CN101634638B - Three-dimensional digital imaging method of large view field cone-beam X-ray tilting scanning of biased detector - Google Patents

Abstract

The invention relates to a three-dimensional digital imaging method of the large view field cone-beam X-ray tilting scanning of a biased detector, belonging to the technical field of X-ray computerized tomography (CT). In the three-dimensional digital imaging method, the area array detector is placed to be biased, and an X-ray source is used for generating cone-beam X-rays which irradiate a member imaging area with a certain angle in a penetrating and tilting way relative to the length and width surface of a member; in the scanning process, the X-ray source and the area array detector are static, the member rotates in an angle of 360 degrees in an equal angle and step length way surrounding a rotating shaft, and the area array detector acquires an X-ray signal modulated by the member under each rotation angle. A three-dimensional computerized tomography image of a scanning area can be reestablished and obtained by a data truncation smoothing preprocessing method and a filtering back projection reestablishing arithmetic according to data obtained by the area array detector under the scanning angle of 360 degrees. Compared with the traditional tilting scanning method, the three-dimensional digital imaging method can double the tilting scanning imaging view field without changing the system hardware and the scanning speed and has high reestablishment quality, simple process and high efficiency.

Description

A kind of large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing

Technical field

The present invention relates to a kind of large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing, belong to X ray computer tomography (CT) technical field.

Background technology

In the X ray CT system; X-ray source sends X ray; Pass a certain zone of object to be detected from different perspectives, the detector that is positioned over the radiographic source opposite is accepted in respective angles, then according to each angle ray decay in various degree; Utilize certain reconstruction algorithm and computing machine to carry out computing; Reconstruct object by the ray line attenuation coefficient distribution map image of scanning area, thereby realize nondestructively reproducing the characteristics such as Media density, composition and structural form of object in this zone by reconstruction from projections imaging.

No matter existing CT technology is 2D-CT, or 3D-CT, all needs the whole cross section at the seized structure tomography of ray scanning place.So and plate that thickness little big for the length and width size, the chromatography of shell structure detect, ray unavoidably will contrast the much bigger cross section, length and width size place of gauge and do perspective scanning.Obvious this scanning perspective projection data sensitivity and spatial resolution and are compared from thickness direction scanning, and be much lower, so the faultage image that reconstructs is inevitable very low to CONSTRUCTED SPECIFICATION resolution; Moreover, when the length and width size reaches several meter level, also can't implement this computed tomography scanning.Therefore, the little structure of thickness can't provide effective chromatography detection technique to existing conventional CT technology to the length and width size is big.For this reason, thin plate tomography (CL) technology is suggested.It adopts circle, straight line or spiral scan trajectory, and plate and shell structure is implemented dip sweeping, utilizes certain reconstruction algorithm to carry out tomography.Wang Hongjun etc., the application of algebraic reconstruction technique in the plate and shell structure cross sectional reconstruction, optical technology, 2006,32 (2): among the 168-170, study a kind of CL method, adopted circular scan track and algebraic reconstruction technique that plate and shell structure is carried out tomography, as shown in Figure 1.When in this method scintigram 1 during member, demand side array detector size is more than or equal to the size of ABCD.

The subject matter that CL faces in practical application is, receives the influence of scanning theory and detector area, and the imaging visual field is little, and detection efficiency is low.At present, do not find to have the method that improves the CL imaging visual field as yet.

Summary of the invention

Technology of the present invention is dealt with problems and is: the problem that the imaging visual field is little, detection efficiency is low that imaging faces to traditional C L; A kind of large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing is provided; Under system hardware and sweep velocity permanence condition; Can the dip sweeping visual field of forming images be improved 1 times, reconstruction quality is high, and process is simple, efficient.

