A compton camera photon spatial action position correction method and product

Abstract

The embodiment of the application relates to the field of Compton camera imaging, and provides a Compton camera photon space action position correction method and product, which comprises the following steps: acquiring photon event information; generating a candidate space action position and a candidate photon count based on the photon event information; if the photon count corresponding to the two-dimensional probability distribution of the candidate space action position is greater than the candidate photon count, the candidate space action position is taken as a corrected photon space action position to replace the original photon space action position. The method of the application obtains the correction value of the space action position by constructing the two-dimensional probability distribution of the space action position and sampling the two-dimensional probability distribution by using the uniformly distributed random number in the pixel interval. The correction accuracy obtained by the method is high, the universality is wide, the calculation complexity is low, and the imaging precision of the Compton camera is effectively improved.

Description

Technical Field

[0001] This application relates to the field of Compton camera imaging, and more specifically, to a method and product for correcting the spatial action position of photons in a Compton camera. Background Technology

[0002] The Compton camera is an imaging mode that locates the spatial position of incident gamma rays by detecting Compton events that occur in the detector. Compared with other gamma imaging modes, the Compton camera does not require a mechanical collimation structure and has excellent characteristics such as a large detection field, high detection efficiency, and single-view three-dimensional imaging. Therefore, the Compton camera has been widely used in many fields such as astronomy, radiation detection, heavy ion therapy, and medical imaging.

[0003] However, existing methods for photon spatial interaction position correction in Compton camera detectors mainly fall into two categories: one involves implicit representation based on the degradation of imaging resolution, which suffers from high computational complexity, lengthy processing times (up to several hours or even days), and poor generalization ability; the other is based on a hypothetical probability distribution of the spatial interaction position and Markov chain Monte Carlo (MCMC) sampling method, but this method is difficult to use in practical Compton imaging due to its complex calculation process and low reception probability in random correction. Therefore, how to effectively improve the imaging accuracy of Compton cameras has become an urgent problem to be solved. Summary of the Invention

[0004] This application provides a method and product for correcting the spatial position of photons in a Compton camera, aiming to solve the problem of how to effectively improve the imaging accuracy of a Compton camera.

[0005] The first aspect of this application provides a method for correcting the spatial interaction position of photons in a Compton camera, including:

[0006] Acquire photon event information, which includes the original photon spatial location, pixel range, and photon count information of the pixel;

[0007] A uniformly distributed random number is generated based on the pixel interval as a candidate spatial action position; a uniformly distributed random number is generated based on the photon count information of the pixel as a candidate photon count.

[0008] If the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is greater than the candidate photon count, the candidate spatial action position is used as the corrected photon spatial action position, replacing the original photon spatial action position.

[0009] In one optional implementation, the photon count information of the pixel includes the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel. A uniformly distributed random number is generated based on the photon count information of the pixel as candidate photon counts, including:

[0010] The minimum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel is obtained as the lower limit of the distribution.

[0011] The maximum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel is used as the upper limit of the distribution.

[0012] A uniform distribution of photon counts is generated based on the upper and lower limits of the distribution.

[0013] Random numbers are obtained within the range of the uniform distribution of the photon counts and used as candidate photon counts.

[0014] In an optional implementation, if the photon count corresponding to the two-dimensional probability distribution at the candidate spatial action location is greater than the candidate photon count, the method further includes:

[0015] Based on the original photon space interaction position, obtain the first weight for the original photon space interaction position;

[0016] Based on the candidate spatial position, obtain a second weight for the candidate spatial position;

[0017] If the first weight and the second weight satisfy a preset judgment condition, the candidate spatial action position is taken as the corrected photon spatial action position. The preset judgment condition is as follows:

[0018]

[0019] Where, n s+1 For the second weight, n s α is the first weight; α is a randomly generated random number uniformly distributed between 0 and 1.

[0020] In one alternative implementation, the two-dimensional probability distribution is constructed according to the following formula:

[0021]

[0022]

[0023] Where, N i,jFor the photon count of pixel (i,j); N i-1,j N i+1,j N represents the photon counts of the horizontally adjacent pixels of pixel (i,j); i,j-1 B i,j+1 p represents the photon counts of the vertically adjacent pixels of pixel (i,j); x (x) represents the horizontal probability distribution; p y (y) represents the longitudinal probability distribution; f is the probability function.

[0024] In an optional implementation, when the pixel interval is a square pixel interval, the photon count corresponding to the two-dimensional probability distribution is constructed according to the following formula:

[0025]

[0026]

[0027]

[0028]

[0029] Among them, B i,j B is the photon count for pixel (i,j); i-1,j N i+1,j N represents the photon counts of the horizontally adjacent pixels of pixel (i,j); i,j-1 N i,j+1 p represents the photon counts of the vertically adjacent pixels of pixel (i,j); x (x) represents the horizontal probability distribution; p y (y) represents the vertical probability distribution; l represents the size of pixel (i,j); N Xmin The photon count for the horizontal lower boundary of pixel (i,j); N Xmax The photon count for the horizontal upper boundary of pixel (i,j); N Ymin The photon count for the vertical lower boundary of pixel (i,j); N Ymax y is the photon count of the vertical upper boundary of pixel (i,j); x is the horizontal spatial position and y is the vertical spatial position.

[0030] In an optional implementation, when the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action location is less than or equal to the candidate photon count, the method includes:

[0031] New uniformly distributed random numbers are generated based on the pixel interval as new candidate spatial action positions; new uniformly distributed random numbers are generated based on the photon count information of the pixel as new candidate photon counts.

[0032] If the photon count corresponding to the two-dimensional probability distribution of the new candidate spatial action position is greater than the new candidate photon count, the new candidate spatial action position is used as the corrected photon spatial action position, replacing the original photon spatial action position.

