High-sensitivity ray imaging linear array detection system and positioning method

Abstract

The invention discloses a high-sensitivity ray imaging linear array detection system and a positioning method. The high-sensitivity ray imaging linear array detection system comprises a linear array detector, a photoelectric detector array, a calibration unit and a signal analysis and processing unit, the linear array detector is of a multi-layer structure formed by I first pixels, projections of the linear array detector on the horizontal plane are not completely overlapped, the photoelectric detector array is of P * Q second pixels formed by P * Q photoelectric detectors, and the calibration unit is used for generating a system matrix. And the action position of the ray and the linear array detector is found in the signal analysis processing unit according to the positioning method in combination with the actual measurement photoelectric detector array response and the system matrix, and the deposition energy is calculated. According to the invention, only one set of photoelectric detector array and the readout electronics system are adopted, so that the action positions and deposition energy of rays and a plurality of linear array detectors can be accurately estimated. And the detection sensitivity can be greatly improved while the same spatial resolution as the original single linear array detector is maintained.

Description

Technical Field

[0001] This invention relates to the field of nuclear radiation detection technology, and in particular to a high-sensitivity X-ray imaging linear array detection system and positioning method. Background Technology

[0002] In radiation imaging applications, pixel-type linear scintillation detectors are often used to obtain the location information of radiation sources. These detectors convert X-rays into fluorescent signals, which are then converted into electrical signals by a photodetector coupled to a scintillation crystal. These electrical signals are then amplified, conditioned, and acquired to obtain digital signals, allowing for the estimation of energy deposition, location, and timing information of the X-rays within the detector. In time-coded imaging and X-ray imaging, the size of a single pixel in the linear array detector significantly impacts both the spatial resolution and system sensitivity: increasing the pixel size improves system sensitivity but reduces spatial resolution; conversely, decreasing the pixel size increases spatial resolution but significantly reduces the overall size of the detector, leading to decreased sensitivity. A performance trade-off exists between these two factors.

[0003] For pixel-type linear array detectors, achieving higher spatial resolution requires smaller pixel sizes, but this significantly reduces detector sensitivity. Existing patents address this issue, such as the invention patent titled "High-Sensitivity 3D Panoramic X-ray Imaging System and Imaging Method" (application number 202310934645.1). This method uses multiple linear array detectors to resolve the trade-off between spatial resolution and sensitivity. However, more linear array detectors require more corresponding photodetector arrays and readout circuits, leading to a significant increase in design costs. Furthermore, existing scintillation detectors and photodetectors employ one-to-one coupling and beam splitting coupling methods. With one-to-one coupling, the position of the interacting crystal and the deposited energy can be directly obtained from the response of each readout channel, resulting in the highest accuracy. However, this configuration in high-resolution applications requires both the linear array detector and the photodetector to have smaller pixel sizes, thus greatly increasing the number of readout channels. Each channel has independent signal amplification, conditioning, and acquisition circuits. Using independent components makes it difficult to achieve a compact design for the detection system, while using ASIC chips to implement these functions presents high costs. The one-to-many splitting configuration of photodetector pixels and scintillation detector pixels can greatly reduce the number of readout channels, but each linear array detector still requires its own photodetector array and readout circuit, resulting in high system design costs. Summary of the Invention

[0004] The purpose of this invention is to provide a high-sensitivity X-ray imaging linear array detection system and positioning method that solves the above-mentioned problems, and achieves the same spatial resolution as the original single linear array detector while greatly increasing the detection sensitivity, using only photodetectors and readout circuits with the same or similar number of pixels as the original single linear array detector.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a high-sensitivity X-ray imaging linear array detection system, comprising a linear array detector, a photodetector array, a calibration unit, and a signal analysis and processing unit; The linear array detector is used to convert ionizing radiation into optical signals, and includes M cuboid scintillators, wherein the m-th scintillator is divided into L sections along its length. m There are N first pixels, 1≤m≤M, all scintillators are parallel to each other and set horizontally, stacked in N layers from top to bottom, and the projections of all first pixels on the horizontal plane do not completely overlap. Linear array detectors Each first pixel is marked as first pixel i. Except for the lower surface of the Nth scintillator and the contact surface between the upper and lower scintillators, the other surfaces of the linear array detector are provided with light-blocking layers. The bottom surface of the linear array detector is optically coupled to the photodetector array. The photodetector array is used to convert optical signals into electrical signals. It includes P×Q photodetectors, each of which is regarded as a second pixel, with a total of P×Q second pixels. The j-th second pixel is marked as second pixel j. The output of each photodetector is connected to a preamplifier module for amplifying the electrical signal. The calibration unit is used to generate the system matrix A and the counting vector V. max The element a in row i and column j of A i,j Let be the probability that the light signal of the first pixel i is detected by the second pixel j; The signal analysis and processing unit is connected to the preamplifier module and the calibration unit, and is used to extract the interaction position and deposited energy of the X-ray and linear array detectors based on the output of the preamplifier module and the calibration unit.

