CN103584877B - A kind of computer chromatography imaging device and method - Google Patents

Abstract

The invention discloses a kind of method that area-of-interest to detected object carries out CT imaging, including step: obtain the CT data for projection of described area-of-interest；Obtain the CT data for projection in B region；Select one group of PI line segment covering described area-of-interest, and be that every PI line segment in described PI sets of line segments calculates reconstruction image value thereon；Then rebuilding image value and obtaining the image of described area-of-interest on all PI line segments in described PI sets of line segments is combined.The invention also discloses and use the CT imaging device of the method and data processing unit therein.Cover area-of-interest and B region i.e. accurate reconstruction can obtain the two-dimensional/three-dimensional faultage image of this area-of-interest owing to having only to X-ray beam, therefore the detector of reduced size can be used to realize the CT imaging of large sized object optional position area-of-interest, and this can be substantially reduced the X-ray radiation dosage during CT scan.

Description

A kind of computer chromatography imaging device and method

The application is filing date on May 26th, 2009, Application No. 200910085612.4 and invention entitled " Kind of computer chromatography imaging device and method " the divisional application of application for a patent for invention.

Technical field

The present invention relates to a kind of computerized tomography (CT) equipment, especially a kind of for (ROI) interested region Carry out the equipment of CT imaging, and the CT formation method used in such devices.

Background technology

Since Hounsfield in 1972 has invented First CT machine, and CT technology is to medical diagnosis and industrial nondestructive testing band Having carried out revolutionary impact, CT has become as one of important detection means of the industries such as medical treatment, biology, Aero-Space, national defence.X Ray Cone-Beam CT is widely used, particularly in medical science in fields such as clinical medicine, safety inspection, Non-Destructive Testings In clinical diagnosis, spiral CT has become as one of indispensable detection methods^[1]。

Although CT technology has achieved huge success in fields such as industry, safety check, medical treatment at present, but owing to engineering should By complexity and the multiformity of condition, the development further to CT technology is had higher requirement.Especially in commercial Application In, CT technology is in aspect bigger difficulties of existence such as large scale, in high precision imaging, medical treatment low dose imagings.This mainly due to: CT sweeps Retouching the visual field (FOV) to be limited by X-ray beam width, detector size and scanning visual angle, this makes the projection scanning big object Data there may be blocking of detector direction and two aspects in scanning angle direction；And existing main flow CT algorithm is both for The overall method for reconstructing of complete object, it is desirable to X-ray beam must be completely covered object tomography, has situation about blocking to data for projection It is difficult to process.Therefore, when at present big object or irregularly shaped object being carried out imaging, it tends to be difficult to be done directly scanning, need logical Relying on the approximate transform method such as data rearrangement just can reconstruct final image after crossing Multiple-Scan, this is to the speed of CT imaging and essence Degree causes negative impact.

Additionally, the detector in CT equipment has become as the most critical link of the hardware cost limiting CT equipment, detector Price be directly directly proportional with detector cells size and quantity, and remaining high of detector price, this greatly limits The cost space of CT product.

On the other hand, in medical treatment CT imaging, in order to ensure that X-ray projection data is not blocked, the X that current CT scan uses Beam width must cover the width of human body tomography, and interested be often certain organ of human body, this is big Add greatly human body unnecessary radiation dosage during CT scan, if not changing the thinking of current CT design, It is difficult to reduce radiation dose.At present, medical exposure has become as the artificial ionization source radiation that the whole people are maximum, reduces CT examination X-ray dose is to be related to all public and the key subjects of offspring's health thereof.

It addition, along with the raising of living standards of the people, people are more and more higher to the requirement of medical diagnosis, especially for certain A little human body privileged sites, such as: the medical diagnosis at the positions such as female mammary gland, cochlea, tooth needs the highest spatial resolution.Right In these situations, current main flow whole body spiral CT machine cannot meet the demand of normal medical diagnosis.Along with large-area flat-plate is visited Surveying developing rapidly of device technology, current Medical flat detector technology is the most ripe, as being applied to high-space resolution The X-ray DR imaging of rate.Being currently based on the flat panel detector of amorphous selenium, amorphous silicon technology, its effective detector area exceedes 500mm × 500mm, and detector pixel size has also reached about 0.1mm, and the detector unit chi of multi-layer spiral CT at present Very little only about 0.5mm, utilizes flat panel detector can realize the CT image more much higher than existing spiral CT spatial resolution.But It is that, owing to flat panel detector data volume is huge, data transmission bauds also cannot meet the requirement of current cone-beam CT imaging, at present also The most really application flat panel detector carries out the CT equipment of whole body imaging.If we are not for Whole Body, but utilize Small-scale Flat detector realizes high accuracy area-of-interest CT imaging to organ interested, then data just can be overcome to transmit Slow-footed technical bottleneck, makes possibility.

