CN116138795A - Chromatography reconstruction method and device based on biplane long-stroke scanning - Google Patents
Chromatography reconstruction method and device based on biplane long-stroke scanning Download PDFInfo
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Abstract
The invention discloses a chromatography reconstruction method and a device based on biplane long-stroke scanning, which are applied to a biplane X-ray machine system and comprise the following steps: setting a biplane X-ray scanning mode and a geometric environment, and acquiring original images of an object to be reconstructed under different relative position relations; preprocessing an original image to obtain a gray value of the original image, carrying out logarithmic transformation to convert the gray value into a corresponding X-ray absorptivity, and determining a tomographic reconstruction range according to a long-stroke scanning geometric environment; selecting a reconstruction width, traversing all reconstruction range points by using the reconstruction width, and completing reconstruction of the coronal plane and sagittal plane tomographic images by filtering back projection; and acquiring an overlapped part of the reconstructed tomographic images, and splicing the overlapped part by using a weighted superposition method to form a long-stroke image, so that a tomographic reconstruction algorithm of double-plane long-stroke scanning is realized, the reconstruction of the coronal and sagittal load-bearing position tomographic images is realized, the tomographic image reconstruction range is enlarged, and the interlayer resolution of the images is improved.
Description
Technical Field
The invention relates to the technical field of medical imaging, in particular to a tomographic reconstruction method and device based on biplane long-stroke scanning.
Background
Orthopedics is a clinical medical discipline that mainly researches the anatomy, physiology, pathology, and treatment modes of the skeletal muscle system.
At present, various secondary disciplines of orthopedics still have clinical problems to be overcome. Adolescent idiopathic scoliosis is a common spinal disorder with an overall prevalence of 0.47-5.2% and a ratio of men to women between 1:1.5 and 1:3 for the diseased population, with a higher Cobb angle in the population with a significantly higher prevalence of women than men; the comprehensive incidence rate of degeneration of adjacent segments after spinal fusion operation is 29.3 percent, the incidence rate of cervical vertebra segments is 32.8 percent, and the incidence rate of lumbar vertebra segments is 26.6 percent; the revision rate after unicondylar knee replacement is higher than that of traditional total knee replacement, of which 36% are due to postoperative non-replacement compartment and patellofemoral progressive arthritis; anterior cruciate ligament rupture accounts for 20% of knee joint movement injuries, and the incidence of progressive knee arthritis 10 years after anterior cruciate ligament rupture exceeds 50%, however, even with anterior cruciate ligament reconstruction treatment, 40-90% of patients will have arthritis in the rest of their lives. The clinical problems objectively existing in the fields of spinal surgery, joint surgery, sports medicine and the like need to be solved by targeted and innovative medical instruments and equipment for assisting orthopedics doctors.
The anatomical morphology of the diseased bones and joints of the patient is evaluated by a medical imaging technology, so that the orthopedic clinical diagnosis of the disease type, the operation planning and the tracking of the postoperative curative effect are facilitated, and the orthopedic clinical disease diagnosis and treatment level is improved. The method is mainly applied to orthopedics clinical imaging diagnosis and comprises the following steps: digital X-ray imaging, computed Tomography (CT), magnetic Resonance Imaging (MRI), ultrasound imaging, tomosynthesis imaging. The digital X-ray imaging technology is easy to store, small in radiation dose and high in imaging quality, but imaging is realized based on cone beam projection, focus information with different depths cannot be distinguished and identified, and three-dimensional measurement cannot be performed; CT can rapidly and clearly realize three-dimensional imaging of skeletal muscle soft tissues, but is not suitable for one-time whole-body examination and periodic follow-up tracking due to high radiation dose; the MRI realizes non-radiative noninvasive imaging of key parts such as bones, muscles and spinal cords through different sequences, but has long imaging time and small domestic loading, and is difficult to ensure wide-range orthopedics clinical application; ultrasonic imaging can clearly realize fracture and muscle ligament injury diagnosis, but the diagnosis of important joint surfaces is difficult to realize by the current ultrasonic signals. The tomosynthesis imaging is a technology for obtaining images at a small projection angle based on digital X-rays and reconstructing the images by using a back projection algorithm, has the advantages of low dosage, short scanning time, capability of removing tissue structure aliasing and enhancing local tissue contrast, and can obviously improve the resolution capability of orthopedics clinic on complex anatomical structures, microfracture and joint surface morphology. Thus, tomosynthesis imaging is a clinical orthopedic imaging technique with substantial potential.
In the prior art, the current chromatographic synthetic reconstruction technology can be divided into three main categories according to the scanning mode: flat panel detector-radiation source co-planar inverse scan, flat panel detector-radiation source parallel circumferential inverse scan, flat panel detector-radiation source co-planar co-directional scan. The key technical characteristics of the three main chromatographic synthetic reconstruction technologies are as follows:
(1) Flat panel detector-radiation source co-planar inverse scanning involves four common scanning modes: (1) the flat panel detector and the radiation source move in opposite directions in synchrony with a linear trajectory (as shown in FIG. 1A); (2) the flat panel detector and the radioactive source synchronously move in opposite directions along a circular arc track (as shown in fig. 1B); (3) the flat panel detector moves in a linear track and the radiation source moves in a synchronous and reverse direction in an arc track (as shown in figure 1C); (4) the flat panel detector remains stationary and the radiation source moves in a circular arc trajectory (as shown in fig. 1D). Because the motion track of the flat panel detector and the radiation source are always in the same plane, the relation among the voxels of the target area, the X-ray position and the absorptivity can be obtained according to the geometrical parameters such as the relative position of the flat panel detector and the radiation source, the opening angle of the radiation source, the rotation angle or the moving distance, the depth of the target area and the like during scanning, and the tomographic image of the target area can be reconstructed by using a back projection method. Because the current clinical equipment is a group of flat panel detectors-radioactive sources, the scanning mode mainly scans and reconstructs the coronal tomographic image.
(2) The flat panel detector-radiation source parallel circumference inverse scan pattern is shown in fig. 2. The flat panel detector center and the radiation source are scanned in two parallel planes in a circumferential orbit about the same axis (Z-axis in fig. 2A), respectively, with the radiation source center ray being maintained perpendicular to the flat panel detector and passing through the flat panel detector center during the scan. In the case of a small radiation source opening angle, the actual cone beam X-rays can be approximately equivalent to a set of parallel beams, and for any flat panel detector-radiation source position to capture the target area, the target area can be approximately equivalent to a cross-section taken at a particular angle (as shown in fig. 2A). In the corresponding three-dimensional Fourier space, the spatial resolution information of the target area can be sampled approximately equivalently as the section of a specific angle, and the tomographic image of the target area can be reconstructed by performing Fourier inverse transformation after frequency filtering. Because the current clinical equipment is a group of flat panel detectors-radioactive sources, the scanning mode mainly scans and reconstructs the coronal tomographic image.
