CN110428370A - A kind of method that utilization is eccentrically rotated raising pencil-beam SPECT imaging resolution - Google Patents
A kind of method that utilization is eccentrically rotated raising pencil-beam SPECT imaging resolution Download PDFInfo
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Abstract
The present invention relates to a kind of utilizations to be eccentrically rotated the method for improving pencil-beam SPECT imaging resolution, include the following steps: step 1, obtain the low resolution projection image under N number of rotation angle, several width low resolution projection images are obtained under each rotation angle, the acquisition of the low resolution projection image will guarantee that detector focus is always same point, and there are geometrical relationships between high-resolution projected image under the low resolution projection image and the rotation angle；Step 2 handles several low resolution projection images under single rotation angle, obtains corresponding to high-resolution projected image under the rotation angle；Step 3 repeats step 2 operation, obtains the high-resolution projected image under N number of rotation angle, finally obtains true high-definition picture.The present invention can be improved the resolution ratio of pencil-beam SPECT image under the premise of not changing detector hardware.
Description
Technical field
The present invention relates to a kind of SPECT imaging mode, in particular to a kind of utilization, which is eccentrically rotated, improves pencil-beam SPECT
The method of imaging resolution belongs to medical image and rebuilds field.
Background technique
Single photon emission computerized tomography (single photon emission computed tomography,
It SPECT) is an important technology in nuclear medicine, radioactive tracer is detected after passing through human body by radiation γ photon
Device detection is surveyed, final rebuild obtains faultage image, in fields such as diagnosing tumor, cardiovascular disease diagnosis and cranial nerve scientific researches
It is used widely.With other medical imaging mode (such as X ray computer tomoscan (CT) and magnetic resonance imaging (MRI)) phases
Than SPECT has the lower limitation of resolution ratio.In SPECT, the key factor of image spatial resolution and sensitivity is limited
For the size of the collimating aperture of detector, collimator aperture is excessive or the too small quality that can all influence image quality.
Super-resolution rebuilding is to reconstruct one using the additional information of the one or more low-resolution image of Same Scene
The technology of width or several high-definition pictures is widely used in remote sensing as a kind of effective method for improving image resolution ratio
Satellite, the fields such as medical image.Super-resolution rebuilding is applied to CT, PET, SPECT, field of magnetic resonance imaging in recent years, with
Image resolution ratio is improved, these methods are mainly used in image area or parallel and fan-shaped detector projections rebuild field.
Conical projection SPECT system has the characteristics that high-resolution compared with parallel beam, fladellum SPECT, is conducive to pair
Small object is detected and is rebuild, and is operated using moving in rotation of detector etc., by cone-beam projections reconstruction and Super-resolution reconstruction
It builds and combines, it will the imaging resolution of SPECT is greatly improved.
Summary of the invention
The present invention provides a kind of method that utilization is eccentrically rotated raising pencil-beam SPECT imaging resolution.This method is not
Change detector in collimator aperture size and guarantee it is each rotation angle under detector focus be always same point premise
Under, using being eccentrically rotated for low resolution detector, improve the resolution ratio of SPECT image.
The low resolution projection image number that the present invention acquires under each angle is M, with practical low resolution projection figure
As size, target high-resolution projected image size is related；If low resolution detector size is Sl×SlA pixel, target are high
Resolution projection images size is Sh×ShA pixel, R be high-definition picture size and low-resolution image size pixel it
Than then M, N, R, Sh、SlIt can be provided by formula (1), (2), (3).
N≥Sh (1)
M≥R×R (3)
The present invention is achieved through the following technical solutions.
