US2972681A - Cinefluorographic apparatus - Google Patents

Description

Feb. 21, 1961 w. s. LUSBY EIAL CINEFLUOROGRAPHIC APPARATUS 3 Sheets-Sheet 1 Filed Aug. 10, 1956 INVENTORS Walter S. Lusby,Fred J. Euler 8 Philip A. Duffy Jr.

ATTORNEY WITNESSES Feb. 21, 1961 w. s. LUSBY ETAL CINEF'LUOROGRAPHIC APPARATUS 3 Sheets-Sheet 2 Filed Aug. 10, 1956 EE a m mmmc o m IIL faaam United States "9:. 1

CINEFLUORQGRAPHIC APPARATUS Walter S. Lusby, Round Bay, Fred J. Euler, Baltimore, and Philip A. Dulfy, Jr., Catonsville, Md, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania 7 Filed Aug. 10, 1956, Ser. No. 603,413

4 Claims. (Cl. 250-65) The present invention relates to X-ray apparatus, and more particularly to X-ray apparatus for use in cinefluorography and fluoroscopy embodying an electronic image intensified of the type described and claimed in Mason et al. Patent 2,523,132, issued September 9, 1950 for an Image intensifier and assigned to the assignee of this present application.

In X-ray apparatus arranged for fluoroscopic examination of the lung field, the heart and the abdominal region it is frequently desirable to provide a photographic record of the organic conditions observed by the fluoroscopist. While some types of apparatus have been devised whereby radiographic plates may be inserted into the fluoroscopic field at intervals to provide chronologically separated radiographs, there has been no apparatus built, to our knowledge, which will permit immediate photographing of the image observed by the fluoroscopist.

Further, in medical studies of the gastro-intestinal tracts wherein an X-ray opaque material is swallowed by the patient there has been an increasing need for means to make moving pictures of the travel of such opaque material through the esophagus, stomach and the duodenal portion of the small intestine. Because of the peristaltic motion of the stomach and intestines it is often possible to observe certain features of interest only for short time intervals which are randomly spaced. A need, therefore, has existed for apparatus associated with a fluoroscop c which is operative to make motion picture photographs either simultaneously with observation of the fluoroscopic image or as an instantaneous alternative to observation.

The production of X-ray motion pictures has been attempted in the past by a method known as cineradiography in which full size X-ray sensitive film is placed adjacent to a subject and is exposed directly to X-radiation passing through the subject. The cineradiographic technique has been unsatisfactory and unaccepted because it requires X-ray generating apparatus of excessively high power ratings, and more important, it necessitates the exposure of the patient to such large quantities of deleterious radiation that a motion sequence of only a few seconds may severely jeopardize the health of the patient.

The fluoroscopic image intensifier, described in detail in Mason and Coltman Patent 2,523,132 is operative to intercept an X-ray beam and to produce a visible image cor responding to said beam, and orders of magnitude brighter than the image appearing on prior art fluoroscopic screens. Our present invention comprises apparatus for enabling the diagnostician to use this image intensifier in connection with conventional X-ray examination tables for making motion pictures of the visible image either at intervals during the course of a fluoroscopic examination or simul- One object of our invention is, accordingly, to provide ,a new and improved apparatus for medical fiuoroscopy and cinefluorography.

Patented Feb. 21, 1961 It is another object of the invention to provide an arrangement by which motion picture fluorography and image-intensified fluoroscopy may be carried out alternately and in quick succession on a single X-ray apparatus, without delay and without exposure of the patient to hazardous quantities of X-radiation.

It is a further object of the present invention to provide apparatus for cinefluorography with which it is feasible and safe to make several minutes of X-ray motion pic-' tures without danger of radiation injury to the subject.

It is a still further object of the present invention to provide apparatus with which it is mechanically conven ient and medically safe to photographically record a prolonged fluoroscopic study of a subject without danger of overexposure of the subject to injurious radiation.

It is an additional object of this invention to provide apparatus for viewing of a fluoroscopic image by an operator and for simultaneous cinephotographic record ing of the same image.

It is a different object of this invention to provide apparatus for automatically and rapidly switching an X-ray machine from continuous output for continuous fluoroscopy to intermittently-pulsed and synchronized output for synchronized photography of sequential X-ray fluorographic images.

