CN109754446B - Method and system for estimating width of splicing seam between detector modules - Google Patents
Method and system for estimating width of splicing seam between detector modules Download PDFInfo
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Abstract
The invention discloses a method and a system for estimating the width of a splicing seam between detector modules. The method comprises the following steps: vertically fixing a thin metal wire at the boundary close to the rotating table, and rotating the rotating table to acquire a projection image of a measured object; obtaining a sinogram from the acquired projection image in a data arrangement mode; dividing and fitting the sinogram to obtain a polynomial curve corresponding to each detector module; translating the abscissa of the polynomial curve corresponding to one detector module, and calculating the number of pixels occupied by the splicing seams according to the translation position when the curve function value corresponding to the abscissa at the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the non-translated start of the next adjacent detector module. The method can rapidly and accurately calculate the number of pixels occupied by the splicing seams of the splicing type detector through the sinogram, and is simple and easy to implement.
Description
Technical Field
The invention relates to a method for estimating the width of a splicing seam between detector modules, and also relates to a system for realizing the method.
Background
As the requirements of radiation imaging technology continue to increase, pixel sizes are being reduced in order to identify higher resolutions. However, this technique also increases the demands on the manufacturing and mounting process. At present, due to the limitations of the technology level and the cost of a detector and a chip, a single detector module cannot be adopted to realize a large-area imaging detector. The photon counting detector in the present stage mainly forms a large-area detector array in a module splicing mode so as to meet the imaging requirement of a large-size object. Seamless splicing is usually difficult to achieve between detector modules, and the existence of the splicing seam can cause the reduction of CT reconstruction accuracy and the generation of artifacts. The size of the splice seam width directly determines the significance of the artifact.
In order to eliminate artifacts and improve image quality, the width of a splicing seam needs to be known, and in order to solve the splicing seam caused by the problem of detector splicing, a geometric correction phantom and a correction method for a spliced detector are disclosed in the Chinese patent application with the application number of 201610877273.3, and the geometric correction phantom and the correction method comprise the following steps: s1, mounting a geometric correction phantom on the top surface of a spliced detector, and uniformly distributing metal dots on a substrate of the geometric correction phantom on a photon counting chip; s2, dividing the top surface of the photon counting detector into a plurality of modules by taking the photon counting chip as a unit, and calculating the central coordinates of all metal dots in each module according to the positions of the metal dots; s3, calculating the pixel of each module image, judging whether a seam exists between adjacent modules according to the pixel of each module image, and if so, turning to the step S4; otherwise, no seam exists between the adjacent modules, and the image does not need to be corrected; and S4, calculating the number of pixels of the seam existing between the adjacent modules, and restoring the pixels at the seam to the image. The method can effectively correct the actual imaging detected by the spliced detector and ensure the accuracy of the image.
However, the method needs two phantoms, needs to manufacture and install the corresponding phantoms, and then carries out related calculation, and has higher manufacturing cost and operation complexity.
Disclosure of Invention
In view of the defects in the prior art, the first technical problem to be solved by the present invention is to provide a method for estimating the width of a splicing seam between detector modules.
Another technical problem to be solved by the present invention is to provide a system for estimating the width of a splice seam between detector modules.
In order to realize the purpose of the invention, the invention adopts the following technical scheme:
according to a first aspect of the embodiments of the present invention, there is provided a method for estimating a width of a splice seam between detector modules, including the steps of:
vertically fixing a thin metal wire on the boundary close to a rotating table, and rotating the rotating table to acquire a projection image of a measured object;
acquiring a sinogram from the acquired projection image in a data arrangement mode;
dividing and fitting the sinogram to obtain a polynomial curve corresponding to each detector module;
translating the abscissa of the polynomial curve corresponding to one detector module, and calculating the number of pixels occupied by the splicing seams according to the translation position when the curve function value corresponding to the abscissa at the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the non-translated start of the next adjacent detector module.
Wherein preferably the sinogram of the fine wire projection passes through all splice seam positions.
Preferably, when the rotary table is rotated to collect the projection drawing of the measured object, the rotary table is rotated to irradiate the measured object within a range of 360 degrees, a picture is taken at intervals of a certain number of degrees, and all projection drawings within the range of 360 degrees are uniformly collected.