A kind of utilization disclosed by the invention is eccentrically rotated the method for improving pencil-beam SPECT imaging resolution, including as follows
Step:
Step 1 obtains the low resolution projection image under N number of rotation angle, obtains several width under each rotation angle
Low resolution projection image, each acquisition for rotating low resolution projection image under angle will guarantee detector focus always
For same point, there are geometrical relationships between high-definition picture under the low-resolution image and the rotation angle；
Low resolution projection Image Acquisition, is realized by the following method；
Low resolution detector is rotated around object center, is rotated every timeAngle, N are that detector is rotated around object
Number；Under each rotation angle, under the premise of guaranteeing that detector focus is always same point, M times is carried out partially to detector
Heart rotation；
Collect M low resolution projection image at each position of n times rotation；Record be eccentrically rotated every time away from
From with angle；
Initial detector plane before note is not eccentrically rotated is benchmark plane, after extending detector focus and being eccentrically rotated
The line of detector centre, makes line intersect at a point with datum plane, which is intersection point；
The detector focus be eccentrically rotated after detector centre line extended line and M of datum plane hand over
It is any multiple of high-resolution pixel size at a distance from point, with datum plane central point, M distance can be equal, can also be with
It is unequal, but to record the distance being eccentrically rotated every time；
The detector focus be eccentrically rotated after detector centre line extended line and M of datum plane hand over
Point can be uniformly distributed, can also be with uneven distribution, but record the position coordinates of each intersection point；
Under the single rotation angle, low resolution projection image and high-resolution perspective view that single is eccentrically rotated
There are geometrical relationships as between:
If detector focus be eccentrically rotated for the m times after detector centre line extended line and datum plane intersection point
Distance with datum plane center is d (m), and the distance (i.e. focal length) of focus to detector centre is sid, high-resolution projection
Image is in datum plane, using high-resolution projected image center as high-resolution projected image coordinate origin, to be eccentrically rotated
Low resolution detector center is low resolution projection image coordinate origin afterwards, for any pixel in low resolution detector
Point, taking four coordinates of pixel boundary is (i, j), and (i, j+1), (i+1, j), it can be obtained in high-resolution in (i+1, j+1)
Block S in corresponding region in rate projected image*Boundary point coordinate, by taking coordinate (i, j) as an example；
φ (j)=θ+δ (j) (6)
G (j)=sid × tan (φ (j)) (7)
Wherein, θ is benchmark plane focal length and the angle being eccentrically rotated between rear detector focal length, and δ (j) is low resolution throwing
Coordinate j and the angle being eccentrically rotated between back focal length in shadow image, φ (j) are coordinate j and benchmark in low resolution projection image
Angle between plane focal length, g (j) are that coordinate j is mapped to the seat in high-resolution projected image in low resolution projection image
Mark, g (i) are that coordinate i is mapped to the coordinate in high-resolution projected image in low resolution projection image；
For any pixel (a, b) in high-resolution projected image, judge whether it belongs to (g (i), g (j)), (g
(i), g (j+1)), (g (i+1), g (j)), the region unit S of (g (i+1), g (j+1)) composition*It is interior, w (a, b) is corresponded to if meeting
=1, w (a, b) indicates S here*Thus interior each full-resolution picture vegetarian refreshments obtains low the coefficient of low-resolution pixel point (a, b)
Mapping relations in resolution projection images between any pixel point and each pixel of high-resolution projected image；
Step 2: handling M low resolution projection image under single rotation angle, obtain under the rotation angle
Corresponding high-resolution projected image；
The method handled low-resolution image includes the following steps:
Remember PH0For original hypothesis high-resolution projected image, i.e., the 1st initial high resolution perspective view rotated under angle
Picture, high-resolution projected image are located in datum plane；PHnmTo be eccentrically rotated at detector the m times under n-th of rotation angle
The corresponding initial high resolution projected image in position, in which: the value range of n is 1-N, and the value range of m is 1-M；PHnm1For
Initial high resolution projected image P under n-th of rotation angle, under the rotation angleHnmIts coordinate system is rotated around picture centre
The high-resolution projected image that γ angle obtains, the γ angle are the lines and of m-th of intersection point and datum plane central point
The angle that the line of one intersection point and datum plane central point is formed；
Step 2.1: under n-th of rotation angle, PHnm1It can be acquired by formula (9):
Wherein: (x, y) is PHnmThe coordinate of middle pixel, (x1,y1) it is respective pixel point after (x, y) rotating coordinate system
It sets；And P is acquired by bilinear interpolation formulaHnm1The coordinate of each pixel after interpolation；
