, the shape of the grating 39 can not yet be inferred. FIG. 5 shows this using the example of a warped grating 41: With otherwise identical projection ratios, ie position of the radiation source 40 and the image plane 42, the projected image 141 can not be distinguished from the image 139 of the undrawn grating 39 from FIG. 3. Equalization - first embodiment

One way to deduce the actual shape of the grating 39 and thus obtain an equalized image is shown in FIG. It is assumed here that the position of a first object plane 46, in which the four corners of the grating 39 facing the radiation source 40 are arranged, is known relative to the radiation source 40 and the image planes 42. If the position of the first object plane 46 is known, the arrangement of the front corners of the grating 39 can be reconstructed in a simple manner by connecting beams emanating from the image 139 to the radiation source 40. The puncture points on the object plane 46 of these beams are then the front four corners of the grid 39 fixed. In this way, in the object plane 46, by back projection of the image 139 onto the object plane 46, an equalized original image of the image 139 is created.

Strictly speaking, of course, the position of the second object plane would have to be known, in which the four corners of the grid 39 facing away from the radiation source 40 are arranged. However, the error that arises from estimating the distance of this second object plane to the first object plane is relatively small. Applied to the projections of the teeth 38, this means that one can easily determine the position of the second object plane by displacing the first object plane by the typical "thickness" of a row of teeth.

FIG. 7 illustrates the corresponding relationships as they exist when the X-ray image is recorded with the X-ray apparatus 12 shown in FIGS. 1 and 2. 48 designates here an object surface whose three-dimensional shape has been determined such that the surfaces of the teeth 38 facing the x-ray source 28 abut the object surface 48 approximately tangentially. Distanced behind it is the Sensor surface 33 of the X-ray detector 32 indicated. The object surface 48 thus corresponds to the object plane 46 and the sensor surface 33 of the image plane 42 in the representation of FIG. 6. On the sensor surface 33, the image 138 of a tooth 38 is indicated as an example, which is produced on the sensor surface 33 by projection as a result of fluoroscopy with x-rays 30. If, by calculation, these points lying on the sensor surface 33 are projected back onto the object surface 48, then an equalized original image of the tooth 38 is produced.

This procedure requires that the coordinates of the sensor surface 33 relative to the position of the X-ray source 28 are known exactly. Furthermore, the position of the object surface 48 must also be known in this reference system. The position of the sensor surface 33 relative to the x-ray source 28 is structurally fixed to one another in the x-ray device 12. However, the position of the object surface 48 in this reference system is initially unknown, since the shape of the mandibular arch and the arrangement of the teeth 38 held therefrom can deviate considerably from one patient to another. In particular, when the straightened X-ray image is also to be used to determine particular proportions of the teeth or periodontal ligaments, it generally does not suffice for all patients to have the same location of the object area 48 or about a limited number of different object areas 48 of equalization based on which one is selected according to the age of the patient.

Therefore, according to the invention, the position of the object surface 48 is metrologically determined in this embodiment by determining coordinates of the teeth 38 at a plurality of measuring points lying on the teeth 38 with the aid of a measuring device. Possible measuring methods used in this are suitable, are described in more detail below with reference to Figures 8 to 12.

4. Measuring method

In the exemplary embodiment shown in FIG. 8, the measuring device is a triangulation sensor 50 which is introduced into the oral cavity 34 of the patient 36. As the front view of the triangulation sensor 50 shown in FIG. 9 shows, it has one

Light source 52, for example, a laser diode or an LED, and a directionally resolved image sensor 54. Of the

Imager 54 typically includes a microlens and a CCD sensor for this purpose.

The light source 52 and the image sensor 54 are arranged on a cross member 56, which is rotatable about a vertical axis 58 by means of a small servomotor (not shown) relative to a longitudinal member 60. In addition, the cross member 56 about a horizontal axis 61 by means of another servo motor (also not shown) can be tilted. In this way, the light beam generated by the light source 52 by pivoting about the vertical

Axis 58 and the horizontal axis 61 are guided according to a defined scanning pattern on the triangulation sensor 50 facing inner surfaces of the teeth 38. This results in a grid-like arrangement of measuring points whose coordinates can be accurately determined by triangulation relative to each other.

In order to be able to set these coordinates in relation to the X-ray apparatus 12, the longitudinal member 60 of the triangulation sensor 50 is provided with a bite bar 62 which is provided on its underside with a notch into which the lower

Incisor teeth of the patient 36 can intervene. If the insertion part 22 of the X-ray device 12 is also provided with a corresponding is provided, the measured results obtained by the triangulation sensor 50 on the position of the incisors of the patient 36, which serve as a reference point, are spatially correlated to the X-ray machine 12. FIGS. 10 and 11 show, in similar representations to FIGS. 8 and 9, an intraoral stereoscopic SD camera which is used as a measuring device for determining the coordinates on the teeth. The 3D camera, designated as a whole by 64, comprises two intraoral cameras 66, 68 which, as can be seen in FIG. 11, are arranged on a common cross member 70. The cross member 70 is attached to the end of a longitudinal member 72 which is provided on its underside again with a Aufbisssteg 74. In the area in which the two intraoral cameras 66, 68 record overlapping images, the distance between the intraoral cameras 66, 68 on the one hand and the recorded teeth 38 on the other hand can be determined by way of image processing (eg by photogrammetry methods) ,