Preferably, for the acquired projection map of each angle, extracting the jth row of the pixel of the first projection image as the first row of the sinogram, wherein j is a positive integer;
extracting the jth row of the second projection image pixel as a second row of the sinogram;
and by analogy, extracting the jth row of each projected image pixel, recombining into an image according to the sequence of projection time, and obtaining a sinogram corresponding to the jth row of the acquired projected image pixel.
Preferably, the method further comprises the following steps before segmenting the sinogram:
and (3) segmenting the fine metal wire part in the sinogram by a threshold segmentation algorithm to obtain a binary image.
Preferably, the method comprises the following steps of segmenting and fitting the sinogram to obtain a polynomial curve corresponding to each detector module:
dividing the sinogram by taking a detector module as a unit;
and selecting a sinogram part corresponding to each detector module, and fitting a polynomial curve corresponding to each detector module on the fine metal wire image by using a least square method.
Preferably, the polynomial curve corresponding to the detector module is translated in abscissa, and when the curve function value corresponding to the abscissa at the end of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the start of the next adjacent detector module which is not translated, the number of pixels occupied by the splicing seam is calculated according to the translation position; further comprising the steps of:
acquiring an abscissa xi of the tail of the polynomial curve fitted by the ith detector module; wherein i =1,2 \ 8230, wherein l 8230and M-1,M are the number of detector modules;
adding a datum N to the abscissa of the tail end of the polynomial curve fitted by the ith detector module, and calculating the curve function value y of the ith detector module iN ；
Calculating a curve function value y corresponding to the addition of the abscissa of the tail of the polynomial curve fitted by the ith detector module and one data N iN ；
Calculating a curve function value y corresponding to the abscissa of the beginning of the polynomial curve fitted by the (i + 1) th detector module i+1 ；
And when the curve function value corresponding to the addition of a datum N to the abscissa at the tail of the polynomial curve fitted by the ith detector module is equal to the curve function value corresponding to the abscissa at the beginning of the polynomial curve fitted by the (i + 1) th detector module, calculating the number of pixels occupied by the splicing seams, namely T = N-1, according to the translation position.
According to a second aspect of the embodiments of the present invention, there is provided a system for estimating a width of a splice seam between detector modules, comprising a processor and a memory; the memory having stored thereon a computer program operable on the processor, the computer program when executed by the processor implementing the steps of:
vertically fixing a thin metal wire on the boundary close to a rotating table, and rotating the rotating table to acquire a projection image of a measured object;
acquiring a sinogram from the acquired projection image in a data arrangement mode;
dividing and fitting the sinogram to obtain a polynomial curve corresponding to each detector module;
translating the abscissa of the polynomial curve corresponding to one detector module, and calculating the number of pixels occupied by the splicing seams according to the translation position when the curve function value corresponding to the abscissa at the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the non-translated start of the next adjacent detector module.
Wherein preferably the sinogram of the fine wire projection passes through all splice seam positions.
Wherein preferably the computer program when executed by the processor prior to segmenting the sinogram further implements the steps of:
and (3) segmenting the fine metal wire part in the sinogram by a threshold segmentation algorithm to obtain a binary image.
According to the method for estimating the width of the splicing seam between the detector modules, a thin metal wire is vertically fixed on the boundary close to an electric control rotating table, and the rotating table is rotated to collect the projection image of a measured object; acquiring a sinogram from the acquired projection image in a data arrangement mode; dividing and fitting the sinogram to obtain a polynomial curve of each detector module; and translating the polynomial curve corresponding to the detector module, and calculating the number of pixels occupied by the splicing seam according to the translation position when the curve function value corresponding to the abscissa of the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa of the non-translated start of the next adjacent detector module. The method can quickly and accurately calculate the number of pixels occupied by the splicing seams of the spliced detector through the sinogram, and is simple and easy to implement.