Wherein, (x0,y0) it is (x1,y1) first integer-valued coordinates being rounded downwards, (x2,y2) it is (x1,y1) after interpolation
PHnm1Pixel coordinate value；
Step 2.2: noteThe real projection that m-th of low resolution detector measurement obtains under angle is rotated for n-th
Image, PLnmFor under n-th of rotation angle to PHnm1It carries out by the down-sampled obtained low resolution projection image of geometrical relationship, i.e.,
By the corresponding high-resolution areas block S of each low resolution projection image slices vegetarian refreshments*All pixels point it is folded according to formula (11)
Add:
Wherein, (x3,y3) it is PLnmIn each pixel coordinate, wherein each pair of point answers high-resolution in low-resolution image
Region unit S in image*, w (x2,y2) it is S*Interior each full-resolution picture vegetarian refreshments is to low-resolution pixel point (x3,y3) coefficient；
Formula (11) is written as complete vector form i.e.:
pLnm=WpHnm1 (12)
Wherein, pLnmIndicate that the column vector of low resolution projection image indicates, length is (Sl×Sl) × 1, pHnm1For high score
The column vector of resolution projected image indicates that length is (Sh×Sh) × 1, W indicates pixel and high score in low resolution projection image
The relational matrix of pixel in resolution projected image, size are (Sl×Sl)×(Sh×Sh)；
Step 2.3: to m-th of low resolution projection image P under n-th of angle that step 2.2 is obtainedLnmWith step 1
Low-resolution image under direct collected n-th of angleIt is compared according to formula (13), acquires true low resolution
The difference DELTA P of projection and current low resolution projectionLnm；
Step 2.4: by the difference DELTA P of the corresponding pixel points obtained through step 2.3LnmIt is written as vector form, i.e. Δ pLnm, benefit
It is obtained multiplied by the step-length adjusted every time as weight is adjusted to high-definition picture p with relational matrix WHnm1In each point tune
Save weight Δ pHnm1；
ΔpHnm1=WTΔpLnm×step (14)
Wherein: step is each adjusting step-length, adjusts step-length value between 0 to 1；
Step 2.5: the adjusting weight Δ p obtained by step 2.4Hnm1It is reduced to matrix form Δ PHnm1, and by its coordinate system
γ degree is reversely rotated around picture centre, by formula (15):
Wherein (x4,y4) it is Δ PHnm1The coordinate of middle pixel, (x5,y5) it is (x4,y4) reversely rotate correspondence after coordinate system
The position of pixel, and according to two-dimensional linear interpolation, obtain PHnmAdjusting weight Δ PHnm；
Wherein, (x50,y50) it is (x5,y5) first integer-valued coordinates being rounded downwards, (x6,y6) it is (x5,y5) after interpolation
ΔPHnmPixel coordinate value；
Step 2.6: weight Δ P will be adjustedHnmIt is added to and is eccentrically rotated the initial high resolution of position at detector the m times
Data for projection PHnmOn, obtain (m+1) secondary initial high resolution data for projection P for being eccentrically rotated positionHn(m+1), by formula
(17) P is updatedHn(m+1)；
PHn(m+1)=PHnm+ΔPHnm (17)
Step 2.7；It is obtained under n-th of rotation angle at this time, is eccentrically rotated the high-resolution projected image of position for the m times,
It is eccentrically rotated the initial high resolution projected image of position for i.e. the m+1 times；Step 2,1-2,6 are repeated, can be accessed n-th
It rotates under angle, by M times treated high-definition picture PHnM；
Whole M adjustings are completed at this time；
Step 2,1-2,6 are repeated, continue to adjust image the 1st position rotated under angle since n-th, until
The iteration termination condition for reaching requirement obtains the high-resolution projected image for meeting projected resolution requirement, terminates iterative process,
It obtains individually rotating the high-resolution projected image under angle when detector is rotated around object；
The iteration termination condition are as follows: calculate two models of the front and back difference of iterative process high-resolution projected image twice
Number, and be compared with iteration threshold condition is terminated, it determines whether to terminate iteration；The iteration threshold condition is according to need
Depending on the high-resolution projected image precision to be obtained；
Step 3: repeating step 2 operation, the high-resolution projected image under N number of angle is obtained, true height is finally obtained
Image in different resolution；
The utility model has the advantages that
1, a kind of utilization disclosed by the invention is eccentrically rotated the method for improving pencil-beam SPECT imaging resolution, due to every
The acquisition of low resolution projection image guarantees that detector focus is always same point, several low resolutions of acquisition under a rotation angle
Rate projected image is all imaged same target, thus, it is possible to according to Step 2: three processing method from each rotation angle
It descends several low resolution projection images to obtain the high-resolution projected image under the angle, can be obtained phase using method for reconstructing
The super-resolution reconstruction figure answered improves the resolution ratio of SPECT image；
2, a kind of utilization disclosed by the invention is eccentrically rotated the method for improving pencil-beam SPECT imaging resolution, utilizes inspection
The mode that device is eccentrically rotated is surveyed, available more low resolution projection images comprising different data especially obtain more
The data in image center region can preferably improve whole image quality.