Technical solution of the present invention: the large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing is characterized in that comprising the steps:

(1) the large view field cone-beam X-ray dip sweeping geometry that planar array detector is setovered is set, forms the digital radial projected image and obtain system;

(2) carry out the large view field cone-beam X-ray dip sweeping that planar array detector is setovered, obtain one group of two-dimensional digital ray projection image sequence;

(3) the recording ray source is to the planar array detector distance z _c, radiographic source is to rotation center z ' _c, the ray angle of inclination

Planar array detector horizontal direction detection channels number m and vertical direction detection channels number n, the digital radial projecting image data blocks length δ;

(4) according to above-mentioned parameter z _c, z ' _c,

M, n and δ; Utilize the large view field cone-beam X-ray dip sweeping 3 D digital imaging data truncation pre-service smoothing method of planar array detector biasing; Two-dimensional digital ray projection image sequence data cutoff edge to step (2) obtains is carried out smoothly, obtains the digital radial projection image sequence after level and smooth;

(5) the digital radial projection image sequence that obtains according to step (4), the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm that utilizes planar array detector to setover is rebuild the three-dimensional tomographic map of scanning area.

Scanning theory of the present invention such as Fig. 1: object rotation under turntable drives; Under each anglec of rotation, the ray that the planar array detector ABGH of biasing will pass object converts electric signal to and delivers to computing machine, forms data for projection; When revolving three-sixth turn, turntable promptly accomplishes scanning; Data for projection according to scanning formation; Utilize large view field cone-beam X-ray dip sweeping 3 D digital imaging data truncation pre-service smoothing method and filtered back projection's reconstruction algorithm of planar array detector biasing of the present invention to carry out pre-service and reconstruction, can obtain the object dimensional tomographic map.

Large view field cone-beam X-ray dip sweeping 3 D digital imaging data truncation pre-service smoothing method of the present invention is following:

P′(X，Y，β)＝P(X，Y，β)·ω(X，Y，β)(1)

Wherein, and P (X, Y, the two-dimensional digital ray projection image sequence of β) obtaining for virtual planar array detector ABCD, zero padding produces on the data basis that actual planar array detector ABGH obtains; (X, Y β) are two-dimensional digital ray projection image sequence after level and smooth to P ', and (X, Y β) are smooth function to ω, and X and Y are virtual planar array detector ABCD detection channels position, and β is the anglec of rotation.

Four large view field cone-beam X-ray dip sweeping 3 D digital imaging data truncation pre-service smooth functions of the present invention are following:

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<0\\ 0.5& Y=0\\ 1& 0<Y<N/2\end{array}\right.$ ①

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<-\mathrm{\&delta;}\\ 0.5+\frac{Y}{2\mathrm{\&delta;}}& -\mathrm{\&delta;}\&le;Y<\mathrm{\&delta;}\\ 1& -\mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ②

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<-\mathrm{\&delta;}\\ {\sin }^2(\frac{\mathrm{\&pi;}}{4}\&CenterDot;\frac{Y+\mathrm{\&delta;}}{\mathrm{\&delta;}})& -\mathrm{\&delta;}\&le;Y<0\\ {\cos }^2(\frac{\mathrm{\&pi;}}{4}\&CenterDot;\frac{Y-\mathrm{\&delta;}}{\mathrm{\&delta;}})& 0\&le;Y<\mathrm{\&delta;}\\ 1& \mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ③

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<-\mathrm{\&delta;}\\ 0.5+\frac{2}{\mathrm{\&pi;}}\arctan \frac{Y}{\mathrm{\&delta;}}& -\mathrm{\&delta;}\&le;Y<\mathrm{\&delta;}\\ 1& \mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ④

Wherein, N is the width of virtual planar array detector ABCD imaging region, and δ is a data truncation length.