[0006] Preferably, the photodetector includes a photomultiplier tube, a PIN photodiode, an avalanche photodiode, and a silicon photomultiplier tube.

[0007] Preferably, during optical coupling, only the lower surface of the Nth layer scintillator of the linear array detector is optically coupled to the photodetector through the light guide layer.

[0008] Preferably, the calibration unit generates a system matrix A and a counting vector V. max The method is as follows: Sa1, using a known energy of E CThe radiation source provides sufficient and uniform illumination to the linear array detector, ensuring that all first pixels of the detector detect N1 valid events. For each valid event, the count value of first pixel i on second pixel j is q. i,j ; Sa2, the average count value of the first pixel i on the second pixel j among N1 valid cases. P×Q second pixels correspond to a total of P×Q average count values; Sa3, mark the maximum value of P×Q average counts as... As V max Calculate a for the i-th element. i,j , , will a i,j a, the element in row i and column j of A i,j , which represents the probability that the light signal of the first pixel i is detected by the second pixel j.

[0009] A positioning method for a high-sensitivity X-ray imaging linear array detection system includes the following steps; S1, Construct a high-sensitivity X-ray imaging linear array detection system, wherein the linear array detector includes The photodetector array includes P×Q second pixels, where the i-th pixel is labeled as first pixel i, and the j-th pixel is labeled as second pixel j, 1≤i≤i, 1≤j≤P×Q; S2, generate system matrix A and counting vector V max ; S3, In actual measurement, the high-sensitivity X-ray imaging linear array detection system is placed in the detection area to detect valid events. For each valid event, the response of the photodetector array is obtained. , where q j Let L be the count value of the second pixel j, and calculate the log-likelihood value L of the first pixel i according to the following formula. i ; , Where maxq is the maximum value of the elements in q, q j ! for q j factorial; S4, mark the first pixel with the largest log-likelihood value as i. ML , change i ML The location is used as the effective position of the ray and linear array detectors, and the deposition energy is calculated according to the following formula. ; , In the formula, E C The energy of the radiation source when constructing the system matrix A, For i ML Corresponding to Vmax The value in.

[0010] In this invention, the methods for generating system matrix A by the calibration unit include analytical calculation, Monte Carlo simulation, and experimental measurement.

[0011] Compared with the prior art, the advantages of the present invention are as follows: (1) A linear array detector structure was designed, which uses linear array scintillators. Each scintillator is a cuboid and its length can be the same or different. For the m-th scintillator, when it is divided into L along the length direction... m When the first pixel is reached, a 1×L matrix is ​​formed. m The linear array structure comprises M scintillators stacked in N layers, arranged horizontally and parallel to each other, increasing in number from top to bottom. The projections of each first pixel in the horizontal plane are not completely overlapping. To achieve this non-overlapping structure, the scintillators in different layers must be offset along their length and / or horizontal direction. This structure, resulting in imperfect alignment between the first pixels of different layers, has the advantage of increasing the scintillator light distribution characteristics of different layers, enabling each pixel to generate a unique scintillator light response. Combined with the positioning method of this invention, it allows for accurate estimation of the interaction position and deposited energy between a ray and multiple linear array detectors using only one set of photodetector arrays and readout electronics systems. The N layers can be stacked into a triangular, trapezoidal, or similar triangular structure.

[0012] (2) In the design of the photodetector array, it contains P×Q photodetectors. Each photodetector is regarded as a second pixel, with a total of P×Q second pixels. A preamplifier module is connected to the output of each photodetector to amplify the electrical signal.

