CN110517330A - A kind of industrial cone-beam CT reconstruction method under biasing scan pattern - Google Patents
A kind of industrial cone-beam CT reconstruction method under biasing scan pattern Download PDFInfo
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Abstract
The present invention provides a kind of industrial cone-beam CT reconstruction method biased under scan pattern, in order to realize that the CT under biasing sample stage scan pattern is rebuild, by establishing dummy detector, practical biasing sample stage CT scan mode is converted into biased detector CT scan mode, existing Wang-FDK biased detector scan pattern method for reconstructing is finally utilized, the accurate CT image of test sample is obtained.The CT Problems of Reconstruction that the present invention solves under biasing sample stage scan pattern substantially increases the visual field of CT system under the premise of not changing standard cone-beam CT scan geometric layout, has preferable engineering application value.
Description
Technical field
The present embodiments relate to the works under Computed tomography field more particularly to a kind of biasing scan pattern
Industry cone-beam CT reconstruction method.
Background technique
CT (Computed Tomography, computerized tomography) is to utilize projection of the object under different perspectives
Information obtains a kind of nondestructiving detecting means of interior of articles quality state and structural information, is curing in conjunction with image reconstruction algorithm
Treatment, Aeronautics and Astronautics, ship domain have a wide range of applications.
For the signal of standard cone-beam CT scan as shown in Figure 1, when regarding standard cone-beam CT scan, x-ray source 1 issues cone-beam x-ray
2, test sample 3 is placed on above sample rotates platform 4, and example cross section is completely by 2 envelope of cone-beam x-ray.Test sample
3 are rotated by 360 ° around 5 stepping of rotation center, the projected image 7 when true detector 6 acquires each stepping angle in this course,
The final faultage image of tested sample 3 is finally calculated according to classical FDK algorithm for reconstructing.However tested sample is usually
Material and shape, in terms of there are biggish uncertainty, when the width dimensions of tested sample 3 are greater than true detection
When the width dimensions of device 6, just it will appear since cross caused by the cross section of tested sample 3 can not be completely covered in CT visual field
To data for projection truncated problem.The signal of standard cone-beam CT system central plane is as shown in Fig. 2 (a), it can be seen that due to being detected
3 size of sample is larger, has exceeded standard cone-beam CT system visual field 8, the data for projection for causing true detector 6 to collect
Bilateral truncation occurs.The data for projection of this bilateral truncation can bring serious artifact to reconstructed results, seriously affect by sample
The accurate interpretation of product fault structure information.At this point, biased detector CT scan mode becomes as a kind of practical solution.
As shown in Fig. 2 (b), when as biasing CT scan, true detector 6 is mobile to the side of tested sample 3, at this time
For rotation center 5 still within the scope of X-ray beam FEG, sample only has side boundary to exceed beam FEG range, and x-ray source
1 with the line of rotation center 5 perpendicular to true detector 6, the collected data for projection of true detector 6 is actually unilateral section
Disconnected data for projection.The data for projection for the One-sided Truncated that Fig. 2 (b) scanning mode obtains carries out figure by Wang-FDK algorithm for reconstructing
The complete cross sectional reconstruction result of tested sample 3 can be obtained as rebuilding.Under biased detector CT scan mode, CT scan imaging
Twice up to common cone-beam CT scan visual field of visual field maximum.
It should be noted that Wang-FDK algorithm for reconstructing is mainly for biased detector CT scan geometry shown in Fig. 2 (b)
Layout, wherein the line of x-ray source focus and rotation center is perpendicular to true detector 6.In reality, biased shown in Fig. 2 (c)
Sample stage scan geometry layout applies wider model.Layout shown in Fig. 2 (c) not only simplifies biasing CT scan geometric layout, and
So that the switching between biasing sample stage CT scan mode shown in standard cone-beam CT scan and Fig. 2 (c) shown in Fig. 2 (a) is more
Flexibly, engineer application is greatly facilitated.However it can be it is clear to see that X-ray in the CT scan geometric layout from Fig. 2 (c)
The line of source 1 and rotation center 5 is not orthogonal to true detector 6, therefore Wang-FDK method for reconstructing will be not suitable for Fig. 2
(c) CT of biasing scan pattern shown in is rebuild.