In a modified measuring method, only the intraoral camera 66 is used. The other intraoral camera 68 is replaced by a light source provided with a grating shutter and capable of projecting a regular light grating 69 onto the teeth 38, as shown in FIG. If this regular light grid 69 is projected onto teeth 38, the intraoral camera 66 takes an image, as shown by way of example in FIG. Due to the curvature of the teeth 38, the originally straight lines of light are also curved. The distance between the light lines is a measure of the distance of the teeth 38 to the intraoral camera 66. By evaluating the distorted light line image, as shown in FIG. 13, it is also possible to obtain a surface relief of the teeth 38. FIG. 14 shows a plan view of a further measuring device with which the coordinates of measuring points lying on the teeth can be measured. The measuring device 73 has a longitudinal member 72, which is dimensioned so that it can be inserted into the oral cavity 34 of the patient 36. On the side member 72, a detector latch 76 is arranged, on which a plurality of detector elements 78, for example photodiodes, are arranged parallel to one another. In this case, each detector element 78 is assigned a cylindrical sleeve 80, which causes light incident on the detector element 78 to be detected only substantially parallel to the longitudinal axis of the sleeve 80. The detector elements 78 thus form together with the sleeves 80 direction-resolving optical sensors. The detector latch 76 in turn carries a laser bar 82, which comprises a plurality of laser diodes 83 arranged next to one another. The laser diodes 83 of the laser bar 82 are driven in the measurement so that they generate a laser beam 84 at short time intervals. As a result of the directional characteristic of the detector elements 78, only certain detector elements 78 can detect the laser light reflected by the teeth 38. In FIG. 14, this is indicated for two detector elements 78 by dashed lines. By triangulation, the distance of the teeth 38 relative to the measuring device 73 can then be determined. In the case of the measuring device 73, therefore, the pivotable head of the triangulation sensor 50 shown in FIGS. 8 and 9 is replaced by a fixed arrangement of a plurality of light sources and a plurality of detectors. 5. Equalization - second embodiment

A second embodiment of the invention will be explained below with reference to FIG.

Reference should again be made to FIGS. 3 to 6. As has already been explained above in connection with FIG. 6, the undistorted original image can be reconstructed from a distorted image 139 if the position of the object plane 46 is known. However, an equalization is also possible if the shape is known at least from a part of the object, here the cube 39, without knowing its position relative to the image plane 42 and to the radiation source 40 exactly. In doing so, one exploits the fact that the transformation rule, which mathematically describes the equalization or equalization, can be assumed to be the same for smaller objects in a good approximation. With a tooth this can be assumed with good approximation; So if you know how to equalize the crown, you can equalize the neck of the tooth with the same transformation rule. In FIG. 15, the steps performed for equalization in this embodiment are shown separated by arrows.

The starting point is the distorted X-ray image taken by the X-ray detector. In FIG. 15, such an X-ray image is designated by 90; For the sake of simplicity, only the images 138 of two teeth 38 are shown.

In a next step, an edge image 92 of the teeth 38 is obtained from the X-ray image 90, which is done using known edge detection algorithms. Subsequently, the identifiable on the X-ray image 90 teeth 38 are measured. From the measurement of the teeth, a surface relief 94 is obtained, which is indicated in FIG. 15 by curved lines 96 on teeth 38. The surface relief 94 is now from a pre-determined

Planned perspective shown. This desired perspective can be fixed by the X-ray examination system 10, but can also be freely selected by an operator. The desired perspective can be determined individually for individual teeth or groups of teeth, so that the rectified X-ray image is composed of a plurality of partial images, which appear to be taken from different perspectives and are composed without gaps to form a panoramic image. In particular, a centrally centered central perspective, as indicated in FIG. 4, or a parallel perspective may be considered. It has been assumed in FIG. 15 that the surface relief 94 is already shown in the desired desired perspective.

On this representation of the surface relief 94 now indicated by cross points bases 98 are determined. This determination is preferably carried out automatically by subjecting the surface relief 84 shown in the desired perspective to edge detection, and then selecting characteristic points of the edges, such as corners or strong curvatures, as support points 88.

Corresponding points 98 'on the edge image 92, which was derived from the X-ray image 90, are now visited at these support points 88.

In a next step, a transformation instruction is defined, which converts the points 98 'to the interpolation points 98. The term "transformation rule" here means any collection of rules. with which a linear or nonlinear distortion or equalization can be described for a group of pixels. If the transformation rule is designated as matrix T in FIG. 15, this represents a rough simplification, because with a matrix alone, the transformation of a larger group of pixels will generally not be described.

The transformation rule is now applied to the entire X-ray image 90, whereby the teeth 138 'shown therein are equalized and displayed so that they appear taken from the desired desired perspective. The result is an equalized x-ray image 100, in which the tooth roots and necks of the teeth, which were not detectable during the measurement, also appear from the desired target perspective.

This process can be repeated for each individual tooth or groups of teeth that can apply the same transformation protocol.

6. Common Process Steps FIG. 16 shows, in the form of a flowchart, essential steps of the method according to the invention, which are common to both exemplary embodiments.

In a step Sl, the X-ray source 28 is placed in the oral cavity 34 of the patient 36. In a second step S2, the X-ray detector 32 is arranged such that it extends around the mandibular arch of the patient 36 from the outside.

In a third step S3, the teeth 38 of the patient 36 are X-rayed. In a fourth step S4, the X-radiation impinging on the X-ray detector 32 is detected.

In a fifth step S5, a digital X-ray image is generated on the basis of the X-radiation detected by the X-ray detector 32.

In a sixth step S6, coordinates of a plurality of measuring points lying on the teeth 38 are measured with the aid of a measuring device, for example the triangulation sensor 50, the 3D camera 64 or the measuring device 73. In a seventh step S7, the digital X-ray image generated in step S5 is equalized using the coordinates measured in step S6.

7. Further embodiments of the invention

Measuring Devices With the measuring devices shown in FIGS. 8 to 14, the teeth of the patient 36 can be measured either before or after the acquisition of the X-ray image. A simultaneous measurement is hardly practical, since the

Longitudinal beams 60 or 72 with the components fastened thereto can only be introduced into the oral cavity 34 of the patient 36 in addition to the insertion part 22 of the X-ray device 12, subject to considerable difficulties.