(3) Flat panel detector-source co-planar co-scanning mode is a long-range tomosynthesis imaging technique first proposed by Koichi Shibata et al, as shown in fig. 3. Unlike the traditional scanning mode of the synchronous reverse motion of the flat-panel detector and the radioactive source, the scanning mode sets the center of the flat-panel detector and the radioactive source to synchronously and equidirectionally scan by taking parallel lines as tracks in the same plane, and the scanning and imaging space range depends on the opening angle of the radioactive source, the linear motion distance and interval of the flat-panel detector and the radioactive source and the depth information of the reconstructed target area. The strip space parallel to the plane of the flat panel detector in any imaging space is taken, a local detector-radioactive source reverse linear scanning mode is simulated through reasonable data rearrangement, the reconstruction of the strip tomographic image is realized by matching with a back projection algorithm, all possible strip space positions in the imaging space range of a target are traversed, and the multi-depth long-stroke tomographic synthetic reconstruction is realized. Because the current clinical equipment is a group of flat panel detectors-radioactive sources, the scanning mode mainly scans and reconstructs the coronal tomographic image.
The disadvantages of the prior art are as follows: (1) The traditional tomosynthesis reconstruction space area is small, and the aliasing of the non-central area image is serious. Traditional chromatographic synthetic reconstruction methods rely on five scanning modes: the flat panel detector-radioactive source reverse linear motion, the flat panel detector-radioactive source reverse circular motion, the flat panel detector linear-radioactive source circular motion, the flat panel detector stationary-radioactive source circular motion and the flat panel detector-radioactive source reverse circular track motion. The five scanning modes determine the reconstruction area with high image quality, and the reconstruction construction space area is small for the most widely used tomosynthesis imaging technology at present and is limited for the orthopaedics three-dimensional measurement analysis area according to parameters such as the space between a flat panel detector and a radioactive source (generally set to 600-1000 mm), the space between the flat panel detector and a scanning object (generally set to 100-500 mm), the opening angle of the radioactive source (generally not exceeding 25 degrees), the rotation angle (generally not exceeding 60 degrees) and the like. Meanwhile, the scanning mode and the back projection reconstruction method of the tomosynthesis technology determine that the center of the target area can obtain higher in-situ resolution and tissue contrast, but the back projection information of the edge of the target area and the non-target area is less, and the image is seriously aliased.
(2) The interlayer resolution is low. Current tomosynthesis techniques use only one set of flat panel detector-radiation sources for scanning and therefore only one direction of tomographic image can be reconstructed. Because the tomosynthesis technology mainly relies on back projection of the processed X-ray perspective image to form an image of a target layer, the frequency response of the flat panel detector-radioactive source co-planar scanning system to the target region in the direction of the normal vector of the flat panel detector is low, the frequency response of the flat panel detector-radioactive source parallel circumferential scanning system to the target region in the direction of the normal vector of the parallel circumferential track plane is low, the reconstructed image layer resolution is low, and the depth information outside the target layer is lost.
(3) Weight position imaging cannot be performed. The existing chromatographic synthetic reconstruction system is designed based on the supine position or the lateral position of the photographed person, and can be fully applied to operation guidance, bone morphometric analysis and shoulder, elbow and wrist joint state evaluation. But for bones and joints of the spine, lower limbs and the like which bear the weight bearing function in daily activities, the clinical value of important orthopedic parameters (such as scoliosis degree, alignment of lower limb force lines, hip joint coverage rate and the like) obtained by supine position measurement is reduced.
In summary, it is necessary to provide a tomographic reconstruction algorithm based on biplane long-stroke scanning, so as to solve the defects of small spatial area, serious aliasing of non-central area image, low interlayer resolution and incapability of carrying out loading position imaging in the traditional tomographic synthesis reconstruction in the prior art.
Disclosure of Invention
The invention aims to provide a tomographic reconstruction method and device based on biplane long-stroke scanning, which combines a biplane X-ray technology and a tomographic synthesis reconstruction technology based on single plane long-stroke scanning to realize a tomographic reconstruction algorithm based on biplane long-stroke scanning, and simultaneously realize the reconstruction of coronal and sagittal plane weight-bearing position tomographic images, expand the tomographic image reconstruction range and improve the interlayer resolution of images.
The invention provides a chromatography reconstruction method based on double-plane long-stroke scanning, which is applied to a double-plane X-ray system, wherein the double-plane X-ray system comprises a first X-ray machine and a second X-ray machine,
the first X-ray machine comprises a first radioactive source for emitting X-rays to a human body; the first detector is arranged opposite to the first radiation source and is used for receiving X-rays passing through a human body;
the second X-ray machine comprises a second radioactive source for emitting X-rays to a human body; the second detector is arranged opposite to the second radioactive source and is used for receiving X-rays passing through a human body;
the reconstruction method comprises the following steps:
setting a biplane X-ray scanning mode and a geometric environment, determining the relative position relationship between a radiation source and a detector on the first X-ray machine and the second X-ray machine, performing long-stroke scanning, and obtaining images of an object to be reconstructed under different relative position relationships to obtain an original image;
Preprocessing the original image, obtaining a gray value of the original image, carrying out logarithmic transformation to convert the gray value into a corresponding X-ray absorptivity, and simultaneously, determining a tomographic reconstruction range according to a long-stroke scanning geometric environment;
selecting a reconstruction width, traversing all reconstruction range points by using the reconstruction width, and completing the reconstruction of all coronal and sagittal plane tomographic images by filtering back projection; and
And acquiring an overlapped part of the tomographic images reconstructed in the vertical direction, and splicing the overlapped part by using a weighted overlap method to form a long-travel image.