[0033] A second aspect of this application provides a Compton camera photon spatial interaction position correction device, comprising:

[0034] The acquisition module is used to acquire photon event information, which includes the original photon spatial location, pixel range, and photon count information of the pixel;

[0035] The generation module generates uniformly distributed random numbers based on the pixel interval as candidate spatial action positions; and generates uniformly distributed random numbers based on the photon count information of the pixels as candidate photon counts.

[0036] The correction module is used to replace the original photon spatial action position with the corrected photon spatial action position if the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is greater than the candidate photon count.

[0037] The generation module includes:

[0038] The lower limit value acquisition submodule is used to acquire the minimum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel, as the distribution lower limit value;

[0039] The upper limit value acquisition submodule is used to acquire the maximum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel, as the upper limit value of the distribution;

[0040] A photon count distribution generation submodule is used to generate a uniform photon count distribution based on the upper limit value and the lower limit value of the distribution;

[0041] The candidate photon count generation submodule is used to obtain random numbers within the range of the uniform distribution of the photon counts, and use them as the candidate photon counts.

[0042] The device further includes:

[0043] The first weight acquisition module is used to acquire a first weight for the original photon space action position based on the original photon space action position.

[0044] The second weight acquisition module is used to acquire a second weight for the candidate space action position based on the candidate space action position;

[0045] The weight correction module is used to take the candidate spatial action position as the corrected photon spatial action position if the first weight and the second weight meet a preset judgment condition. The preset judgment condition is as follows:

[0046]

[0047] Where, n s+1 For the second weight, n s α is the first weight; α is a randomly generated random number uniformly distributed between 0 and 1.

[0048] The correction module includes:

[0049] The photon counting construction submodule corresponding to the two-dimensional probability distribution is used to construct according to the following formula:

[0050]

[0051]

[0052]

[0053]

[0054] Where, N i,j For the photon count of pixel (i,j); N i-1,j N i+1,j N represents the photon counts of the horizontally adjacent pixels of pixel (i,j); i,j-1 N i,j+x1 p represents the photon counts of the vertically adjacent pixels of pixel (i,j); x (x) represents the horizontal probability distribution; p y (y) represents the vertical probability distribution; l represents the size of pixel (i,j); N Xmin The photon count for the horizontal lower boundary of pixel (i,j); N Xmax The photon count for the horizontal upper boundary of pixel (i,j); N Ymin The photon count for the vertical lower boundary of pixel (i,j); N Ymax y is the photon count of the vertical upper boundary of pixel (i,j); x is the horizontal spatial position and y is the vertical spatial position.

[0055] The device further includes:

[0056] The second generation module is used to generate new uniformly distributed random numbers based on the pixel interval as new candidate spatial action positions; and to generate new uniformly distributed random numbers based on the photon count information of the pixel as new candidate photon counts.

[0057] The second correction module is used to replace the original photon spatial action position with the new candidate spatial action position if the photon count corresponding to the two-dimensional probability distribution of the new candidate spatial action position is greater than the new candidate photon count.

[0058] A third aspect of this application provides an electronic device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps in the Compton camera photon spatial action position correction method described in any of the first aspects.

[0059] The fourth aspect of this application provides a computer-readable storage medium storing a computer program / instructions thereon, which, when executed by a processor, implements the steps in the Compton camera photon spatial action position correction method described in any of the first aspects.

[0060] The fifth aspect of this application provides a computer program product, including a computer program / instruction that, when executed by a processor, implements the steps in the Compton camera photon spatial action position correction method described in any of the first aspects.

[0061] Beneficial effects:

[0062] This application provides a method and product for correcting the spatial interaction position of a Compton camera, comprising: acquiring photon event information, the photon event information including the original photon spatial interaction position, a pixel interval, and photon count information of the pixels; generating uniformly distributed random numbers based on the pixel interval as candidate spatial interaction positions; generating uniformly distributed random numbers based on the photon count information of the pixels as candidate photon counts; if the photon count corresponding to the two-dimensional probability distribution of the candidate spatial interaction position is greater than the candidate photon count, using the candidate spatial interaction position as the corrected photon spatial interaction position and replacing the original photon spatial interaction position. The method of this application has the following advantages:

[0063] (1) By constructing a two-dimensional probability distribution of the spatial action position, the computational load of spatial action position correction is greatly reduced. Moreover, the two-dimensional probability distribution is simple and intuitive, has less computational load, and is faster to calculate. It is more in line with the actual projection data collected by the detector and can effectively improve the imaging accuracy of the Compton camera.

[0064] (2) The two-dimensional probability distribution is sampled by uniformly distributed random numbers within the pixel range to obtain the correction value of the spatial action position. The correction obtained by this method has high accuracy, wide applicability and low computational complexity, which effectively improves the imaging accuracy of the Compton camera. Attached Figure Description

[0065] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0066] Figure 1 This is a flowchart of a Compton camera photon spatial interaction position correction method according to an embodiment of this application;

[0067] Figure 2 This is a schematic diagram of a pixel array detector receiving photons from a radiation source according to an embodiment of this application;

[0068] Figure 3 This is a schematic diagram illustrating the calculation of the lateral probability distribution of spatial position effects according to an embodiment of this application;

[0069] Figure 4 This is a schematic diagram of detector spatial position correction according to an embodiment of this application;

[0070] Figure 5 This is a schematic diagram of the Compton camera proposed in Embodiment 1 of this application;

[0071] Figure 6 This is a schematic flowchart of the Compton camera photon spatial interaction position correction method proposed in Embodiment 1 of this application;

[0072] Figure 7 This is a comparison diagram of the reconstruction results proposed in Embodiment 1 of this application;