It is an even further object of this invention to provid X-ray apparatus with which the diagnostician, during the making of a fluoroscopic examination can readily, conveniently and rapidly make a series of cinefluorographic exposures on moving picture film, said cinefluorographic exposures being conveniently made either with or without simultaneous viewing of the image being photographed' It is an even still different object of this invention to provide an X-ray cinefluorographic apparatus in which a motion picture camera film drive mechanism is accurately synchronized with an X-ray generator energizing circuit so that the X-ray generator will be energized only in synchronism with the recurring time periods during which the camera film is stationary.

It is still another object of the invention to provide an X-ray apparatus which is conveniently and selectively operable in two difierent modes of operation as follows: (1) image intensifier fluoroscopy in which a visible image of the internal structure of the object examined is presented on a conveniently located viewing plate or mirror positioned adjacent the object to be examined; (2) cinefluorographic recording in which a percentage of the light from the visible image is diverted to a photographic camera system and in which the X-ray generator creating the image beam is periodically energized synchronously with the camera film transport mechanism.

These and other ob ects and advantages of our invention will be apparent from the following description taken in accordance with the accompanying drawing, throughout which like reference characters indicate like parts, and in which:

Figure 1 is a view in perspective showing an X-ray table having a patient support surface, a housing for an image intensifier, its optical viewing system and a motion picture camera mechanism;

Fig. 2 is a block diagram of the apparatus in accordance with the present invention showing the operative relationships between the various circuits for energizing and controlling the X-ray generator, the image intensifier and the motion picture camera; and

Fig. 3 is a schematic diagram of the apparatus including the X-ray tube high voltage supply circuit and the control circuits for the X-ray tube energizing circuits.

Proceeding now to a consideration of the varrangements specifically disclosed and referring to Figs. 1 and 2, the fluoroscopic and cinefluorographic apparatus comprises an X-ray table 9, having an object support surface or zsiassl 17 to support a patient in position for projecting a beam of radiation through said patient. An X-ray tube 19 is supported beneath the object support surface and within the X-ray table. As in the usual X-ray table the Y- ray tube may be movably mounted so that it may be caused to traverse a considerable area of the support surface 17.

At one side of the X-ray table is provided a tower which is movable lengthwise of the table and which is rigidly attached to an image intensifier housing 16 so as to cause the X-ray tube to follow motions of the image intensifier both lengthwise and crosswise of the table, thereby maintaining the X-ray beam projected by the X-ray tube in continuous alignment with the image intensifier. It will be seen that when a patient lies prone on the object support surface 17, the foregoing arrangement enables the image intensifier and the X-ray tube to be moved to project its beam through any selected portion of the patients body. US. Patent No. 2,841,714 of E. W. Vaughn, issued July 1, 1958 for an X-Ray Apparatus and assigned to the assignee of the present application, describes a table suitable for use with the apparatus of the present application.

An image intensifier tube 62 is shown diagrammatically in Fig. 3 and comprises essentially a container 62 having at one end an X-ray sensitive and photoelectrically emissive screen 63. An electron image created by screen 63 is electrostatically projected to an electron sensitive fluorescent screen 65 where it produces a visible image of contracted dimensions and increased brightness. The above-mentioned Mason et al. Patent 2,523,132 is referred to for further details of the image intensifier tube 62.

- Optical system For convenience of the fiuoroscopist in viewing the fluorescent image, an optical system is provided which collects the light from output screen 65 and projects the light through a series of mirrors and lenses to a viewing member 19, which is mounted in a convenient position adjacent the image intensifier, to provide maximum flexibility and ease in continuous observation by the diagnostician or radiologist.

More specifically, the optical system comprises a collecting lens 91 positioned in close adjacency to output screen 65 and being capable of collecting light over a wide solid angle. The light collected by lens 91 is projected along an optical axis 96 coincident with the axis of the image intensifier tube to a partially reflecting mirror 92 which is rigidly positioned to angularly intercept the light beam. A large proportion of the light is transmitted through mirror 92 to the focal plane 110 of the motion picture camera. The camera mechanism is enclosed in a housing 23 positioned directly above the optical system housing 21 as seen in Fig. 2. Included in the camera is a roll film transport mechanism adapted to successively position adjacent frames of film in alignment with the light beams projected through mirror 92. The camera further includes a synchronous motor 112 for driving the film transport mechanism and an appropriate gear transmission means connecting the motor 112 to the transport mechanism 111.