For disadvantages mentioned above and the limitation of CT system, we start to explore new CT image rebuilding method and CT imaging mould Formula.It is true that a lot of engineer applied are not required for complete object carries out overall situation CT imaging, it is only necessary to obtain some sense emerging In the subject image of interest region (ROI), particularly medicinal diagnosis, as long as being capable of the one-tenth to suspicious lesions position As^[2]。

Early 1980s, people have begun working on the Local C T imaging problem of object, but are rebuild by CT at that time and manage Opinion limited, people cannot accurate reconstruction go out object local CT image, therefore then seek one relevant to object faultage image Approximate function.1985, Smith etc. proposed the partial reconstruction algorithm of a kind of lambda tomography, and this algorithm utilizes Local projection data reconstructs a function having identical singularity with ROI density function^[3].Subsequently, Katsevich proposes The partial reconstruction algorithm of a kind of pseudolocal tomography, this algorithm becomes by rebuilding the Hilbert of density function The part changed is to replace original function^[4].But, all cannot replace real object faultage image due to these functions, it is difficult to full The demand of foot practical engineering application, significantly reduces the Local C T imaging meaning for practical engineering application.The longest Following period of time, for object local ROI imaging research always sink into pause, it is impossible to have been resolved.

Recent years, CT reconstruction theory gets a larger development.2002, Katsevich first proposed a kind of base Cone-beam helical CT exact reconstruction algorithm in filtered back projection (Filtered Back Projection, FBP) form.This algorithm Solving long materials Problems of Reconstruction well, in the case of Z-direction data for projection blocks, this algorithm remains able to accurately Reconstruct the subject image of scanned part, and owing to this algorithm is FBP form, reconstruction speed is rebuild with Class of Iterative Algorithm is compared has the biggest advantage, and Katsevich is that the development of CT algorithm provides a brand-new thinking^[5-6].2004, The spiral CT that Zou and Pan proposes a kind of backprojection-filtration (Back Projection Filtration, BPF) form is accurate Algorithm for reconstructing, the method has only to the data for projection of theoretical minimum just accurate reconstruction can go out the faultage image of object^[7-8].Extremely This, the Issues of Basic Theory of Spiral CT Reconstruction has obtained preferably solving.Subsequently, BPF algorithm is expanded is applied to parallel beam, fan During bundle, pyramidal CT image are rebuild.The BPF algorithm of Zou and Pan is algorithm for reconstructing based on PI line, and PI line is that scanning track is taken up an official post Anticipate a line segment on 2 lines, BPF algorithm require two end points of every PI line outside object support, its sharpest edges Being to remain able to accurate reconstruction when some blocks go out the image on PI line when data for projection exists, this makes for ROI not Be complete object CT rebuild be possibly realized.2006, Defrise etc. achieved further on the basis of BPF algorithm Achievement, relaxes the restriction of PI line, it was demonstrated that when PI line only one of which end points is when object support is outer, by the throwing by this PI line Shadow data remain able to accurate reconstruction and go out PI line epigraph^[9].2007, Wang et al. further demonstrated when PI line exists completely During interior of articles, if it is known that the image information of last point of this PI line, it becomes possible to by the data for projection accurate reconstruction blocked Go out the subject image on this PI line^[10].But, the reconstruction numerical information in actual CT engineer applied, on interior of articles PI line Being difficult to obtain in advance, therefore, the method for Wang et al. has certain limitation in actual applications.

Pertinent literature:

[1] Li Liang. CT projective transformation is theoretical and cone beam reconstruction method studies [Ph.D. Dissertation]. Beijing: Tsing-Hua University is big Department of Engineering Physics, 2007.