[0073] Figure 8 This is a schematic diagram of a Compton camera photon spatial interaction position correction device according to an embodiment of this application;

[0074] Figure 9 This is a schematic diagram of an electronic device according to an embodiment of this application. Detailed Implementation

[0075] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0076] In related technologies, existing methods for photon spatial interaction position correction in Compton camera detectors mainly fall into two categories: one category implicitly expresses the photon spatial interaction position through the degradation of imaging resolution, that is, it evaluates the point spread function caused by the deviation in photon spatial interaction position and then performs inverse recovery in the reconstruction process. This category does not directly and explicitly correct the photon spatial interaction position. This type of method has the advantages of good single-point source correction effect and high-quality reconstructed image restoration; however, the evaluation of the point spread function is extremely time-consuming, and it cannot achieve continuous correction throughout the entire space for complex Compton camera systems. It suffers from high computational complexity, lengthy processing time (up to several hours or even days), and poor generalization ability.

[0077] Another type of correction is based on the assumed probability distribution of the spatial interaction location and the Markov Chain Monte Carlo (MCMC) sampling method. This type of method directly addresses the source of the photon spatial interaction location deviation, achieving explicit correction through direct random sampling of the spatial interaction location and the rejection-acceptance strategy of MCMC. However, current methods for evaluating the probability distribution of the spatial interaction location either directly assume a uniform distribution within the pixel or rely on millions of additional transmission probability calculations per pixel. The former has been applied in practice, but suffers from poor correction performance and image reconstruction accuracy heavily dependent on the detector pixel size. The latter, due to its complex computational process and low acceptance probability in random correction, is difficult to use in practical Compton imaging.

[0078] In view of this, embodiments of this application propose a method for correcting the spatial interaction position of photons in a Compton camera. Figure 1 A flowchart of a Compton camera photon spatial interaction position correction method is shown, as follows: Figure 1 As shown, it includes the following steps:

[0079] S101, Obtain photon event information.

[0080] Acquire photon event information, which includes the original photon spatial location, pixel range, and photon count information of the pixel.

[0081] S102. Generate uniformly distributed random numbers based on the pixel interval as candidate spatial action positions; generate uniformly distributed random numbers based on the photon counting information of the pixel as candidate photon counts.

[0082] S103. If the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is greater than the candidate photon count, the candidate spatial action position is used as the corrected photon spatial action position, replacing the original photon spatial action position.

[0083] In this embodiment, the photon event information refers to the information on effective photon events generated by photons collected by the Compton camera and excited on the pixels of the detector. The Compton camera structure can be a traditional dual-layer / multi-layer detector structure or a single-layer detector structure. The detector type can also be varied, not limited to semiconductor detectors, but can also be a scintillator or other types of detector. The specific Compton camera structure and detector type can be determined according to actual conditions, and this application does not impose any restrictions.

[0084] In this embodiment, the photon event information includes the original photon spatial location, pixel range, and photon count information of the pixel. The original photon spatial location is the two-dimensional planar coordinate (x0, y0) of the responding pixel position in the xy plane; the pixel range is the size range of the responding pixel of the photon event, which depends on the shape and size of the responding pixel; and the photon count is the number of photon events occurring within the responding pixel of the photon event.

[0085] In this embodiment, the two-dimensional probability distribution refers to the horizontal probability distribution (one-dimensional direction) and the vertical probability distribution (one-dimensional direction perpendicular to the horizontal direction). Specifically, based on the left and right adjacent pixels of the responding pixel of the photon event in the horizontal direction, and the photon count of the responding pixel, a probability function is established to show the change of the count rate with the horizontal scale of the pixel, which serves as the horizontal probability distribution. Based on the upper and lower adjacent pixels of the responding pixel of the photon event in the vertical direction, and the photon count of the responding pixel, a probability function is established to show the change of the count rate with the vertical scale of the pixel, which serves as the vertical probability distribution.

[0086] Subsequently, the horizontal probability distribution is truncated based on the pixel interval in which the response pixel is located to obtain the horizontal probability distribution of the photon interaction position within the response pixel; the vertical probability distribution is truncated based on the pixel interval in which the response pixel is located to obtain the vertical probability distribution of the photon interaction position within the response pixel.

[0087] Next, in order to enable those skilled in the art to better understand this application, the above S101-S103 will be described in detail as follows:

[0088] In the specific implementation step S101, Figure 2 A schematic diagram of a pixel array detector receiving photons from a radiation source is shown, such as... Figure 2As shown, the Compton camera collects photons and generates responses as photon events on pixels of each detector layer. It records the pixel range of each photon event on the responding pixel, the original photon spatial position, and the photon count information on the responding pixel. The responding pixel can be a square pixel or a rectangular pixel; the specific shape of the responding pixel can be determined according to actual conditions, and this application does not impose any restrictions. The original photon spatial position is the two-dimensional planar coordinate (x0, y0) of the responding pixel position of the photon event in the xy plane.

[0089] In one optional implementation, after obtaining the photon count information on the response pixel corresponding to each photon event, a two-dimensional probability distribution of the photon spatial action position is constructed by linear weighted fitting and peak normalization. Specifically, the horizontal probability distribution is calculated using the photon count information of each response pixel and the photon count information of the two horizontally adjacent left and right pixels; the vertical probability distribution is calculated using the photon count information of each response pixel and the photon count information of the two vertically adjacent up and down pixels.

[0090] The specific calculation is performed according to the following formula:

[0091]

[0092]

[0093] Where, N i,j For the photon count of pixel (i,j); N i-1,j N i+1,j N represents the photon counts of the horizontally adjacent pixels of pixel (i,j); i,j-1 N i,j+x1 p represents the photon counts of the vertically adjacent pixels of pixel (i,j); x (x) represents the horizontal probability distribution; p y (y) represents the longitudinal probability distribution; f is the probability function.