Drawings
FIG. 1 is a flow chart of a method for estimating a width of a splice seam between detector modules according to the present invention;
FIG. 2 is a schematic view of a sinogram of a fine wire at position 1 with the splice seam removed in accordance with an embodiment of the present invention;
FIG. 3 is an enlarged partial sinogram of a fine wire at position 1 in an embodiment of the present invention;
FIG. 4 is a sinogram of a fine wire at position 2 after removal of the splice seam in one embodiment provided by the present invention;
FIG. 5 is an enlarged partial sinogram at position 2 of a fine wire in an embodiment of the present invention;
FIG. 6 is a schematic diagram of a fitted curve corresponding to a continuous sinogram for each module for a fine wire at position 1 in accordance with an embodiment of the present invention;
FIG. 7 is a schematic graph of a fitted curve corresponding to a continuous sinogram for each module for a fine wire at position 2 in accordance with an embodiment of the present invention;
FIG. 8 is a schematic view of a sinogram of a thin wire at position 1 with the splice seam removed in accordance with another embodiment of the present invention;
FIG. 9 is an enlarged partial sinogram of a fine wire at position 1 in another embodiment provided by the present invention;
FIG. 10 is a sinusoidal plot of fine wire at position 2 with the splice seam removed in accordance with another embodiment of the present invention;
FIG. 11 is an enlarged partial sinogram at position 2 of a fine wire in another embodiment provided by the present invention;
FIG. 12 is a schematic view of a fitted curve corresponding to a continuous sinogram for each module for a fine wire at position 1 in accordance with another embodiment of the present invention;
FIG. 13 is a schematic view of a fitted curve corresponding to a continuous sinogram for each module for a fine wire at position 2 in accordance with another embodiment of the present invention;
FIG. 14 is a schematic structural diagram of a system for estimating the width of a splice seam between detector modules according to the present invention.
Detailed Description
The technical contents of the invention are described in detail below with reference to the accompanying drawings and specific embodiments.
The invention designs and realizes a sinogram-based splicing seam width estimation method for a spliced detector. The estimation method can effectively detect the number of pixels occupied by the splicing seams of the splicing type detector, and achieves the effects of reducing CT artifacts and improving imaging accuracy for subsequent data correction and compensation of the splicing seams. The detector module includes, but is not limited to, an X-ray (or gamma ray) detector used in radiation imaging technology, and in the embodiment provided by the present invention, a photon counting detector is taken as an example for illustration. The method only adopts fine metal wires and carries out detection based on the sinogram, and is a method for detecting the width of the splicing seam with low cost and easy realization.
As shown in fig. 1, the method for estimating the width of the splicing seam between the detector modules provided by the present invention includes the following steps: firstly, vertically fixing a thin metal wire on the boundary close to an electric control rotary table, and rotating the rotary table to acquire a projection drawing of a measured object; secondly, obtaining a sinogram from the acquired projection image in a data arrangement mode; then, dividing and fitting the sinogram to obtain a polynomial curve corresponding to each detector module; and finally, translating the polynomial curve corresponding to one detector module, and calculating the number of pixels occupied by the splicing seams according to the translation position when the curve function value corresponding to the abscissa at the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the start of the next adjacent detector module which is not translated. This process is described in detail below.
S1, vertically fixing a thin metal wire on the boundary close to an electric control rotary table, and rotating the rotary table to acquire a projection drawing of a measured object.
In the embodiment provided by the invention, the boundary close to the electric control rotating platform is near the boundary of the electric control rotating platform, and is a certain distance away from the boundary of the electric control rotating platform, wherein the certain distance can be several millimeters, and the distance is set according to the requirements in actual use. The fine wire projection sinogram passes through all splice seam locations.
When the rotary table is rotated to collect the projection drawing of the measured object, the rotary table is rotated to irradiate the measured object within a range of 360 degrees, a picture is taken at intervals of a certain degree, and all the projection drawings within the range of 360 degrees are uniformly collected. In the embodiment provided by the present invention, a certain degree is 0.05 degrees as an example. Every 0.05 degree, one photo and 7200 projection images are collected.
And S2, obtaining a sinogram from the acquired projection image in a data arrangement mode.