Preferably, the setting the biplane X-ray scanning mode and the geometric environment, determining the relative positional relationship between the radiation source and the detector on the first X-ray machine and the second X-ray machine, and performing long-stroke scanning includes:
setting a first interval between the first flat panel detector and the first radiation source, setting a second interval between the second flat panel detector and the second radiation source, wherein the first interval and the second interval are the same, and the first interval and the second interval are kept unchanged in the scanning process;
setting a scanning range, wherein when an object to be imaged is positioned in a beam public area formed by the first radiation source and the second radiation source, the first flat panel detector and the first radiation source and the second flat panel detector and the second radiation source synchronously run along a vertical direction;
From an initial height h 1 Starting, the first flat panel detector and the first radiation source and the second flat panel detector and the second radiation source synchronously move along the vertical direction at the same linear speed, and the interval delta h finishes one X-ray exposure until the whole scanning range is covered, and the first X-ray machine and the second X-ray machine reach the end height h N The whole process is completed for exposure for N times; and
Acquiring a specific height h k And the lower biplane X-ray image respectively takes the image space of the first X-ray machine and the image space of the second X-ray machine as a reference, and a rigid body orthogonal space coordinate system is established according to the relative position relation of the first X-ray machine and the second X-ray machine in the initial position.
Preferably, obtaining the original image after obtaining the image of the object to be reconstructed under different relative positional relationships includes:
for a certain height h k Then, a rigid body orthogonal space coordinate system (R) is established by taking the image space of the first X-ray machine as a reference 1 ,V 1,k ) The method comprises the following steps:
wherein R is 1 For a 3X 3 size matrix, each column representing a coordinate axis unit vector of the first X-ray machine image coordinate system; v (V) 1，k A column vector of 3X 1 size representing the first X-ray machine image coordinatesTying an origin position; h is a k Is scalar and represents the current vertical height of the first detector center and the first radioactive source;
For a certain height h k Then, a rigid body orthogonal space coordinate system (R) is established by taking the image space of the second X-ray machine as a reference 2 ，V 2，k ) Wherein R is 2，k For a 3X 3 size matrix, each column representing a coordinate axis unit vector of the second X-ray machine image coordinate system; v (V) 2，k A column vector with the size of 3 multiplied by 1 represents the origin position of the coordinate system of the second X-ray machine image;
rigid body orthogonal space coordinate system (R 2 ，V 2，k ) The relative position relation between the first X-ray machine and the second X-ray machine under the initial position is determined:
R 2,k ＝R 2 ，V 2,k ＝V 21 +V 1,k 。
wherein V is 21 The relative position of the second X-ray machine image space relative to the first X-ray machine image space at the initial height. Preferably, the acquiring the gray value of the original image performs logarithmic transformation to convert the gray value into the corresponding X-ray absorption rate, and logarithmic transformation is performed:
wherein I is the gray value of an original X-ray image obtained by shooting by the first X-ray machine or the second X-ray machine at any height, and represents the residual ray intensity after the X-ray penetrates through tissues; i 0 The intensity of X-rays emitted by the radioactive source; mu (mu) n D for absorption rate of photographed object tissue n For the tissue thickness of the object, C is a constant after logarithmic transformation.
Preferably, the method comprises determining a tomographic reconstruction range based on a long-stroke scan geometry,
The chromatographic heavy range includes a biplane chromatographic zone and a non-biplane chromatographic zone,
the double-plane chromatographic area is a common area where the conical beam X-rays emitted by the first X-ray machine and the second X-ray machine intersect, and double-plane chromatographic synthetic reconstruction can be performed;
only cone beam X-rays emitted by the first X-ray machine or the second X-ray machine pass through the non-biplane chromatographic area, and only single-plane chromatographic synthetic reconstruction can be carried out.
Preferably, the method comprises determining a tomographic reconstruction range based on a long-stroke scan geometry,
for any point P within the reconstruction range, a height H is determined 1 ，H 2 ，…，H n X-ray transmission points P emitted by the first X-ray machine and the second X-ray machine are recorded at different positions of the image, wherein H 1 ，H 2 ，…，H n The method meets the following conditions:
H 1 ,H 2 ,…,H n ∈{h k |k＝1,2,...,N}，
according to the geometric environment (R) photographed by the first X-ray machine and the second X-ray machine of the rigid body orthogonal space coordinate system 1 ，V 1，k )，(R 2 ，V 2，k ) The spacing from the flat panel detector and the radiation source is set to SID,
determining a first projection point P of the point P on said first detector plane 1 A second projection point P on said second detector plane with point P 2 The first projection point P 1 And the second projection point P 2 The local coordinates relative to the first detector and the second detector plane satisfy:
Where T is the operation on the matrix in linear algebra, representing the transpose, V 1 Namely V 1，k ，V 2 Namely V 2，k 。
Preferably, the selecting a reconstruction width, traversing all reconstruction range points with the reconstruction width, and completing the reconstruction of all coronal and sagittal tomographic images through filtering back projection includes:
projecting a point set with any height range in a reconstruction range being the selected reconstruction width to the first detector plane by the first X-ray machine based on a geometric environment to form a first rearranged image;
projecting the point set with any height range in the reconstruction range being the selected reconstruction width to the second detector plane by the second X-ray machine based on the geometric environment to form a second rearrangement image;
performing one-dimensional Fourier transform on the first rearranged image and the second rearranged image respectively according to columns to obtain a primary transformed image, wherein the primary transformed image comprises an image of the first rearranged image subjected to primary Fourier transform and an image of the second rearranged image subjected to primary Fourier transform;
setting a slope filter according to the selected reconstruction width, carrying out one-dimensional Fourier transform on the slope filter, superposing a window function, filtering each column of the primary transformed image, and carrying out one-dimensional inverse Fourier transform to obtain a secondary transformed image, wherein the secondary transformed image comprises an image of the first rearranged image subjected to secondary Fourier transform and an image of the second rearranged image subjected to secondary Fourier transform;
The secondary transformation image is back projected to the space where the point set is located according to the geometric projection environment, and a first filtering back projection image and a second filtering back projection image are respectively obtained;
and carrying out weighted superposition on the first filtered back projection image and the second filtered back projection image to obtain a finally reconstructed chromatographic strip image.
Preferably, the acquiring the overlapping portion of the tomographic image reconstructed in the vertical direction, and the stitching the overlapping portion using the weighted overlap method to form the long-run image includes:
for height h i Tomographic image ff of the site width w i Adjacent height h of i-1 And h i+1 There is a tomographic image ff of wide w i-1 And ff is equal to i+1 ，ff i And ff is equal to i-1 ，ff i And ff is equal to i+1 The overlap height of (2) is d, a weighted overlap-add function W (n) is used:
wherein f (n) is any strictly monotonically increasing function defined as a value range of 0,1 at 0,1 and a derivative of 0 at n=0, 1;
for ff i-1 ，ff i And ff is equal to i+1 Then there are:
ff(n)＝W(n-d)ff i-1 (n)+W(n)ff i (n)+W(n+d)ff i+1 (n)，
wherein ff is i-1 Is at height h i-1 Lower reconstructed image, ff i+1 Is at height h i+1 A reconstructed image below.