[0094] Finally, after obtaining the horizontal and vertical probability distributions, the pixels are truncated according to the pixel interval where the response pixel is located to obtain the horizontal and vertical probability distributions within the response pixel interval. It should be noted that the number of consecutive adjacent pixels in both the horizontal and vertical directions on the detector is at least three; for edge pixels, the photon count information of the adjacent pixels on the side not located on the detector is set to 0.

[0095] In one optional implementation, when the pixel interval is a square pixel interval, the calculation is taken as an example of horizontal probability distribution. Figure 3 A schematic diagram illustrating the calculation of the lateral probability distribution of spatial location effects is shown, such as... Figure 3As shown, the pixels are square pixels with a size of l. For the response pixel (i,j), its photon count is N. i,j The horizontally adjacent pixels of this responding pixel are (i-1,j) and (i+1,j) respectively, and their photon counts are N. i-1,j N i+1,j ; will N i,j and N i-1,j n i+1,j The probability function for lateral scale variation is represented by the lateral probability distribution p. x The size of the response pixel (i,j) is l. Within its pixel range [0,l], when x = l, the photon count at the upper boundary of the response pixel (i,j) reaches N. Xmax And N Xmax For N i,j and N i+1,j The midpoint value; when x = 0, the lower boundary photon count of the responding pixel (i,j) is N. Xmin And N Xmin For N i,j and N i-1,j The midpoint value.

[0096] For the calculation of the longitudinal probability distribution, the photon count for the response pixel (i,j) is N. i,j The vertically adjacent pixels of this response pixel are (i,j-1) and (i,j+1) respectively, and their photon counts are n. i,j-1 n i,j+1 ; will N i,j and N i,j-1 N i,j+1 The probability function for longitudinal scale variation is represented by the longitudinal probability distribution p. y The size of the response pixel (i,j) is l. Within its pixel range [0,l], when y = l, the upper boundary photon count of the response pixel (i,j) reaches an upper limit N. Ymax And N Ymax For N i,j and N i,j+1 The midpoint value; when y=0, the lower boundary photon count of the responding pixel (i,j) is obtained as N. Ymin And N Ymin For N i,j and N i,j-1 The midpoint value.

[0097] Specifically, the photon counts corresponding to the two-dimensional probability distributions in the horizontal and vertical directions are constructed according to the following formula:

[0098]

[0099]

[0100]

[0101]

[0102] Where, N i,j For the photon count of pixel (i,j); N i-1,j N i+1,j Let n be the photon count of the horizontally adjacent pixels of pixel (i,j); i,j-1 B i,j+1 p represents the photon counts of the vertically adjacent pixels of pixel (i,j); x (x) represents the horizontal probability distribution; p y (y) represents the vertical probability distribution; l represents the size of pixel (i,j); N Xmin The photon count for the horizontal lower boundary of pixel (i,j); N Xmax The photon count for the horizontal upper boundary of pixel (i,j); N Ymin The photon count for the vertical lower boundary of pixel (i,j); N Ymax y is the photon count of the vertical upper boundary of pixel (i,j); x is the horizontal spatial position and y is the vertical spatial position.

[0103] In the specific implementation step S102, Figure 4 A schematic diagram of the detector's spatial position correction is shown, such as... Figure 4 As shown, the photon interaction position measured by the detector is L′. s and L′ a These are the centers of the pixels where the two detector layers interact with photons, and this photon interaction location is relative to the precise photon interaction location L. s and L a There is a certain deviation, therefore L′ needs to be adjusted. s and L′ a The correction is performed to obtain the corrected photon interaction position, making it closer to the accurate photon interaction position L. s and L a The photon interaction position includes both horizontal and vertical directions, and the correction process for both is the same. The following describes the correction process in detail using the horizontal photon interaction position as an example. The correction process for the vertical photon interaction position can be referred to the correction process for the horizontal photon interaction position, except that the relevant processing for the horizontal position x is replaced with the vertical position y. This will not be elaborated further.

[0104] First, select a photon event from the photon event information received by the Compton camera, with its original photon spatial position being (x0, y0). Generate a uniform distribution within the pixel interval of its response pixel (i, j), and obtain a random number x from this uniform distribution. i The random number xi As a candidate spatial action location. For example, if the pixel size of the response pixel of the photon event information is l, and its pixel interval is [0, l], then first generate a uniform distribution U[0, l] corresponding to the pixel interval, and obtain a random number x from the uniform distribution. i ~U[0,l], serves as the candidate spatial action position.

[0105] Subsequently, a uniform distribution of photon counts is obtained, and the upper and lower limits of this uniform distribution are determined. Specifically, the photon counts at the upper and lower boundaries of the horizontal photon counts of the responding pixel of the photon event information, as well as the photon count at the center of the responding pixel, are obtained from the photon count information of the photon event information. The minimum value among these three values ​​is taken as the lower limit of the photon count; the maximum value among these three values ​​is taken as the upper limit of the photon count. The specific formula is as follows:

[0106] N min =min{N Xmin N i,j N Xmax};

[0107] N max =max{N Xmin N i,j N Xmax};

[0108] Where, N min N is the lower limit of the photon count for pixel (i,j); i,j Count the number of photons at the center position of pixel (i,j); N max N represents the upper limit of the photon count for pixel (i,j); Xnin The photon count for the horizontal lower boundary of pixel (i,j); N Xmax The photon count is the horizontal upper boundary of pixel (i,j).