[2] Li Liang, Chen Zhiqiang, Kang Kejun, Zhang Li, Xing Yuxiang. area-of-interest CT image rebuilding method and simulation experiment, CT theory and application research, 18:1-7,2009.

[3]A Faridani, E L Ritman, K T Smith. “Local tomography”, SIAM Appl Math, 52: 459-484, 1992.

[4]A Katsevich, A. G. Ramm. “Pseudolocal tomography”, SIAM Appl Math, 56: 167-191, 1996.

[5]Katsevich A. A general scheme for constructing inversion algorithms for cone beam CT. Int J Math Math Sci, 2003, 21:1305-1321.

[6]Katsevich A. An improved exact filtered backprojection algorithm for spiral computed tomography. Adv Appl Math, 2004, 32:681-697.

[7]Zou Y, Pan X. Exact image reconstruction on PI-lines from minimum data in helical cone-beam CT. Phys Med Biol, 2004, 49:941-959.

[8]Zou Y, Pan X. Image reconstruction on PI-lines by use of filtered backprojection in helical cone-beam CT. Phys Med Biol, 2004, 49:2717-2731.

[9]M Defrise, F Noo, R Clackdoyle, H Kudo. “Truncated Hilbert transform and image reconstruction from limited tomographic data”, Inverse Problems, 22: 1037-1053, 2006.

[10]Y B Ye, H Y Yu, Y Wei, G Wang. “A General Local Reconstruction Approach Based on a Truncated Hilbert Transform”, International Journal of Biomedical Imaging, Volume 2007, Article ID 63634。

Summary of the invention

Applicant of the present invention is found that a brand-new CT accurate reconstruction data extrapolating condition:

For any pointIf data for projection meets following condition, then image function simultaneouslyCan be by accurate reconstruction:

1. there is vectorWith two lines section、, whereinIt is to pass throughPoint And be parallel toAt functionLine segment in support,；

2. line segmentAt least an end points is outside function support, or line segmentOnKnown；

3. for arbitrfary point, by comprising the arbitrarily angled of arbitrfary point in the small neighborhood of this pointUnder projectionThe most collected obtain, wherein。

Above-mentioned condition can be explained by Fig. 1, and when region of interest ROI is positioned at object support inside, FOV only covers ROI can not accurate reconstruction ROI image, need to increase extra projection information and can reconstruct the faultage image of this ROI, In two kinds of situation: (a) (b) belongs to a class situation, i.e. increases an extra dark shaded areas, by the throwing of this shadow region Shadow data are also required to collect, and the image of this dark shaded areas is known；C () (d) belongs to an other class situation, i.e. increase Add an extra shadow region B, this region some or all outside object support.As long as meeting both above situation One of, the accurate CT imaging of region of interest ROI can be realized.Four kinds of situations in comparison diagram 1, we it appeared that for Two kinds of situations (c) (d) next are owing to need not the image information of this extra shadow region known, and therefore both of these case is more convenient Engineer applied realizes；Particularly last a kind of situation (d) is positioned at outside object support due to shadow region B, thus has only to Measuring the faultage image being got final product accurate reconstruction ROI by the x-ray projection of ROI and region B, this means that this CT scan side Formula is for imaging of medical, and detected person can accept less radiation dose.Detected person has only to accept scanning, and it can Doubt the x-ray dose of tissue regions and by the x-ray dose of the outer air section the least of its health, compare current Whole body Spiral CT scan, it is possible to reduce the radiation dose that detected person accepts to a great extent.

The present invention is based on above-mentioned CT accurate reconstruction data extrapolating condition, is based especially on above-mentioned situation (d) and does Go out.

According to an aspect of the invention, it is provided a kind of area-of-interest to detected object carries out the side of CT imaging Method, including step: obtain the CT data for projection of described area-of-interest；Obtain the CT data for projection in B region, wherein said B district Outside the support remaining at least partially within described detected object in territory, and described B region is chosen as making it possible to select one Group covers the PI line segment of described area-of-interest, and wherein every PI line segment through described area-of-interest is all by B region；With And rebuild described area-of-interest according to the CT data for projection of described area-of-interest and the CT data for projection in described B region CT data for projection.