Detailed description of the invention
Fig. 1 is taper SPECT detector model schematic；
Fig. 2 is taper detector around object center rotating acquisition schematic diagram, and solid line is detector initial position, and dotted line is inspection
It surveys device to rotate by a certain angle the position of arrival around object, detector can rotate a circle around the circle of dotted line in figure；
Fig. 3 is under individually rotation angle, and low resolution detector is eccentrically rotated schematic diagram, is rotated to be with circular offset
Example；
Fig. 4 be individually rotation angle under, detector focus be eccentrically rotated after detector centre line extended line
With M intersection point schematic diagram of high-resolution projected image (datum plane), by taking circular offset rotates as an example；
Fig. 5 is under individually rotation angle, and the coordinate system of high-resolution projected image rotates γ angle around picture centre, just
It is calculated in coordinate；
Fig. 6 is under individually rotation angle, and low resolution detector is eccentrically rotated schematic diagram and low resolution projection figure
The geometrical relationship of any pixel and pixel region unit in high-resolution projected image as in, by taking circular offset rotates as an example；
Fig. 7 is to obtain a panel height resolution projection images by several low resolution projection images under individually rotation angle
Flow chart；
Fig. 8 is that single iteration adjusts process schematic when obtaining high-resolution projected image by low resolution projection image,
It (a) is (b) projected image after high-resolution projected image transformed coordinate system, (c) for by height to assume high-resolution projected image
The hypothesis low resolution projection image that resolution projection images (b) obtain after relational matrix is down-sampled is (d) collected
Practical low resolution projection image, the image that the difference that (c) and (d) subtracts each other of (e) serving as reasons obtains, by obtained (e) as adjusting
High-resolution projected image (b) is adjusted in foundation, obtains high-resolution projected image (f), (g) is by (f) reciprocal transformation
Image is moved back to initial position by coordinate system, finally obtain adjust after high-resolution projected image (h), (h) then obtained into
Enter adjustment process next time；
Fig. 9 is different layers original image, simulation high-resolution projection is used through FDK reconstruction image, by low resolution projection
This patent method obtains high-resolution projection through FDK reconstruction image, low resolution projection through FDK reconstruction image；Wherein detector
Center is located at 44 layers of object, and the distance of detector focus to detector centre is 380 pixels, focus to object center away from
From for 310 pixels；, data are by taking circular offset rotating acquisition as an example.
Specific embodiment
It elaborates in the following with reference to the drawings and specific embodiments to the embodiment of the method for the present invention.
Embodiment 1:
While detector is rotated around object, under each rotation angle, detector need to be eccentrically rotated operation, obtain
Several low resolution projection images.This example with low resolution detector resolution ratio be 32 × 32 pixels, target obtain height
Definition pixel is 128 × 128, N=128, is illustrated for R=4, M=16, but does not illustrate that the invention is only limitted to this
A little conditions, the present invention involved in range only limited by claims.