[0109] Then, using the upper and lower limits of the photon count as the upper and lower limits of the uniform distribution, a uniform photon count distribution U[N] is generated for the corresponding photon event information in the response pixel. min N max Finally, in the uniform distribution of photon counts U[N] min N max Get a random number N within the range of ] ti ~U[N min Nmax ], as the candidate photon count.

[0110] In one optional implementation, after obtaining the upper limit and lower limit of photon distribution, the upper limit and lower limit of photon distribution are normalized. The normalized upper limit of photon distribution is used as the upper limit of uniform distribution, and the normalized lower limit of photon distribution is used as the lower limit of uniform distribution.

[0111] After obtaining the candidate photon count and candidate spatial interaction position, the candidate spatial interaction position x i Substituting the lateral probability distribution within the pixel interval (i,j) obtained in S101, the value p of the lateral probability distribution of the candidate spatial action position is obtained. x (x i Finally, the values ​​p of the lateral probability distribution of the candidate spatial action locations are compared. x (x i The relationship between the number of candidate photons and the number of candidate photons.

[0112] In specific implementation step S103, if the photon count p corresponding to the two-dimensional probability distribution of the candidate spatial action position... x (x i The number of candidate photons is greater than N. ti Then the candidate spatial action position x i The original photon spatial interaction position x0 is replaced by the corrected photon spatial interaction position.

[0113] If the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is less than or equal to the candidate photon count, a new uniformly distributed random number is generated based on the pixel interval as a new candidate spatial action position; a new uniformly distributed random number is generated based on the photon count information of the pixel as a new candidate photon count; if the photon count corresponding to the two-dimensional probability distribution of the new candidate spatial action position is greater than the new candidate photon count, the new candidate spatial action position is used as the corrected photon spatial action position, replacing the original photon spatial action position.

[0114] In one alternative implementation, the photon count p corresponding to the two-dimensional probability distribution at the candidate spatial action location x ( i The number of candidate photons is greater than N. tiIn this case, it is necessary to jointly determine whether the candidate spatial action position is available based on the weight information of the pixel mapped to the imaging space. Specifically, firstly, based on the original photon spatial action position x0 of the photon event, obtain the weights of its back-projected cone surface and any reconstructed spatial pixel, and use this as the first weight n for the original photon spatial action position x0. s Subsequently, for the photon count p corresponding to the two-dimensional probability distribution satisfying the candidate spatial action position... x ( i The number of candidate photons is greater than N. ti Candidate space action position x i Replace the original photon spatial position x0 of photon event i with x i Obtain the weights of its back-projected conical surface and any reconstructed spatial pixel, and use them as the weights for the candidate spatial action position x. i The second weight n s+1 Finally, a judgment is made based on the following preset judgment conditions:

[0115]

[0116] Where, n S+1 For the second weight, n s α is the first weight; α is a randomly generated random number uniformly distributed between 0 and 1.

[0117] If the above-mentioned preset judgment condition is met, it means that the first weight and the second weight satisfy the preset judgment condition, and at this time the candidate space action position x i The results mapped to the imaging space demonstrate that they can be used to correct the original spatial action position, and the candidate spatial action position x i This serves as the corrected photon spatial interaction position. Simultaneously, the first and second weights are updated as follows:

[0118] n S+1 = s+1 +1;

[0119] n s = s -1;

[0120] Where, n s+1 For the second weight, n s This is the first weight.

[0121] Furthermore, during the correction process of the spatial position of each sample, the second weight n updated in the previous sample is... s+1 As the first weight n in this sampling s That is, n s =ns+1 .

[0122] If the above preset judgment condition is not met, it means that the first weight and the second weight do not meet the preset judgment condition, and the candidate space action position x is then determined. i If the result mapped to the imaging space cannot be used to correct the original spatial position of action, then this x-axis is rejected. i The process of the rejection-acceptance strategy is repeated until a candidate spatial action position that meets the conditions is obtained, and new candidate spatial action positions and new candidate photon counts are obtained.

[0123] In one optional implementation, each photon event information is sampled a preset number of times. Each photon event information will yield multiple corrected photon spatial interaction positions corresponding to the preset number of sampling times. The average of these multiple corrected photon spatial interaction positions (i.e., the expected value) is taken as the corrected photon spatial interaction position for each photon event information. It should be noted that the preset number of training iterations can be determined according to actual conditions, and this application does not impose any limitations on it. Taking the lateral spatial interaction position as an example, the corrected lateral spatial interaction position is calculated according to the following formula:

[0124]

[0125] in, The corrected lateral spatial position; x i The corrected photon spatial position is the location of the photon in each sampling; N is the preset number of samplings, N = 1, ..., n.

[0126] It should be noted that the above S102-S103 process is described using the lateral photon interaction position as an example in order to enable those skilled in the art to better understand the method of this application. In actual operation, it is also necessary to follow the same correction process to replace the relevant processing of the lateral position x with the longitudinal position y to obtain the corrected longitudinal photon interaction position. For details, please refer to the above content, which will not be repeated here.

[0127] Thus, the projection data of the response pixel (i,j) for the photon event information has been obtained. Finally, the projection data is mapped in the imaging space to obtain the image reconstruction result, which is the projection data. The corresponding set of weight counts for reconstructed spatial pixels {n s}

[0128] This application provides a method for correcting the spatial interaction position of a Compton camera, comprising: acquiring photon event information, the photon event information including the original spatial interaction position, a pixel interval, and photon count information of the pixels; generating uniformly distributed random numbers based on the pixel interval as candidate spatial interaction positions; generating uniformly distributed random numbers based on the photon count information of the pixels as candidate photon counts; if the photon count corresponding to the two-dimensional probability distribution of the candidate spatial interaction position is greater than the candidate photon count, using the candidate spatial interaction position as the corrected spatial interaction position and replacing the original photon spatial interaction position. The method of this application has the following advantages:

[0129] (3) By constructing a two-dimensional probability distribution of the spatial action position, the amount of computation for spatial action position correction is greatly reduced. Moreover, the two-dimensional probability distribution is simple and intuitive, has less computation, and is faster. It is more in line with the actual projection data collected by the detector and can effectively improve the imaging accuracy of the Compton camera.