In the following, measuring devices are described which make it possible to carry out the surveying and the fluoroscopy of the teeth 38 simultaneously or in succession so that no modifications of the X-ray device, eg a pivoting away of certain parts of the measuring device, are required. Simultaneous measurement and fluoroscopy reduce the susceptibility to error, because the simultaneity ensures that the measurement in the condition in which the patient's teeth are illuminated. The longer the time span between the two processes and the more steps that have to be taken (eg removal of parts of the measuring device, taking of a new picking position) during this period, the higher the likelihood that errors will occur, for example because of Patient accidentally takes another than the desired Aufbissposition or he initially occupies this, but then leaves again unintentionally by small Kieferbewegungen.

However, a simultaneous measurement requires that no or at least no parts of the measuring device that are impermeable to X-rays are arranged in the beam path of the X-radiation such that the images of these parts cover the images of the teeth and other structures of interest on the recorded X-ray images. In the embodiments of measuring devices described below, this is achieved in different ways.

FIG. 17 shows, in a vertical section, an exemplary embodiment of an x-ray device 12 in which two of the stereoscopic 3D cameras shown in FIGS. 10 and 11 are fastened to the distal end of the insertion part 22. The 3D cameras denoted by 64a, 64b in this exemplary embodiment each comprise two intraoral cameras 66, 68, as shown in FIG. 11 (in the vertical section of FIG. 17, only the intraoral cameras 66 facing the observer are discernible). The two 3D cameras 64a, 64b are mounted so far behind the X-ray source 28 that they do not hinder the propagation of the X-rays in the direction of the teeth 38 of the patient 36. By means of this arrangement behind the X-ray source 28, the teeth 38 can be simultaneously illuminated and measured with the aid of the two SD cameras 64a, 64b. Since the insertion part 22 in comparison to the side member 72 has relatively large dimensions, neither of the two 3D cameras 64a, 64b both rows of teeth of the patient 36 can be optically detected simultaneously. For this reason, two independent SD cameras 64a, 64b are provided in this exemplary embodiment, each of which measures the row of teeth lying on its side. Alternatively, it is possible to provide only a 3D camera 64a which can be swiveled through 180 ° about the longitudinal axis of the insertion part 22, so that the two rows of teeth can be measured sequentially by a 3D camera 64a.

The intraoral cameras 66, 68, which are part of the 3D cameras 64a, 64b, may be endoscope cameras. This has the advantage that the intraoral cameras 66, 68 can have very small dimensions, which makes the recording of the 3D

Cameras 64 a, 64 b facilitated in the oral cavity of the patient 36. The captured by the intraoral cameras 66, 68 images can, for. B. are transmitted via a fiber optic to the main part 20 of the X-ray device 12. A free-ray transmission with the aid of angle optics is also considered for this purpose. The intraoral cameras 66, 68 can also be designed as so-called video endoscopes, in which electronic image sensors are arranged in the receiving heads of the intraoral cameras. The image transfer to an evaluation, the z. B. can be configured as software executable in the computer 16, then takes place not on optical but electronic way. The same applies to the intraoral cameras of the embodiment shown in Figures 10 and 11. In the figure 17, a marker object is indicated at reference numeral 102, which is impermeable to X-rays and in the illustrated embodiment, the shape of a small ball, which has a short foot is attached to the insertion part 22. The marking object 102 is arranged so that it does not lie in the beam path of X-ray radiation that penetrates the teeth or other structures of interest in the jaw region of the patient 36. As a result, the image of the marker object 102 does not overlap the images of the structures of interest. Since the patient 36 has to keep his mouth open anyway in order to be able to receive part of the insertion part 22 into his oral cavity 34, a central strip always remains on the X-ray image between the two illustrated rows of teeth on which the marking object 102 should preferably appear.

The provision of such a marking object 102 is particularly advantageous if the X-ray detector is not a CCD or a CMOS sensor, but the X-ray detector is an interchangeable image carrier, for example a CCD. B. a storage film or an X-ray film having. With such interchangeable image carriers, it may occasionally happen that the image carrier is not positioned exactly in a suitable receptacle. Since the equalization according to the invention requires that the position of the X-ray detector 32 relative to the X-ray source 28 be known exactly, such replacements of a replaceable image carrier may result in the rectification being erroneously performed and the teeth 38 of the patient 36 thus not being correct the rectified X-ray image appear.

With the aid of the marking object 102, which is likewise located in the beam path of the X-radiation and is imaged onto the exchangeable image carrier, the computer 16 can determine the position of the image carrier relative to the X-ray source 28 from the position of the image of the marking object 102 on the replaceable image carrier , Dodge the picture of the marking object 102 from its nominal position on the image carrier, the image carrier was not exactly aligned in its recording during the X-ray exposure. From the displacement of the actual image relative to the desired position of the image, the computer 16 can then determine the amount and direction of the misalignment and correct the other pixels accordingly. In order to increase the accuracy of the correction, it is also possible to provide a spatially extended marking object or a plurality of distributed marking objects.

FIG. 18 shows, in a horizontal section, an exemplary embodiment of an X-ray device 12 according to the invention, in which the measuring device is arranged not intraorally but extraorally between the teeth 38 of the patient and the X-ray detector 32. In this exemplary embodiment, the measuring device comprises four triangulation sensors 50a, 50b, 50c, 50d, whose measuring apertures are indicated in each case by gestri ^¬ smiled lines. The triangulation sensors 50a to 50d are fastened to a support 104, which in turn is fixed to the insertion part 22 in a manner not shown.

FIG. 19 shows the measuring device in a front view at the level of the line XIX-XIX, wherein the X-ray detector 32 is indicated only with its outline for the sake of clarity, and the holder 31 with which the X-ray detector 32 is attached to the main part 20 of the X-ray device 12 , not shown at all. As can be seen in this illustration, the carrier 104 is oriented in the vertical direction such that both the carrier 104 itself and the triangulation sensors 50a to 50d carried thereon extend along a gap left between the two rows of teeth of the patient 36. The height of this gap is in the sentlichen determined by the diameter of the insertion part 22 and the dimensions of the Aufbissstege 63.