Large view field cone-beam X-ray dip sweeping 3 D digital imaging of the present invention filtered back projection reconstruction algorithm is following:

$f(x^{\&prime;\&prime;},y^{\&prime;\&prime;},z^{\&prime;\&prime;})=\underset{0}{\overset{2\mathrm{\&pi;}}{\&Integral;}}\underset{-\&infin;}{\overset{\&infin;}{\&Integral;}}{P}^{\&prime;}(X,Y,\mathrm{\&beta;})h(Y-Y^{\&prime;})\mathrm{dYd\&beta;}---\left(2\right)$

$h\left(Y\right)=\underset{-\&infin;}{\overset{\&infin;}{\&Integral;}}\left|\mathrm{\&rho;}\right|e^{i2\mathrm{\&pi;\&rho;Y}}\mathrm{d\&rho;}---\left(5\right)$

Wherein, f (x ", y ", the three-dimensional function of z ") for rebuilding; (and x ", y ", z ") be coordinate system X " coordinate among the Y " Z ", P ' (X; Y β) be two-dimensional digital ray projection image sequence after smoothly, h (Y) be desirable filter function h (ρ)=| ρ | the Fourier variation; X and Y are virtual planar array detector ABCD detection channels position, and β is the anglec of rotation, z _cFor radiographic source arrives planar array detector distance, z ' _cFor rotation center arrives the planar array detector distance,

Be the ray angle of inclination.

Below further computing formula (3) and (4) of derivation X and Y.

According to Fig. 1 geometry, equality (6) has provided XYZ and X " Y " Z " between coordinate transform relation.For given reconstruction coordinate system X " Y " Z " in arbitrarily reconstruction point (x ", y ", z "), can pass through equality (7) in coordinate system XYZ with (x ^*, y ^*, z ^*) expression.Equality (8) has represented that is passed a reconstruction point (x ^*, y ^*, z ^*) the space equation of ray.Equality (9) has been represented detector plane.Simultaneous equality (7), (8) and (9), we can obtain computing formula (10) and (11) of X and Y.According to Fig. 1 Scan Architecture, we can also obtain equality (12).Utilize equality (12), can formula (10) and (11) simplification be obtained formula (3) and (4).

[x，y，z，1]＝[x″，y″，z″，1]·R ₃·R ₂·R ₁(6)

$R_3=\left[\begin{array}{cccc}\cos \mathrm{\&beta;}& -\sin \mathrm{\&beta;}& 0& 0\\ \sin \mathrm{\&beta;}& \cos \mathrm{\&beta;}& 0& 0\\ 0& 0& 1& 0\\ 0& 0& 0& 1\end{array}\right]$

$R_1=\left[\begin{array}{cccc}1& 0& 0& 0\\ 0& 1& 0& 0\\ 0& 0& 1& 0\\ {x_c}^{\&prime;}& {y_c}^{\&prime;}& {z_c}^{\&prime;}& 1\end{array}\right]$

x ^*＝x″cosβ+y″sinβ+x _c′

$\frac{x-x_c}{x^{*}-x_c}=\frac{y-y_c}{y^{*}-y_c}=\frac{z-z_c}{z^{*}-z_c}=t---\left(8\right)$

z＝0(9)

$X=x=\frac{x_c\&CenterDot;z^{*}-z_c\&CenterDot;x^{*}}{z^{*}-z_c}---\left(10\right)$

$Y=y=\frac{y_c\&CenterDot;z^{*}-z_c\&CenterDot;y^{*}}{z^{*}-z_c}---\left(11\right)$

x _c＝0，y _c＝0，x _c′＝0，y _c′＝0(12)

Like Fig. 1, in order to obtain the scanning imagery visual field of ABCD, traditional C L need adopt the detector of size greater than ABCD.But,, adopt size can obtain the scanning imagery visual field of ABCD greater than the detector of ABEF for the inventive method.Therefore, using under the identical big or small detector situation, the inventive method can be expanded into 1 times in the picture visual field.

The present invention's advantage compared with prior art is following:

(1) the present invention uses onesize detector, can be expanded into 1 times in the picture visual field;

(2) the present invention only need carry out one time 360 degree scanning, and detection efficiency is high;

(3) Scan Architecture of the present invention is simple, is easy to Project Realization.