[0130] (4) The two-dimensional probability distribution is sampled by uniformly distributed random numbers within the pixel range to obtain the correction value of the spatial action position. The correction obtained by this method has high accuracy, wide applicability and low computational complexity, which effectively improves the imaging accuracy of the Compton camera.

[0131] To enable those skilled in the art to better understand this application, the Compton camera photon spatial interaction position correction method described in this application will now be explained in detail through the following embodiments.

[0132] Example 1

[0133] The Compton camera collects photons. In this embodiment, Geant4 is used to simulate a three-layer CZT Compton camera to detect transient photons generated by a proton beam hitting a water model. The application scenario requires accurate reconstruction of the peak position and far-end falling edge of the Bragg peak region of the transient photon distribution. Figure 5 A schematic diagram of a Compton camera is shown, such as Figure 5 As shown, the first and third stage detectors of the Compton camera consist of 11×11 pixelated CZT crystal arrays with a total CZT area of ​​5.5cm×5.5cm. The second stage consists of a 21×21 array with a total area of ​​10.5cm×10.5cm. The detectors in adjacent layers are spaced 3cm apart. The detector pixel size is 5×5mm. 2 The response is generated as a photon event on the pixels of each detector layer. In this embodiment, the Compton camera collects a total of [number missing] photos. 12 C, 15 O and 16A total of 171,000 effective photon events were generated by the de-excitation of O atoms. The pixel range, the original photon spatial position, and the photon count information of each photon event on the response pixel were recorded.

[0134] For all pixels on the three-layer detector, a two-dimensional probability distribution of the photon spatial interaction position of each layer of the detector is obtained by combining the photon count of each pixel with the photon counts of its four adjacent pixels (left, right, top, and bottom). Specifically, the horizontal probability distribution is calculated using the photon count information of each responding pixel and the photon count information of its two horizontally adjacent pixels (left and right); the vertical probability distribution is calculated using the photon count information of each responding pixel and the photon count information of its two vertically adjacent pixels (top and bottom). Finally, after obtaining the horizontal and vertical probability distributions, the pixels are truncated according to the pixel interval in which the responding pixel is located, resulting in the horizontal and vertical probability distributions within that interval.

[0135] Figure 6 This embodiment shows a schematic flowchart of the Compton camera photon spatial interaction position correction method. Figure 6 As shown, firstly, a photon event is selected from the photon event information received by the Compton camera, with its original photon spatial position being (x0, y0). A uniform distribution is generated within the pixel interval of its response pixel (i, j), and a random number x is obtained from this uniform distribution. i The random number x i As a candidate spatial location.

[0136] Subsequently, a uniform distribution of photon counts is first obtained, and the upper and lower limits of the uniform distribution of photon counts are determined. Specifically, the photon counts at the horizontal upper boundary, the horizontal lower boundary, and the center of the responding pixel of the photon event information are obtained from the photon count information of the photon event information. The minimum value among the three values ​​is taken as the lower limit of the photon count; the maximum value among the three values ​​is taken as the upper and lower limit of the photon count. Then, the uniform distribution of photon counts U[N] for the responding pixel of the corresponding photon event information is generated using the upper and lower limits of the photon count as the upper and lower limits of the uniform distribution. min N max Finally, in the uniform distribution of photon counts U[N] min N max Get a random number N within the range of ] ti ~U[N min Nmax ], as the candidate photon count.

[0137] After obtaining the candidate photon count and candidate spatial interaction position, the candidate spatial interaction position x i Substituting the values ​​into the lateral probability distribution within the pixel interval (i,j), we obtain the photon count p corresponding to the lateral probability distribution of the candidate spatial action position. x (x i Finally, the photon counts p corresponding to the lateral probability distributions of the candidate spatial action positions are compared. x (x i The relationship between the number of candidate photons and the number of candidate photons.

[0138] The photon count p corresponding to the two-dimensional probability distribution at the candidate spatial action location x (x i The number of candidate photons is greater than N. ti In this case, first, based on the original photon spatial interaction position x0 of the photon event, obtain the weights of its back-projected cone surface and any reconstructed spatial pixel, and use them as the first weight n for the original photon spatial interaction position x0. s Subsequently, for the photon count p corresponding to the two-dimensional probability distribution satisfying the candidate spatial action position... x (x i The number of candidate photons is greater than N. ti Candidate space action position x i Replace the original photon spatial position x0 of photon event i with x i Obtain the weights of its back-projected conical surface and any reconstructed spatial pixel, and use them as the weights for the candidate spatial action position x. i The second weight n s+1 Finally, a judgment is made based on the following preset judgment conditions:

[0139]

[0140] Where, n s+1 For the second weight, n s α is the first weight; α is a randomly generated random number uniformly distributed between 0 and 1.

[0141] If the above-mentioned preset judgment condition is met, it means that the first weight and the second weight satisfy the preset judgment condition, and at this time the candidate space action position x i The results mapped to the imaging space demonstrate that they can be used to correct the original spatial action position, and the candidate spatial action position x i This serves as the corrected photon spatial interaction position. Simultaneously, the first and second weights are updated as follows:

[0142] n s+1 =n s+1 +1;

[0143] n s =n s -1;

[0144] Where, n s+1 For the second weight, n s This is the first weight.