According to a further aspect in the invention, it is provided that a kind of for the area-of-interest of detected object is carried out CT imaging CT imaging device, including x ray generator, for producing the X-ray beam for scanning；Detector assembly, is used for detecting Cross the X equipment in scanned region to produce data for projection；Detected object bogey, is used for carrying described detected object and enters Go out described CT imaging device；Master controller, for controlling the operation of described CT imaging device, so that described x ray generator The X-ray sent only covers described area-of-interest to carry out CT scan to obtain the projection number of described area-of-interest According to, and the X-ray that described x ray generator is sent only cover B region described B region is carried out CT scan with Obtain the data for projection in described B region, outside the support remaining at least partially within described detected object in described B region, and And described B region is chosen as making it possible to select one group of PI line segment covering described area-of-interest, wherein described in every process The PI line segment of area-of-interest is all by B region；And data processing unit, for throwing based on the area-of-interest obtained The data for projection in shadow data and B region rebuilds the image of described area-of-interest.

The X ray CT imaging device proposed according to the present invention and method, it is only necessary to the X-ray beam that X source sends covers sense Interest region i.e. accurate reconstruction can obtain the two-dimensional/three-dimensional faultage image of this area-of-interest, therefore can use less chi Very little detector realizes the CT imaging of large sized object optional position area-of-interest, improves the speed of CT scan and image reconstruction Degree, reduces the hardware cost of CT equipment, can be substantially reduced the X-ray radiation dosage during CT scan simultaneously.Therefore, originally Invention has the highest market application potential.

Accompanying drawing explanation

By reading the detailed description of hereafter preferred implementation, various other advantage and benefit common for this area Technical staff will be clear from understanding.Accompanying drawing is only used for illustrating the purpose of preferred implementation, and is not considered as the present invention Restriction.And in whole accompanying drawing, it is denoted by the same reference numerals identical parts.In the accompanying drawings:

Fig. 1 illustrates the CT accurate reconstruction data extrapolating condition according to the present invention；

Fig. 2 describes the flow chart of Computerized chromatographic (CT) formation method according to an embodiment of the invention；

The data for projection reconstruction that Fig. 3 describes according to an embodiment of the invention, performs in the CT formation method of Fig. 2 The flow chart of method；

Fig. 4 shows the structured flowchart of CT imaging device 400 according to an embodiment of the invention；

Fig. 5 shows the structural frames of the front collimator apparatus 420 in CT imaging device 400 according to an embodiment of the invention Figure；

Fig. 6 shows that the detector position in CT imaging device 400 according to an embodiment of the invention controls device 440 Structured flowchart；And

Fig. 7 shows that CT imaging device according to an embodiment of the invention carries out the numerical simulation result of CT imaging.

Specific embodiment

The invention will be further described with specific embodiment below in conjunction with the accompanying drawings.

Situation (d) as mentioned above for CT accurate reconstruction data extrapolating condition is described, it is only necessary to obtained by scanning The faultage image of accurate reconstruction ROI is got final product by the x-ray projection in ROI and B region.

Fig. 2 describes Computerized chromatographic according to an embodiment of the invention (CT) formation method.In step s 201, Determine (ROI) the interested region in the detected object of CT imaging to be carried out, and according to determined by ROI region determine Remain at least partially within the B region outside detected object supports.B region is chosen as making it possible to select to cover a ROI district The PI line segment in territory, wherein ensures that the every PI line through ROI region is all by B region (situation as shown in Figure 1 (d) shows).B region It can be an arbitrary size and the area of space of shape, it is contemplated that the radiation that the size of actual detector unit and patient accept Two factors of dosage, usually, B region can be chosen as circle or the diameter of Spherical Volume region that diameter is detector cells 10 times.When So, B region can be with more than one.It addition, in order to improve image reconstruction speed and precision further, may further determine that other Reference zone.

After determining ROI region and B region, in step S203, ROI region is adjusted to scan vision scope In, so that scanning X-ray beam only covers this ROI, and this ROI region is carried out CT scan to obtain the CT throwing of ROI region Shadow data.Then in step S205, in the range of B region is adjusted to scan vision, so that X-ray beam only covers this B Region, and this B region is carried out CT scan to obtain the CT data for projection in B region.Subsequently in step S207, based in step The CT data for projection of the ROI region that S203 obtains and the CT data for projection in the B region in the acquisition of step S205, according to following such as ginseng Examine the method for reconstructing described in Fig. 3 to reconstruct the CT image of this ROI region.In the CT formation method of the present invention, while it is desirable to Carry out twice CT scan and can reconstruct the CT image of ROI region, but in scanning every time, X-ray beam only covers ROI With B region, total X-ray radiation dosage that therefore in twice sweep, detected object is subject to is far smaller than radiating of conventional CT scans Dosage.