As a result of this arrangement of the measuring device in the space between the two rows of teeth, the measuring device is indeed imaged with the X-ray image, but their image covers neither the teeth 38 themselves nor other structures of the mandibular arch, which may be of interest. Nevertheless, the central arrangement between the two rows of teeth makes it possible to optically measure them simultaneously with the triangulation sensors 50a to 50d.

As can be seen in particular in FIG. 18, the carrier 104 does not extend over the entire length of the patient's dental arch. This is due to the fact that in an extra-oral optical measurement, even if the patient's lips are pushed up or down, the molars of the patient can not be measured, since they are covered by the cheeks. However, the position of those molars can be extrapolated with sufficient accuracy, it being possible to resort to statistical data of patients of the same age and sex or other typifying parameters.

FIGS. 20 and 21 show, in illustrations similar to FIGS. 18 and 19, an exemplary embodiment of an X-ray device 12 according to the invention, in which the triangulation sensors 50a to 50d are also arranged extraorally but on a rear side of the X-ray detector 32 facing away from the patient. In order for the optical triangulation triangulation sensors 50a to 50d to have a visual connection to the front area of the two rows of teeth of the patient, the X-ray detector 32 has a central strip-shaped opening 105 which is located in that bene between the two rows of teeth, in which the triangulation sensors 50a to 50d of the embodiment shown in Figures 18 and 19 are arranged. This ensures that X-radiation which strikes through the opening 105 has not been previously illuminated by teeth 38 or other structures of the mandibular arch of interest.

Of course, it is possible to extend the opening 105 to the two shorter transverse sides of the X-ray detector 32, so that it is divided into two halves, which are spaced apart.

FIG. 22 shows, in a vertical section, an exemplary embodiment of an X-ray device 12 according to the invention, in which the measuring device has reflectors 106a, 106b, which are arranged between the patient 36 and the X-ray detector 32. In this exemplary embodiment, the measuring device has two 3D cameras for each row of teeth, each of which comprises two individual cameras, one of which is shown in FIG. 22 for each row of teeth and designated 66a and 66b. The cameras 66a, 66b are arranged on the two upper and lower longitudinal edges of the X-ray detector 32 and are therefore located outside the beam path of the X-radiation.

The reflectors 106a, 106b, on the other hand, are located in the path of the X-radiation, which also passes through the teeth 38 of the patient 36. Therefore, the reflectors 106a, 106b for X-ray must be at least largely transparent. This also applies to feet 110a, 110b, on which the reflectors 106a, 106b are supported on the insertion part 22. For a wearer of the reflectors 106a, 106b and the feet 110a, 110b, for example, plastic may be considered as the material. A strapped on the straps inflective coating of the reflectors 106a, 106b may for example consist of aluminum, which only weakly absorbs X-rays.

In the illustrated embodiment, the supports of the reflectors 106a and 106b are planar plates that extend across the entire width of the mouth of the patient 36. As a result, the cameras 66a, 66b can receive an undistorted image of the teeth of the patient 36 lying in the region of the mouth opening. In order that the lips of the patient 36 do not obscure these teeth, two likewise strip-shaped support surfaces 108a, 108b are attached to the X-ray detector 32, over which the patient's lips are pushed and made of a material permeable to both visible light and X-radiation is, for. Glass.

FIGS. 23 and 24 show, in illustrations similar to FIGS. 18 and 19, an exemplary embodiment of an X-ray device 12 according to the invention, the measuring device of which comprises an upper and a lower contour measuring arc 110a or 110b. Each contour measuring arc 110a, 110b in turn has a plurality of abutment members 112, which are connected to each other via joints 114. The joints 114 thereby enable a deflection of the abutment members 112 perpendicular to a measuring plane in which the contour measuring arcs 110a, 110b respectively extend.

As can be seen in the front view of Figure 24 at the height of the line XXIV-XXIV, each hinge 114 is associated with an angle encoder 116. This generates an electrical output signal in dependence on the angle formed between the abutment members 112, which are connected to each other via the respective joint 114. The electrical output signals of the angle sensor 116 are connected via a not shown electrical signal line supplied to the computer 16. If the electrical signal lines consist of X-ray radiation only weakly absorbing material such as aluminum, they may be guided along the back of the contact members 112 facing away from the teeth 38. Otherwise, it is possible to guide the signal lines in the space between the rows of teeth of the patient.

The Anlageglieder- 112 and the joints 114 consist of a permeable to X-ray material.

z. B. plastic. As can be seen in FIG. 24, the angle encoders 116 are arranged at the end of the joints 114 so that they are located in the space between the two rows of teeth of the patient during the measuring process. The angle encoders 116 must therefore contain materials that are impermeable to X-rays.

The respective central abutment member of each contour measuring blade 110a, 110b is fixedly connected to the insertion part 22 of the X-ray apparatus 12 via one of the webs 118a or 118b (see FIG. 24) and constitutes a stop for the incisors of the patient Engage the patient's incisors on the central abutment member 112, the rest of the abutment members 112 are pivoted by means of the joints 114 that to the teeth 38 facing bearing surfaces 120 of the abutment members 112 are brought into contact with the row of teeth of the patient. The angle changes occurring during the adjustment of the joints 114 are detected by the angle transmitter 116 and transmitted to the computer 16. This then determines on the basis of the angle changes the shape of the two contour measuring sheets 110a, 110b, from which finally the positions of the teeth 38 can be derived. FIGS. 25 and 26 show, in illustrations similar to FIGS. 23 and 24, an exemplary embodiment of an X-ray device 12 according to the invention in which the contour measuring arcs 110a, 110b each have a plastically deformable carrier 122, its inner surface facing the teeth 38 as abutment surfaces 120 are formed. Each carrier 122 carries a plurality of absorbent bodies 124 which are secured by feet 126 to the respective carrier 122. The feet and the carrier 122 are made of a material transparent to X-ray light material, while the absorption body 124, which may for example have the form of small balls, X-rays almost completely absorbie ^¬ ren. The legs 126 are dimensioned so that the absorption body 124 in the space between the rows of teeth are arranged, as can be seen in the figure 26. As a result, when the teeth 38 are illuminated, the absorption bodies are detected by the X-ray detector 32, without their images, however, covering the images of the teeth 38.