[0145] Furthermore, during the correction process of the spatial position of each sample, the second weight n updated in the previous sample is... s+1 As the first weight n in this sampling s That is, n s =n s+1 .

[0146] If the above-mentioned preset judgment conditions are not met, or if the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is less than or equal to the candidate photon count, a new candidate spatial action position and a new candidate photon count are obtained, and the above rejection-acceptance strategy process is repeated until a candidate spatial action position that meets the conditions is obtained.

[0147] For each photon event, the above steps are repeated 100 times, for a total of 100 × 171000 iterations. Each photon event will yield 100 corrected photon spatial interaction positions corresponding to these 100 samples. The average of these corrected photon spatial interaction positions (i.e., the expected value) is taken as the corrected photon spatial interaction position for each photon event. Finally, the projection data is mapped in the imaging space to obtain the image reconstruction result.

[0148] Figure 7 A comparison diagram of the reconstruction results of this embodiment is shown, such as... Figure 7 As shown, the image quality reconstructed after photon spatial action position correction using the correction method of this application is better, and the reconstruction of the shape of the radiation source (hot spot area) is closer to the accurate value. Moreover, as can be seen from the cross-sectional view, the correction method of this application significantly improves the accuracy of the reconstruction of the radiation source boundary and peak position. Compared with the uniform distribution correction method of the prior art, the peak position corrected by the method of this application is closer to the accurate value, and has higher reconstruction accuracy.

[0149] Based on the same inventive concept, this application discloses a Compton camera photon spatial interaction position correction device. Figure 8 A schematic diagram of a Compton camera photon spatial interaction position correction device is shown, such as... Figure 8 As shown, it includes:

[0150] The acquisition module is used to acquire photon event information, which includes the original photon spatial location, pixel range, and photon count information of the pixel;

[0151] The generation module generates uniformly distributed random numbers based on the pixel interval as candidate spatial action positions; and generates uniformly distributed random numbers based on the photon count information of the pixels as candidate photon counts.

[0152] The correction module is used to replace the original photon spatial action position with the corrected photon spatial action position if the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is greater than the candidate photon count.

[0153] The generation module includes:

[0154] The lower limit value acquisition submodule is used to acquire the minimum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel, as the distribution lower limit value;

[0155] The upper limit value acquisition submodule is used to acquire the maximum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel, as the upper limit value of the distribution;

[0156] A photon count distribution generation submodule is used to generate a uniform photon count distribution based on the upper limit value and the lower limit value of the distribution;

[0157] The candidate photon count generation submodule is used to obtain random numbers within the range of the uniform distribution of the photon counts, and use them as the candidate photon counts.

[0158] The device further includes:

[0159] The first weight acquisition module is used to acquire a first weight for the original photon space action position based on the original photon space action position.

[0160] The second weight acquisition module is used to acquire a second weight for the candidate space action position based on the candidate space action position;

[0161] The weight correction module is used to take the candidate spatial action position as the corrected photon spatial action position if the first weight and the second weight meet a preset judgment condition. The preset judgment condition is as follows:

[0162]

[0163] Where, n S+1For the second weight, n s α is the first weight; α is a randomly generated random number uniformly distributed between 0 and 1.

[0164] The correction module includes:

[0165] The two-dimensional probability distribution construction submodule is used to construct the distribution according to the following formula:

[0166]

[0167]

[0168]

[0169]

[0170] Where, N i,j For the photon count of pixel (i,j); N i-1,j N i+1,j N represents the photon counts of the horizontally adjacent pixels of pixel (i,j); i,j-1 N i,j+1 p represents the photon counts of the vertically adjacent pixels of pixel (i,j); x (x) represents the horizontal probability distribution; p y (y) represents the vertical probability distribution; l represents the size of pixel (i,j); N Xmin The photon count for the horizontal lower boundary of pixel (i,j); N Xmax The photon count for the horizontal upper boundary of pixel (i,j); N Ymin The photon count for the vertical lower boundary of pixel (i,j); N Ymax y is the photon count of the vertical upper boundary of pixel (i,j); x is the horizontal spatial position and y is the vertical spatial position.

[0171] The device further includes:

[0172] The second generation module is used to generate new uniformly distributed random numbers based on the pixel interval as new candidate spatial action positions; and to generate new uniformly distributed random numbers based on the photon count information of the pixel as new candidate photon counts.

[0173] The second correction module is used to replace the original photon spatial action position with the new candidate spatial action position if the photon count corresponding to the two-dimensional probability distribution of the new candidate spatial action position is greater than the new candidate photon count.

[0174] Based on the same inventive concept, embodiments of this application disclose an electronic device. Figure 9A schematic diagram of an electronic device disclosed in an embodiment of this application is shown, such as... Figure 9 As shown, the electronic device 100 includes a memory 110 and a processor 120. The memory 110 and the processor 120 are connected via a bus for communication. The memory 110 stores a computer program that can run on the processor 120 to implement the steps in the Compton camera photon spatial action position correction method disclosed in the embodiments of this application.

[0175] Based on the same inventive concept, embodiments of this application disclose a computer-readable storage medium storing a computer program / instruction thereon, which, when executed by a processor, implements the steps in the Compton camera photon spatial action position correction method disclosed in embodiments of this application.

[0176] Based on the same inventive concept, this application also provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps in the Compton camera photon spatial action position correction method disclosed in the embodiments of this application.