A kind of method that utilization is eccentrically rotated raising pencil-beam SPECT imaging resolution, specific disclosed in the present embodiment
Implementation steps are as follows:
Step 1 obtains the low resolution projection image under 128 rotation angles, obtains 16 width under each rotation angle
Low resolution projection image, each acquisition for rotating low resolution projection image under angle will guarantee detector focus always
For same point, there are geometrical relationships between high-definition picture under the low-resolution image and the rotation angle；
Low resolution projection Image Acquisition is realized by the following method by the way of circular offset rotation；
Low resolution detector is rotated around object center, is rotated every timeAngle, 128 revolve for detector around object
The number turned；Fig. 1 is pencil-beam SPECT detector model schematic, and pencil-beam SPECT detector is a plate, and it is all
Collimator holes correspond to an identical focus.Object to be detected is located among detector and detector focus, issues from object
Gamma ray can be received by detector.Fig. 2, which rotates for detector around object, carries out photon collection schematic diagram, and solid line is detector
Initial position, dotted line is detector to rotate by a certain angle the position of arrival around object, and detector can be revolved around the circle of dotted line in figure
It circles；
Under each rotation angle, under the premise of guaranteeing that detector focus is always same point, detector is carried out 16 times
It is eccentrically rotated；
Initial detector plane before note is not eccentrically rotated is benchmark plane, after extending detector focus and being eccentrically rotated
The line of detector centre, makes line intersect at a point with datum plane, which is intersection point, totally 16 friendships under each rotation angle
Point, intersection point is constant at a distance from datum plane central point, i.e. composition circular offset, as shown in Figure 3；
The low resolution projection image under 128 rotation angles is collected, there are 16 low resolutions under each rotation angle
Rate projected image；Record bias turns every time distance and angle；
The detector focus be eccentrically rotated after detector centre line extended line and 16 of datum plane friendships
It is a high-resolution pixel size at a distance from point, with datum plane central point；
The detector focus be eccentrically rotated after detector centre line extended line and 16 of datum plane friendships
Point is is uniformly distributed, as shown in figure 3, the pore in figure is 16 intersection points；
Under the single rotation angle, low resolution projection image and high-resolution perspective view that single is eccentrically rotated
It is as follows that there are geometrical relationships as between:
If detector focus be eccentrically rotated after the extended line of detector centre line and the intersection point of datum plane and base
The distance at directrix plane center is d, and d=1px, the distance (i.e. focal length) of focus to detector centre is sid, sid=380px, height
Resolution projection images are in datum plane, using high-resolution projected image center as high-resolution projected image coordinate origin,
To be eccentrically rotated rear low resolution detector center as low resolution projection image coordinate origin, in low resolution detector
Any pixel, take pixel boundary four coordinates be (i, j), (i, j+1), (i+1, j), it can be obtained in (i+1, j+1)
The corresponding region block S in high-resolution projected image*Boundary point coordinate；
For any pixel (a, b) in high-resolution projected image, judge whether it belongs to (g (i), g (j)), (g
(i), g (j+1)), (g (i+1), g (j)), the region unit S of (g (i+1), g (j+1)) composition*It is interior, w (a, b) is corresponded to if meeting
=1, w (a, b) indicates S here*Thus interior each full-resolution picture vegetarian refreshments obtains low the coefficient of low-resolution pixel point (a, b)
Mapping relations in resolution projection images between any pixel point and each pixel of high-resolution projected image；
Step 2: handling 16 width low resolution projection images under single rotation angle, the rotation angle is obtained
Lower corresponding high-resolution projected image；
The method handled low-resolution image includes the following steps:
Remember PH0For original hypothesis high-resolution projected image, i.e., the 1st initial high resolution perspective view rotated under angle
Picture, high-resolution projected image are located in datum plane；PHnmTo be eccentrically rotated at detector the m times under n-th of rotation angle
The corresponding initial high resolution projected image in position, in which: the value range of n is 1-128, and the value range of m is 1-16；PHnm1
For the initial high resolution projected image P under n-th of rotation angle, under the rotation angleHnmIts coordinate system is revolved around picture centre
Turn the high-resolution projected image that γ angle obtains, the γ angle be m-th of intersection point and datum plane central point line and
The angle that the line of first intersection point and datum plane central point is formed,
Step 2.1: under n-th of rotation angle, to be calculated convenient for coordinate, by PHnmCoordinate system is rotated around its picture centre
γ degree, and P is obtained according to two-dimensional linear interpolationHnm1, as shown in Figure 5；