In this exemplary embodiment, too, the contour measuring arches 110a, 110b are fixed on the insertion part 22 via webs 118a, 118b, so that the middle section of the contour measuring arcs 110a, 110b serves in each case as a stop for the rows of teeth of the patient. If the carriers 122 are shaped in such a way that they can be plugged onto the rows of teeth in a self-clamping manner, the webs 118a, 188b can be dispensed with. The plastically deformable supports 122 are now bent so that their contact surfaces 120 come into contact with the teeth 38, as can be seen in FIG. If an x-ray of the teeth 38 is now made, the images of the absorption bodies 124 appear on the x-ray image as two rows of dots in the space between the rows of teeth. From the size and location of the points, the computer 16 on the location of the absorption body 124th during fluoroscopy of teeth 38. In the case of this ^exemplary embodiment, the outlay for a sensor system integrated into the contour measurement sheets 110a, 110b and the wiring required for this purpose are therefore eliminated. 8. Bite sensor

In many cases, it may be sufficient to measure only the coordinates eini ^¬ ger fewer measuring points on the teeth 38 of the patient 36, z. B. the coordinates of measuring points on the cutting edges of the incisors. If these coordinates are known relative to the position of the X-ray source 28 and the X-ray detector 32, then the X-ray images can be equalized if the position of the remaining teeth is extrapolated on the basis of typical mandibular arch forms. Often it will be desirable to be able to freely determine the position of the X-ray source 28 in the oral cavity 34 of the patient 36 in order to obtain an optimal image of the teeth 38. In principle, it would be conceivable to provide a plurality of bite notches on the insertion part, of which a suitable bite notch is selected for the reception. Al ^¬ lerdings it is relatively expensive to ensure that the patient's front teeth actually engage in the desired Aufbisskerbe and not leave this position until the light through ^¬. Because with every unintentional opening of the mouth, the bite is lost and must be re-established.

In the following, various embodiments of Aufbisssensoren will be described, in their use, the difficulties described above can not occur. The Aufbisssensoren make it possible to measure the position of the incisors of the patient with high accuracy and extremely reliable ^¬ . As a result, incorrect exposures are If the patient has left the desired bite position or has not even taken it properly, it is largely excluded.

FIG. 27 shows a first embodiment of a bite sensor in a horizontal intersection. The Aufbisssensor 130 generally designated 130 has a tubular and closed at its distal end sleeve 132 which is pushed onto the likewise tubular insertion part 22 end and locked in a manner not shown. In the wall of the sleeve 132, a plurality of pressure sensors designed as piezoelectric elements are arranged one behind the other in the longitudinal direction of the sleeve 132, which will be explained in more detail below with reference to FIG.

FIG. 28 shows an enlarged section of the wall of the sleeve 132 designated 134. The sleeve wall 134 has over a section of a few centimeters an elastic outer wall 136 and a fixed inner wall 138, between which the piezo elements designated 140 are arranged. Each piezo element 140 is designed as a so-called stacked piezo element, in which two piezoelectric crystals 142a, 142b are sandwiched between three metal electrodes. One of the two outer metal electrodes is in each case on the elastic outer wall 136, while the other metal electrode is supported in a manner not shown on the fixed inner wall 138.

If the patient bites the sleeve 132 with an incisor 38, the biting pressure generated in this case is transmitted via the elastic outer wall 136 to those piezoelements 140 which are located near the exiting point. The pressure applied to the respective piezoelectric element 140 generates an electrical signal, which is transmitted via signal lines 144 is transmitted to the computer 16. From the height and the assignment of the signal to the relevant piezoelectric elements 140, the computer 16 can close the location at which the tooth 38 rests against the elastic outer wall 136 of the bite sensor 130. Along the longitudinal direction of the bite sensor 130, the coordinates of the contact surfaces of the incisors can be measured in this manner with an accuracy that depends in this embodiment on the number of per unit length longitudinally provided piezoelectric elements 140. The longitudinal direction of the bite sensor 130 in this embodiment coincides with an insertion direction along which the insertion member 22 is inserted into the oral cavity 34 of the patient 36 together with the bite sensor 130 pushed thereon. The part of the sleeve wall 134, which is diametrically opposite to the cutout shown in FIG. 28 and serves to measure the biting surfaces of the lower incisors, has the same construction and the same function.

The piezo elements 140 of the embodiment shown in FIGS. 27 and 28 can also be replaced by other pressure sensors. It is also possible to replace the pressure sensors with proximity sensors. In this way, additionally or exclusively, the position of the lips of the patient 36 along the insertion direction can be measured, since the lips of the patient may not even touch the bite sensor 130 when the mouth is slightly open.

FIG. 29 shows a detail of an embodiment of a bite block in a representation similar to FIG. 28, in which a plurality of proximity sensors are arranged one behind the other along the insertion direction in the sleeve wall 134, which act as capacitive proximity sensors 146 are formed. The outer wall 136 of the sleeve wall 134 need not be deformable in this case, since the proximity sensors 146 are responsive only to approach, but not pressure of body tissue, so that at the same time the position of a lip 148 and an adjacent incisor 38 can be detected. Proximity sensors 146 may also be designed to respond only to the approach of hydrous tissue so that incisor 38 is not detected. Also in this embodiment, the density of the Nä ^¬ herungssensoren 146 determines the spatial resolution of the Aufbisssensors 130 in the insertion direction. In the in Figs. 28 and

29 illustrated embodiments, the spatial resolution can be increased when interpolated between electrical signals generated by adjacent piezo elements 140 or proximity sensors 146.