Summary of the invention
The embodiment of the present invention provides a kind of industrial cone-beam CT reconstruction method biased under scan pattern, existing inclined to solve
Set the complete tomography Exact Reconstruction problem of test sample under sample stage scan pattern.
The present invention provides a kind of industrial cone-beam CT reconstruction methods under biasing scan pattern, comprising:
S1, starts CT scanning device, and true detector acquires tested original of the sample in the case where biasing sample stage scan pattern
Beginning sequential projection image；
S2 establishes dummy detector and determines the spatial position of the dummy detector；
S3, according to the space coordinate relationship of true detector and dummy detector, the original sequence that true detector is obtained
Column projected image is transformed on dummy detector, forms the sequential projection image on the dummy detector；
S4, according to the space coordinate relationship of true detector CT system and dummy detector CT system, by true detector
Reconstructing parameters in CT system are transformed into dummy detector CT system；
S5 adjusts the angle of the sequential projection image on dummy detector with corrected reconstructed image torsion angle；
S6, the CT reconstructing parameters based on dummy detector upper angle sequential projection image adjusted and after converting,
The CT image of test sample is calculated using Wang-FDK method for reconstructing.
Based on the above technical solution, the present invention can also be improved as follows.
Further, the CT scanning device includes x-ray source, test sample, sample rotates platform and true detector,
The x-ray source, test sample, sample rotates platform and true detector are placed in X-ray shield lead room, described by sample
Product are placed on the sample rotates platform, and the x-ray source emits X-ray to test sample, and the true detector receives
X-ray signal after decaying forms projected image；
The step S1 is specifically included:
It is rotated by the sample rotates platform with fixed angle interval stepping, so that it is detected 360 ° of sample rotates,
The projected image of tested sample when true detector acquires each step angle, obtains original series projected image.
Further, the step S2 is specifically included:
The central plane of cone-beam CT system is FEG, and on central plane, the rotation center of the sample rotates platform is true
Point S is projected as on real detector0, crossing point S0And perpendicular to straight line FS0, establish dummy detector, wherein F is that the X is penetrated
Source focal spot, the central plane of the cone-beam CT system are the horizontal plane across x-ray source focus；
The space coordinate of 4 boundary points of the dummy detector is calculated with the space bit of the determination dummy detector
It sets.
Further, the step S3 is specifically included:
S31, according to horizontal coordinate of the detector cells P ' any on the dummy detector on the dummy detector
With the spatial position of vertical coordinate and the dummy detector, the space coordinate of the detector cells P ' is calculated；
S32 calculates detector cells P corresponding with the detector cells P ' on the dummy detector on true detector
Space coordinate, and then determine the horizontal coordinate and vertical coordinate of the detector cells P on the true detector；
S33 obtains the projection value of dummy detector unit P ' according to the projection value of true detector cells P；
Test sample wherein a rotation position when, the projection value group of each detector cells on the dummy detector
At the secondary projected image on the dummy detector, each width projected image under all rotation angles forms the virtual spy
Survey the sequential projection image on device.
Further, the step S4 is specifically included:
S41 calculates rotation angle of the dummy detector CT system relative to true detector CT system；
S42 calculates virtual detection according to the space geometry relationship of true detector CT system and dummy detector CT system
The reconstructing parameters of device CT system.
Further, the reconstructing parameters include that distance, the x-ray source focus of x-ray source focus to detector arrive
The projection coordinate of the distance of the rotation center of rotating platform and the rotation center on the detector.
Further, the step S5 is specifically included:
Rotation angle according to the dummy detector CT system of the calculating relative to true detector CT system, to described
The angle of sequential projection image on dummy detector is adjusted.
The invention has the benefit that in order to realize that the CT under biasing sample stage scan pattern is rebuild, it is virtual by establishing
Practical biasing sample stage CT scan mode is converted to biased detector CT scan, finally utilizes existing Wang- by detector
Method for reconstructing under FDK biased detector scan pattern, obtains the accurate CT image of test sample, and the present invention solves biasing sample
CT Problems of Reconstruction under sample platform scan pattern greatly increases under the premise of not changing standard cone-beam CT scan geometric layout
The visual field of CT system has preferable engineering application value.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is this hair
Bright some embodiments for those of ordinary skill in the art without creative efforts, can be with root
Other attached drawings are obtained according to these attached drawings.