The invention also provides a chromatography reconstruction device based on the biplane long-stroke scanning, which is applied to a biplane X-ray system, wherein the biplane X-ray system comprises a first X-ray machine and a second X-ray machine,
The first X-ray machine comprises a first radioactive source for emitting X-rays to a human body; the first detector is arranged opposite to the first radiation source and is used for receiving X-rays passing through a human body;
the second X-ray machine comprises a second radioactive source for emitting X-rays to a human body; the second detector is arranged opposite to the second radioactive source and is used for receiving X-rays passing through a human body;
the reconstruction device includes:
the scanning mode and geometric environment setting module is used for setting a biplane X-ray scanning mode and geometric environment, determining the relative position relationship between the radiation source and the detector on the first X-ray machine and the second X-ray machine, then carrying out long-stroke scanning, and obtaining images of the object to be reconstructed under different relative position relationships to obtain an original image;
the image preprocessing module is used for preprocessing the original image, acquiring a gray value of the original image, carrying out logarithmic transformation to convert the gray value into a corresponding X-ray absorptivity, and simultaneously determining a tomographic reconstruction range according to a long-stroke scanning geometric environment;
the reconstructed tomographic image module is used for selecting a reconstruction width, traversing all reconstruction range points with the reconstruction width, and completing the reconstruction of all coronal and sagittal tomographic images through filtering back projection;
And the long-travel image stitching module is used for acquiring overlapped parts of the tomographic images reconstructed in the vertical direction, and stitching the overlapped parts by using a weighted superposition method to form a long-travel image.
The invention also provides a computer readable medium loaded with a computer program for implementing the tomographic reconstruction method based on the biplane long-stroke scanning according to the embodiment of the invention.
Aiming at the prior art, the invention has the following beneficial effects:
the tomographic reconstruction method based on the biplane long-stroke scanning, provided by the invention, combines a biplane X-ray technology and a tomographic synthesis reconstruction technology based on single plane long-stroke scanning to realize a tomographic reconstruction algorithm based on the biplane long-stroke scanning, and simultaneously realizes the reconstruction of the coronal plane and sagittal plane weight-bearing position tomographic images, expands the tomographic image reconstruction range and improves the interlayer resolution of the images;
the invention adopts a vertical scanning mode, can scan in a long range from top to bottom, scan out images of the whole body of a patient containing the loading position of the coronal plane and the sagittal plane, form long-stroke images, and ensure that the reconstruction space area is large when scanning in a long range from top to bottom;
the chromatographic synthesis reconstruction method adopted by the invention not only can be suitable for the supine position or the lateral position of a photographed person, but also can carry out the imaging of the loading position, has high clinical value on bones and joints bearing the loading function in daily activities, such as the spine, the lower limbs, and the like, and important orthopedic parameters obtained by measuring the supine position and the loading position, such as the scoliosis degree, the alignment of lower limb force lines, the hip joint coverage rate, and the like.
Drawings
FIG. 1 is a schematic diagram of a planar reverse scanning mode of a flat panel detector-radioactive source in the background art of the invention, wherein A is the reverse linear motion of the flat panel detector-radioactive source; b is the reverse circular arc motion of the flat panel detector-radioactive source; c is the linear-radial source circular arc reverse motion of the flat panel detector; d is the stationary motion of the flat panel detector and the circular arc motion of the radioactive source;
FIG. 2 is a schematic view of parallel circumferential inverse scanning of a flat panel detector-radiation source in accordance with the background of the invention;
FIG. 3 is a schematic illustration of a flat panel detector-radiation source co-planar co-scanning in accordance with the background of the invention;
FIG. 4 is a schematic diagram of steps of a tomographic reconstruction method based on biplane long-stroke scanning in an embodiment of the present invention;
FIG. 5 is a schematic diagram of a biplane long-stroke scanning structure and a coordinate system according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a tomographic reconstruction range and a projection relationship based on a biplane long-stroke scan in an embodiment of the present invention;
FIG. 7 is a diagram illustrating a biplane data reordering and spatial geometry according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The invention provides a chromatography reconstruction method based on double-plane long-stroke scanning, which is applied to a double-plane X-ray system, wherein the double-plane X-ray system comprises a first X-ray machine and a second X-ray machine. The first X-ray machine and the second X-ray machine are arranged at a certain angle. The first X-ray machine comprises a first radiation source and a first detector, wherein the first radiation source is used for emitting X-rays to a human body; the first detector is arranged opposite to the first radioactive source and is used for receiving X-rays passing through a human body.
The second X-ray machine comprises a second radiation source and a second detector, and the second radiation source is used for emitting X-rays to a human body; the second detector is arranged opposite to the second radioactive source and is used for receiving X-rays passing through a human body. The biplane X-ray machine system used in the present embodiment includes a first X-ray machine (hereinafter referred to as F1) and a second X-ray machine (hereinafter referred to as F2), and a frame connected to a hardware device, a control motor, and the like. When reconstructing in a computer system, the first X-ray machine, the second X-ray machine, the machine frame and other hardware devices are mainly considered to ensure the geometric environment required by scanning and reconstruction. The first detector and the second detector employed in this embodiment may be flat panel detectors.
As shown in fig. 4, the reconstruction method thereof includes the steps of:
s1: setting a biplane X-ray scanning mode and a geometric environment, determining the relative position relationship between a radiation source and a detector on the first X-ray machine and the second X-ray machine, performing long-stroke scanning, and obtaining images of an object to be reconstructed under different relative position relationships (namely different height positions) to obtain an original image; it can be understood by those skilled in the art that in the present embodiment, the relative position relationship between the first and second X-ray machines is determined before the long-stroke stitching, and then the long-stroke scanning is performed, where the method for determining the relative position relationship between the first and second X-ray machines is disclosed and will not be described herein.
S2: preprocessing the original image, obtaining a gray value of the original image, carrying out logarithmic transformation to convert the gray value into a corresponding X-ray absorptivity, and simultaneously, determining a tomographic reconstruction range according to a long-stroke scanning geometric environment;
s3: selecting a reconstruction width, traversing all reconstruction range points by using the reconstruction width, and completing the reconstruction of all coronal and sagittal plane tomographic images by filtering back projection; the range of tomographic reconstruction includes depth, i.e., z-axis position and width, i.e., y-axis upper and lower boundary positions, is a narrow rectangle,
S4: and acquiring an overlapped part of the tomographic images reconstructed in the vertical direction, and splicing the overlapped part by using a weighted overlap method to form a long-travel image. The long-range image formed by the embodiment refers to a whole body scanning output image of a patient including coronary and sagittal loading positions, and is scanned from top to bottom in a long range.