To achieve a spatial resolution, not necessarily several sensors must be arranged one behind the other. The figure

FIG. 30 shows a detail of a sensor element of the stem sensor 130, which is designed as a linear potentiometer 150 in a representation similar to FIGS. 28 and 29. The linear potentiometer shown only schematically in FIG. 30 has a resistance surface 152 extending along the insertion direction and an elastic electrode 154 guided parallel thereto at a small distance, which is connected in common with the resistance surface 152 in the manner of a voltage divider circuit. The movable tapping point required with a linear potentiometer is generated at the linear potentiometer 150 where the elastic electrode 154 is deflected by a tooth 38 or the patient's lip through an elastic outer wall 136 so that the elastic electrode 154 contacts the resistance surface 152 is present. The Position point represents the tapping point of the linear potentiometer. The position of the point of attachment along the insertion direction can then be derived from the measured voltage with high accuracy in a conventional manner. FIG. 31 shows in a manner similar to FIG. 27

Representation of another embodiment of a Aufbisssensor 130, in which the sleeve 132 is not locked against the insertion part 22 or fixed in any other way, but linearly movable on this can be moved, as indicated in Figure 31 by a double arrow 162. The sleeve 132 is provided at its top and bottom, each with a single bite notch 160a, 160b, which are provided for engagement of the incisors of the patient 36. In order for the patient to feel clearly whether their incisors are properly engaging the bite notches 160a, 160b, they may be laid out at their bottom with a tough and plastically deformable material, while the other surface of the sleeve 132 may be made of a smooth hard material. As a result, the sensory impression in the patient 36 is quite different with smaller jaw movements, depending on whether his incisors engage in the bite notches 160a, 160b or (accidentally) rest on the smooth hard surface of the sleeve 12 next to them. In the illustrated embodiment, the sleeve 132 is by means of a servomotor 164 along its _. Displaced longitudinally. The servomotor 164 is in turn driven by the computer 16. The control of the servomotor 164 takes place in such a way that it is given a desired distance between the bite notches 160a, 160b on the one hand and the x-ray source 28 on the other hand. This desired distance can be calculated in the computer 16 by a program, the patient-specific parameters such as age, gender o. Ä. Are supplied. The nominal distance can, however, also be predefined directly to the computer 16 with the aid of suitable input means. The servomotor 164 moves the sleeve 132 with the bite notches 160a, 160b arranged thereon so that the desired setpoint distance is achieved. Of the

Servomotor 164 serves as a position sensor at the same time, so that the computer 16 is always aware of the actual distance between the bite notches 160a, 160b and the X-ray source 28. In order to eliminate the need for periodic calibration of servomotor 164, the up-gauge sensor shown includes an additional position sensor 166 for measuring the position of sleeve 132 relative to insertion portion 122 along the longitudinal direction thereof. The position sensor 166 optically scans one in this embodiment

Rack 168, which is combed by a pinion 170 of the servo motor 164.

Since only one bite kerf 160a, 160b on the top and bottom is arranged on the sleeve 132, there is no risk that the patient 36 accidentally bites into an incorrect bite notch or changes over to another bite notch, as is the case with bite elements may be, in which a plurality of bite notches are arranged at a close distance to the top and / or bottom. As a result, it is reliably ensured that the x-ray source 28 is exactly at the desired position during the transillumination of the teeth of the patient 36, for which an optimal imaging of the teeth on the x-ray detector 32 is expected.

In a modification of the embodiment shown in Figure 31, the servo motor 164 is replaced by a locking device, which may be manually or electrically operated. Position sensor 166 outputs the measured position tion preferably to a well-recognizable display device on which an operator can read the distance between the Aufbisskerben 160a, 160b on the one hand and the X-ray source 28 (or another derived therefrom size). As its incisors engage the bite notches 160a, 160b, the patient 36 moves his head along the longitudinal axis of the insertion member 22 until the desired distance appears on the display. At this distance, the locking device is then actuated by the operator or by a command from the computer 16, whereby the sleeve 132 detected and thus can not be moved in the direction of the double arrow 162.

Claims

A method for the preparation of rectified X-ray images for dental or orthodontic diagnostics, comprising the following steps: a) arranging (S1) an X-ray source (28) in the oral cavity (34) of a patient (36); b) arranging (S2) an X-ray detector (32) in such a way that it extends from outside at least around a part of the mandibular arch of the patient (36); c) X-raying (S3) the teeth of the patient (36); d) detecting (S4) the X-radiation incident on the X-ray detector (32); e) generating (S5) a digital X-ray image on the basis of the X-ray radiation detected by the X-ray detector; characterized by the following further steps: f) measuring (S6) coordinates of a plurality of measuring points on the teeth (38) by means of a measuring device (50; 64; 73; 50a to 50d; 106a, 106b, 66a, 66b; 110a, 110b) 130); g) equalizing (S7) the digital X-ray image using the coordinates measured in step f).

2. Method according to claim 1, characterized in that in step f) the coordinates of the measuring points are are determined relative to a reference point whose position relative to the X-ray detector (32) and the X-ray source (28) is known.

3. The method according to claim 2, characterized in that the reference point is defined by a bite point of the patient (36).

4. The method according to any one of claims 2 or 3, characterized in that in step g) from the measured coordinates of the measuring points between the X-ray source (28) and the X-ray detector (32) arranged object surface (48) determines and the rectified X-ray image by backprojection of the X-ray image on the object surface (48) is determined.

5. The method according to claim 1, characterized in that in step f) the coordinates of the measuring points are determined relative to each other, and that the

Step g) comprises the following further steps: ga) determining a desired perspective for the rectified X-ray image; gb) equalizing the X-ray image in such a way that the X-ray image appears from the desired perspective determined in step ga).