As diagrammatically shown in Fig. 3, the optical system further includes first and second fixedly positioned mirrors 94 and 95 and an auxiliary lens 99. Mirrors 94 and 95 are positioned on opposite sides of optical axis 96' so as to intercept the portion of the light which is reflected by mirror 92 and project that light to viewing mirror 19.

The optical system and camera have been described as they are arranged when operated for cinefluorography alone or for cincfluorography together with simultaneous viewing. Thus, it is seen that means is provided by the apparatus for both of the mentioned radiological techniques.

Because of the use of partially reflecting mirror 92 in the optical system the light transmission efiiciency of the system between output screen 65 and viewing member 19 is substantially below the efficiency desired for imageintensified fluoroscopy. Such reduced efficiency is not undesirably restrictive in the case of simultaneous viewing and cine'fluorographing because in that instance a relatively high X-ray intensity is used (as compared to fluoroscopic viewing alone) in order to obtain optimum film exposure.

For the fluoroscopic viewing mode of operation, means is provided for adjusting the optical system to a maximum efiiciency whereby the maximum amount of light collected by lens 91 is projected through the optical system to the eyes of the observer.

The said adjustable means comprises a manually operable positioning member 97, a movable mirror 93 of maximum reflectivity and an operating linkage 98 for said mirror connecting mirror 93 to positioning member 7 so as to be moved thereby from a first position as shown in Fig. 3 to a second position substantially adjacent to and substantially parallel to mirror 92. As seen in Fig. 2, positioning member 97 is readily accessible to the observer and is capable of being actuated in a fractional part of a second so as to adapt the apparatus from image intensifier fluoroscopy to apparatus for cinefiuorography and vice versa.

in addition to the operative connection of mirror 93 to positioning member 97, a pair of switches 64 and 66 are also operatively connected to positioning member 97 for operation thereby. As seen in Fig. 3, switches 64 and 66 constitute part of a circuit means for adjusting the X-ray tube and its energizing circuits for either of two selectable modes of operation. The details of such circuit will be further described hereinafter.

The switches 6d and 66 may conveniently comprise'a double pole double throw switch of a well known type and is preferably mounted inside the optical system h'ous ing 21 with its operating member being mechanically Referring to the X-ray tube energizing circuit as shown by Fig. 3, an X-ray tube 10 including an anode l1 and a filament 12 is connected through a full-wave high voltage rectifying circuit comprising high voltage rectifiers 35 to the secondary windings 3-1 of a high tension transformer 23 having a primary winding 30. The secondary windings 31 are connected to the full wave rectifier 35 in additive relation such that the voltage applied to the rectifier is substantially the sum of the voltages of the two secondary windings. Between the low tension ends of the secondary windings are connected a rectifier 33 and an impedance member 34 such that a direct current voltage proportional to the X-ray tube anode current appears across impedance member 34 and at conductor 37.

The X-ray tube energizing circuit further includes a filament support transformer 36 having a secondary Winding connected to the filament to supply low voltage alternating current thereto. The filament transformer primary winding is connected to a source of A.C. supply voltage X, Y in series with a variable impedance circuit 32 generally referred to as an ma. stabilizer.

The ma. stabilizer may be a circuit of the type shown by Weisglass Patent 2,319,378 or may be other well known power amplifier circuits which are adapted to control the current in an A.C. circuit in inverse proportion to variations in a DC. voltage applied as at input conductor 38.

In the present apparatus relay switch 81 is provided to selectively connect the input conductor 38 to either of. two sources of DO. voltage. When relay switch 81 is not energized the ma. stabilizer input conductor 38 is connected through contacts 81a to-conductor 37, so that the ma. stabilizer is controlled in response to the D.C.

voltage appearing across impedance 34. Thus a slight increase in X-ray tube anode current will automatically produce an increase in the D.C. voltage appearing at conductor 37. The ma. stabilizer immediately responds to that voltage to decrease the filament heating current to thereby efliciently stabilize the X-ray tube anode current and the radiation emanating from the X-ray tube.

When relay switch S1 is energized the ma. stabilizer input circuit 38 is connected through contacts 81b to the output signal of the brightness preamplifier so that the X-ray tube anode current is controlled in response to the brightness of the image appearing at fluorescent screen 65. Thus the X-ray tube anode current will be continuously controlled as different thicknesses of objects are subjected to the X-rays, to substantially main-' tain constant the brightness of the resultant X-ray picture at fluorescent screen 65.