Fig. 1 is the standard cone-beam CT scan schematic diagram of the prior art；
Fig. 2 (a) is standard cone-beam CT scan schematic diagram；
Fig. 2 (b) is biased detector scanning theory figure；
Fig. 2 (c) is biasing sample stage scanning theory figure；
Fig. 3 is that biasing sample stage scans schematic diagram；
Fig. 4 (a) is the schematic diagram being transformed into CT reconstructing parameters in dummy detector CT system；
Fig. 4 (b) is that reconstruction image torsion angle corrects schematic diagram；
Fig. 5 (a) is dummy detector data for projection sequence；
Fig. 5 (b) is angle dummy detector data for projection sequence adjusted.
In attached drawing, element title representated by each label is as follows:
1, x-ray source, 2, cone-beam x-ray, 3, test sample, 4, sample rotates platform, 5, rotation center, 6, true detection
Device, 7, projected image, 8, standard cone-beam CT scan visual field range, 9, dummy detector.
Specific embodiment
With reference to the accompanying drawings and examples, specific embodiments of the present invention will be described in further detail.Implement below
Example is not intended to limit the scope of the invention for illustrating the present invention.
In order to make the object, technical scheme and advantages of the embodiment of the invention clearer, below in conjunction with the embodiment of the present invention
In attached drawing, technical scheme in the embodiment of the invention is clearly and completely described, it is clear that described embodiment is
A part of the embodiment of the present invention, instead of all the embodiments.Based on the embodiments of the present invention, those of ordinary skill in the art
Every other embodiment obtained without creative efforts, shall fall within the protection scope of the present invention.
The present invention will be schemed for the layout of biasing sample stage scan geometry shown in Fig. 2 (c) using the method for data for projection conversion
Biasing sample stage scanning mode shown in 2 (c) is transformed into biased detector scanning mode shown in Fig. 2 (b), and then uses
Wang-FDK algorithm for reconstructing realizes that the accurate CT of test sample 3 is rebuild, final to obtain the complete fault information of test sample 3.
Industrial cone-beam CT reconstruction method under biasing scan pattern provided in an embodiment of the present invention includes: S1, and starting CT is swept
Imaging apparatus obtains tested original series projected image of the sample in the case where biasing sample stage scan pattern by true detector 6；
S2 establishes dummy detector 9 and determines the spatial position of the dummy detector 9；S3 is visited according to true detector 6 with virtual
The space coordinate relationship for surveying device 9, the original series projected image that true detector 6 obtains is transformed on dummy detector 9, shape
At the sequential projection image on the dummy detector 9；S4, according to true detector CT system and dummy detector CT system
Reconstructing parameters in true detector CT system are transformed into dummy detector CT system by space coordinate relationship；S5 is adjusted
The angle of sequential projection image on whole dummy detector 9 is with corrected reconstructed image torsion angle；S6, based on dummy detector 9
CT reconstructing parameters after angle sequential projection image adjusted and conversion, are calculated using Wang-FDK method for reconstructing
The CT image of test sample 3.
The present invention, will be practical by establishing dummy detector 9 in order to realize that the CT under biasing sample stage scan pattern is rebuild
Biasing sample stage CT scan mode is converted to biased detector CT scan, is finally swept using existing Wang-FDK biased detector
Mode reconstruction method is retouched, the accurate CT image of test sample 3 is obtained, the present invention solves the CT under biasing sample stage scan pattern
Problems of Reconstruction substantially increases the visual field of CT system under the premise of not changing standard cone-beam CT scan geometric layout,
With preferable engineering application value.
In one embodiment of the invention, CT scanning device includes x-ray source 1, test sample 3, sample rotates platform 4
With true detector 6, wherein x-ray source 1, test sample 3, sample rotates platform 4 and true detector 6 are placed in X-ray
It shields in lead room.The step S1 is specifically included: it is rotated by sample rotates platform 4 with fixed angle interval stepping, so that
It is detected 360 ° of sample rotates, the projected image of tested sample when true detector 6 acquires each step angle obtains original
Beginning sequential projection image.
In one embodiment of the invention, it establishes dummy detector 9 and determines the spatial position of dummy detector 9
Method are as follows: the rotation center 5 of sample rotates platform 4 is projected as point S in the central plane of cone-beam CT system0, crossing point S0And it hangs down
Directly in straight line FS0, establish dummy detector 9, wherein F is the focus of x-ray source 1；It calculates and determines the dummy detector 9
The space coordinate of four boundary points is with the spatial position of the determination dummy detector 9.