The method comprises the steps of obtaining a sinogram from the collected projection drawings in a data arrangement mode, namely obtaining the projection drawings collected by cone beam scanning, selecting projection data of a certain same row from the collected projection drawings of each angle for row arrangement, and obtaining the sinogram of a projection image. Then, a polynomial curve of each detector module is obtained by using the sinusoidal image as an input image. The method comprises the following steps of acquiring a projection diagram, wherein the acquired projection diagram is subjected to data arrangement to obtain a sinogram, and the method specifically comprises the following steps:
extracting the jth line of a first projection image pixel from the acquired projection image of each angle to be used as the first line of the sinogram Aj; extracting the jth line of the second projection image pixel as the second line of the sinogram Aj; and by analogy, extracting the jth row of each projected image pixel, and recombining into an image according to the sequence of projection time to obtain a sinogram Aj corresponding to the jth row of the acquired projected image pixel, wherein j is a positive integer.
And S3, segmenting and fitting the sinogram to obtain a polynomial curve corresponding to each detector module.
In an embodiment provided by the present invention, before segmenting the sinogram, the method further includes the following steps:
and (3) segmenting the thin metal wire part in the sinogram by a threshold segmentation algorithm to obtain a binary image. Namely, the sinusoidal image is converted into a binary image by setting a segmentation threshold value.
Then, segmenting and fitting the sinogram to obtain a polynomial curve corresponding to each detector module, which specifically comprises the following steps:
s31, dividing the sinogram by taking a detector module as a unit;
and S32, selecting a continuous sinogram part of each detector module, and fitting a polynomial curve corresponding to each detector module to the fine metal wire image by using a least square method. Taking a cubic polynomial as an example, y = ax 3 +bx 2 + cx + d. Other degree polynomials are also possible according to actual data requirements. In the examples provided by the present invention, no particular limitation is imposed.
S4, translating the abscissa of the polynomial curve corresponding to the detector module, and calculating the number of pixels occupied by the splicing seam according to the translation position when the curve function value corresponding to the abscissa at the tail of the translated polynomial curve (namely the curve function value corresponding to the last value of the abscissa of the translated polynomial curve) is equal to the curve function value corresponding to the abscissa at the non-translated start of the next adjacent detector module (namely the curve function value corresponding to the first value of the abscissa of the non-translated polynomial curve); the method specifically comprises the following steps:
s41, acquiring an abscissa (width position) xi at the tail of the polynomial curve fitted by the ith detector module; wherein i =1,2 \ 8230 \8230: \ 8230and M-1,M is the number of detector modules.
S42, adding data N to the abscissa of the tail of the polynomial curve fitted by the ith detector module, namely translating the polynomial curve fitted by the ith detector module to the right by N units; calculating the curve function value y of the ith detector module iN 。
S43, calculating a corresponding curve function value y after adding one data N to the abscissa of the tail of the polynomial curve fitted by the ith detector module iN 。
S44, calculating a curve function value y corresponding to the abscissa of the beginning of the polynomial curve fitted by the (i + 1) th detector module i+1 。
S45, when the curve function value corresponding to the addition of the abscissa at the tail of the polynomial curve fitted by the ith detector module and one data N is equal to the polynomial curve fitted by the (i + 1) th detector moduleWhen the value of the curve function corresponds to the abscissa of the beginning of the formula curve, i.e. y iN ＝y i+1 And then, calculating the number of the pixels occupied by the splicing seam T = N-1 according to the translation position.
S46, when i is smaller than M-1; i = i +1; turning to step S41; otherwise, obtaining the number of pixels occupied by all the splicing seams.
Taking the first detector module as an example, when the number of pixels occupied by the width of the splicing seam is calculated, adding a datum N to an abscissa x1 at the end of a curve fitted by the first detector module, that is: y is 1N ＝a 1 (x1+N) 3 +b 1 (x1+N) 2 +c 1 (x1+N)+d 1 Fitting a first value x2 (value corresponding to the abscissa of the start) of the curve to the next adjacent detector module (second detector module), i.e. the value
The comparison is made when the corresponding values of the two positions are equal, i.e. y 1N = y2 (or y) 1N Y 2), N is the evaluated value, and (N-1) is the number of pixels occupied by the splicing seam.
The simulation data are used for verification according to the steps, and the effect of the method for estimating the width of the splicing seam between the detector modules is verified through a specific test.
Simulating a thin metal wire with the radius of 0.3mm, and rotating for one circle to acquire 7200 projection images; and adjusting the position of the fine metal wire, and scanning twice to obtain 2 times of sinograms so as to investigate the stability of the algorithm.
