CN1989909A - Image reconstruction, projection data evaluating method and X ray CT device - Google Patents

Abstract

A method which can reconstruct good quality images even without corresponding data according portion projection data of scanning and X-ray CT devices which can process said images reconstruction. It replaces the data points A without actual measuring projection data by its mirror point A 'with actual measuring projection data in image channel space collecting part of scanning actual measuring projection data to forming complete scanning projection data, reconstructs images according complete scanning projection data; when the mirror point A 'has not actual measuring projection data, it makes use of the actual measuring projection data of its near several data points B,C to building in data.

Description

Image reconstruction, data for projection evaluation methodology and calculating X line ordography

The application is female case (application number: division 03164845.2).

Technical field

The present invention relates to calculating X line laminagraphy [CT (Computed the Tomography)] device of a kind of image reconstructing method, data for projection (data) evaluation methodology and X ray, specifically relate to according to the data for projection of part scanning (partial san) come reconstructed image method, estimate the method for data for projection normality and carry out this image reconstruction or X ray CT device that data for projection is estimated.

Background technology

In X ray CT device, only the half actual measurement data for projection that scans (half scan) is being collected in picture channel (view-channel) space, replenish insufficient part in the scanning (full scan) fully, reconstructed image with the relative data that comprises in the actual measurement data for projection.(for example the spy opens flat 4-84940 communique (the 34th page, 2-3 figure)).

Because the data point in the picture channel space is discrete, so correct relative data may not be present in the actual measurement data for projection.In this case, though utilize best relatively data in the actual measurement data for projection, because be not complete relative data, so the poor quality of reconstructed image.

Therefore, even problem of the present invention is to realize the X ray CT device that also can come the method for the good image of reconstruction quality according to the data for projection of part scanning and can carry out this image reconstruction under the situation that does not have relative data fully.In addition, problem is to realize judging the method for data for projection normality in the picture channel space and the X ray CT device that carries out this judgement.

Summary of the invention

(1) invention of an aspect of the above-mentioned problem of solution is a kind of image reconstructing method, in the picture channel space of the actual measurement data for projection of collecting part scanning, to there not being the data point of surveying data for projection, actual measurement data for projection with its mirror point replenishes, form the data for projection of scanning fully, come reconstructed image according to the described data for projection that this scans fully, it is characterized in that: when not surveying data for projection in the described mirror point, utilize the data of carrying out interpolation by the actual measurement data for projection near a plurality of data points it.

(2) invention on the other hand of the above-mentioned problem of solution is a kind of X ray CT device, has: data collection module, utilize X ray, and image reconstruction in the reference object is collected in the picture channel space with data for projection; Reconfiguration unit, in the described picture channel space of the actual measurement data for projection of collecting part scanning, to there not being the data point of surveying data for projection, actual measurement data for projection with its mirror point replenishes, form the data for projection of scanning fully, come reconstructed image according to the described data for projection that this scans fully, it is characterized in that: described reconfiguration unit utilizes the data of carrying out interpolation by the actual measurement data for projection near a plurality of data points it when not surveying data for projection in the described mirror point.

In the invention of (1) or (2) described each side, when not surveying data for projection in the mirror point, utilize the data of carrying out interpolation by the actual measurement data for projection near a plurality of data points it, so available complete relative data is replenished, thus, can obtain the measured reconstructed image of matter.In addition, the part description is that half advantage that scans is to obtain necessary data for projection fully by minimal scanning.

(3) invention on the other hand of the above-mentioned problem of solution is the method that a kind of evaluation is collected in the data for projection normality in the picture channel space, it is characterized in that: obtain the difference of the right data for projection of the data point that is in mirror point relation in the described picture channel space each other, estimate the normality of data for projection in view of the above.

(4) invention on the other hand of the above-mentioned problem of solution is a kind of X ray CT device, has: data collection module, utilize X ray, and image reconstruction in the reference object is collected in the picture channel space with data for projection; Reconfiguration unit comes reconstructed image according to described data for projection, it is characterized in that: possess evaluation unit, obtain the difference of the right data for projection of the data point that is in mirror point relation in the described picture channel space each other, estimate the normality of data for projection in view of the above.

In the invention of (3) or (4) described each side, obtain the difference of the right data for projection of the data point that is in mirror point relation in the picture channel space each other, estimate the normality of data for projection in view of the above.The right data for projection of data point that is in mirror point relation each other constitutes relative data each other, should constitute original identical value, so can estimate normality according to their difference.