6. The method according to claim 5, characterized in that step gb) comprises the following further steps: gba) generating an edge image (92) of the x-ray image (90) using an edge detection algorithm; gbb) deriving a three-dimensional surface relief (94) of the teeth from the coordinates obtained at the measurement points; gbc) Representation of the surface relief from the in

Step ga) specified target perspective; gbd) Selection of vertices (98) on the in

Step gbc) surface relief and assigning the support points to corresponding points (98 ') on the edge image (92) generated in step gba); gbe) deriving a transformation rule which converts the corresponding points (98 ¹ ) on the edge image (92) into the bases (98) selected in step gbd); gbf) applying the transformation rule to the digital x-ray image (90) taken in step e).

7. The method according to claim 6, characterized in that the transformation rule contains a plurality of sub-rules that convert portions of the X-ray image.

8. The method according to claim 7, characterized in that on each portion of a tooth (38) or a plurality of teeth are shown.

9. The method according to claim 6, characterized in that the assignment of the support points (98) to corresponding points (98 ') on the edge image generated in step gba) is performed automatically, wherein from the surface relief (94) shown in step gbc) by means of edge detection a Kan image of the surface relief is generated, and wherein

Corners or other characteristic support points are automatically selected according to predefinable selection criteria based on the edge image

Method according to one of claims 5 to 9, characterized in that the desired perspective corresponds to a development of a row of teeth.

Method according to one of the preceding claims, characterized in that an optical triangulation sensor (50) or an ultrasonic sensor is used as the measuring device.

Method according to one of the preceding claims 1 to 10, characterized in that in step f) a plurality of overlapping camera images taken from different intraoral positions and derived therefrom, the coordinates of the measuring points.

Method according to one of the preceding claims 1 to 10, characterized in that in step f) generates a light pattern on the teeth and this light pattern is detected by optical sensors (78, 80).

Method according to one of the preceding claims, characterized in that light or sound waves used for the measurement in step f) pass through an opening (105) provided in the X-ray detector (32) before they strike the measuring device (50a to 50d). Method according to one of the preceding claims, characterized in that for the measurement in

Step f) taken light or sound waves from a extraorally arranged and transparent to the X-ray reflector (106a, 106b) are reflected before they hit a sensor (66a, 66b) of the measuring device.

16. The method according to any one of the preceding claims, characterized. characterized in that a calibration step is carried out in which an X-ray image is recorded without patients and pixel or area determined by which correction amounts the intensity must be changed in order to obtain a constant intensity across the X-ray image, and the later generated X-ray images of teeth corrected for their intensity taking into account the correction amounts.

Method according to one of the preceding claims, characterized in that the X-ray detector (32) has an exchangeable image carrier, in particular a storage film or an X-ray film, in that a marking object (102) is located in the beam path of the X-radiation which is imaged onto the image carrier and in that the position of the image carrier relative to the X-ray source (28) is determined from the position of the image of the marking object (102) on the image carrier. Method according to one of the preceding claims, characterized in that the X-ray detector (32) has an exchangeable image carrier, in particular a storage film or X-ray film, and carries a plurality of markings which are transmitted to the digital X-ray image when the image carrier is read, and from the position of the markings on the digital X-ray image inhomogeneities of the image carrier are detected and corrected by calculation in the equalization.

Method according to one of the preceding claims, characterized in that the steps c) and f) are carried out simultaneously. ,

A system for the preparation of rectified X-ray images for dental or orthodontic diagnostics, comprising: a) an X-ray source (28) which can be arranged in an oral cavity of a patient (36); b) an X-ray detector (32) which can be arranged such that it extends from the outside at least around a part of the patient's mandibular arch (36) and with which X-ray radiation impinging on the X-ray detector (32) can be detected; c) a digital memory (39) for storing an X-ray image taken by the X-ray detector (32) after examining teeth of the patient (36); characterized by d) a measuring device (50; 64; 73; 50a to 50d;

106a, 106b, 66a, 66b; 110a, 110b; 130) for measuring coordinates of a plurality of measuring points located on the teeth; e) an equalization device (16) which is set up for the computer-aided equalization of an X-ray image using the coordinates measured by the measuring device.

21. System according to claim 20, characterized in that the measuring device is adapted to determine the coordinates of the measuring points relative to a reference point whose position relative to the Röntgend- detector (32) and the X-ray source (28) is known.

22. System according to claim 21, characterized in that the reference point is defined by a bite point of the patient (36).

23. System according to one of claims 20 to 22, characterized in that the equalization device is set up to determine from the measured by the measuring device coordinates of the measuring points between the X-ray source (28) and the X-ray detector (32) arranged object surface (48) and to determine the rectified X-ray image by backprojection of the X-ray image onto the object surface (48).

24. System according to claim 20, characterized in that the measuring device is set up to determine the coordinates of the measuring points relative to each other, and that the equalizing device is set up to equalize the X-ray image in such a way that that the X-ray image appears taken from a predetermined desired perspective.

A system according to claim 24, characterized in that the equalization means is arranged to perform the following steps:

Generating an edge image (92) of the X-ray image (90) using an edge detection algorithm;

Deriving a three-dimensional surface relief (94) of the teeth from the coordinates obtained at the measurement points;

Representation of the surface relief from the given desired perspective;

Selecting vertices (98) on the surface relief and associating the vertices with corresponding points (98 ') on the edge image (92);

Deriving a transformation rule that converts the corresponding points (98 ') on the edge image (92) into the selected vertices (98);

Applying the transformation rule to an X-ray image (90) stored in the digital memory (39).

26. System according to any one of claims 20 to 25, characterized in that the measuring device comprises an optical triangulation sensor (50) and / or an ultrasonic sensor and / or a 3D camera (64).