[0013] (3) Existing linear array detectors cannot overcome the trade-off between spatial resolution and sensitivity in applications such as time-coded imaging. If the application scenario requires a high level of one parameter, the other parameter must be sacrificed in the detector design. This invention solves this problem well, and only uses the same or similar photodetector as a single linear array detector and a set of readout electronics system (including a preamplifier module and a signal analysis and processing unit) to accurately estimate the position and energy of the interaction between multiple linear array detectors and rays. Based on this structure, the positioning method of this invention can greatly increase the detection sensitivity while maintaining the same spatial resolution as the original single linear array detector. Attached Figure Description

[0014] Figure 1 A schematic diagram of a linear array detector where scintillators are stacked together when N=2. Figure 2A schematic diagram of a linear array detector where N=3 scintillators are stacked together. Figure 3 A schematic diagram of another structure for a linear array detector when N=3 scintillators are stacked. Figure 4 This is a schematic diagram showing the connection between a linear array detector and a photodetector array. Figure 5 This is a schematic diagram of a high-sensitivity X-ray imaging linear array detection system. Figure 6 This is the photodetector array response diagram corresponding to a valid case measured in Example 2.

[0015] In the diagram: 1. Scintillator; 2. First pixel; 3. Second pixel; 4. Linear array detector; 5. Photodetector array; 6. Optical guide layer; 7. Signal analysis and processing unit. Detailed Implementation

[0016] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0017] Example 1: See Figures 1 to 6 A high-sensitivity X-ray imaging linear array detection system includes a linear array detector 4, a photodetector array 5, a calibration unit, and a signal analysis and processing unit 7. The linear array detector 4 is used to convert ionizing radiation into optical signals, and includes M rectangular scintillators 1, wherein the m-th scintillator 1 is divided into L sections along its length. m There are N first pixels 2, 1≤m≤M, all scintillators 1 are parallel to each other and horizontally set, stacked in N layers in a manner that increases from top to bottom, and the projections of all first pixels 2 on the horizontal plane do not completely overlap. Linear array detector 4 Each first pixel 2, wherein the i-th pixel is marked as first pixel 2i, and the linear array detector 4 is provided with a light-blocking layer on all surfaces except the lower surface of the Nth scintillator 1 and the contact surface between the upper and lower scintillators 1. The bottom surface of the linear array detector 4 is optically coupled to the photodetector array 5. The photodetector array 5 is used to convert optical signals into electrical signals. It includes P×Q photodetectors, each of which is regarded as a second pixel 3, with a total of P×Q second pixels 3. The j-th pixel is marked as second pixel 3j. The output of each photodetector is connected to a preamplifier module for amplifying the electrical signal. The calibration unit is used to generate the system matrix A and the counting vector V. max The element a in row i and column j of A i,j The probability that the light signal of the first pixel 2i is detected by the second pixel 3j;

[0018] The signal analysis and processing unit 7 is connected to the preamplifier module and the calibration unit, and is used to extract the action position and deposited energy of the X-ray and linear array detector 4 based on the output of the preamplifier module and the calibration unit.

[0019] In this invention, the photodetector includes a photomultiplier tube, a PIN photodiode, an avalanche photodiode, and a silicon photomultiplier tube.

[0020] During optical coupling, only the lower surface of the Nth layer scintillator 1 of the linear array detector 4 is optically coupled to the photodetector through the light guide layer 6.

[0021] The calibration unit generates a system matrix A and a counting vector V. max The method is as follows: Sa1, using a known energy of E C The radiation source provides sufficient and uniform illumination to the linear array detector 4, ensuring that all first pixels 2 of the linear array detector 4 detect N1 valid events. For each valid event, the count value of the first pixel 2i on the second pixel 3j is q. i,j ; Sa2, the average count value of the first pixel 2i on the second pixel 3j among N1 valid cases. P×Q second pixels 3 correspond to a total of P×Q average count values; Sa3, mark the maximum value of P×Q average counts as... As V max Calculate a for the i-th element. i,j , , will a i,j a, the element in row i and column j of A i,j , which represents the probability that the light signal of the first pixel 2i is detected by the second pixel 3j.

[0022] A positioning method for a high-sensitivity X-ray imaging linear array detection system includes the following steps; S1, Construct a high-sensitivity X-ray imaging linear array detection system, wherein the linear array detector 4 includes The first pixel 2 is labeled as the first pixel 2i, and the photodetector array 5 includes P×Q second pixels 3, where the j-th pixel is labeled as the second pixel 3j, 1≤i≤1, 1≤j≤P×Q; S2, generate system matrix A and counting vector V max ; S3, In actual measurement, the high-sensitivity X-ray imaging linear array detection system is placed in the detection area to detect valid events. For each valid event, the response of the photodetector array 5 is obtained. , where q jLet 3j be the count value of the second pixel, and calculate the log-likelihood value L of the first pixel 2i according to the following formula. i ; , Where maxq is the maximum value of the elements in q, q j ! for q j factorial; S4, mark the first pixel 2 with the largest log-likelihood value as i. ML , change i ML The location is used as the effective position of the ray and linear array detector 4, and the deposition energy is calculated according to the following formula. ; , In the formula, E C The energy of the radiation source when constructing the system matrix A, For i ML Corresponding to V max The value in.