[0177] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0178] Embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, apparatuses, electronic devices, and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0179] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0180] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal equipment, causing a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0181] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0182] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0183] The Compton camera photon spatial action position correction method and product provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for correcting the spatial interaction position of photons in a Compton camera, characterized in that, include: Photon event information is acquired, including the original photon spatial location, pixel range, and photon count information of the pixel. The original photon spatial location is the two-dimensional planar coordinate (x0, y0) of the pixel position of the photon event in the xy plane; the pixel range is the size range of the pixel of the photon event, which depends on the shape and size of the pixel; the photon count of the pixel is the number of photon events occurring within the pixel of the photon event. A uniformly distributed random number is generated based on the pixel interval as a candidate spatial action position; a uniformly distributed random number is generated based on the photon count information of the pixel as a candidate photon count. If the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is greater than the candidate photon count, the candidate spatial action position is used as the corrected photon spatial action position, replacing the original photon spatial action position. Generating uniformly distributed random numbers based on the pixel interval as candidate spatial action positions includes: generating a uniform distribution within the pixel interval of pixel (i,j), and obtaining a random number x from the uniform distribution. i , the random number x i As the candidate spatial action location; The photon count information of the pixel includes the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel. Based on the photon count information of the pixel, uniformly distributed random numbers are generated as candidate photon counts, including: The minimum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel is obtained as the lower limit of the distribution. The maximum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel is used as the upper limit of the distribution. A uniform distribution of photon counts is generated based on the upper and lower limits of the distribution. Random numbers are obtained within the range of the uniform distribution of the photon counts and used as candidate photon counts. The two-dimensional probability distribution is constructed according to the following formula: ； ； in, Count the number of photons for pixel (i,j); , The photon counts of the pixels horizontally adjacent to pixel (i,j) are respectively. , These are the photon counts of the vertically adjacent pixels of pixel (i,j); It is a horizontal probability distribution; It is a vertical probability distribution; Let be a probability function.

2. The Compton camera photon spatial interaction position correction method according to claim 1, characterized in that, If the photon count corresponding to the two-dimensional probability distribution at the candidate spatial action location is greater than the candidate photon count, the method further includes: Based on the original photon space interaction position, obtain the first weight for the original photon space interaction position; Based on the candidate spatial position, obtain a second weight for the candidate spatial position; If the first weight and the second weight satisfy a preset judgment condition, the candidate spatial action position is taken as the corrected photon spatial action position. The preset judgment condition is as follows: in, This is the second weight. This is the first weight; A random number that is uniformly distributed between 0 and 1.

3. The Compton camera photon spatial interaction position correction method according to claim 1, characterized in that, When the pixel interval is a square pixel interval, the photon count corresponding to the two-dimensional probability distribution is constructed according to the following formula: ； ； ； ； in, Count the number of photons for pixel (i,j); , The photon counts of the pixels horizontally adjacent to pixel (i,j) are respectively. , These are the photon counts of the vertically adjacent pixels of pixel (i,j); It is a horizontal probability distribution; represents the vertical probability distribution; l is the size of pixel (i,j); The photon count for the horizontal lower boundary of pixel (i,j); Photon count for the horizontal upper boundary of pixel (i,j) The photon count for the vertical lower boundary of pixel (i,j); y is the photon count of the vertical upper boundary of pixel (i,j); x is the horizontal spatial position and y is the vertical spatial position.

4. The Compton camera photon spatial interaction position correction method according to claim 1, characterized in that, When the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is less than or equal to the candidate photon count, the method further includes: New uniformly distributed random numbers are generated based on the pixel interval as new candidate spatial action positions; new uniformly distributed random numbers are generated based on the photon count information of the pixel as new candidate photon counts. If the photon count corresponding to the two-dimensional probability distribution of the new candidate spatial action position is greater than the new candidate photon count, the new candidate spatial action position is used as the corrected photon spatial action position, replacing the original photon spatial action position.

5. A Compton camera photon spatial interaction position correction device, characterized in that, include: The acquisition module is used to acquire photon event information, which includes the original photon spatial location, pixel range, and photon count information of the pixel. The original photon spatial location is the two-dimensional planar coordinate (x0, y0) of the pixel position of the photon event in the xy plane; the pixel range is the size range of the pixel of the photon event, which depends on the shape and size of the pixel; and the photon count of the pixel is the number of photon events that occurred within the pixel of the photon event. The generation module generates uniformly distributed random numbers based on the pixel interval as candidate spatial action positions; and generates uniformly distributed random numbers based on the photon count information of the pixels as candidate photon counts. The correction module is used to replace the original photon spatial action position with the corrected photon spatial action position if the photon count corresponding to the two-dimensional probability distribution of the candidate spatial action position is greater than the candidate photon count. The photon count information of the pixel includes the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel; the generation module is specifically used for: Generate a uniform distribution within the pixel interval (i,j), and obtain a random number x from this uniform distribution. i , the random number x i As the candidate spatial action location; The minimum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel is obtained as the lower limit of the distribution. The maximum value among the photon count at the upper boundary of the pixel, the photon count at the lower boundary of the pixel, and the photon count at the center of the pixel is used as the upper limit of the distribution. A uniform distribution of photon counts is generated based on the upper and lower limits of the distribution. Random numbers are obtained within the range of the uniform distribution of the photon counts and used as candidate photon counts. The correction module is specifically used for: The two-dimensional probability distribution is constructed according to the following formula: ； ； in, Count the number of photons for pixel (i,j); , The photon counts of the pixels horizontally adjacent to pixel (i,j) are respectively. , These are the photon counts of the vertically adjacent pixels of pixel (i,j); It is a horizontal probability distribution; It is a vertical probability distribution; Let be a probability function.

6. An electronic device, characterized in that, The system includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps in the Compton camera photon spatial action position correction method according to any one of claims 1-4.

7. A computer-readable storage medium having a computer program / instructions stored thereon, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps in the Compton camera photon spatial action position correction method according to any one of claims 1-4.

8. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps in the Compton camera photon spatial action position correction method according to any one of claims 1-4.

Images