Specifically, cone-beam CT system signal is as shown in figure 3, the focus of x-ray source 1 and true under biasing sample stage scan pattern
Real detector 6 is respectively point F and plane ABCD, and the width and height of true detector 6 are respectively W and H pixel.True detector
Projection of the focus F of 6 center and x-ray source 1 on true 6 place plane ABCD of detector is point O, straight line FO perpendicular to
Plane where true detector 6.In order to realize the CT detection of large scale sample, sample rotates platform 4 is to 3 side of test sample
The mobile needs to meet biasing scan pattern.The rotation center 5 of sample rotates platform 4 is in true 6 place plane of detector
It is projected as O ' O ", the central plane of cone-beam CT system is FEG, and on central plane, rotation center 5 is where true detector 6
Plane is projected as point S0, crossing point S0And perpendicular to straight line FS0, a dummy detector 9 is established, such as the A ' B ' C ' D ' in Fig. 3
It is shown.Due to the focus of x-ray source 1 and the line FS of rotation center 50Perpendicular to plane A ' B ' C ' D ', therefore in virtual detection
In device CT system, the accurate CT that Wang-FDK method for reconstructing can be used under biasing scan pattern is rebuild.
The CT system coordinate system of foundation is as shown in XYZ in Fig. 3, distance of the focus F of x-ray source 1 apart from true detector 6
For FDD.Therefore x-ray source 1 focus space coordinate value be F:(FDD, 0,0), the normal vector of true 6 place plane of detector isTherefore the equation of the plane where true detector 6 are as follows:
FDDx=0 (1)
Crossing point S0And perpendicular to straight line FS0, establish a dummy detector 9, the normal direction of 9 place plane of dummy detector
Amount is defined asRotation center 5 is defined as COR, therefore point S in the projection coordinate of Y-axis0Space coordinate be defined as (0,
COR, 0), andThe equation of 9 place plane of dummy detector are as follows:
FDDx-COR (y-COR)=0 (2)
As shown in figure 3, the boundary point of dummy detector 9 is A ', B ', C ', D ', the space coordinate difference of A ', B ', C ', D '
It is determined by the intersection point of plane A ' B ' C ' D ' and X-ray FA, FB, FC and FD.It is assumed that any one detector on true detector 6
The space coordinate of unit M is pM:(xM,yM,zM), the X-ray across detector cells M is defined as LM, LMEquation can be by
It indicates are as follows:
X-ray LMIt can be represented as with the intersection point of 9 place plane of dummy detector:
A, the coordinate of B, C, D are respectively pA: (0 ,-W/2, H/2), pB: (0, W/2, H/2), pC: (0, W/2 ,-H/2) and
pD: (0 ,-W/2 ,-H/2), by pA、pB、pC、pDIt is updated in formula (4) respectively, obtains the boundary point of dummy detector 9
pA′、pB′、pC′With pD′Space coordinate are as follows:
According to formula (5), the geometry of dummy detector 9 is an isosceles trapezoid, and A ' B '=C ' D ', B ' C ' >
A ' D ',However, in reality detector it is generally rectangular in shape, therefore, be arranged zB′=zA′And
zC′=zD′, the geometry of dummy detector 9 is adjusted to a rectangle, in this way, the boundary point coordinate quilt of dummy detector 9
Adjustment are as follows:
The width of dummy detector 9 can be calculated with height by formula (7):
In formula (7), [] is rounding operation.
In one embodiment of the invention, the step S3 specifically includes: S31 and is taken up an official post according to the dummy detector
The space of horizontal coordinate and vertical coordinate and the dummy detector of the one detector cells P ' on the dummy detector
The space coordinate of the detector cells P ' is calculated in position；S32, calculate on true detector with the dummy detector
On the corresponding detector cells P of detector cells P ' space coordinate, and then determine the detector cells P described true
Horizontal coordinate and vertical coordinate on detector；S33 obtains dummy detector list according to the projection value of true detector cells P
The projection value of first P '；Wherein, test sample wherein a rotation position when, each detector cells on the dummy detector
Projection value form the secondary projected image on the dummy detector.Each width projected image composition under all rotation angles
Sequential projection image on the dummy detector.