Referring now to the control circuits as shown by Figs. 2 and 3, the X-ray tube is connected to high tension voltage source 29 as previously described in detail. The high tension generator 29 is connected through a con tactor 25 to a suitable source of alternating current 24.

A first contactor control circuit including commutator 113 is connected to contactor 25. As seen in detail in Fig. 3, commutator 113 has conductive segments 115 on its periphery, said segments being operative as the commutator rotates to periodically complete a circuit from contactor 25 through brush 118 and brush 120 to ground. As seen in Fig. 2, it may be considered that camera 23 provides periodic pulses in synchronism with the positioning of successive film frames. The pulses provided by the camera are operative to permit contactor 25 to conduct thereby supplying current to X-ray tube 10.

Also connected to contactor 25 is a signal from relay circuit 70 which is in turn controlled by switches 64 and 66 in the optical system housing. The signal from relay circuit 70 applies a continuous voltage to contactor 25 to permit the contactor to conduct continuously when the apparatus is adjusted for fluoroscopy.

The relay circuit 70 of Fig. 2 includes time delay relays 73 and 75 and relay switches 77, 79, 81 and 83 as shown in Fig. 3. The plurality of relay switches 77, 79, 81 and 83 are operative in response to a manually operable switch 85 which maybe a pushbutton or a conventional foot switch. Switch 85 is connected between a source of control voltage X, Y and switch 66.

Operation for fluoroscopy The control circuit will first be considered as it 0perates for the fluoroscopic technique, in which technique camera motor 112 and camera 110 are not operated. For fluoroscopic operation, positioning member 97 is in the upper position as shown in Fig. 2. Switches 64 and 66 are in the upper position opposite to that shown in Fig. 3, with switch 64 being open and with contacts 66a and 66b of switch 66 being closed.

Time delay relay switch 73 is energized through contacts 66a and 66b and closes its contacts 74 after a suitable time delay, thereby energizing relay switch 83 through a circuit including conductor 124 and contacts 78 of relay 77. Relay switch 83 operates when energized to close contacts 83a thereby completing the main power circuit from A.C. source 24 through contactor 25 and primary winding 39 of high tension transformer 28. Thus it is seen that with switches 64 and 66 in the fluoroscopic position, the X-ray tube 10 will be continuously energized so long as the operator holds the switch 85 closed. It is to be noted that with switch 64 open, relay 77 is not energized, and contacts 77b remain open so that motor 112 is not operated. Also contacts 77a remain open so that relay switches 79 and 81 are not energized. Relay switch 79 has its contacts 79a connected between the brightness preamplifier and the kv. stabilizer 41. Contacts 7% are connected between the kvistabilizer' il and a fixed bias voltage source 86. The fixed bias voltage 86 is such that the kv. stabilizer has essentially no effect on the conductivity of contactor 25. Thus the kv. stabilizer is in effect inoperative when the fluoroscopy technique of operation is used. In view of the foregoing, the structure and operation of kv. stabilizer 41 will be discussed in detail hereinafter in connection with the oinefluorographic mode of operation.

As previously mentioned, relay switch 81 is not energized in the fluoroscopic condition of operation. Normally closed contacts 81a therefore connect the input circuit 38 of the ma. stabilizer to a signal from impedance member 34, and the ma. stabilizer operates to maintain the X-ray tube current substantially constant regardless of changes in X-ray tube voltage, line voltage and the like. The operation of the ma. stabilizer circuit has been described in greater detail heretofore in connection with the description of the X-ray tube energizing circuit.

Operation for cinefluorography During the course of a fluoroscopic examination the diagnostician frequently may observe some organic condition or function of an unusual nature in the anatomy of the patient, such as a tumor, a suspected ulcer or perhaps an abnormal functioning of the heart. In such instances it is desirable to provide a permanent photo graphic record having superior detail and contrast which may be restudied at a subsequent time. To be successful, an apparatus for providing such a photographic rec- 0rd must be instantly operable and available without distracting the fluoroscopist from the image being examined. Likewise the diagnostic value of the apparatus will be greatly enhanced by provision of means for visually monitoring the image simultaneously with actual film exposure. 1

In the apparatus or" the present application we have achieved the above-mentioned desiderata by provision of a single manually operable control member of positioning member 97 which is operable to make all electrical and mechanical adjustments necessary to provide cinefluorographic recording of the image at screen 65. During the course of such recording the fluoroscopist may con-. tinue to view essentially the same image as that observed during the immediately preceding fluoroscopic examination. It is to be noted that control member 97 is located within easy reach of the fluoroscopist while viewing the image at viewing member 1Q. It is further noted that the change for fluoroscopic technique to cinefiuorographic technique may be accomplished without any conscious de-energization of the apparatus, as by opening of foot switch 85.