The sizes of 7200 projection graph simulation splicing seams are sequentially set as follows:
table 1 show table for simulating seven splicing seams by projection diagram
The fine wires placed at different positions are adjusted twice to remove the splicing seams to form a sinogram as shown in fig. 2-5. Fig. 2 and 3 show the sinogram of the fine wire at position 1 and a partial enlargement of the sinogram of the fine wire at position 1. Fig. 4 and 5 are a partial enlargement of the sinogram of the thin wire at position 2 and the sinogram of the thin wire at position 2.
The continuous sinogram region of each detector module (note: in order to make the obtained fitted curve approach to a straight line, only half of the sinograms of the first detector module and the last detector module are selected, that is, the sinogram on the right of the first detector module is selected, the sinogram on the left is removed, the sinogram on the left of the last detector module is selected, the sinogram on the right is removed), fitting is performed, and the display graphs of the obtained fitted curves are shown in fig. 6 and 7. Wherein fig. 6 is a fitted curve corresponding to the continuous sinogram of each detector module for which the fine wire is at position 1. FIG. 7 is a fitted curve corresponding to the continuous sinogram for each detector module for which the fine wire is at position 2.
And obtaining the number of pixels occupied by the splicing seams according to the theoretical formula in the step S4, wherein the number is shown in the following table 2:
TABLE 2 comparison table of the number of pixels occupied by the theoretical joints and the actual number of pixels
In addition, the collected real data is verified according to the steps, and the specific process is as follows:
fixing a thin copper wire with the radius of 0.3mm on a rotating table, enabling the thin copper wire to be full of the whole visual field after the thin copper wire rotates for one circle, and collecting 7186 projection drawings for one circle of the experiment platform. The position of the metallic copper wire is also adjusted, and two scans are performed.
The acquired projection images are converted into sinusoidal images, which are shown in fig. 8-11. Fig. 8 is a sinusoidal image when the real data fine metal wire is adjusted to the position 1 by rotating one circle, and fig. 9 is a partial enlarged view of the sinusoidal image of the real data fine metal wire at the position 1. Fig. 10 is a partial enlarged view of the sinogram of the real data fine wire at position 2, which is a sine image of the real data fine wire adjusted to position 2 by one rotation.
The method comprises the steps of (1) continuously obtaining sinogram areas of each detector module, (note that in order to enable an obtained fitting curve to approach to a straight line, the sinograms of a first detector module and a last detector module are only selected generally, namely the sinogram on the right side of the first detector module is selected, the sinogram on the left side is removed, the sinogram on the left side of the last detector module is selected, the sinogram on the right side is removed), fitting is carried out, and display graphs of the obtained fitting curves are shown in figures 12 and 13. FIG. 12 true data fitting curves for continuous sinograms of a thin wire at position 1 for each detector module. FIG. 13 true data fitting curves for continuous sinograms of a thin wire at position 2 for each detector module.
Obtaining the number of pixels occupied by the splicing seams according to the theoretical formula in the step S4, as shown in table 3 below:
TABLE 3 demonstration table of the number of pixels occupied by the real data theory splice joint
In conclusion, the stability and the accuracy of the method for estimating the width of the splicing seam between the detector modules are verified.
In addition, the method for estimating the width of the splicing seam between the detector modules has the following beneficial effects:
1) The method is simple and easy to realize;
2) The manufacturing cost is low;
3) The number of pixels occupied by the splicing seams of the spliced detector can be rapidly and accurately calculated through the sinogram.
The invention also provides a system for estimating the width of the splicing seam between the detector modules. As shown in fig. 14, the system includes a processor 142 and a memory 141 storing instructions executable by the processor 142;
The memory 61 is used for storing the program codes and transmitting the program codes to the CPU. Memory 141 may include volatile memory, such as Random Access Memory (RAM); the memory 141 may also include non-volatile memory, such as read-only memory, flash memory, a hard disk, or a solid state disk; memory 141 may also comprise a combination of the above types of memory.