Description of drawings

Fig. 1 is the corresponding scan-geometries figure of large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of a kind of detector biasing of the present invention;

Fig. 2 is classical human chest realistic model;

Fig. 3 is that the angle of inclination is 45 when spending, the two-dimensional projection image of the human chest realistic model that detector ABGH obtains under a plurality of scanning angles;

Fig. 4 is that the angle of inclination is 45 when spending, the two-dimensional projection image of the human chest realistic model that detector ABCD obtains under a plurality of scanning angles;

Fig. 5 a is that the angle of inclination is 45 when spending; Adopt the two-dimensional projection image of the human chest realistic model that 1. smoothing formula obtain under a plurality of scanning angles detector ABCD to handle the image of acquisition, Fig. 5 b adopts the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing of the present invention to rebuild the three-dimensional chromatography sectioning image of acquisition;

Fig. 6 a is that the angle of inclination is 45 when spending; Adopt the two-dimensional projection image of the human chest realistic model that 2. smoothing formula obtain under a plurality of scanning angles detector ABCD to handle the image of acquisition, Fig. 6 b adopts the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing of the present invention to rebuild the three-dimensional chromatography sectioning image of acquisition;

Fig. 7 a is that the angle of inclination is 45 when spending; Adopt the two-dimensional projection image of the human chest realistic model that 3. smoothing formula obtain under a plurality of scanning angles detector ABCD to handle the image of acquisition, Fig. 7 b adopts the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing of the present invention to rebuild the three-dimensional chromatography sectioning image of acquisition;

Fig. 8 a is that the angle of inclination is 45 when spending; Adopt the two-dimensional projection image of the human chest realistic model that 4. smoothing formula obtain under a plurality of scanning angles detector ABCD to handle the image of acquisition, Fig. 8 b adopts the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing of the present invention to rebuild the three-dimensional chromatography sectioning image of acquisition.

Fig. 9 is the curve comparison diagram of four smooth functions.

Embodiment

The problem that the imaging visual field is little, detection efficiency is low that imaging faces to traditional C L; The present invention proposes a kind of large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing; According to its geometry characteristics; Derive its filtered back projection's reconstruction algorithm and the level and smooth preprocess method of data truncation utilize the data that planar array detector obtains under the 360 degree scanning angles, can rebuild the three-dimensional computer faultage image that obtains scanning area.

As shown in Figure 1, the concrete realization as follows:

1, the large view field cone-beam X-ray dip sweeping geometry of planar array detector biasing is set, forms the digital radial projected image and obtain system, concrete performing step is:

(1) be the position of δ detection channels at the virtual planar array detector ABGH imaging region edge GH of distance, selected two-dimensional digital ray projection image sequence data cutoff boundary EOF, δ is that two-dimensional digital ray projection image sequence data blocks length; δ gets positive integer, and minimum value is 1; For obtaining the maximum imaging visual field, guarantee enough regularization smooth effects simultaneously, the δ value is generally greater than 5;

(2) make data truncation border EOF vertical with principal ray SO, OI is vertical with detector row;

(3) make turning axle z " in principal ray planar S OI, intersect with principal ray SO; form ray angle of inclination

for guaranteeing ray penetration capacity preferably,

generally gets 45 degree.

2, carry out the large view field cone-beam X-ray dip sweeping of planar array detector biasing, obtain one group of two-dimensional digital ray projection image sequence, concrete performing step is:

(1) will be positioned over the digital radial projected image that step 1 forms by the scanning member obtains on the turntable of system;

(2) implemented transillumination with the cone-beam x-ray that forms through collimation to scanning member; Simultaneously; Turntable rotates at the uniform velocity continuously, is crossed by the ray projection of scanning member with the transmission of fixed sample speed continuous acquisition by planar array detector ABGH, obtains one group of two-dimensional digital ray projection image sequence;

(3) when turntable revolves three-sixth turn, planar array detector ABGH stops sampling, and turntable and radiographic source stop simultaneously, promptly accomplish a large view field cone-beam X-ray dip sweeping.