By adopting the tomographic reconstruction algorithm based on the biplane long-stroke scanning, the tomographic reconstruction of the coronal and sagittal loading position can be realized at the same time, the tomographic reconstruction range is enlarged, and the interlayer resolution of the image is improved.
Specifically, the setting of the biplane X-ray scanning mode and the geometric environment in step S1 includes:
setting a first interval between the first flat panel detector and the first radiation source, setting a second interval between the second flat panel detector and the second radiation source, wherein the first interval and the second interval are the same, and the first interval and the second interval are kept unchanged in the scanning process; for F1 and F2, the spacing between the flat panel detector and the radiation source is set to SID and remains unchanged during the scan.
Setting a scanning range, wherein when an object to be imaged is positioned in a beam public area formed by the first radiation source and the second radiation source, the first flat panel detector and the first radiation source and the second flat panel detector synchronously run with the second radiation source and move along a track in a vertical direction; the object to be imaged stands in the common area of the cone beams formed by the F1 and F2 radioactive sources, and as shown in fig. 5, the y1 axis and the y2 axis are in the same direction, and are the directions of the movement tracks of the F1 and the F2.
After setting the vertical scanning range, the first flat panel detector and the first radiation source of F1, the second flat panel detector and the second radiation source of F2 are all from the initial height h 1 At first, the X-ray exposure is completed at intervals delta h along the y1 axis at the same linear speed in the same direction synchronously to obtain a specific height h k And the lower biplane X-ray image respectively takes the image space of the first X-ray machine F1 and the image space of the second X-ray machine F2 as a reference, and a rigid body orthogonal space coordinate system is established according to the relative position relation of the first X-ray machine F1 and the second X-ray machine F2 in the initial position.
The first X-ray machine F1 and the second X-ray machine F2 are keptThe first X-ray machine F1 and the second X-ray machine F2 reach a termination height h N The whole process is completed for exposure N times.
Specifically, obtaining the original image after obtaining the image of the object to be reconstructed under different relative positional relationships includes:
for a certain height h k A rigid body orthogonal space coordinate system (R) is established based on the image space of the first X-ray machine F1 1 ,V 1,k ) The method comprises the following steps:
wherein R is 1 For a 3X 3 size matrix, each column represents a coordinate axis unit vector of the first X-ray machine F1 image coordinate system; v (V) 1，k A column vector with the size of 3 multiplied by 1 represents the origin position of the first X-ray machine F1 image coordinate system; h is a k Is scalar and represents the vertical height of the first detector center and the first radiation source described in the current F1.
For a certain height h k Then, a rigid body orthogonal space coordinate system (R) is established by taking the image space of the second X-ray machine F2 as a reference 2 ，V 2，k ) Wherein R is 2，k For a 3X 3 size matrix, each column represents a coordinate axis unit vector of the second X-ray machine F2 image coordinate system; v (V) 2，k And the column vector is 3 multiplied by 1, and represents the origin position of the coordinate system of the image of the second X-ray machine F2.
Since the relative positional relationship of the first detector of F1 and the first radiation source, the second detector of F2 and the second radiation source does not change during long-stroke scanning, a rigid body orthogonal space coordinate system (R 2 ，V 2，k ) The relative positional relationship between the first X-ray machine F1 and the second X-ray machine F2 at the initial position is determined:
R 2,k ＝R 2 ，V 2,k ＝V 21 +V 1,k 。
v in the formula 21 For the second X-ray image at the initial heightThe image space is relative to the first X-ray machine image space.
Specifically, in the step S2, the gray value of the original image is obtained, logarithmic transformation is performed to convert the gray value into the corresponding X-ray absorptivity, and because the data obtained by the flat panel detector is the residual radiation intensity after the X-ray penetrates through the object to be photographed, the obtained image is preprocessed to optimize the subsequent linear operation, and logarithmic transformation is performed:
Wherein I is the gray value of an original X-ray image obtained by shooting by the first X-ray machine or the second X-ray machine at any height, and represents the residual ray intensity after the X-ray penetrates through tissues; i 0 The intensity of X-rays emitted by the radioactive source; mu (mu) n D for absorption rate of photographed object tissue n For the tissue thickness of the object, C is a constant after logarithmic transformation.
Specifically, in the step S2, according to the long-stroke scanning geometry environment, a tomographic reconstruction range is determined, where the tomographic reconstruction range includes a biplane tomographic area and a non-biplane tomographic area, and the biplane tomographic area is a common area where cone-beam X-rays emitted by the first X-ray machine F1 and the second X-ray machine F2 intersect, and can perform a biplane tomographic synthetic reconstruction. Only cone beam X-rays emitted by the first X-ray machine or the second X-ray machine pass through the non-biplane chromatographic area, and only single-plane chromatographic synthetic reconstruction can be carried out. Those skilled in the art will appreciate that for the F1 and F2 long-stroke scan geometries, the tomographic reconstruction range can be determined as shown in fig. 6. Gray areas represent common areas where the cone beam X-rays emitted by F1 and F2 intersect, and biplane tomosynthesis reconstruction can be performed; the non-gray areas indicate that only cone beam X-rays from either F1 or F2 pass through and only single plane tomosynthesis reconstruction is possible.
Specifically, for any point P within the reconstruction range, a height H is determined 1 ，H 2 ，…，H n The first X-ray machine and the second X-ray machine are arranged belowX-ray transmission point P recorded at different positions of image, wherein H 1 ，H 2 ，…，H n The method meets the following conditions:
H 1 ,H 2 ,…,H n ∈{h k |k＝1,2,...,N}，
according to the geometrical environment (R) of the first X-ray machine and the second X-ray machine 1 ，V 1，k )，(R 2 ，V 2，k ) The distance between the flat panel detector and the radioactive source is set to be SID, and a first projection point P of the point P on the first detector plane is determined 1 A second projection point P on said second detector plane with point P 2 As shown in fig. 6. First projection point P 1 And a second projection point P 2 The local coordinates relative to the first detector and the second detector plane satisfy:
where T is the operation on the matrix in linear algebra, representing the transpose, V 1 Namely V 1，k ，V 2 Namely V 2，k 。
F1 first flat panel detector and first radiation source at different heights H 1 ，H 2 ，…，H n Projection P of a specific spatial point P 1 The second flat panel detector and the second radiation source stored in different rows and columns F2 at different heights H 1 ，H 2 ，…，H n Projection P of a specific spatial point P 2 Stored in different rows and columns.