In order to initiate cinefiuorography, the operator moves control member 97 from the uppermost position, as shown in Fig. 2, to the lowermost position, as shown in Fig. 3, and in dotted lines in Fig. 2. Such actuation of. control member 97 moves mirror 93 to the position shown in Fig. 3 as previously described. Simultaneously, lever 97 operates switches 64 and 66, closing a circuit through switch 64 to energize the coil of relay 77 and connecting contacts 66a and 660 of switch 66 to thereby energize the coil of relay '75. Contact 66c is also connected to motor 112 through relay contacts a and 7715, so that, after a predetermined time delay, motor 112 will reach synchronous speed. Also connected to contacts 77b of relay 77 is a time delay means 88, capable of providing a fractional-second time delay of consistent duration. After such predetermined time delay, means 88 operates to complete a circuit from contacts 77b to conductor 89 thereby energizing the respective coils of relay switches 79, 81 and 83. Relay 83 closes its contacts 83a immediately to apply power from source 24 to contactor 25 and thence to X-ray tube 1% through high tension unit 29. It is to be noted that power is not applied directly from source 24 to high tension unit- 29, but is applied under the control of contactor 25 and its associated circuits which are hereinafter described.

In use of the present apparatus for making X-ray motion pictures, the brightness at screen 65 will tend to vary inversely as the thickness of the object being examined. In order to maintain consistent film density, in cinefluorography, while scanning objects or body portions of varying thickness and absorption, it is necessary to provide automatic means for controlling the brightness of the image at screen 65 and at film plane 116. Accordingly, we provide within the optical system housing 22 a light responsive member adapted to produce a signal proportional to the brightness of the image at the screen 65. As shown in Fig. 2, the signal from light responsive member 54 is applied to a brightness preamplifier 48 which may be any well known circuit for stable and consistent power amplification of a direct current input signal. The output signal for brightness preamplifier 48 is a D.C. voltage proportional to the image brightness at screen 65. This output signal voltage is applied to two separate and distinct brightness control circuits, the kv. stabilizer 4i and the ma. stabilizer 32.

When the apparatus as shown in Fig. 3 is operated for cinefluorography, the ma. stabilizer input conductor 38 is connected to the output signal of the brightness preamplifier by means of contacts 31!; of relay switch. Thus, as the brightness at screen 65 increases, an increased DC. voltage is applied to the ma. stabilizer input 38 thereby causing a decrease in the A.C. voltage applied to filament transformer 36, and a consequent decrease in the emissivity of filament 12. As .is well known, decrease of the heating current applied to filament 12 results in a corresponding decrease in X-ray tube anode current and hence a decrease in brightness at screen 65. Thus it is seen that light responsive member 65, brightness amplifier 48, and ma. stabilizer 32 are operable as a feedback circuit for stabilizing image brightness at screen 65.

Without brightness stabilization the light intensity of the image at screen 65 will increase by a factor of or more as human body parts varying from 10 cm. to 38 cm. in thickness are scanned. Because of limitations on the minimum and maximum practical X-ray tube current and on the maximum permissible patient radiation exposure, the permissible range of X-ray tube current variation for control of image brightness is limited.

In order to increase the range of body thicknesses which may be scanned while maintaining consistent exposure of film at camera 119, an additional brightness stabilization circuit is provided by means of kv. stabilizer 32. The kv. stabilizer operates simultaneously and cooperatively with the ma. stabilizer to stabilize the brightness of the fluoroscopic image at screen 65.

The kv. stabilizer Electronic contactor is shown in Figs. 2 and 3 in block diagram form. Contactor 25 comprises a pair of inversely connected thyratron discharge devices (not shown) with the anode of the first and the cathode of the second being connected to switch contacts 83a. The cathode of the first and the anode of the second are connected toget er and to conductor 26. Thus the contactor 25 constitutes an inverse-parallel connection operative to pass alternating current to transformer 28 and to act as a single pole switch or contactor. Such arrangements of inverse-parallel thyratron contactors are known in the art and so will not be described in detail here. US. Patent No. 2,785,343, of R. L. Wright et al., issued March 12, 1957, for Xmay Apparatus and assigned to the assignee of the present application, describes a suitable contactor for the purposes of the present system.