3, the recording ray source is to the planar array detector distance z _c, rotation center is to detector distance z ' _c, the ray angle of inclination

Planar array detector horizontal direction detection channels number m and vertical direction detection channels number n, the digital radial projecting image data blocks length δ, and concrete performing step is:

(1) adopt tape measure radiographic source target spot to the detector surface distance, this is z _c

(2) adopt tape measure radiographic source target spot to the rotation center distance, this is z ' _c

(3) adopt tape measure line radiographic source target spot and detector surface center; Utilize set square to measure the angle of this line and turning axle again, this is

(4) m and n are directly provided by the planar array detector instructions;

(5) δ is set by manual work.

4, utilize the large view field cone-beam X-ray dip sweeping 3 D digital imaging data truncation pre-service smoothing method of planar array detector biasing, two-dimensional digital ray projection image sequence data cutoff edge is carried out smoothly, concrete performing step is:

(1) from following four functions, choose one as two-dimensional digital ray projection image sequence data smooth function:

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<0\\ 0.5& Y=0\\ 1& 0<Y<N/2\end{array}\right.$ ①

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<-\mathrm{\&delta;}\\ 0.5+\frac{Y}{2\mathrm{\&delta;}}& -\mathrm{\&delta;}\&le;Y<\mathrm{\&delta;}\\ 1& -\mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ②

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<-\mathrm{\&delta;}\\ {\sin }^2(\frac{\mathrm{\&pi;}}{4}\&CenterDot;\frac{Y+\mathrm{\&delta;}}{\mathrm{\&delta;}})& -\mathrm{\&delta;}\&le;Y<0\\ {\cos }^2(\frac{\mathrm{\&pi;}}{4}\&CenterDot;\frac{Y-\mathrm{\&delta;}}{\mathrm{\&delta;}})& 0\&le;Y<\mathrm{\&delta;}\\ 1& \mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ③

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<-\mathrm{\&delta;}\\ 0.5+\frac{2}{\mathrm{\&pi;}}\arctan \frac{Y}{\mathrm{\&delta;}}& -\mathrm{\&delta;}\&le;Y<\mathrm{\&delta;}\\ 1& \mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ④

Wherein, X and Y are virtual planar array detector ABCD detection channels position, and β is the anglec of rotation, and N is the width of the last imaging region of dummy detector ABCD, and δ is that two-dimensional digital ray projection image sequence data blocks length.

Fig. 9 has provided the curve of above-mentioned four smooth functions.Can know that by Fig. 9 these four smooth functions have different smoothness propertieses and characteristic retentivity.The flatness of function refers to, and function is removed the ability of data noise and gibbs artifact; The characteristic retentivity of function refers to, the ability of function retention data useful feature.They have reflected the function removal data noise ability of keeping characteristics simultaneously together.Can confirm the flatness and the characteristic retentivity of function according near the rate of curve data truncation point.Rate of curve is big more, then flatness more a little less than, the characteristic retentivity is good more.Can qualitatively obtain as drawing a conclusion according to Fig. 9: in four smooth functions, smooth function 1. flatness a little less than, the characteristic retentivity is best; 3. a little less than the flatness time, the characteristic retentivity is better for smooth function; Smooth function 4. flatness is stronger, the characteristic retentivity a little less than; Smooth function 2. flatness is best, the characteristic retentivity a little less than.Therefore, should choose smooth function according to the data characteristics that blocks district EFGH.If it is many to block district's data characteristics, then should choose smooth function 1., 3.; If it is few to block district's data characteristics, then should choose smooth function 2., 4..How block district's data characteristics is judged according to reconstructed image by manual work with few judgement.