As shown in fig. 7, grid points in fig. 7A represent pixel center points of the preprocessed image, and black dots represent projection points P 1 And P 2 Local coordinate position relative to the image. Due to the projection point P 1 And P 2 Does not necessarily coincide with the pixel center at the grid point, so two-dimensional linear interpolation is used to obtain the position of the projection pointData.
In order to expand the reconstruction range of the tomographic image, realize the reconstruction of the coronal and sagittal load-bearing position tomographic image, and improve the resolution between image layers, the step S3 selects the reconstruction width to traverse all the reconstruction range points with the reconstruction width, and the completion of the reconstruction of all the coronal and sagittal tomographic images by the filtered back projection comprises:
projecting the first X-ray machine F1 to the first detector plane based on the geometric environment to form a first rearranged image F, wherein the arbitrary height range in the reconstruction range is a point set of the selected reconstruction width w 1 ；
Projecting the point set with any height range within the reconstruction range being the selected reconstruction width w of the second X-ray machine F2 on the basis of the geometric environment to the second detector plane to form a second rearrangement image F 2 ；
For the first rearranged image f 1 And the second rearrangement image f 2 Performing one-dimensional Fourier transform on each column to obtain primary transformed images, wherein the primary transformed images comprise the first rearranged image f 1 Image FF after one fourier change 1 And an image FF of the second rearranged image subjected to a one-time Fourier transform 2 ；
Selecting reconstruction width w in vertical direction, and selecting point set P with arbitrary height range w in reconstruction range by F1 geometric environment Pset Projecting onto a first flat panel detector plane to form a vertical stripe image f 1 The F2 geometric environment reconstructs a point set P with any height range w in the range Pset Projecting onto a second flat detector plane to form a vertical stripe image f 2 Image f 1 ，f 2 And a filter h [ n ]]From physical space to frequency space, satisfies:
wherein f 1,Hn At a height H n Lower F1 Point set P Pset Is a w x 1 size vector; f (f) 2,Hn At a height H n Lower F2 Point set P Pset Is a w x 1 size vector; f (f) 1 And f 2 Is a matrix of size w×n. For f 1 And f 2 Performing one-dimensional Fourier transform to obtain FF 1 And FF (FF) 2 。
In order to filter noise, an enhancement effect is achieved on the image edge, a slope filter is arranged according to the selected reconstruction width w, one-dimensional Fourier transform is conducted on the slope filter, a window function is overlapped, filtering is conducted on each column of the primary transformed image, one-dimensional inverse Fourier transform is conducted on the primary transformed image, and a secondary transformed image is obtained, wherein the secondary transformed image comprises an image, subjected to secondary Fourier transform, of the first rearranged image and an image, subjected to secondary Fourier transform, of the second rearranged image. And back-projecting the secondary transformation image to a space where the point set is located according to the geometric projection environment to respectively obtain a first filtered back-projection image and a second filtered back-projection image.
Setting a ramp filter h [ n ] according to the selected reconstruction width w:
where mod (n, 2) is a remainder of the remainder of integer division of n by 2, where n is an odd number, 1, and 0.
Carrying out one-dimensional Fourier transform on the slope filter H [ n ] to obtain H [ v ] and overlapping the Shepp-Logan window to obtain:
where a (v) is a window function in one-dimensional fourier space. Using H filter Filtering each column of FF1 and FF2, performing one-dimensional Fourier inverse transformation, and back-projecting to point set P according to geometric projection environment Pset In the space of respectivelyTo the first filtered backprojected image ff 1 And a second filtered backprojected image ff 2 。
For the first filtered back projection image ff obtained for the biplane 1 And the second filtered back-projected image ff 2 And carrying out weighted superposition to obtain a finally reconstructed chromatographic strip image:
ff＝ωff 1 +(1-ω)ff 2 ,ω∈(0,1)
and traversing all reconstruction range points by using the reconstruction width w to finish the reconstruction of all coronal and sagittal tomographic images.
Specifically, the step S4 of acquiring the overlapping portion of the tomographic image reconstructed in the vertical direction, and the step of stitching the overlapping portion to form the long-stroke image by using a weighted overlap-add method includes:
for height h i Tomographic image ff of the site width w i Adjacent height h of i-1 And h i+1 There is a tomographic image ff of wide w i-1 And ff is equal to i+1 ，ff i And ff is equal to i-1 ，ff i And ff is equal to i+1 The overlap height of (2) is d, a weighted overlap-add function W (n) is used:
wherein f (n) is any strictly monotonically increasing function defined as a value range of 0,1 at 0,1 and a derivative of 0 at n=0, 1;
for ff i-1 ，ff i And ff is equal to i+1 Then there are:
ff(n)＝W(n-d)ff i-1 (n)+W(n)ff i (n)+W(n+d)ff i+1 (n)，
wherein ff is i-1 Is at height h i-1 Lower reconstructed image, ff i+1 Is at height h i+1 A reconstructed image below.
The chromatographic reconstruction method based on the biplane long-stroke scanning provided by the invention has the scanning range of 2m in the vertical direction, and the total time of the long-stroke scanning is less than 15s; the resolution in the reconstructed tomographic image layer reaches 0.2mm, the resolution between layers reaches 1mm, the reconstruction range of the tomographic image is enlarged, and the resolution between layers of the image is improved.
Example two
The invention also provides a chromatography reconstruction device based on the biplane long-stroke scanning, which is applied to a biplane X-ray system, wherein the biplane X-ray system comprises a first X-ray machine and a second X-ray machine.
The first X-ray machine comprises a first radioactive source for emitting X-rays to a human body; the first detector is arranged opposite to the first radioactive source and is used for receiving X-rays passing through a human body.
The second X-ray machine comprises a second radioactive source for emitting X-rays to a human body; and the second detector is arranged opposite to the second radioactive source and is used for receiving the X-rays passing through the human body.
The reconstruction device comprises a scanning mode and geometric environment setting module, an image preprocessing module, a reconstructed tomographic image module and a long-stroke image splicing module. And the scanning mode and geometric environment setting module is used for setting a biplane X-ray scanning mode and geometric environment, determining the relative position relationship between the radiation source and the detector on the first X-ray machine and the second X-ray machine, then carrying out long-stroke scanning, and obtaining the images of the object to be reconstructed under different relative position relationships to obtain the original images.