Fig. 3 specifically describes the method for reconstructing performed in step S207 shown in Fig. 2.In step S301, select one Group can cover the PI line segment of ROI region, and ensures that the every PI line through ROI region is all by B region.

The method subsequently enters step S303-S307, wherein every in PI sets of line segments selected in step S301 Bar PI line, carries out image reconstruction along this PI line.Then, in step S309, the reconstruction data on all PI lines are carried out group Close and obtain final ROI image.This image reconstruction process based on PI line is the same in two and three dimensions is rebuild, under Face illustrates perform, image reconstruction process based on a PI line in step S303-S307 as a example by two-dimension image rebuild.

Function will be defined as along the two dimensional image of a PI line, then image reconstruction process is found exactly Meet the intersection function of all 5 constraints of formula below (1).

(1)

Wherein,Can by measurement to CT data for projection be directly calculated.It addition,Represent the one-dimensional PI line segment after normalization,It is the B being positioned at outside detected object supports on this PI line segment Region B, andThen being in the part in the PI line segment in ROI region, this is as shown in Figure 1 (d) shows.

It is the subject image in the PI line segment part in B region, owing to it is outside the support of detected object, And usually air, so typically can arrange its image reconstruction value is 0.Represent the possible maximum rebuild in image Value, the attenuation factor value of the maximal density material can being arranged in this object according to the feature of detected object, the most right In medical treatment CT imaging, detected object is typically people, and its maximum rebuilding image is usually osseous tissue, then can be byThe attenuation factor value of the osseous tissue being configured as under corresponding X-ray energy.

It is the one-dimensional Hilbert(Hilbert on PI line segment) transformed value, i.e. ask difference the most anti-data for projection Projecting to the result on PI line segment, this can be calculated by formula below:

(2)

Herein,Being point on one-dimensional PI line represents at faultage image two-dimensional coordinate spatially, WithIn some x one_to_one corresponding.Wherein,Represent data for projection,It is the one-dimensional coordinate on detector,It it is projection Employing angle,.Here,WithThere is identical implication, for no other reason than that at different coordinates Different variablees it is expressed as under system.

Constraints in above-mentioned formula (1)Easy to understand and realize, conditionAvailable POCS (Projection onto Convex Set, convex set projection) iterative computation realizes, specifically, and conditionCan utilize Following iterative computation realizes:

,(3)

Wherein,Represent the intermediate reconstructed images of iteration,Represent iterative steps.Iteration initial picturesCan Arrange with the most artificial, usually take complete zero.Representing Hilbert inverse transformation, this transformation for mula is:

(4)

Wherein P.V. represents Cauchy principal value integral.

In formula (3)It is defined as:

(5)

Wherein,It is calculated by preceding formula (2), in POCS iterative process,Keep constant, Need not repeat back projection calculate.

Constraints in formula (1)Computing formula be:

(6).

According to the above-mentioned concrete description processed to solution formula (1), it is known that all in searching meets formula below (1) In the intersection function of 5 constraints, need first to carry out backprojection-filtration and (i.e. obtainValue), then carry out POCS iteration Calculate and obtainValue.And POCS iterative process is all to rebuild between image area and two territories of Hilbert transformation space Iterate, there is not forward projection problem, therefore, the speed of image reconstruction is quickly.

Specifically, in step S303, select a PI line segment in PI sets of line segments.Then in step S305, meter Calculating the one-dimensional Hilbert transformed value on selected PI line segment, this can be calculated according to formula (2).Subsequently, in step S307 In, one-dimensional Hilbert transformed value calculated to step S305 carries out limited Hilbert inverse transformation, to obtain at PI line segment On reconstruction image value.In the process of step S307, need rebuild image area and Liang Ge territory, Hilbert transformation space territory it Between iterate, i.e. POCS iterative process obtains the reconstruction image of the satisfied requirement meeting required precision.In step S307 Process can carry out according to above-mentioned formula (1) and (3)-(6).

