CN1602810A - Image reconstruction method and X ray CT device - Google Patents
Image reconstruction method and X ray CT device Download PDFInfo
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- CN1602810A CN1602810A CN03164844.4A CN03164844A CN1602810A CN 1602810 A CN1602810 A CN 1602810A CN 03164844 A CN03164844 A CN 03164844A CN 1602810 A CN1602810 A CN 1602810A
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Abstract
Disclosed are a method for rebuilding image with good quality in the condition of no relative data and X-ray CT device which can do the image rebuilding. In the image signal channel space for collecting projected data based on spiral scanning, using interpolation of the data in the pair (A,A')of data point, make the projected data of multi-image of the designed segment and according to which to rebuild the image. In the signal channel space, when the position of one point(A') from the pair of data points doesn't have data, use the projected data of the multi data points(B,C)adjacent for interpolation.
Description
Technical field
The present invention relates to calculating X line laminagraphy [CT (Computed the Tomography)] device of a kind of image reconstructing method and X ray, specifically relate to come the method and the X ray CT device that carries out this image reconstruction of reconstructed image according to the data for projection of collecting by helical scanning (helicalscan).
Background technology
In X ray CT device, in picture channel (viewchannel) space of collection based on the data for projection of helical scanning, the data for projection of a plurality of views of the fragment (Slice) that formation is scheduled to about the data for projection interpolation each other that has relativeness by use comes reconstructed image according to these data for projection.(for example the spy opens flat 6-181919 communique (page 3, Fig. 5-6)).
Because the data point in the picture channel space is discrete, so correct relative data may not be present in the measured data.In this case, though utilize data best relatively in the measured data, because be not complete relative data, so the poor quality of reconstructed image.
Therefore, even problem of the present invention is to realize do not having under the situation of complete relative data the also method of the measured image of restructural matter and can carry out the X ray CT device of this image reconstruction.
Summary of the invention
(1) invention of an aspect of the above-mentioned problem of solution is a kind of reconstructing method, in the picture channel space of collection based on the data for projection of helical scanning, make the data for projection of relevant segmental a plurality of views of being scheduled to by the interpolation between the data point centering data for projection that uses into the pip relation, come reconstructed image according to these data for projection, it is characterized in that: in described picture channel space, when be equivalent to described data point to one of the position on when not having data for projection, utilize the data of carrying out interpolation according to the data for projection near a plurality of data points it.
(2), the invention that solves another aspect of above-mentioned problem is a kind of X ray CT device, have: data collection module, helical scanning that will be by utilizing X ray, image reconstruction in the reference object is collected in the picture channel space with data for projection; Reconfiguration unit, in described picture channel space, make the data for projection of relevant segmental a plurality of views of being scheduled to by the interpolation between the data point centering data for projection that uses into the pip relation, come reconstructed image according to these data for projection, it is characterized in that: described reconfiguration unit is in described picture channel space, when be equivalent to described data point to one of the position on when not having data for projection, utilize the data of carrying out interpolation according to the data for projection near a plurality of data points it.
In the invention of above-mentioned each side, in the picture channel space, when be equivalent to data to one of the position on when not having data for projection, the data of interpolation are carried out in utilization according to the data for projection near a plurality of data points it, so can obtain relative data completely, thus, can obtain the measured reconstructed image of matter.Described interpolation is based on 1 interpolation of data for projection near two data points, and its advantage is to simplify and calculates.
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.
Fig. 7 is the figure of presentation video channel space.
The specific embodiment
Below, describe enforcement state of the present invention in detail with reference to accompanying drawing.The invention is not restricted to the enforcement state.Fig. 1 represents the block diagram of X ray CT device.This device is enforcement state one example of the present invention.Structure by this device illustrates enforcement state one example about apparatus of the present invention.By the action of this device, enforcement state 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.