The image preprocessing module is used for preprocessing the original image, acquiring the gray value of the original image, carrying out logarithmic transformation to convert the gray value into corresponding X-ray absorptivity, and simultaneously determining the tomographic reconstruction range according to the long-stroke scanning geometric environment.
And the reconstructed tomographic image module is used for selecting a reconstruction width, traversing all reconstruction range points with the reconstruction width, and completing the reconstruction of all coronal and sagittal tomographic images through filtering back projection.
And the long-travel image stitching module is used for acquiring overlapped parts of the tomographic images reconstructed in the vertical direction, and stitching the overlapped parts by using a weighted superposition method to form a long-travel image.
The tomographic reconstruction algorithm based on the biplane long-stroke scanning can simultaneously reconstruct a coronal plane and a sagittal plane loading position tomographic image, expand the tomographic image reconstruction range and improve the interlayer resolution of the image.
The specific contents and implementation methods of the scan mode and geometry setting module, the image preprocessing module, the reconstructed tomographic image module, and the long-travel image stitching module are as described in the first embodiment, and are not described herein.
Finally, in order to apply the tomographic reconstruction method based on the biplane long-stroke scanning to an image acquisition generation system, an image acquisition generation device or an image acquisition generation device with related hardware conditions, the application further provides a computer readable storage medium, wherein the computer readable storage medium is loaded with a computer program, and the computer program realizes the functions of the corresponding method embodiments when being executed by a computer.
Also, the present application also protects a computer readable storage medium loaded with a computer program for implementing the tomographic reconstruction method based on a biplane long-stroke scan.
In the above embodiments, the implementation may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program. The computer program comprises one or more computer programs. When the computer program is loaded and executed on a computer, the flow or functions described in accordance with the embodiments of the present disclosure are produced in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer program may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer program may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by a wired (e.g., coaxial cable, fiber optic, DDL (digital subscriber line)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that contains an integration of one or more available media. The usable medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a Digital Video Disc (DVD)), or a semiconductor medium (e.g., a solid state disk (DDD)), etc.
It should be noted that in the above-described embodiments, the terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," and "having" are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein should not be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically indicated to be performed in the order of the steps set forth. It should also be appreciated that additional or alternative steps may be employed.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A chromatography reconstruction method based on biplane long-stroke scanning is characterized by being applied to a biplane X-ray system, wherein the biplane X-ray system comprises a first X-ray machine and a second X-ray machine,
the first X-ray machine comprises a first radioactive source for emitting X-rays to a human body; the first detector is arranged opposite to the first radiation source and is used for receiving X-rays passing through a human body;
the second X-ray machine comprises a second radioactive source for emitting X-rays to a human body; the second detector is arranged opposite to the second radioactive source and is used for receiving X-rays passing through a human body;
the reconstruction method comprises the following steps:
setting a biplane X-ray scanning mode and a geometric environment, determining the relative position relationship between a radiation source and a detector on the first X-ray machine and the second X-ray machine, performing long-stroke scanning, and obtaining images of an object to be reconstructed under different relative position relationships to obtain an original image;
preprocessing the original image, obtaining a gray value of the original image, carrying out logarithmic transformation to convert the gray value into a corresponding X-ray absorptivity, and simultaneously, determining a tomographic reconstruction range according to a long-stroke scanning geometric environment;
Selecting a reconstruction width, traversing all reconstruction range points by using the reconstruction width, and completing the reconstruction of all coronal and sagittal plane tomographic images by filtering back projection; and
And acquiring an overlapped part of the tomographic images reconstructed in the vertical direction, and splicing the overlapped part by using a weighted overlap method to form a long-travel image.
2. The tomographic reconstruction method according to claim 1, wherein the setting of the biplane X-ray scanning mode and the geometric environment, determining the relative positional relationship between the radiation source and the detector on the first X-ray machine and the second X-ray machine, and performing the long-stroke scanning comprises:
setting a first interval between the first flat panel detector and the first radiation source, setting a second interval between the second flat panel detector and the second radiation source, wherein the first interval and the second interval are the same, and the first interval and the second interval are kept unchanged in the scanning process;
setting a scanning range, wherein when an object to be imaged is positioned in a beam public area formed by the first radiation source and the second radiation source, the first flat panel detector and the first radiation source and the second flat panel detector and the second radiation source synchronously run along a vertical direction;
From an initial height h 1 Starting, the first flat panel detector and the first radiation source and the second flat panel detector and the second radiation source synchronously move along the vertical direction at the same linear speed, and the interval delta h finishes one X-ray exposure until the whole scanning range is covered, and the first X-ray machine and the second X-ray machine reach the end height h N The whole process is completed for exposure for N times; and
Acquiring a specific height h k And the lower biplane X-ray image respectively takes the image space of the first X-ray machine and the image space of the second X-ray machine as a reference, and a rigid body orthogonal space coordinate system is established according to the relative position relation of the first X-ray machine and the second X-ray machine in the initial position.
3. The tomographic reconstruction method based on the biplane long-stroke scan as claimed in claim 2, wherein obtaining the original image after obtaining the image of the object to be reconstructed under different relative positional relationships comprises:
for a certain height h k Then, a rigid body orthogonal space coordinate system (R) is established by taking the image space of the first X-ray machine as a reference 1 ,V 1,k ) The method comprises the following steps:
wherein R is 1 For a 3X 3 size matrix, each column representing a coordinate axis unit vector of the first X-ray machine image coordinate system; v (V) 1，k A column vector with the size of 3 multiplied by 1 represents the origin position of the coordinate system of the first X-ray machine image; h is a k Is scalar and represents the current vertical height of the first detector center and the first radioactive source;
for a certain height h k Then, a rigid body orthogonal space coordinate system (R) is established by taking the image space of the second X-ray machine as a reference 2 ，V 2，k ) Wherein R is 2，k For a 3X 3 size matrix, each column representing a coordinate axis unit vector of the second X-ray machine image coordinate system; v (V) 2，k A column vector with the size of 3 multiplied by 1 represents the origin position of the coordinate system of the second X-ray machine image;
rigid body orthogonal space coordinate system (R 2 ，V 2，k ) The relative position relation between the first X-ray machine and the second X-ray machine under the initial position is determined:
R 2,k ＝R 2 ，V 2,k ＝V 21 +V 1,k ，
wherein V is 21 The relative position of the second X-ray machine image space relative to the first X-ray machine image space at the initial height.