It should be strongly noted that above-mentioned method for reconstructing is not limited to certain scan mode, it can be applicable to utilize The CT scan of parallel beam, fan-beam or cone-beam X-ray, simultaneously for different scanning tracks, this method for reconstructing is equally applicable, The most different is that back projection's formula (2) can be because the change of concrete scan mode be slightly different on weight coefficient, only Need to adjust accordingly according to concrete scan mode, do not repeat at this.

It addition, it may also be noted that Fig. 3 simply show a kind of CT data for projection according to ROI region and B region CT data for projection rebuilds a kind of concrete mode of the CT image of ROI region.There is also other according to the principle of the present invention, utilization The CT data for projection of ROI region and the CT data for projection in B region rebuild the method for the CT image of ROI region, and all these Method is all within protection scope of the present invention.

Fig. 4 shows CT imaging device 400 according to an embodiment of the invention, and it utilizes the CT imaging according to the present invention Method carries out CT imaging.CT imaging device 400 include for produce for scanning X-ray beam x ray generator 410, Front collimator apparatus 420, detector assembly 430, detector position control device 440, rotating mechanism 450, detected object carrying Device 460, master controller 470, data processing unit 480 and display device 490.

The X-ray that x ray generator 410 sends is typically fladellum (corresponding to linear array detector) or cone beam is (right Should be in area array detector).Front collimator apparatus 420 is arranged on the ray of x ray generator 410 and goes out to restraint the position of window, uses In the width of restriction X-ray beam, so that the width of X-ray beam is consistent with the detector width in detector assembly.As above Describing described in the CT formation method according to the present invention, the present invention needs to be scanned ROI region and B region respectively, because of Before this needs, collimator apparatus 420 possesses regulation X-ray beam width, in order to X-ray beam only covers ROI region or B region Function.Fig. 5 shows the detailed construction of front collimator apparatus 420.As shown in Fig. 5 (a), this front collimator apparatus 420 is penetrated by four pieces of X Line blocks block 421a-421d composition, forms the effigurate X-ray of tool and goes out to restraint window 423, and this shape can be circular, square Shape or other shapes.In the present embodiment, as shown in Fig. 5 (b), illustrate as a example by rectangle.X-ray blocks block 421a- 421d is made by the material (it can be the highdensity material such as lead, tungsten) effectively absorbing X-ray energy, and possesses certain thickness Degree is can stop passing through of X-ray.Each X-ray blocks the servo electricity having one group of independent operation after block 421a-421d Shown in machine 425 and precision lead screw 427(such as Fig. 5 (c)), servomotor 425 and precision lead screw 427 can be at master controllers 470 Under control, drive corresponding X-ray to block block 421a-421d and move along precision lead screw 427 according to given parameter and advance Or retreat.Four groups of servomotors 425 and precision lead screw 427 allow for X-ray according to the operating of set parameter simultaneously and go out to restraint window Mouthfuls 423 changes realizing corresponding window size and position for different ROI region or B region, thus reach X-ray beam ROI region or the requirement in B region is only covered in scanning process.Certainly, X-ray is blocked block and is not necessarily lucky four pieces, The polylith X-ray that any X-ray that can form definite shape goes out to restraint window blocks block all within protection scope of the present invention.

Detector assembly 430 can use linear array detector or area array detector, it would however also be possible to employ flat panel detector, And corresponding auxiliary equipment.Detector assembly 430 detection through the X-ray in scanned region to produce data for projection, and with Optical cable, netting twine etc. are wired or data for projection is transferred to data processing unit 480 and is further processed by wireless mode.

Detector position controls device 440 and is used for controlling the position of detector assembly 430, and includes servomotor 441 He Precision lead screw 443 etc..Fig. 6 illustrates in the embodiment that detector assembly 430 is area array detector, and detector position controls The detailed construction of device 440.As shown in Figure 6, detector assembly 430 is fixed on precision lead screw 443 by the groove that is installed, Ke Yiyou Servomotor 441 drives this detector assembly 430 to move along a straight line along leading screw 443 under the control of master controller 470.Due to can With selection ROI region and B region, it is therefore desirable to the scope of detector assembly 430 motion is wanted to cover the most possible selection ROI region and B regional location, therefore the detector assembly 430 position under each x-ray projection angle is probably change , to change the position of detector assembly 430 the most as required under the control of master controller 270.