In the use of inversely connected thyratron contactors of the aforementioned type it is known in the art to pro vide continuous control or" phase angle at which the thyratrons fire by applying a phase-shiftable A.C. control voltage to the grid control electrodes of each tube. The

kv. stabilizer circuit 41 as shown in Fig. 3 is a circuit means for controlling the voltage applied to transformer 30 in response to changes in the D.C. signal output of brightness preamplifier 48., i

More specifically, the kv. stabilizer 41 comprises a. discharge device 42 having an anode 43, cathode '45 and control grid 4. The control grid 44 is connected to contacts 79a of relay switch 79 so as to be responsive to the output signal of brightneess preamplifier as when the apparatus is arranged for cinefiuorography. A resistor 46 is connected from the control grid 44 to chassis ground. Cathode 45 is connected to the same chassis ground through resistor 40. The anode 43 of discharge device '42 is connected to a source of DC. voltage (not shown) through the DC. control winding 49 of a saturable reactor 47. Variation in the output signal voltage of brightness preamplifier 48 will produce a corresponding variation in the anode current of discharge device 412, and hence a like variation in the impedance of A.C. windings 50 of saturable reactor 47. Windings 50 of reactor 47 are connected in series with a resistance 52 across a center-tapped source of A.C. voltage 51 which source may conveniently comprise a transformer having a primary connected to an A.C. supply voltage source through a circuit including contacts 77a and contacts 79c of relays 77 and 79, and having a center-tapped secondary winding 51 The primary winding of a second trans former 53 is connected across one half of secondary winding 51 and resistor 52. Thus, transformer 53 will be supplied with an A.C. voltage of substantially constant amplitude but having a variable phase depending on the impedance of A.C. windings 5%. As the DC. voltage in control winding is varied, the impedance of A.C. windings 5t will be varied in response thereto, with corresponding variation in the phase angle of the voltage applied to transformer 53. Transformer 53 has a pair of similar secondary windings 57 which are respectively connected across the grid-cathode circuits of the first and second inversely connected thyratrons in contactor 25.

From the foregoing it is seen that as the output signal of brightness preamplifier 48 increases, the phase angle of the control voltage applied to the contactor thyratrou grids will be shifted to smoothly decrease the conduction period of each thyratron. By proper selection of component values the thyratrons are smoothly controlled to initiate conduction at any point ranging from the first 30 of each half cycle to the 170 point of each half cycle. The time period during which the thyratrons conduct in each half cycle of applied voltage from source 24 is dependent on the brightness of the image at screen 65. Thus, the peak kv. applied through high tension unit 29 to X-ray tube 10 is varied in response to changes in brightness at screen 65 so that light intensity at camera focal plane 110 is maintained substantially constant at a brightness level commensurate with optimum photographic results. It has been found that voltage developed across X-ray tube 10 by high voltage circuit 29 is not a function of the R.M.S. voltage or the average voltage applied to primary winding 30. Rather, the peak kilovoltage at X-ray tube 10 is dependent on the peak voltage applied to the transformer. By controlling contactor 25 so as to conduct at phase angles later than the point of each half cycle of voltage source 24, we have achieved smooth continuous variability of the X-ray tube anode to cathode potential in response to changes in brightness of the image at screen 65.

The light responsive member 54 in a preferred embodiment comprises a photomultiplier type tube having a plurality of dynodes, a cathode and an anode, such as for example the RCA #931A phototube. The voltage supply source for the photomultiplier tube may be any conventional source of regulated high voltage direct current power; however, a power source of the type shown and described in copending application Serial No. 476,- 246 of ZL'L. Collinset al., filed December 20, 1954,11OW

U.S. Patent 2,913,582, issued November 17, 1959 and assigned to the same assignee as the present application, is preferred.

It is well known that D.C. amplifiers are subject to difficulties of operation such as instability of zero setting and instability of gain. For this reason a preferred embodiment of the brightness preamplifier 48 comprises a modulator for converting the D.C. input signal into an A.C. signal which is then amplified by conventional means. The signal is then rectified to produce a D0. output signal corresponding in amplitude to the light intensity of the image at screen 65.

Although we have shown and described certain specific embodiments of the present invention, it should be apparent to those skilled in the art that many modifications thereof may be made.