27. The system according to any one of claims 20 to 26, characterized in that the measuring device is a light source (82) with which a light pattern (69) on the inner or outer surfaces of the teeth (38) can be projected, and an optical sensor (66 78, 80) for detecting the light pattern.

A system according to any one of claims 20 to 27, characterized in that the measuring device (50; 64; 73; 50a to 50d; 106a, 106b, 66a, 66b; 110a, 110b; 130) is arranged for an arrangement in which Parts of the measuring device, which are impermeable to X-radiation, will not be penetrated by X-radiation, which has previously illuminated the teeth (38).

29. System according to one of claims 20 to 28, characterized in that the measuring device (50; 64; 73; 130) is set up for an intraoral arrangement.

30. System according to one of claims 20 to 28, characterized in that the measuring device (50a to 50d; 106a, 106b, 66a, 66b; 110a, 110b) is adapted for an extra-oral arrangement.

31. A system according to claim 30, characterized in that parts (50a to 50d; 116; 124) of the measuring device which are opaque to X-ray radiation can be arranged in a plane which, when the patient's mouth (36) is open, is between its upper and lower sides extends its lower row of teeth.

32. System according to one of claims 30 or 31, characterized in that the measuring device (50a to 50d; 106a, 106b; 110a, 110b) at least partially for an arrangement is established between the patient (36) and the x-ray detector (32).

33. System according to one of claims 30 to 32, characterized in that the measuring device comprises a contour measuring arc (110a, 110b) which extends in a measuring plane and bearing surfaces (120) for engagement with a row of teeth of the patient, said Shape of the contour measuring arc (110a, 110b) is adjustable in the measuring plane to bring the contact surfaces (120) into contact with the row of teeth, and the measuring means comprises means (114, 116; 124) for determining the shape of the contour measuring arc.

34. System according to claim 33, characterized in that the means comprise sensors (116) which are integrated in the contour measuring arc (110a, 110b).

35. System according to claim 34, characterized in that the contour measuring arc (110a, 110b) has a plurality of abutment members (112) which are interconnected by joints (114), and in that the deflections of the joints (114) by the sensors (116) can be determined.

36. System according to one of claims 33 to 35, characterized in that the means with the contour measuring arc (110a, 110b) comprise associated absorption bodies (124) which are opaque to the X-radiation and arranged such that X-radiation emitted by the absorption bodies ( 1214) is absorbed, has not been previously illuminated teeth (38), and that the position of the absorption body (124) of the equalization device (16) can be determined.

37. System according to one of claims 33 to 36, characterized in that the contour measuring arc (110a, 110b) comprises a plastically deformable carrier (122).

38. System according to one of claims 20 to 31, characterized in that the measuring device (50a to 50d in Figures 20 and 21) at least partially for an arrangement on one of the patient (36) facing away from the back of the X-ray detector (32) is established.

39. A system according to claim 38, characterized in that the X-ray detector (32) has an opening (105) arranged such that X-radiation passing through the opening (105) has not previously illuminated teeth (38), and in that the measuring device (50a to 50d) is arranged behind the x-ray detector (32) in the region of the opening (105) such that the opening (105) permits visual contact between the measuring device (50a to 50d) and the teeth (38) ,

40. System according to one of claims 20 to 32 and 38, characterized in that the measuring device comprises a reflector (106a, 106b) arranged for an arrangement between the patient (36) and the X-ray detector (32) and for light or sound waves reflective and permeable to X-rays.

41. System according to claim 20, characterized in that the measuring device comprises a spatially resolving upbeat sensor (130), by which the coordinates of a contact surface of a (38) tooth and / or the lip (148) of the patient (36) at least can be measured along one direction. A system according to claim 41, characterized in that the bite sensor comprises a bite element (132) displaceable along an adjustment direction (162) and provided with a bite notch (160a, 160b) and a position sensor (164, 166) with which the Position of the bite element (132) along the adjustment direction (162) is measurable.

A system according to claim 42, characterized in that the bite sensor comprises a motor (164) for displacing the bite element (132).

A system according to claim 43, characterized in that the motor is a servomotor (164) which simultaneously serves as a position sensor.

A system according to any one of claims 42 to 44, characterized in that the bite element (132) has a sleeve-shaped base body which is slidably disposed on an insertion part (22) containing the X-ray source (28) along a longitudinal axis of the insertion part (22) ,

A system according to claim 41, characterized in that the bite sensor (130) comprises at least one sensor element

(140, 146, 150) and a support (132) carrying the at least one sensor element and at least partially into the oral cavity (34) of the patient

(36) is insertable, wherein at least the coordinates of the contact surface along a reference direction can be determined by the at least one sensor element.

A system according to claim 46, characterized in that the at least one sensor element comprises a plurality of successively arranged pressure or proximity sensors (140, 146) whose size and arrangement are the location requirements. determined with which the coordinates of the contact surface can be measured.

48. System according to claim 46, characterized in that the at least one sensor element is a linear potentiometer (150) which has a resistance surface (152) and an elastic electrode (154), wherein a movable tapping point of the linear potentiometer (150) can be generated there, where the elastic electrode (154) is deflected by a tooth (38) and / or the lip (148) of the patient (36) so far that the electrode (154) rests against the resistance surface (152).

49. System according to one of claims 46 to 48, characterized in that the carrier (132) on an insertion part (22) is fixed, which contains the X-ray source (28).

50. System according to claim 49, characterized in that the carrier is a sleeve (132) which is pushed onto the insertion part (22).

51. 'System according to one of claims 20 to 50, characterized in that the X-ray detector (32) comprises an exchangeable image carrier, in particular a storage film or an X-ray film, and that the measuring device has a marking object (102) which between the X-ray source (28 ) and the image carrier, wherein the position of the image carrier relative to the X-ray source (32) can be determined by the equalization device from the position of the image of the marking object (102) on the image carrier.