Specifically, the system for estimating the width of the splicing seam between the detector modules provided by the embodiment of the present invention includes a processor 142 and a memory 141; the memory 141 has stored thereon a computer program operable on the processor 142, which when executed by the processor 142, performs the steps of:
vertically fixing a thin metal wire at the boundary close to the rotating table, and rotating the rotating table to acquire a projection image of a measured object;
acquiring a sinogram from the acquired projection image in a data arrangement mode;
dividing and fitting the sinogram to obtain a polynomial curve corresponding to each detector module;
translating the abscissa of the polynomial curve corresponding to one detector module, and calculating the number of pixels occupied by the splicing seams according to the translation position when the curve function value corresponding to the abscissa at the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the non-translated start of the next adjacent detector module.
Wherein the following steps are implemented when the computer program is executed by the processor 142;
the sinogram of the fine wire projection passes through all splice seam locations.
Wherein the following steps are implemented when the computer program is executed by the processor 142;
when the rotary table is rotated to collect the projection images of the measured object, the rotary table irradiates the measured object within a range of 360 degrees, a picture is taken at intervals of a certain degree, and all the projection images within the range of 360 degrees are uniformly collected.
Wherein, when the acquired projection image is processed by the processor 142 to obtain the sinogram in a data arrangement manner, the following steps are implemented;
extracting the jth line of a first projection image pixel from the acquired projection image of each angle to be used as the first line of the sinogram, wherein j is a positive integer;
extracting the jth row of the second projection image pixel as a second row of the sinogram;
and by analogy, extracting the jth row of each projected image pixel, and recombining the jth row of each projected image pixel into an image according to the sequence of projection time to obtain a sinogram corresponding to the jth row of the acquired projected image pixel.
Wherein, before segmenting the sinogram, the computer program when executed by the processor 142 further performs the following steps;
and (3) segmenting the thin metal wire part in the sinogram by a threshold segmentation algorithm to obtain a binary image.
When the sinogram is segmented and fitted to obtain a polynomial curve corresponding to each detector module, the computer program is executed by the processor 142 to implement the following steps;
dividing the sinogram by taking a detector module as a unit;
and selecting a sinogram part corresponding to each detector module, and fitting a polynomial curve corresponding to each detector module on the fine metal wire image by using a least square method.
When the abscissa of the polynomial curve corresponding to the detector module is translated, and when the curve function value corresponding to the abscissa of the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa of the start of the next adjacent detector module, which is not translated, the number of pixels occupied by the stitching seams is calculated according to the translation position, the computer program is executed by the processor 142 to implement the following steps;
preferably, the polynomial curve corresponding to the detector module is translated in abscissa, and when the curve function value corresponding to the abscissa at the end of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the start of the next adjacent detector module which is not translated, the number of pixels occupied by the splicing seam is calculated according to the translation position; further comprising the steps of:
acquiring an abscissa xi of the tail of the polynomial curve fitted by the ith detector module; wherein i =1,2 \ 8230, wherein l 8230and M-1,M are the number of detector modules;
adding a datum N to the abscissa of the tail end of the polynomial curve fitted by the ith detector module, and calculating the curve function value y of the ith detector module iN ；
Calculating a curve function value y corresponding to the addition of the abscissa of the tail of the polynomial curve fitted by the ith detector module and one data N iN ；
Calculating a curve function value y corresponding to the abscissa of the beginning of the polynomial curve fitted by the (i + 1) th detector module i+1 ；
And when the curve function value corresponding to the addition of a datum N to the abscissa at the tail of the polynomial curve fitted by the ith detector module is equal to the curve function value corresponding to the abscissa at the beginning of the polynomial curve fitted by the (i + 1) th detector module, calculating the number of pixels occupied by the splicing seams, namely T = N-1, according to the translation position.
The embodiment of the invention also provides a computer readable storage medium. The computer-readable storage medium herein stores one or more programs. Among other things, computer-readable storage media may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as read-only memory, flash memory, a hard disk, or a solid state disk; the memory may also comprise a combination of memories of the kind described above. The one or more programs in the computer readable storage medium may be executed by the one or more processors to implement some or all of the steps of the method for estimating a splice width between detector modules in the above-described method embodiments.
The method and system for estimating the width of the splicing seam between the detector modules provided by the invention are explained in detail above. Any obvious modifications thereof, which would be obvious to one skilled in the art without departing from the true spirit of the invention, would constitute a violation of the patent rights of the present invention and would bear corresponding legal responsibility.