For example, the image amplifier 62 may not be desired and instead the light or X-ray responsive member may include a phosphor or like material which is directly responsive to X-rays from the tube 10.

We claim as our invention:

1. In an X-ray apparatus including an X-ray tube having a filament and an alternating current power source for said tube, the combination of, an X-ray sensitive image intensifier for providing a visible image mounted in movable alignment with said X-ray tube, an object support surface disposed between said X-ray tube and said image intensifier with said intensifier being spaced from said surface, an electronic contactor including a pair of inversely connected discharge devices electrically connected between said power source and said X-ray tube and operative to accurately control energization of said tube from said source for predetermined time intervals, a moving picture camera having a film transport mechanism, an electric motor operatively connected to said mechanism, said camera being disposed adjacent said image intensifier and in optical relation to said image intensifier for periodically recording said visible image, a commutator type electrical switch operatively connected to said film drive mechanism, circuit means connecting said switch to said electronic contactor to operate said contactor in synchronism with said film drive mechanism, an optical focusing system including a plurality of mirrors disposed between said image intensifier and said camera for projecting a light image from said intensifier to said camera, a first one of said mirrors having a partially reflecting surface whereby a first portion of the light from said image is reflected and a second portion is transmitted to said camera, a second one of said mirrors having at least a first position and a second position, said second position being outside the light pathbetween said intensifier and said camera, a manually operable positioning member connected to said second mirror for moving the latter between said first and second positions, circuit means connected for operation by said positioning member, said circuit means including a switch associated with said positioning means and electrically connected to said elec-;

tronic contactor and adapted to energize said X-ray tube at a different power level when said second mirror is in said first position.

2. In X-ray apparatus including an X-ray generator, a

aforesaid certain light transmission condition, X-ray generator control means selectively conditionable for effecting different degrees of X-ray intensity output from said X-ray generator, and interlock means for coordinating conditioning of said optical means and of said generator control means whereby X-ray output from said generator during observer-viewing-only condition of said optical means will be of lesser intensity than during observer-and-camera-viewing condition of said optical means.

3. In X-ray apparatus including an X-ray generator, a fluorescent screen for producing a luminous image which may be viewed by an observer or by an observer and a camera for recording the image, the combination of optical means selectively conditionable for observer viewing of said image under influence of a certain light transmission condition and for simultaneous observer viewing and camera viewing under influence of respective light transmission conditions of less eificiency than that of the aforesaid certain light transmission condition, X- ray generator control means selectively conditionable for effecting different degrees of X-ray intensity output from said X-ray generator, camera drive means selectively conditionable for on-off operation, and means controlled by a single manually operable member for controlling selective conditioning of said optical means, of said generator control means and of said camera drive means, whereby X-ray output from said generator during observer-viewing-only condition of said optical means will be of lesser intensity than during observer-and-cameraviewing condition of said optical means, and whereby said camera drive means will be off and on, respectively, during observer-viewing-only and observer-and-cameraviewing conditions of said optical system.

4. For use in X-ray apparatus having an X-ray source and an image intensifier screen for producing a luminous X-ray image which may be viewed by an operator either separately for fluoroscopic examination or in conjunction with camera-recording of such image in cinefluorography, the combination of partial mirror means for diverting light from the screen into two paths which may be respectively viewed by observer and camera, full mirror means for diverting light into a path for observer viewing only, means controlled by a manually operable member to effect relative movement between the full and the partial mirror means for selectively rendering one or the other of such means etfective, and other means controlled by said manually operable member to control output from said X-ray source.

References Cited in the file of this patent UNITED STATES PATENTS 1,470,770 Siedentopfv Oct. 16, 1923 2,158,853 Coolidge May 16, 1939 2,217,939 Bischoff et al. Oct. 15, 1940 2,517,781 Gacki et al. Aug. 8, 1950 2,537,914 Roop Jan. 9, 1951 2,561,085 Zavales et al. July 17, 1951 2,584,007 Fischer Jan. 29, 1952 2,616,050 Marshall Oct. 28, 1952 2,631,244 Longini Mar. 10, 1953 2,679,598 Wright et al. May 25, 1954 2,719,234 Wright Sept. 27, 1955 2,812,687 Eitel Nov. 12, 1957 2,837,657 Craig et al. June 3, 1958 2,857,523 Corso Oct. 21, 1958 2,874,300 Van Alphen Feb. 17,1959

. FOREIGN PATENTS 721,072

Great Britain Dec. 29, 1954

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