Specifically, the coordinate of detector cells can be determined by the space coordinate of dummy detector 9 on dummy detector 9.
As shown in figure 3, the horizontal and vertical coordinate on dummy detector 9 of detector cells P ' is respectively VD on dummy detector 9i
With VDj, the actual spatial coordinates (space coordinate i.e. in CT coordinate system XYZ) of dummy detector unit P ' are defined as pP′:
(xP′,yP′,zP′).It is available according to the spatial position of dummy detector 9 and true detector 6:
The actual spatial coordinates of dummy detector unit P ' can be acquired by above-mentioned formula (8), pass through dummy detector list
The X-ray of first P ' is defined as:
As shown in figure 3, plane and straight line L where true detector 6P′Intersection point be point P, point P is and dummy detector 9
On the corresponding true detector cells of detector cells P '.The x-axis coordinate value of all the points is 0 on plane ABCD, therefore root
According to formula (9), the space coordinate of point P isAnd then detector cells P is really being detected
Level on device 6 is respectively as follows: with vertical coordinateWithFinal virtual spy
The projection value for surveying each detector cells P ' on device 9 is calculated by formula (10).
In formula (10),For test sample 3, level is respectively with vertical coordinate on true detector 6
RDiWith RDjDetector cells P projection value,It is horizontal and vertical on dummy detector 9 for test sample 3
Coordinate is respectively VDiWith VDjDetector cells P ' projection value.Due to RDiWith RDjFor decimal, thusBy
Interpolation obtains, and the projection value of each detector cells is available on such dummy detector 9 accurately calculates.Test sample exists
Wherein when a rotation angle, the projection value of each detector cells forms one on the dummy detector on dummy detector
Width projected image, all each width projected images rotated under angles form the sequential projection image on the dummy detector.
In one embodiment of the invention, the step S4 is specifically included: S41, calculates dummy detector CT system phase
For the rotation angle of true detector CT system；S42, according to the sky of true detector CT system and dummy detector CT system
Between geometrical relationship, calculate dummy detector CT system reconstructing parameters.
Specifically, the reconstructing parameters of dummy detector CT system have distance of the focus of x-ray source 1 to detector
FDD ', x-ray source 1 arrive the projection COR ' of the distance FOD ' and rotation center 5 of rotation center 5 on the detector.Bias sample
Under platform scan pattern, shown in the schematic diagram of central plane such as Fig. 4 (a).On central plane, true detector CT system and virtual
The geometric layout of detector CT system is respectively FEG and FE ' G ', and wherein EG, E ' G ' respectively represent true detector 6 and visit with virtual
Device 9 is surveyed, point O and M ' are respectively the midpoint of EG and E ' G '.In true detector CT system the length of FDD and FOD be respectively FO with
FK, FDD ' and FOD ' is respectively FS in dummy detector CT system0With FR, COR is OS on true detector 60Length, virtually
COR ' is M ' S on detector 90Length, and stipulated that on the left of rotation center 5 deviate when COR be negative value.
It is available according to Fig. 4 (a):
In dummy detector CT system, since COR ' is rotation center subpoint S0The distance between to point M ', three
Angular S0It is available in EE ':
According to above-mentioned formula (11) and formula (12) can by reconstructing parameters FDD, FOD of true detector CT system and
COR is transformed into dummy detector CT system, the reconstructing parameters after converting into FDD ', FOD ' and COR ',
As shown in Fig. 4 (b), true detector CT system geometric layout FEG, the geometry cloth of dummy detector CT system are compared
Office has rotated α angle, i.e. coordinate system X ' S counterclockwise0Y ' has rotated α angle relative to XOY counterclockwise.Sample in reconstruction image at this time
The pose of product has rotated clockwise α angle relative to the pose that test sample 3 is placed on coordinate system XOY.Therefore, in order to more square
Just reconstruction image torsion angle, which needs accurately to be corrected, to be identified to reconstruction image detail.
In one embodiment of the invention, the step S5 is specifically included: according to the dummy detector CT being calculated
The rotation angle of system geometric layout adjusts the angle of the sequential projection image on dummy detector 9, corrected reconstructed image torsion
Angle.