Claims (8)
1. A method for estimating the width of a splicing seam between detector modules is characterized by comprising the following steps:
vertically fixing a thin metal wire on the boundary close to a rotating table, and rotating the rotating table to acquire a projection image of a measured object;
obtaining a sinogram from the acquired projection image in a data arrangement mode, wherein the sinogram projected by the thin metal wire passes through all splicing seam positions;
dividing and fitting the sinogram to obtain a polynomial curve corresponding to each detector module;
translating the abscissa of the polynomial curve corresponding to one detector module, and calculating the number of pixels occupied by the splicing seams according to the translation position when the curve function value corresponding to the abscissa at the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the non-translated start of the next adjacent detector module.
2. The method of estimating a splice width between detector modules as claimed in claim 1, wherein:
when the rotary table is rotated to collect the projection images of the measured object, the rotary table irradiates the measured object within a range of 360 degrees, a picture is taken at intervals of a certain degree, and all the projection images within the range of 360 degrees are uniformly collected.
3. The method according to claim 1, wherein the step of obtaining the sinogram from the acquired projection map by data arrangement comprises the steps of:
extracting the jth line of a first projection image pixel from the acquired projection image of each angle to be used as the first line of the sinogram, wherein j is a positive integer;
extracting a jth line of the second projection image pixel as a second line of the sinogram;
and by analogy, extracting the jth row of each projected image pixel, recombining into an image according to the sequence of projection time, and obtaining a sinogram corresponding to the jth row of the acquired projected image pixel.
4. The method of estimating a width of a splice between detector modules as set forth in claim 1, wherein the step of prior to segmenting the sinogram further includes the steps of:
and (3) segmenting the fine metal wire part in the sinogram by a threshold segmentation algorithm to obtain a binary image.
5. The method of claim 1, wherein the dividing and fitting of the sinogram to obtain a polynomial curve for each detector module comprises:
dividing the sinogram by taking a detector module as a unit;
and selecting a sinogram part corresponding to each detector module, and fitting a polynomial curve corresponding to each detector module on the fine metal wire image by using a least square method.
6. The method according to claim 1, wherein the polynomial curve corresponding to the detector modules is translated in abscissa, and when the curve function value corresponding to the abscissa at the end of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the non-translated start of the next adjacent detector module, the number of pixels occupied by the splice is calculated according to the translation position; the method comprises the following steps:
acquiring an abscissa xi of the tail of the polynomial curve fitted by the ith detector module; wherein i =1,2 \ 8230, M-1, M is the number of detector modules;
calculating a curve function value y corresponding to the addition of the abscissa of the tail of the polynomial curve fitted by the ith detector module and one data N iN ；
Calculating a curve function value y corresponding to the abscissa of the beginning of the polynomial curve fitted by the (i + 1) th detector module i+1 ；
And when the curve function value corresponding to the addition of the abscissa at the tail of the polynomial curve fitted by the ith detector module and one datum N is equal to the curve function value corresponding to the abscissa at the beginning of the polynomial curve fitted by the (i + 1) th detector module, calculating the number of pixels occupied by the splicing seams, namely T = N-1 according to the translation position.
7. A system for estimating the width of a splicing seam between detector modules is characterized by comprising a processor and a memory; the memory has stored thereon a computer program operable on the processor, which when executed by the processor, performs the steps of:
vertically fixing a thin metal wire on the boundary close to a rotating table, and rotating the rotating table to acquire a projection image of a measured object;
obtaining a sinogram from the acquired projection image in a data arrangement mode, wherein the sinogram projected by the thin metal wire passes through all splicing seam positions;
dividing and fitting the sinogram to obtain a polynomial curve corresponding to each detector module;
translating the abscissa of the polynomial curve corresponding to one detector module, and calculating the number of pixels occupied by the splicing seams according to the translation position when the curve function value corresponding to the abscissa at the tail of the translated polynomial curve is equal to the curve function value corresponding to the abscissa at the non-translated start of the next adjacent detector module.
8. The system according to claim 7, wherein the computer program when executed by the processor further performs the steps of, prior to segmenting the sinogram:
and (3) segmenting the fine metal wire part in the sinogram by a threshold segmentation algorithm to obtain a binary image.
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