Rotating mechanism 450 includes a gantry that can rotate, x ray generator 410, front collimation around certain fixed center Device 420, detector assembly 430, detector position control device 440 etc. and are each attached on this gantry.During CT scan, This gantry drives above-mentioned each device to rotate under the control of master controller 470, and while rotating, x ray generator 410 Send down X-ray beam to be visited through detected region (after ROI region or B region) by detector device 430 Measure, and the data processing unit 480 that data for projection is transferred to rear end processes.Rotating mechanism 450 can carry out multi-turn Rotation sweep, individual pen rotation sweep or the scanning of reciprocal multipurpose rotary, as long as these scan modes are sufficient for CT imaging device 400 obtain enough data for projection rebuilds image, and the most all these scan modes are all within protection scope of the present invention.

Detected object bogey 460 carries detected object turnover CT imaging device 400, its structure and existing dress Put similar.Generally, detected object bogey 460 is positioned near the center of rotation of rotating mechanism 450, and ROI region It is typically a part for detected object.

Master controller 470 controls whole scanning process, and in an embodiment of the present invention, master controller 470 is with corresponding to Fig. 2 The mode of described CT formation method controls CT imaging device 400.ROI region determined by master controller 470 first basis, Before controlling, collimator apparatus 420 and detector position control device 440 so that the X-ray that x ray generator 410 is sent only is covered Lid ROI region.Then master controller 470 controls CT imaging device 400 ROI region to carry out CT scan to obtain ROI region Data for projection and send the data to data processing unit 480.Subsequently, master controller 470 is first according to the B district determined Territory, before controlling collimator apparatus 420 and detector position control device 440 in case the X-ray that sent of x ray generator 410 only Only cover B region.Finally, master controller 470 controls CT imaging device 400 ROI region to carry out CT scan to obtain B region Data for projection and send the data to data processing unit 480.

Data processing unit 480 is after obtaining the data for projection in ROI region and B region, according to reconstruction as described in Figure 3 Method rebuilds the image of ROI region.Specifically, data processing unit 480 includes that PI line divides device 481, Hilbert becomes Change calculating device 483, Hilbert inverse transformation calculates device 485 and rebuilds data set locking device 487.Wherein, PI line divides dress Put 481 according to the relative position of ROI region with B region, select one group of PI line segment that can cover ROI region, and ensure every Through the PI line of ROI region all by B region.Hilbert transformation calculations device 483 is every PI line computation in one group of PI line One-dimensional Hilbert transformed value along this PI line.Hilbert inverse transformation calculates device 485 to utilizing Hilbert transformation calculations to fill Put 483 calculated one-dimensional Hilbert transformed values and carry out limited Hilbert inverse transformation, to obtain the reconstruction on PI line segment Image value, wherein in Hilbert inverse transformation calculates device 485, needs rebuilding image area and Hilbert transformation space territory two Iterating between individual territory, i.e. POCS iterative process obtains the reconstruction image meeting required precision.Reconstruction data set attaches together Put 487 and divide, for according to PI line, the PI line group that device 481 is provided, to every PI line in PI line group, inverse by Hilbert Transformation calculations device 485 calculated reconstruction image is combined, and obtains final ROI image.Data processing unit 480 In the detail of process had been described in above, be not discussed here.

Additionally, data processing unit 480 also performs such as to harden, scatter correction, metal artifacts reduction, and image procossing The image real time transfer performed in the CT scan traditional with pattern recognition etc. and imaging device.

The ROI region image that obtains is rebuild in display device 490 display, and display device 490 can also show and sweeps with CT simultaneously The information that control during retouching is relevant with parameter, in order to operator can obtain above-mentioned information intuitively.

CT imaging device 400 according to the present invention can by respectively ROI region and B region being scanned quickly and Accurately reconstruct the image of ROI region.Although needing twice sweep, but owing to needing only to ROI region and B region are entered Row scanning, so scanning and reconstruction speed accelerate on the contrary.Additionally, the region that detected object is exposed under X-ray also shows Work decreases.