[0023] In this embodiment, the stacking of scintillators 1 can be configured according to actual needs, see [reference]. Figures 1-3 Three specific stacking methods are given. Figure 1 Three scintillators 1 are stacked into two layers. At this time, each scintillator 1 is divided into 12 first pixels 2 along the length direction. Figure 1 By misaligning the elements, the projections of each first pixel 2 on the horizontal plane will not completely overlap. Figure 1 The medium-length strip shadow structure is a scintillator 1 containing 12 first pixels 2. Figure 2 A method of stacking 6 scintillators in 13 layers is given. The scintillators 1 in the second and third layers are divided into 12 first pixels 2 along the length direction and the ends are aligned. The second layer is aligned with the middle seam of the third layer. If the first layer still has 12 first pixels 2 and is aligned with the middle seam of the second layer, the first pixels 2 in the first layer and the first pixels 2 in the middle of the third layer will overlap in projection on the horizontal plane. Therefore, the length of the first scintillator 1 is shortened to contain 11 first pixels 2, and compared with the second and third layers, it is reduced by half the size of the first pixel 2 in the length direction. In this way, the first pixels 2 in the three layers can achieve "incomplete overlap in projection on the horizontal plane". Figure 3 Similarly, Figure 3 The first, second, and third layers have 2, 3, and 4 scintillators 1, respectively. The length of the scintillators 1 in the second and third layers is 12 first pixels 2. The length of the scintillators 1 in the first layer is shortened to 11 first pixels 2, and the length is reduced by 0.25 to 0.75 first pixels.

[0024] Example 2: See Figures 4 to 6For a high-sensitivity X-ray imaging linear array detection system, this embodiment provides a more specific structure as follows.

[0025] Linear detector 4 and photodetector array 5, as Figure 4 The structure shown is such that the linear array detector 4 consists of three scintillators 1 stacked in two layers. Each scintillator 1 is composed of 1×12 independent high-yield GAGG(Ce) scintillating crystal pixels, which are the first pixels 2. Each crystal pixel has six polished surfaces, and the single crystal size is 2.935×2.935×2.935 mm³. The linear array detector 4 is a two-layer stack. The part with the light-blocking layer has a thickness of 0.065 mm. In this embodiment, the linear array detector 4 contains a total of 36 first pixels, which are labeled as G0~G35 for easy differentiation.

[0026] The photodetector array 5 consists of 2×7 photodetectors (SiPMs) with a single pixel cross-sectional area of ​​6.0×6.0 mm². Each SiPM has a separate preamplifier module to amplify the output signal of the SiPM. Here, each SiPM is regarded as a second pixel 3, with a total of 14, labeled S0~S13. The output of each preamplifier module is connected to a signal analysis and processing unit 7, which processes the signal to obtain the measured charge or scintillation fluorescence of each second pixel 3.

[0027] The light guide layer 6 is a 1mm thick silicone pad, placed between the linear array detector 4 and the photodetector array 5 for optical coupling. A power supply module is also required to supply power to each power-consuming unit.

[0028] The rest of the high-sensitivity X-ray imaging linear array detection system in this embodiment is the same as in Embodiment 1.

[0029] A positioning method for a high-sensitivity X-ray imaging linear array detection system includes steps S1-S4, wherein S1 and S2 are the same as S1 and S2 in the positioning method of Example 1. S3 and S4 involve setting up a valid case for verification, specifically:

[0030] S3, in actual measurement, uses an energy of E c After a gamma ray of 511 keV undergoes photoelectric deposition on the first pixel 2G26, the energy is deposited. The number of fluorescent photons detected by each SiPM is used as the count value to obtain the response q of the photodetector array 5: q = (26,965,137,5,1,0,0,18,868,150,4,2,1,0), which can then be visualized as... Figure 6 , Figure 6The 14 SiPMs in the middle are S0~S13 from left to right and top to bottom. The red numbers represent the count value corresponding to each SiPM, and the color band on the right represents the count value. Then, the log-likelihood value of each first pixel 2 is calculated based on q. To reduce the computational load, it is observed that the maximum value of q in this embodiment is 965, corresponding to the second pixel 3S1. The first pixels 2 closest to S1 are G0, G1, G2, G3, G24, G25, and G26. Therefore, we only calculate the log-likelihood values ​​of these 7 first pixels 2, which are -3887.87, -792.839, -320.307, -2987.03, -3899.15, -510.588, and -30.0439, respectively.