(2) carry out the smooth operation of two-dimensional digital ray projection image sequence data according to following formula:

P′(X，Y，β)＝P(X，Y，β)·ω(X，Y，β)(1)

Wherein, and P (X, Y, the two-dimensional digital ray projection image sequence of β) obtaining for virtual planar array detector ABCD, zero padding produces on the data basis that actual planar array detector ABGH obtains, and (X, Y β) be two-dimensional digital ray projection image sequence after smoothly to P '.

5, the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of planar array detector biasing is:

$f(x^{\&prime;\&prime;},y^{\&prime;\&prime;},z^{\&prime;\&prime;})=\underset{0}{\overset{2\mathrm{\&pi;}}{\&Integral;}}\underset{-\&infin;}{\overset{\&infin;}{\&Integral;}}{P}^{\&prime;}(X,Y,\mathrm{\&beta;})h(Y-Y^{\&prime;})\mathrm{dYd\&beta;}---\left(2\right)$

$h\left(Y\right)=\underset{-\&infin;}{\overset{\&infin;}{\&Integral;}}\left|\mathrm{\&rho;}\right|e^{i2\mathrm{\&pi;\&rho;Y}}\mathrm{d\&rho;}---\left(5\right)$

Wherein, f (x ", y ", the three-dimensional function of z ") for rebuilding; (and x ", y ", z ") be coordinate system X " coordinate among the Y " Z ", P ' (X; Y β) be two-dimensional digital ray projection image sequence after smoothly, h (Y) be desirable filter function h (ρ)=| ρ | the Fourier variation; X and Y are virtual planar array detector ABCD detection channels position, and β is the anglec of rotation, z _cFor radiographic source arrives planar array detector distance, z ' _cFor rotation center arrives the planar array detector distance,

Be the ray angle of inclination.

For checking the present invention, carried out emulation experiment on computers.The concrete steps of emulation experiment are following:

(1) sets up 3-D view model to be rebuild.Fig. 2 (a) has shown the classical human chest emulation three-dimensional model that emulation experiment of the present invention adopts, and Fig. 2 (b) has shown this realistic model typical case faultage image.This realistic model is made up of 25 cylindroids of differing heights, different radii, and the height of cylindroid 1,2,3 is 20, and other cylindroid height are 10.

(2) the emulation experiment parameter is provided with.z _c=2000, z ' _c=200, the ray angle of inclination

It is that increment is got 360 projection angles that β spends with 1 in 360 degree scopes, and detector horizontal direction passage number is 133, and detector vertical direction passage number is 256, and data truncation length is 5, and the reconstructed image size is 256x256.For showing that conveniently reconstructed image is reduced.

(3) according to the perspective geometry relation, generate data for projection.

(4) the large view field cone-beam X-ray dip sweeping 3 D digital imaging data truncation pre-service smoothing method of detector biasing according to the present invention carries out smoothly two-dimensional digital ray projection image sequence data cutoff edge.

(5) the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing according to the present invention is rebuild the 3-dimensional digital tomographic map of scanning area, obtains tomographic map.

Fig. 3 is that the angle of inclination is 45 when spending, the two-dimensional projection image of the human chest realistic model that detector ABGH obtains under a plurality of scanning angles; Fig. 4 is that the angle of inclination is 45 when spending, the two-dimensional projection image of the human chest realistic model that detector ABCD obtains under a plurality of scanning angles; Fig. 5 (a) is that the angle of inclination is 45 when spending; Adopt the two-dimensional projection image of the human chest realistic model that 1. smoothing formula obtain under a plurality of scanning angles detector ABCD to handle the image of acquisition, Fig. 5 (b) adopts the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing of the present invention to rebuild the three-dimensional chromatography sectioning image of acquisition; Fig. 6 (a) is that the angle of inclination is 45 when spending; Adopt the two-dimensional projection image of the human chest realistic model that 2. smoothing formula obtain under a plurality of scanning angles detector ABCD to handle the image of acquisition, Fig. 6 (b) adopts the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing of the present invention to rebuild the three-dimensional chromatography sectioning image of acquisition; Fig. 7 (a) is that the angle of inclination is 45 when spending; Adopt the two-dimensional projection image of the human chest realistic model that 3. smoothing formula obtain under a plurality of scanning angles detector ABCD to handle the image of acquisition, Fig. 7 (b) adopts the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing of the present invention to rebuild the three-dimensional chromatography sectioning image of acquisition; Fig. 8 (a) is that the angle of inclination is 45 when spending; Adopt the two-dimensional projection image of the human chest realistic model that 4. smoothing formula obtain under a plurality of scanning angles detector ABCD to handle the image of acquisition, Fig. 8 (b) adopts the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of detector biasing of the present invention to rebuild the three-dimensional chromatography sectioning image of acquisition.