Although it is to be herein pointed out in description above for the embodiment of CT imaging device 400, illustrating elder generation Obtain the CT data for projection of ROI region, then obtain the order of the CT data for projection in B region, but, this order is can be any , for example, it is possible to then the CT data for projection first obtaining B region obtains the CT data for projection of ROI region.Even, according to this In one embodiment of invention, the CT data for projection in ROI region and B region can be obtained simultaneously.All these acquisition ROI region With the mode of the CT data for projection in B region all within protection scope of the present invention.

Fig. 7 is the numerical simulation result utilizing and carrying out CT image scanning and reconstruction according to the CT imaging device of the application.Real We used Shepp-logan head model in testing, this head model is limited in the circle of an a diameter of 20cm, and ROI region is One length of side is the square of 6cm, is placed on head model center, and two other elongated rectangular region B1, B2 are individually positioned inPlace.By the definition of head model it is recognised that the image values in the two elongated rectangular region B1, B2 is 0. When carrying out ROI region CT scan, parallel beam X-ray only covers ROI and region B1, B2 in 180 degree of scanning processes, such as Fig. 7 (a) Shown in.Fig. 7 (b) is to utilize through ROI and the data for projection of region B1, B2, rebuilds according to the image rebuilding method of the present invention The ROI image arrived；And Fig. 7 (c) is only to utilize through ROI and the data for projection of region B1, calculate according to the image reconstruction of the present invention Method rebuilds the ROI image obtained.Reconstructed results according to (b) and (c) is it is found that utilize the CT formation method of the present invention, energy Enough in the case of X-ray only covers the scanning of ROI region and the little object exterior domain of another one, rebuild obtain high-quality ROI image, it is possible to meet the demand of practical engineering application.And this CT imaging technique can save detection to a great extent The size of device, reduces data for projection amount, improves CT image reconstruction speed, it is most important that ensureing ROI region CT picture quality On the premise of, significantly reducing the X-ray radiation dosage of object/patient, this point is particularly important for medical treatment CT imaging.

The present invention will be described rather than limits the invention to it should be noted above-described embodiment, and ability Field technique personnel can design alternative embodiment without departing from the scope of the appended claims.In the claims, Any reference marks that should not will be located between bracket is configured to limitations on claims.Word " comprises " and does not excludes the presence of not Arrange element in the claims or step.Word "a" or "an" before being positioned at element does not excludes the presence of multiple such Element.The present invention and can come real by means of including the hardware of some different elements by means of properly programmed computer Existing.If in the unit claim listing equipment for drying, several in these devices can be by same hardware branch Specifically embody.Word first, second and third use do not indicate that any order.These word explanations can be run after fame Claim.

Claims (4)

1. the method area-of-interest of detected object being carried out CT imaging, including step:

Obtaining the CT data for projection of described area-of-interest and the CT data for projection in B region, wherein said B region is at least simultaneously A part is positioned at outside the support of described detected object, and described B region is chosen as making it possible to select to cover an institute Stating the PI line segment of area-of-interest, wherein every PI line segment through described area-of-interest is all by B region；And

CT data for projection and the CT data for projection in described B region according to described area-of-interest rebuild described area-of-interest CT data for projection.

2. the method as claimed in claim 1 area-of-interest of detected object being carried out CT imaging, wherein said basis The CT data for projection of described area-of-interest and the CT data for projection in described B region rebuild the CT projection of described area-of-interest Data include step:

Every PI line segment in described PI sets of line segments:

Calculate the one-dimensional Hilbert transformed value on described PI line segment, and

The one-dimensional Hilbert transformed value calculated is carried out limited Hilbert inverse transformation, to obtain the weight on described PI line segment Build image value；

Combine rebuilding image value and obtaining the image of described area-of-interest on all PI line segments in described PI sets of line segments.

3. the method as claimed in claim 2 area-of-interest of detected object being carried out CT imaging, wherein said limited Hilbert inverse transformation step includes:

Carry out convex set projection iteration between image area and Liang Ge territory, Hilbert transformation space territory and obtain rebuilding and meet precision and want The reconstruction image value on described PI line segment asked.

4. the method as claimed in claim 1 area-of-interest of detected object being carried out CT imaging, wherein said acquisition The CT data for projection of described area-of-interest and the CT data for projection in described acquisition B region include:

Utilize parallel beam, fan-beam or cone-beam X-ray that described area-of-interest and B region are carried out CT scan, to obtain State the CT data for projection in area-of-interest and B region.