[0031] S4, according to S3, shows that G26 has the largest log-likelihood value. Therefore, the position of G26 is the interaction position between the ray and the linear array detector 4, and according to the formula... Calculate the deposition energy, and finally: =0.511(19.086+934.085+167.329+4.189+0.565+0.202+0.082+19.016+939.17+166.828+4.133+0.578+0.174+0.083) / ( 965*(0.00317+0.165711+1+0.018877+0.001245+0.002583+0.082455+0.37935+0.013968+0.001124+0.000267))=0.690 MeV.

[0032] This embodiment runs at approximately 1 million times per second on a Mac computer with an Apple M4 chip, thus fully meeting the requirements of applications with high real-time performance and demonstrating practical feasibility.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-sensitivity X-ray imaging linear array detection system, characterized in that, It includes a linear array detector, a photodetector array, a calibration unit, and a signal analysis and processing unit; The linear array detector is used to convert ionizing radiation into optical signals, and includes M cuboid scintillators, wherein the m-th scintillator is divided into L sections along its length. m There are N first pixels, 1≤m≤M, all scintillators are parallel to each other and set horizontally, stacked in N layers from top to bottom, and the projections of all first pixels on the horizontal plane do not completely overlap. Linear array detectors Each first pixel is marked as first pixel i. Except for the lower surface of the Nth scintillator and the contact surface between the upper and lower scintillators, the other surfaces of the linear array detector are provided with light-blocking layers. The bottom surface of the linear array detector is optically coupled to the photodetector array. The photodetector array is used to convert optical signals into electrical signals. It includes P×Q photodetectors, each of which is regarded as a second pixel, with a total of P×Q second pixels. The j-th second pixel is marked as second pixel j. The output of each photodetector is connected to a preamplifier module for amplifying the electrical signal. The calibration unit is used to generate the system matrix A and the counting vector V. max The element a in row i and column j of A i,j Let be the probability that the light signal of the first pixel i is detected by the second pixel j; The signal analysis and processing unit is connected to the preamplifier module and the calibration unit, and is used to extract the interaction position and deposited energy of the X-ray and linear array detectors based on the output of the preamplifier module and the calibration unit.

2. The high-sensitivity X-ray imaging linear array detection system according to claim 1, characterized in that, The photodetector includes a photomultiplier tube, a PIN photodiode, an avalanche photodiode, and a silicon photomultiplier tube.

3. The high-sensitivity X-ray imaging linear array detection system according to claim 1, characterized in that, During optical coupling, only the lower surface of the Nth layer scintillator of the linear array detector is optically coupled to the photodetector through the light guide layer.

4. The high-sensitivity X-ray imaging linear array detection system according to claim 1, characterized in that, The calibration unit generates a system matrix A and a counting vector V. max The method is as follows: Sa1, using a known energy of E C The radiation source provides sufficient and uniform illumination to the linear array detector, ensuring that all first pixels of the detector detect N1 valid events. For each valid event, the count value of first pixel i on second pixel j is q. i,j ; Sa2, the average count value of the first pixel i on the second pixel j among N1 valid cases. P×Q second pixels correspond to a total of P×Q average count values; Sa3, mark the maximum value of P×Q average counts as... As V max Calculate a for the i-th element. i,j , , will a i,j a, the element in row i and column j of A i,j , which represents the probability that the light signal of the first pixel i is detected by the second pixel j.

5. A positioning method for a high-sensitivity X-ray imaging linear array detection system, characterized in that: Includes the following steps; S1, Construct a high-sensitivity X-ray imaging linear array detection system, wherein the linear array detector includes The photodetector array includes P×Q second pixels, where the i-th pixel is labeled as first pixel i, and the j-th pixel is labeled as second pixel j, 1≤i≤i, 1≤j≤P×Q; S2, generate system matrix A and counting vector V max ; S3, In actual measurement, the high-sensitivity X-ray imaging linear array detection system is placed in the detection area to detect valid events. For each valid event, the response of the photodetector array is obtained. , where q j Let L be the count value of the second pixel j, and calculate the log-likelihood value L of the first pixel i according to the following formula. i ; ， Where maxq is the maximum value of the elements in q, q j ! for q j factorial; S4, mark the first pixel with the largest log-likelihood value as i. ML , change i ML The location is used as the effective position of the ray and linear array detectors, and the deposition energy is calculated according to the following formula. ; ， In the formula, E C The energy of the radiation source when constructing system matrix A, For i ML Corresponding to V max The value in.

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