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 enforcement state 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 views in the storage device 66 by data collection buffer 64, carries out image reconstruction.In image reconstruction, for example use projection (filteredback projection) method etc. that filters.Data processing equipment 60 is enforcement state 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 detection device 24 (ik) is constituting by flasher (scintillator) and light emitting diode (photo diode) 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 (fanangle).
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 thickness direction of fan beam X ray 400.The thickness 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 fragments (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, continuously around the axon of rotation (scanning) object 8.In the rotation while of x-ray bombardment, checkout gear, as shown in arrow 42, to take platform 4 continuous when mobile along the axon direction of object 8 when making, and x-ray bombardment, checkout gear carry out so-called helical scanning for object 8, relatively along the helical track rotation of surrounding object 8.Collect the data for projection of a plurality of views by helical scanning.Memorizer (memory) space of storage data for projection is called as the spatial figure of picture channel
The schematic diagram of Fig. 6 presentation video channel space.Among the figure, the longitudinal axis is a view, and transverse axis is a channel.View 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.Is channel the angle of the X-ray beam of benchmark in order to central beam? represent.2? max is the segment angle of fan beam X ray 400.Each detecting element row is formed this view channel space.
1 rotation by helical scanning obtains the data for projection of the scope of β from 0 to 2p by actual measurement.In this picture channel space,, pip A ' is arranged all to arbitrary data point A.The picture channel space of data point A (β A,? A) with the picture channel of pip A ' (β A ',? A ') the following formula relation is arranged.
Formula 1
The data point that is in this relation becomes pip each other.The data of these data points become so-called relative data each other.Relative data is to being used to expect the formation of the locational data for projection of fragment.Right according to relative data, obtain the locational data for projection of expectation fragment by interpolative operation.The weight coefficient of interpolative operation is corresponding to the distance from the position of fragment position on the axon of collecting relative data respectively of expectation.
All data points are carried out interpolative operation, obtain the data of all views, but in the actual scanning, because the value of view β discrete (discrete), so by data point A, for example shown in Figure 7, on the position of pip A ', do not have data, how near its data point B and C is only arranged.
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.
Here, the view of β B: data point B
The view of β C: data point C
Thus, can obtain correct relative data.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.In addition, the advantage of 1 dimension interpolation is to calculate simple.
Data processing equipment 60 is carrying out carrying out image reconstruction after above data form.By above-mentioned processing, obtain correct relative data, so the quality of reconstructed image is good.
As above described in detail, according to the present invention, even can realize under the situation that does not have relative data fully the also method of the measured image of restructural matter and can carry out the X ray CT device of image reconstruction.
Claims (4)
1, a kind of reconstructing method, in the picture channel space of collection based on the data for projection of helical scanning, make the data for projection of relevant segmental a plurality of views of being scheduled to by the interpolation between the data point centering data for projection that uses into the pip relation, come reconstructed image according to these data for projection, it is characterized in that
In described picture channel space, when be equivalent to described data point to one of the position on when not having data for projection, utilize the data of carrying out interpolation by the data for projection near a plurality of data points it.
2, reconstructing method according to claim 1 is characterized in that,
Described interpolation is based on 1 interpolation of data for projection near two data points.
3, a kind of X ray CT device has: data collection module, helical scanning that will be by utilizing X ray, image reconstruction in the reference object is collected in the picture channel space with data for projection; Reconfiguration unit in described picture channel space, makes the data for projection of relevant predetermined segmental a plurality of views by the interpolation between the data point centering data for projection that uses into pip relation, comes reconstructed image according to these data for projection, it is characterized in that,
Described reconfiguration unit in described picture channel space, when be equivalent to described data point to one of the position on when not having data for projection, utilize the data of carrying out interpolation according to the data for projection near a plurality of data points it.
4, X ray CT device according to claim 3 is characterized in that,
Described interpolation is to use 1 interpolation of data for projection in two data points.
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US6522712B1 (en) * | 1999-11-19 | 2003-02-18 | General Electric Company | Reconstruction of computed tomographic images using interpolation between projection views |
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