When not surveying data for projection in the mirror point, utilization is to improve evaluation system by the advantage that the actual measurement data for projection near a plurality of data points it carries out the data of interpolation.

Description of drawings

Fig. 1 is the block diagram of X ray CT device.

Fig. 2 is the figure of the mode configuration of expression X-ray detector.

Fig. 3 is the figure of the mode configuration of expression X-ray detector.

Fig. 4 is the figure of the mode configuration of expression x-ray bombardment, checkout gear.

Fig. 5 is the figure of the mode configuration of expression x-ray bombardment, checkout gear.

Fig. 6 is the figure of presentation video channel space.

The specific embodiment

Below, describe example of the present invention in detail with reference to accompanying drawing.The invention is not restricted to example.Fig. 1 represents the block diagram of X ray CT device.Example of the present invention one example of this device.Structure by this device illustrates example one example about apparatus of the present invention.By the action of this device, example one example about method of the present invention is shown.

As shown in Figure 1, this device possesses scanning stand (gantry) 2, takes platform (table) 4 and operating console (console) 6.Scanning stand 2 has X-ray tube 20.The not shown X ray that radiates from X-ray tube 20 forms fan-shaped x-ray beam (beam), is fan beam (fan beam) by collimator (collimator) 22, shines X-ray detector 24.

X-ray detector 24 has a plurality of detecting elements that are arranged in array (array) shape along the width of fan-shaped X-ray beam.The back describes the structure of X-ray detector 24 in detail.X-ray tube 20, collimator 22 and X-ray detector 24 constitute x-ray bombardment, checkout gear.The back describes the x-ray bombardment checkout gear in detail.

Data collection portion 26 is connected in X ray test section 24.The detection signal of each detecting element of X-ray detector 24 is collected by data collection portion 26, as numerical data (digital data).

X-ray bombardment from X-ray tube 20 is controlled by X ray controller (controller) 28.Omit the annexation of diagram X-ray tube 20 and X ray controller 28.Collimator 22 is by 30 controls of collimator controller.Omit the annexation of diagram collimator 22 and collimator controller 30.

Above parts from X-ray tube 20 to collimator controller 30 are loaded on the rotating part 34 of scanning stand 2.The rotation of rotating part 34 is controlled by Rotation Controllers 36.Omit the annexation of diagram rotating part 34 and Rotation Controllers 36.

Take platform 4 and not shown reference object is moved into and taken out of the x-ray bombardment space of scanning stand 2.The back describes object and the spatial relation of x-ray bombardment in detail.

Operating console 6 has data processing equipment 60.Data processing equipment 60 is by for example computer formations such as (computer).Connect control interface (interface) 62 on the data processing equipment 60.On control interface 62, connect scanning stand 2 and take platform 4.Data processing equipment 60 comes gated sweep stand 2 and takes platform 4 by control interface 62.

Come data collection portion 26, X ray controller 28, collimator controller 30 and Rotation Controllers 36 in the gated sweep stand 2 by control interface 62.These each ones of omission diagram are connected with each of control interface 62.

Also connect data collection buffer 64 on the data processing equipment 60.The data collection portion 26 that on data collection buffer 64, connects scanning stand 2.The data that data collection portion 26 collects are transfused to data processing equipment 60 by data collection buffer 64.

Connect storage device 66 on the data processing equipment 60.The data that storage device 66 memory scanning stands 2 are collected.The part that is made of scanning stand 2, data collection buffer 64, data processing equipment 60 and storage device 66 is example one example of data collection module among the present invention.

Storage device 66 is also stored the program (program) of data processing equipment 60 usefulness.Data processing equipment 60 carries out the various date processing about taking by carrying out program stored in the storage device 66.

Data processing equipment 60 uses the data for projection of collecting a plurality of images in the storage device 66 by data collection buffer 64, carries out image reconstruction.In image reconstruction, for example use projection (the filtered back projection) method etc. that filters.Data processing equipment 60 is example one examples of reconfiguration unit among the present invention.

On data processing equipment 60, also connect display device 68 and operating means 70.Display device 68 shows from the reconstructed image or the out of Memory of data processing equipment 60 outputs.Come operating means 70 is operated by user, with input data processing equipments 60 such as various indications or information.User uses display device 68 and operating means 70 mutual (interactive) to operate this device.