Specifically, sample rotates platform 4 is walked in complete 360 °C of T scanning with fixed angle interval step
Into rotation, and obtain the N width projected image of test sample 3.Therefore the angle of projected image is respectively 0, step ...,
(N-1)·step.As shown in Fig. 5 (a), N width projected image is respectively on dummy detector
It is assumed that α is one of true step angle, then when step angle is α, projection of the test sample 3 on dummy detector 9
Image isOriginal series projected image PS so on dummy detector 9 contains 2 sub- sequential projection images, i.e.,For corrected reconstructed image torsion angle, virtually
Sequential projection image on detector 9 is adjusted to
As shown in Fig. 5 (b).Since width projected image each in PS ' can find corresponding projection in original series projected image PS
Image, therefore every width projected image in PS ' is all accurately, so that angle projected image adjusted not will lead to reconstruction figure
As error.When angle [alpha] is not true step angle a period of time, i.e. angle [alpha] and any one step angle is unequal, then sequence
Each projected image in column projected image PS ' just needs the data for projection interpolation at two adjacent real projection angles to obtain
.In this case, although the projected image in PS ' is all that interpolation obtains, but as long as projection angle interval is sufficiently small, this
The data for projection of a little interpolation will not bring apparent influence to image result is rebuild.
Accurate Calibration is obtained in reconstructing parameters FDD ', FOD ' and COR ' and reconstruction image torsion angle is corrected
Afterwards, the reconstructing parameters after sequential projection image correction-based and conversion, Wang-FDK method for reconstructing may be used for
The Exact Reconstruction of faultage image.
Below with a specific example to the industrial cone-beam CT reconstruction method under biasing scan pattern provided by the invention
It is described.
It is as follows to test the scanning means parameter used:
(1) x-ray source: tube voltage 150kV, tube current 0.145mA；
(2) true detector: true detector pixel number is 900 (width) × 766 (height), and pixel dimension 0.2mm has
Imitate 200 × 153.2mm of imaging area2。
(3) x-ray source focus is to the distance FDD=852mm of true detector, and x-ray source focus is into sample stage rotation
The distance FOD=291.8mm of the heart, rotation center project COR=-391.0 pixel.
Experimental procedure:
(1) a detected cylindric sample of organic glass is placed on sample rotates platform, opens x-ray source and true
Detector, starting sample rotates platform drive tested sample stepping to be rotated by 360 °, and stepping angle is 0.5 °, and true detector is adopted altogether
Collect 720 width projected images under different step angles, formation sequence projected image.
(2) it according to formula (1)~(6), establishes dummy detector and positions the spatial position of dummy detector, and according to public affairs
Formula (7) calculates the width and height of dummy detector, and the wide height for obtaining dummy detector is respectively the pixel of W '=912, the picture of H '=765
Element.
(3) spatial relation based on dummy detector Yu true detector determines virtual visit by formula (8)~(10)
Survey the projection value of each detector cells on device.
(4) according to the space coordinate relationship of true detector CT system and dummy detector CT system, pass through formula (11)
True detector CT system reconstructing geometric parameter FDD, FOD and COR are transformed into dummy detector CT system by~(12)；Most
The reconstructing parameters of whole dummy detector CT system are as shown in table 1.
(5) angle of dummy detector CT system sequential projection image is adjusted with corrected reconstructed image torsion angle, is obtained
Angle sequential projection image adjusted.
1 dummy detector CT system geometric parameter of table
(6) it based on dummy detector upper angle sequential projection image adjusted and CT reconstructing parameters (table 1), uses
The accurate CT image of test sample is calculated in Wang-FDK method for reconstructing.
Industrial cone-beam CT reconstruction method under a kind of biasing scan pattern provided by the invention, in order to realize biasing sample stage
CT under scan pattern is rebuild, and by establishing dummy detector, practical biasing sample stage CT scan mode is converted to biasing and is visited
Device CT scan is surveyed, existing Wang-FDK biased detector scan pattern method for reconstructing is finally utilized, it is accurate to obtain test sample
CT image.The present invention solves the CT Problems of Reconstruction under biasing sample stage scan pattern, is not changing standard cone-beam CT scan
Under the premise of geometric layout, the visual field of CT system is substantially increased, there is preferable engineering application value.