Step 2.2: noteThe real projection that m-th of low resolution detector measurement obtains under angle is rotated for n-th
Image, PLnmFor under n-th of rotation angle to PHnm1It carries out by the down-sampled obtained low resolution projection image of geometrical relationship, and
Relational matrix W is recorded, pixel is corresponding with high-resolution projected image pixel region unit in low resolution projection image closes
System is as shown in Figure 6；
Step 2.3: to m-th of low resolution projection image P under n-th of angle that step 2.2 is obtainedLnmWith step 1
Low-resolution image under direct collected n-th of angleIt is compared according to formula (13), acquires true low resolution
The difference DELTA P of projection and current low resolution projectionLnm；
Step 2.4: by the difference DELTA P of the corresponding pixel points obtained through step 2.3LnmIt is written as vector form, i.e. Δ pLnm, benefit
It is obtained multiplied by the step-length adjusted every time as weight is adjusted to high-definition picture p with relational matrix WHnm1In each point tune
Save weight Δ pHnm1；
Step 2.5: the adjusting weight Δ p obtained by step 2.4Hnm1It is reduced to matrix form Δ PHnm1, and by its coordinate system
γ degree is reversely rotated around picture centre, and according to two-dimensional linear interpolation, obtains PHnmAdjusting weight Δ PHnm；
Step 2.6: weight Δ P will be adjustedHnmIt is added to and is eccentrically rotated the initial high resolution of position at detector the m times
Data for projection PHnmOn, obtain (m+1) secondary initial high resolution data for projection P for being eccentrically rotated positionHn(m+1), update
PHn(m+1)；
Step 2.7；It is obtained under n-th of rotation angle at this time, is eccentrically rotated the high-resolution projected image of position for the m times,
It is eccentrically rotated the initial high resolution projected image of position for i.e. the m+1 times；Step 2,1-2,6 are repeated, can be accessed n-th
It rotates under angle, by 16 times treated high-definition picture PHnM；
All 16 adjustings are completed at this time；
Step 2,1-2,6 are repeated, continue to adjust image the 1st position rotated under angle since n-th, until
The iteration termination condition for reaching requirement obtains the high-resolution projected image for meeting projected resolution requirement, terminates iterative process,
It obtains individually rotating the high-resolution data for projection under angle when detector is rotated around object；
Fig. 7 is to obtain 1 128 × 128 pixel high-resolution by the low resolution projection image of 16 32 × 32 pixels to throw
Shadow image flow chart, corresponding process are as shown in Figure 8；
Initial high resolution projected image is illustrated in flow chart:
Initial high resolution projected image, which obtains, selects one of following two methods: (1), to high-resolution projected image with
Machine assignment, such method have a large amount of random noise after final iteration；(2), by collected low-resolution image interpolation
At high-resolution projected image size, and using this image as original high resolution projected image, such method is in final iteration
It is preferable that high-resolution projected image is obtained afterwards, and convergence rate is very fast；
Iteration termination condition: iteration termination condition can be actually the same, (1) there are two types of method, both methods,
By calculating (a) and two norms of the difference of (h) in Fig. 8 and being compared with iteration threshold condition is terminated, determine whether
Terminate iteration；(2), two norms of (e) matrix in Fig. 8 are calculated and are compared with iteration threshold condition is terminated, so that it is determined that being
No end iteration；
In addition to circular offset rotation, other forms are eccentrically rotated, equally applicable if oval eccentric rotates；
Step 3: repeating step 2 operation, the high-resolution projected image under 128 angles is obtained, is finally obtained true
High-definition picture；
According to Step 2: three obtained high-resolution projections reconstruct high-resolution SPECT figure according to FDK algorithm for reconstructing
Picture.Fig. 9 is using FDK algorithm for reconstructing to backprojection image reconstruction acquired results.Comparison low resolution projection directly reconstructs as a result, changing
It is kind obvious, result is directly reconstructed substantially close to patented method can effectively improve resolution ratio with the projection of direct high-resolution.
This method can be not only used for the reconstruction of SPECT oversubscription, but this method can be applied in other oversubscription algorithm for reconstructing,
Such as PET oversubscription is rebuild, CT oversubscription is rebuild.
Technical solution of the present invention and specific embodiment are described in conjunction with specific embodiments above, but these explanations
It cannot be considered as limiting the scope of the present invention, these are merely examples, and a variety of changes can be made to these embodiments
It more or modifies, without departing from the principle and substance of the present invention.Protection scope of the present invention is limited by appended claims, is appointed
Where the change on the basis of the claims in the present invention is all protection scope of the present invention.