4. The tomographic reconstruction method based on biplane long-stroke scanning according to claim 1, wherein the obtaining the gray value of the original image, performing logarithmic transformation to convert the gray value into the corresponding X-ray absorptivity, and the logarithmic transformation formula is:
wherein I is the gray value of an original X-ray image obtained by shooting by the first X-ray machine or the second X-ray machine at any height, and represents the residual ray intensity after the X-ray penetrates through tissues; i 0 The intensity of X-rays emitted by the radioactive source; mu (mu) n D for absorption rate of photographed object tissue n For the tissue thickness of the object, C is a constant after logarithmic transformation.
5. A tomographic reconstruction method as in claim 1 wherein said determining a tomographic reconstruction range based on a long-stroke scan geometry,
the chromatographic heavy range comprises a biplane chromatographic area and a non-biplane chromatographic area;
the double-plane chromatographic area is a common area where the conical beam X-rays emitted by the first X-ray machine and the second X-ray machine intersect, and double-plane chromatographic synthetic reconstruction can be performed;
only cone beam X-rays emitted by the first X-ray machine or the second X-ray machine pass through the non-biplane chromatographic area, and only single-plane chromatographic synthetic reconstruction can be carried out.
6. A tomographic reconstruction method based on a bi-planar long-stroke scan as in claim 3 wherein said determining a tomographic reconstruction range based on a long-stroke scan geometry,
for any point P within the reconstruction range, a height H is determined 1 ，H 2 ，…，H n X-ray transmission points P emitted by the first X-ray machine and the second X-ray machine are recorded at different positions of the image, wherein H 1 ，H 2 ，…，H n The method meets the following conditions:
H 1 ,H 2 ,…,H n ∈{h k |k＝1,2,...,N}，
according to the rigid body orthogonal space coordinate system (R 1 ，V 1，k )，(R 2 ，V 2，k ) The spacing from the flat panel detector and the radiation source is set to SID,
determining a first projection point P of the point P on said first detector plane 1 A second projection point P on said second detector plane with point P 2 The first projection point P 1 And the second projection point P 2 The local coordinates relative to the first detector and the second detector plane satisfy:
where T is the operation on the matrix in linear algebra, representing the transpose, V 1 Namely V 1，k ，V 2 Namely V 2，k 。
7. A tomographic reconstruction method based on a bi-planar long-pass scan as in claim 1 wherein said selecting a reconstruction width to traverse all reconstruction range points with the reconstruction width, and wherein performing a filtered back projection to reconstruct all coronal and sagittal tomographic images comprises:
projecting a point set with any height range in a reconstruction range being the selected reconstruction width to the first detector plane by the first X-ray machine based on a geometric environment to form a first rearranged image;
projecting the point set with any height range in the reconstruction range being the selected reconstruction width to the second detector plane by the second X-ray machine based on the geometric environment to form a second rearrangement image;
Performing one-dimensional Fourier transform on the first rearranged image and the second rearranged image respectively according to columns to obtain a primary transformed image, wherein the primary transformed image comprises an image of the first rearranged image subjected to primary Fourier transform and an image of the second rearranged image subjected to primary Fourier transform;
setting a slope filter according to the selected reconstruction width, carrying out one-dimensional Fourier transform on the slope filter, superposing a window function, filtering each column of the primary transformed image, and carrying out one-dimensional inverse Fourier transform to obtain a secondary transformed image, wherein the secondary transformed image comprises an image of the first rearranged image subjected to secondary Fourier transform and an image of the second rearranged image subjected to secondary Fourier transform;
the secondary transformation image is back projected to the space where the point set is located according to the geometric projection environment, and a first filtering back projection image and a second filtering back projection image are respectively obtained;
and carrying out weighted superposition on the first filtered back projection image and the second filtered back projection image to obtain a finally reconstructed chromatographic strip image.
8. The tomographic reconstruction method based on the biplane long-stroke scan as claimed in claim 1, wherein the acquiring the overlapping portion of the tomographic image reconstructed in the vertical direction, and the stitching the overlapping portion using the weighted overlap method to form the long-stroke image comprises:
For height h i Tomographic image ff reconstructed at a width w i Adjacent height h of i-1 And h i+1 There is a tomographic image ff of wide w i-1 And ff is equal to i+1 ，ff i And ff is equal to i-1 ，ff i And ff is equal to i+1 The overlap height of (2) is d, a weighted overlap-add function W (n) is used:
wherein f (n) is any strictly monotonically increasing function defined as a value range of 0,1 at 0,1 and a derivative of 0 at n=0, 1;
for ff i-1 ，ff i And ff is equal to i+1 Then there are:
ff(n)＝W(n-d)ff i-1 (n)+W(n)ff i (n)+W(n+d)ff i+1 (n)，
wherein ff is i-1 Is at height h i-1 Lower reconstructed image, ff i+1 Is at height h i+1 A reconstructed image below.
9. A chromatography reconstruction device based on double-plane long-stroke scanning is characterized by being applied to a double-plane X-ray system, wherein the double-plane X-ray system comprises a first X-ray machine and a second X-ray machine,
the first X-ray machine comprises a first radioactive source for emitting X-rays to a human body; the first detector is arranged opposite to the first radiation source and is used for receiving X-rays passing through a human body;
the second X-ray machine comprises a second radioactive source for emitting X-rays to a human body; the second detector is arranged opposite to the second radioactive source and is used for receiving X-rays passing through a human body;
the reconstruction device includes:
the scanning mode and geometric environment setting module is used for setting a biplane X-ray scanning mode and geometric environment, determining the relative position relationship between the radiation source and the detector on the first X-ray machine and the second X-ray machine, then carrying out long-stroke scanning, and obtaining images of the object to be reconstructed under different relative position relationships to obtain an original image;
The image preprocessing module is used for preprocessing the original image, acquiring a gray value of the original image, carrying out logarithmic transformation to convert the gray value into a corresponding X-ray absorptivity, and simultaneously determining a tomographic reconstruction range according to a long-stroke scanning geometric environment;
the reconstructed tomographic image module is used for selecting a reconstruction width, traversing all reconstruction range points with the reconstruction width, and completing the reconstruction of all coronal and sagittal tomographic images through filtering back projection;
and the long-travel image stitching module is used for acquiring overlapped parts of the tomographic images reconstructed in the vertical direction, and stitching the overlapped parts by using a weighted superposition method to form a long-travel image.
10. A computer readable medium, characterized in that the readable storage medium is loaded with a computer program for implementing a tomographic reconstruction method based on a biplane long-stroke scan according to any one of claims 1 to 8.
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