Finally, it should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention, rather than its limitations；Although
Present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that: it still may be used
To modify the technical solutions described in the foregoing embodiments or equivalent replacement of some of the technical features；
And these are modified or replaceed, technical solution of various embodiments of the present invention that it does not separate the essence of the corresponding technical solution spirit and
Range.
Claims (7)
1. a kind of industrial cone-beam CT reconstruction method under biasing scan pattern characterized by comprising
S1 starts CT scanning device, acquires tested original of the sample in the case where biasing sample stage scan pattern by true detector
Beginning sequential projection image；
S2 establishes dummy detector and determines the spatial position of the dummy detector；
S3, according to the space coordinate relationship of true detector and dummy detector, the original series that true detector is obtained are thrown
Shadow image is transformed on dummy detector, forms the sequential projection image on the dummy detector；
S4, according to the space coordinate relationship of true detector CT system and dummy detector CT system, by true detector CT system
Reconstructing parameters in system are transformed into dummy detector CT system；
S5 adjusts the angle of the sequential projection image on dummy detector with corrected reconstructed image torsion angle；
S6 is used based on the reconstructing parameters after dummy detector upper angle sequential projection image adjusted and conversion
The CT image of test sample is calculated in Wang-FDK method for reconstructing.
2. the industrial cone-beam CT reconstruction method under biasing scan pattern according to claim 1, which is characterized in that the CT
Scanning means includes x-ray source, test sample, sample rotates platform and true detector, the x-ray source, test sample, sample
Product turntable and true detector are placed in X-ray shield lead room, and it is flat that the test sample is placed in the sample rotates
On platform, the x-ray source emits X-ray to test sample, and the X-ray signal after the true detector receiving attenuation, which is formed, to be thrown
Shadow image；
The step S1 is specifically included:
It is rotated by the sample rotates platform with fixed angle interval stepping, so that being detected 360 ° of sample rotates, is passed through
The projected image of tested sample when true detector acquires each step angle, obtains original series projected image.
3. the industrial cone-beam CT reconstruction method under biasing scan pattern according to claim 2, which is characterized in that the step
Rapid S2 is specifically included:
The central plane of cone-beam CT system is FEG, and on central plane, the rotation center of the sample rotates platform is really being visited
It surveys on device and is projected as point S0, crossing point S0And perpendicular to straight line FS0, establish dummy detector, wherein F is the x-ray source
Focus, the central plane of the cone-beam CT system are the horizontal plane across x-ray source focus；
The space coordinate of 4 boundary points of the dummy detector is calculated with the spatial position of the determination dummy detector.
4. the industrial cone-beam CT reconstruction method under biasing scan pattern according to claim 1, which is characterized in that the step
Rapid S3 is specifically included:
S31 according to horizontal coordinate of the detector cells P ' any on the dummy detector on the dummy detector and is erected
The spatial position of straight coordinate and the dummy detector, is calculated the space coordinate of the detector cells P '；
S32 calculates the sky of detector cells P corresponding with the detector cells P ' on the dummy detector on true detector
Between coordinate, and then determine the horizontal coordinate and vertical coordinate of the detector cells P on the true detector；
S33 obtains the projection value of dummy detector unit P ' according to the projection value of true detector cells P；
Test sample wherein a rotation angle when, the projection value of each detector cells forms institute on the dummy detector
The width projected image on dummy detector is stated, each width projected image under all rotation angles forms the dummy detector
On sequential projection image.
5. the industrial cone-beam CT reconstruction method under biasing scan pattern according to claim 2, which is characterized in that the step
Rapid S4 is specifically included:
S41 calculates rotation angle of the dummy detector CT system relative to true detector CT system；
S42 calculates dummy detector CT according to the space geometry relationship of true detector CT system and dummy detector CT system
The reconstructing parameters of system.
6. biasing the industrial cone-beam CT reconstruction method under scan pattern according to claim 1 or 5, which is characterized in that institute
Stating reconstructing parameters includes x-ray source focus to the distance of detector, the rotation center of x-ray source focus to rotating platform
The projection coordinate of distance and the rotation center on the detector.
7. the industrial cone-beam CT reconstruction method under biasing scan pattern according to claim 5, which is characterized in that the step
Rapid S5 is specifically included:
Rotation angle according to the dummy detector CT system of the calculating relative to true detector CT system, to described virtual
The angle of sequential projection image on detector is adjusted.
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