Claims (4)
1. a kind of utilization is eccentrically rotated the method for improving pencil-beam SPECT imaging resolution, it is characterised in that: including walking as follows
It is rapid:
Step 1 obtains the low resolution projection image under N number of rotation angle, obtains several low point under each rotation angle
Resolution projected image, each acquisition for rotating low resolution projection image under angle will guarantee that detector focus is always same
A bit, there are geometrical relationships between high-definition picture under the low-resolution image and the rotation angle；
Low resolution projection Image Acquisition, is realized by the following method；
Low resolution detector is rotated around object center, is rotated every timeAngle, N are time that detector is rotated around object
Number；Under each rotation angle, under the premise of guaranteeing that detector focus is always same point, M eccentric rotation is carried out to detector
Turn；
Collect M low resolution projection image at each position of n times rotation；Record the distance that is eccentrically rotated every time with
Angle；
Step 2: handling M low resolution projection image under single rotation angle, obtain corresponding under the rotation angle
High-resolution projected image；
The method handled low-resolution image includes the following steps:
Initial detector plane before note is not eccentrically rotated is benchmark plane, the detection after extending detector focus and being eccentrically rotated
The line at device center, makes line intersect at a point with datum plane, which is intersection point, total M intersection point under each rotation angle；
Remember PH0For original hypothesis high-resolution projected image, i.e., the 1st initial high resolution projected image rotated under angle, height
Resolution projection images are located in datum plane；PHnmTo be eccentrically rotated position pair at detector the m times under n-th of rotation angle
The initial high resolution projected image answered, in which: the value range of n is 1-N, and the value range of m is 1-M；PHnm1It is revolved for n-th
Initial high resolution projected image P under gyration, under the rotation angleHnmIts coordinate system is rotated into γ angle around picture centre
The high-resolution projected image obtained afterwards, the γ angle be m-th of intersection point and datum plane central point line and first
The angle that the line of intersection point and datum plane central point is formed；
Step 2.1: under n-th of rotation angle, PHnm1It is acquired by formula (9):
Wherein: (x, y) is PHnmThe coordinate of middle pixel, (x1,y1) it is corresponding pixel points position after (x, y) rotating coordinate system；And
P is acquired by bilinear interpolation formulaHnm1The coordinate of each pixel after interpolation；
Wherein, (x0,y0) it is (x1,y1) first integer-valued coordinates being rounded downwards, (x2,y2) it is (x1,y1) P after interpolationHnm1's
Pixel coordinate value；
Step 2.2: noteThe real projection image that m-th of low resolution detector measurement obtains under angle is rotated for n-th,
PLnmFor under n-th of rotation angle to PHnm1It carries out by the down-sampled obtained low resolution projection image of geometrical relationship, i.e., it will be each
The corresponding high-resolution areas block S of low resolution projection image slices vegetarian refreshments*All pixels point according to formula (11) be superimposed:
Wherein, (x3,y3) it is PLnmIn each pixel coordinate, wherein each pair of point answers high-definition picture in low-resolution image
In region unit S*, w (x2,y2) it is S*Interior each full-resolution picture vegetarian refreshments is to low-resolution pixel point (x3,y3) coefficient；
Formula (11) is written as complete vector form i.e.:
pLnm=WpHnm1 (12)
Wherein, pLnmIndicate that the column vector of low resolution projection image indicates, length is (Sl×Sl) × 1, pHnm1For high-resolution
The column vector of projected image indicates that length is (Sh×Sh) × 1, W indicates pixel and high-resolution in low resolution projection image
The relational matrix of pixel in projected image, size are (Sl×Sl)×(Sh×Sh)；
Low resolution detector size is Sl×SlA pixel, target high-resolution projected image size are Sh×ShA pixel；
Step 2.3: to m-th of low resolution projection image P under n-th of angle that step 2.2 is obtainedLnmIt is direct with step 1
Low-resolution image under collected n-th of angleIt is compared according to formula (13), acquires true low resolution projection
With the difference DELTA P of current low resolution projectionLnm；
Step 2.4: by the difference DELTA P of the corresponding pixel points obtained through step 2.3LnmIt is written as vector form, i.e. Δ pLnm, utilize pass
It is matrix W, multiplied by the step-length adjusted every time as weight is adjusted, obtains to high-definition picture pHnm1In each point adjusting power
Weight Δ pHnm1；
ΔpHnm1=WTΔpLnm×step (14)
Wherein: step is each adjusting step-length, adjusts step-length value between 0 to 1；
Step 2.5: the adjusting weight Δ p obtained by step 2.4Hnm1It is reduced to matrix form Δ PHnm1, and by its coordinate system around figure
Inconocenter reversely rotates γ degree, by formula (15):