Fig. 2 represents the mode configuration of X-ray detector 24.As shown in the figure, X-ray detector 24 constitutes the multi channel X-ray detector that a plurality of x-ray detection devices 24 (i) is arranged in 1 dimension array-like.I is a channel number, for example i=1-1000.X-ray detection device 24 (i) forms the X ray plane of incidence that bends to the cylinder concave shape as a whole.

X-ray detector 24 also can be arranged in a plurality of x-ray detection devices 24 (ik) 2 dimension array-likes as shown in Figure 3.A plurality of x-ray detection devices 24 (ik) form the X ray plane of incidence that bends to the cylinder concave shape as a whole.K is a column number, and for example k is 1,2,3,4.X-ray detection device 24 (ik) constitutes the detecting element row respectively by column number k components identical.The detecting element of X-ray detector 24 row are not limited to 4 row, also are greater than or less than 4 a plurality of.

X-ray detection device 24 (ik) is constituting by flasher (scintillator) and light emitting diode (photodiode) for example.But be not limited thereto, for example also utilize the quasiconductor x-ray detection device of cadmium tellurium (CdTe) etc. or utilize the ionization box x-ray detection device of xenon (Xe) gas.

Fig. 4 represents the mutual relation of X-ray tube 20 in x-ray bombardment, the checkout gear, collimator 22 and X-ray detector 24.Fig. 4 (a) is the figure of expression from the state seen of front of scanning stand 2, (b) is to represent the state diagram seen from the side.As shown in the figure, the X ray that radiates from X-ray tube 20 forms fan-shaped x-ray beam 400 by collimator 22, shines on the X-ray detector 24.Below, fan-shaped x-ray beam is also referred to as the fan beam X ray.

Among Fig. 4 (a), the width of expression fan beam X ray 400.The width of fan beam X ray 400 is consistent with the channel bank column direction in the X-ray detector 24.Collimator 22 has clearance space 1 collimation instrument blade (collimator blade) 222,224 respect to one another.Space between the collimator blade 222,224 constitutes the opening (aperture: aperture) of the width of fan beam X ray 400.The open angle of this aperture decision fan beam X ray 400.Open angle is also referred to as segment angle (fan angle).

The thickness of fan beam X ray 400 shown in Fig. 4 (b).In the thickness direction of fan beam X ray 400 and the X-ray detector 24 a plurality of detecting elements row and set direction consistent.Collimator 22 has clearance space 1 collimation instrument blade 226,228 respect to one another.Space between the collimator blade 226,228 constitutes the aperture of the width of fan beam X ray 400.The open angle of this aperture decision fan beam X ray 400.

Axon is intersected, for example shown in Figure 5, move into the x-ray bombardment space with being loaded in the object of taking on the platform 48.Scanning stand 2 constitutes the inner tubular structure that comprises x-ray bombardment, checkout gear.

The x-ray bombardment space is formed in the inner space of the tubular structure that scans stand 2.To project on the X-ray detector 24 by the picture of the object 8 of fan beam X ray 400 section (slice).By X-ray detector 24, detect the X ray that sees through object 8.Determine to shine the thickness t h of the fan beam X ray 400 on the object 8 by the aperture of collimator 22.

Keep these mutual relation constant by X-ray tube 20, collimator 22 with x-ray bombardment, the checkout gear that X-ray detector 24 constitutes, rotation (scanning: scan) around the axon of object 8 continuously.Thus, carry out axle scanning (axial scan).Scan the data for projection of collecting a plurality of images by axle.Memorizer (memory) space of storage data for projection is called as the picture channel space.

The schematic diagram of Fig. 6 presentation video channel space.Among the figure, the longitudinal axis is an image, and transverse axis is a channel.Image is represented with the anglec of rotation β of the central beam of fan beam X ray 400.Central beam is the bundle by center of rotation.Channel is that the angle of the X-ray beam of benchmark is represented in order to central beam.Each detecting element row is formed this picture channel space.

When scanning fully, obtain the data for projection of the scope of β from 0 to 2p by actual measurement, when carrying out half scanning and since not to β from 0 to p+2? the data for projection of the scope of max is surveyed, therefore, and at p+2? max does not have data in the 2p scope.2? max is the segment angle of fan beam X ray 400.

When the data for projection according to half scanning forms the data for projection of scanning fully, to p+2? max replenishes the data for projection of half scanning to the 2p scope.Utilize the relation of mirror point (mirror point) to carry out replenishing of data.

From p+2? max has mirror point A ' to the data point A in the 2p scope.The picture channel space of data point A (β A,? A) with the picture channel of mirror point A ' (β A ',? A ') the following formula relation is arranged.