Can know that by Fig. 2 and Fig. 5,6,7,8 the inventive method can realize correct tomographic reconstruction.The inventive method sweep velocity is fast, and process of reconstruction is simple, efficient, under the constant situation of detector size, can improve 1 times of imaging visual field.

The content of not doing in the instructions of the present invention to describe in detail belongs to this area professional and technical personnel's known prior art.

The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; Can also make some improvement and retouching, these improvement and retouching also should be regarded as protection scope of the present invention.

Claims (5)

1. the large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of a detector biasing is characterized in that comprising the steps:

(1) the large view field cone-beam X-ray dip sweeping geometry that planar array detector is setovered is set, forms the digital radial projected image and obtain system;

(2) carry out the large view field cone-beam X-ray dip sweeping that planar array detector is setovered, obtain one group of two-dimensional digital ray projection image sequence;

(3) the recording ray source is to the planar array detector distance z _c, rotation center is to detector distance z ' _c, the ray angle of inclination

Planar array detector horizontal direction detection channels number m and vertical direction detection channels number n, the digital radial projecting image data blocks length δ;

(4) according to above-mentioned parameter z _c, z ' c,

M, n and δ; Utilize the large view field cone-beam X-ray dip sweeping 3 D digital imaging data truncation pre-service smoothing method of planar array detector biasing; Two-dimensional digital ray projection image sequence data cutoff edge to step (2) obtains is carried out smoothly, obtains the digital radial projection image sequence after level and smooth;

(5) the digital radial projection image sequence that obtains according to step (4), the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm that utilizes planar array detector to setover is rebuild the three-dimensional tomographic map of scanning area.

2. the large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing according to claim 1; It is characterized in that: the large view field cone-beam X-ray dip sweeping geometry of planar array detector biasing is set in the said step (1), and the step that formation digital radial projected image obtains system is:

A. be the position of δ detection channels apart from planar array detector ABGH imaging region edge GH, selected two-dimensional digital ray projection image sequence data cutoff boundary EOF, δ is that two-dimensional digital ray projection image sequence data blocks length; δ gets positive integer, and minimum value is 1;

B. make data truncation border EOF vertical with principal ray SO, OI is vertical with detector row;

C. make turning axle z " in principal ray planar S OI, intersect with principal ray SO, form ray angle of inclination

3. the large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing according to claim 1; It is characterized in that: carry out the large view field cone-beam X-ray dip sweeping of planar array detector biasing in the said step (2), the step that obtains one group of two-dimensional digital ray projection image sequence is:

A. will be positioned over the digital radial projected image that claim 1 step (1) forms by the scanning member obtains on the turntable of system;

B. implemented transillumination with the cone-beam x-ray that forms through collimation to scanning member; Simultaneously; Turntable rotates at the uniform velocity continuously, is crossed by the ray projection of scanning member with the transmission of fixed sample speed continuous acquisition by planar array detector ABGH, obtains one group of two-dimensional digital ray projection image sequence;

C. when turntable revolved three-sixth turn, planar array detector ABGH stopped sampling, and turntable and radiographic source stop simultaneously, promptly accomplish a large view field cone-beam X-ray dip sweeping.