Wherein (x4,y4) it is Δ PHnm1The coordinate of middle pixel, (x5,y5) it is (x4,y4) reversely rotate corresponding pixel points after coordinate system
Position obtain P and according to two-dimensional linear interpolationHnmAdjusting weight Δ PHnm；
Wherein, (x50,y50) it is (x5,y5) first integer-valued coordinates being rounded downwards, (x6,y6) it is (x5,y5) Δ P after interpolationHnm
Pixel coordinate value；
Step 2.6: weight Δ P will be adjustedHnmIt is added to and is eccentrically rotated the initial high resolution projection of position at detector the m times
Data PHnmOn, obtain (m+1) secondary initial high resolution data for projection P for being eccentrically rotated positionHn(m+1), more by formula (17)
New PHn(m+1)；
PHn(m+1)=PHnm+ΔPHnm (17)
Step 2.7；It is obtained under n-th of rotation angle at this time, is eccentrically rotated the high-resolution projected image of position, i.e. m for the m times
It is eccentrically rotated the initial high resolution projected image of position for+1 time；Step 2,1-2,6 are repeated, n-th of rotation angle can be accessed
Under degree, by M times treated high-definition picture PHnM；
Whole M adjustings are completed at this time；
Step 2,1-2,6 are repeated, continue to adjust image the 1st position rotated under angle since n-th, until reaching
It is required that iteration termination condition, obtain meeting the high-resolution projected image of projected resolution requirement, terminate iterative process to get
The high-resolution projected image under angle is individually rotated when rotating to detector around object；
The iteration termination condition are as follows: two norms of the front and back difference of iterative process high-resolution projected image twice are calculated,
And be compared with iteration threshold condition is terminated, it determines whether to terminate iteration；The iteration threshold condition is as needed
Depending on the high-resolution projected image precision of acquisition；
Step 3: repeating step 2 operation, the high-resolution projected image under N number of angle is obtained, true high-resolution is finally obtained
Rate image.
2. a kind of utilization as described in claim 1 is eccentrically rotated the method for improving pencil-beam SPECT imaging resolution, feature
Be: detector focus be eccentrically rotated after detector centre line extended line and datum plane M intersection point, with benchmark
The distance of planar central point is any multiple of high-resolution pixel size.
3. a kind of utilization as described in claim 1 is eccentrically rotated the method for improving pencil-beam SPECT imaging resolution, feature
Be: detector focus be eccentrically rotated after detector centre line extended line and datum plane M intersection point, Ke Yijun
Even distribution, can also be with uneven distribution, but to record the position coordinates of each intersection point.
4. a kind of utilization as described in claim 1 is eccentrically rotated the method for improving pencil-beam SPECT imaging resolution, feature
It is: under single rotation angle, between the single low resolution projection image being eccentrically rotated and high-resolution projected image
There are geometrical relationships:
If detector focus be eccentrically rotated for the m times after the extended line of detector centre line and the intersection point of datum plane and base
The distance at directrix plane center is d (m), and the distance (i.e. focal length) of detector focus to detector centre is sid, high-resolution projection
Image is in datum plane, using high-resolution projected image center as high-resolution projected image coordinate origin, to be eccentrically rotated
Low resolution detector center is low resolution projection image coordinate origin afterwards, for any pixel in low resolution detector
Point, taking four coordinates of pixel boundary is (i, j), and (i, j+1), (i+1, j), (i+1, j+1) obtains it and throw in high-resolution
Block S in corresponding region in shadow image*Boundary point coordinate, by taking coordinate (i, j) as an example；
φ (j)=θ+δ (j) (6)
G (j)=sid × tan (φ (j)) (7)
Wherein, θ is benchmark plane focal length and the angle being eccentrically rotated between rear detector focal length, and δ (j) is low resolution projection figure
Coordinate j and the angle being eccentrically rotated between rear detector focal length as in, φ (j) are coordinate j and base in low resolution projection image
Angle between directrix plane focal length, g (j) are that coordinate j is mapped in high-resolution projected image in low resolution projection image
Coordinate, g (i) are that coordinate i is mapped to the coordinate in high-resolution projected image in low resolution projection image；
For any pixel (a, b) in high-resolution projected image, judge whether it belongs to (g (i), g (j)), (g (i), g
(j+1)), (g (i+1), g (j)), the region unit S of (g (i+1), g (j+1)) composition*It is interior, w (a, b)=1 is corresponded to if meeting, this
In w (a, b) indicate S*Interior each full-resolution picture vegetarian refreshments thus obtains low resolution to the coefficient of low-resolution pixel point (a, b)
Mapping relations in projected image between any pixel point and each pixel of high-resolution projected image.
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