Formula 1

$\left\{\begin{array}{cc}{\mathrm{\β}}_A={\mathrm{\β}}_{A^{\′}}+\mathrm{\π}+2{\mathrm{\γ}}_{A^{\′}}& \\ {\mathrm{\γ}}_A=-{\mathrm{\γ}}_{A^{\′}}& {\mathrm{\β}}_{A^{\′}}-{\mathrm{\β}}_C\end{array}\right.$

The data that are in the data point of this relation constitute so-called relative data each other, have identical value, so copy to data point A by the data with data point A ', can obtain the data with the actual scanning equivalence.

To from p+2? max carries out this processing to all data points in the 2p scope, obtain the data of half scanning, but in actual scanning, because the value of image β disperses (discrete), so by data point A, how not having data on the position of its mirror point A ', only data point B in its vicinity and C have data.

Therefore, in this case, obtain the data of data point A ', be made as the data of data point A by the interpolation of the data among data point B, the C.

Formula 2

$A=A^{\′}=\frac{{\mathrm{\β}}_{A^{\′}}-{\mathrm{\β}}_C}{{\mathrm{\β}}_B-{\mathrm{\β}}_C}\×B+\frac{{\mathrm{\β}}_B-{\mathrm{\β}}_{A^{\′}}}{{\mathrm{\β}}_B-{\mathrm{\β}}_C}\×C$

Here, the image of β B: data point B

The image of β C: data point C

The channel of data point B, C is identical.

Thus, the just data that can be scanned fully.Interpolation is not limited to above-mentioned 1 dimension interpolation, also can carry out suitable higher-dimension interpolations such as 2 dimensions or 3 dimensions.

Data processing equipment 60 is carrying out carrying out image reconstruction after above complete scan-data forms.By above-mentioned processing, the just data that is scanned fully according to the data of half scanning is so the quality of reconstructed image is good.In addition, the data that are used for image reconstruction are the data of half scanning originally, so can obtain temporal resolution than carrying out the good image of complete scan condition.In addition, scan and be not limited to half scanning, also greater than partly scanning, scanning (partial scan) less than the suitable part that scans fully.

In the time needn't improving temporal resolution especially, also can scan fully.Carrying out under the complete scan condition, obtaining the data for projection of β from 0 to 2p scope, the data of data point A also constitute measured value.

In this complete scan-data, the data of data point A should constitute the value identical with the data of mirror point A ' ideally, because moving etc. of noise (noise) or object 8 produces difference sometimes.When this species diversity was big, because the contradiction between relative data, the quality of reconstructed image was low.

Therefore, data processing equipment 60 is obtained the difference of the data A ' of the data of data point A and its mirror point, has detected no abnormal according to this difference.At this moment, when not corresponding to the correct mirror point A ' of data point A, utilization comes the data of interpolation according to the data of near data point B, C.Thus, can improve the system of evaluation.

When detecting data exception by this judgement, show this situation and end image reconstruction, or additional abnormality warnings, show reconstructed image.Thus, can reform scanning etc. of user is suitably disposed.

As above described in detail, according to the present invention, even can realize under the situation that does not have relative data fully the X ray CT device that also can come the method for the good image of reconstruction quality and can carry out this image reconstruction according to the data for projection of part scanning.In addition, can realize judging the method for data for projection normality in the picture channel space and the X ray CT device that carries out this judgement.

Claims (4)

1. an evaluation is collected in the data for projection evaluation methodology of the data for projection normality in the picture channel space, it is characterized in that,

Obtain the difference of the right data for projection of the data point that is in mirror point relation in the described picture channel space each other, estimate the normality of data for projection in view of the above.

2. data for projection evaluation methodology according to claim 1 is characterized in that,

When not surveying data for projection in the described mirror point, utilize the data of carrying out interpolation by the actual measurement data for projection near a plurality of data points it.

3. an X ray CT device is characterized in that,

Have:

Data collection module utilizes X ray that image reconstruction in the reference object is collected in the picture channel space with data for projection,

Reconfiguration unit comes reconstructed image according to described data for projection;

Possess evaluation unit, obtain the difference of the right data for projection of the data point that is in mirror point relation in the described picture channel space each other, estimate the normality of data for projection in view of the above.

4. X ray CT device according to claim 3 is characterized in that,

Described evaluation unit utilizes the data of carrying out interpolation by the actual measurement data for projection near a plurality of data points it when not surveying data for projection in the described mirror point.

Images