4. the large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing according to claim 1; It is characterized in that: utilize the large view field cone-beam X-ray dip sweeping 3 D digital imaging data truncation pre-service smoothing method of planar array detector biasing in the said step (4), two-dimensional digital ray projection image sequence data cutoff edge is carried out level and smooth step be:

A. from following four functions, choose one as two-dimensional digital ray projection image sequence data smooth function:

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<0\\ 0.5& Y=0\\ 1& 0<Y<N/2\end{array}\right.$ ①

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y-\mathrm{\&delta;}\\ 0.5+\frac{Y}{2\mathrm{\&delta;}}& -\mathrm{\&delta;}\&le;Y<\mathrm{\&delta;}\\ 1& -\mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ②

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<-\mathrm{\&delta;}\\ {\sin }^2(\frac{\mathrm{\&pi;}}{4}\&CenterDot;\frac{Y+\mathrm{\&delta;}}{\mathrm{\&delta;}})& -\mathrm{\&delta;}\&le;Y<0\\ {\cos }^2(\frac{\mathrm{\&pi;}}{4}\&CenterDot;\frac{Y-\mathrm{\&delta;}}{\mathrm{\&delta;}})& 0\&le;Y<\mathrm{\&delta;}\\ 1& \mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ③

$\mathrm{\&omega;}(X,Y,\mathrm{\&beta;})=\left\{\begin{array}{cc}0& -N/2\&le;Y<-\mathrm{\&delta;}\\ 0.5+\frac{2}{\mathrm{\&pi;}}\arctan \frac{Y}{\mathrm{\&delta;}}& -\mathrm{\&delta;}\&le;Y<\mathrm{\&delta;}\\ 1& \mathrm{\&delta;}\&le;Y<N/2\end{array}\right.$ ④

Wherein, X and Y are virtual planar array detector ABCD detection channels position, and β is the anglec of rotation, and N is the width of the last imaging region of dummy detector ABCD, and δ is that two-dimensional digital ray projection image sequence data blocks length;

B. carry out the smooth operation of two-dimensional digital ray projection image sequence data according to following formula:

P′(X，Y，β)＝P(X，Y，β)·ω(X，Y，β) (1)

Wherein, and P (X, Y, the two-dimensional digital ray projection image sequence of β) obtaining for virtual planar array detector ABCD, zero padding produces on the data basis that actual planar array detector ABGH obtains, and (X, Y β) be two-dimensional digital ray projection image sequence after smoothly to P '.

5. the large view field cone-beam X-ray dip sweeping three-dimension digital imaging method of detector biasing according to claim 1 is characterized in that: the large view field cone-beam X-ray dip sweeping 3 D digital imaging filtered back projection reconstruction algorithm of the planar array detector biasing in the said step (5) is:

$f(x^{\&prime;\&prime;},y^{\&prime;\&prime;},z^{\&prime;\&prime;})=\underset{0}{\overset{2\mathrm{\&pi;}}{\&Integral;}}\underset{-\&infin;}{\overset{\&infin;}{\&Integral;}}{P}^{\&prime;}(X,Y,\mathrm{\&beta;})h(Y-Y^{\&prime;})\mathrm{dYd\&beta;}---\left(2\right)$

$h\left(Y\right)=\underset{-\&infin;}{\overset{\&infin;}{\&Integral;}}{\left|\mathrm{\&rho;}\right|e}^{i2\mathrm{\&pi;\&rho;Y}}\mathrm{d\&rho;}---\left(5\right)$

Wherein, f (x ", y ", the three-dimensional function of z ") for rebuilding; (and x ", y ", z ") be coordinate system X " coordinate among the Y " Z ", P ' (X; Y β) be two-dimensional digital ray projection image sequence after smoothly, h (Y) be desirable filter function h (ρ)=| ρ | the Fourier variation; X and Y are virtual planar array detector ABCD detection channels position, and β is the anglec of rotation, z _cFor radiographic source arrives planar array detector distance, z ' _cFor rotation center arrives the planar array detector distance, Be the ray angle of inclination.

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