Photon detection method, detector and imaging device

Abstract

The application discloses a photon detection method, a detector and an imaging device. The photon detection method comprises: receiving incident photons by using a photoelectric converter having a plurality of pixel units, so as to generate scintillation pulses from the corresponding pixel units receiving the incident photons, the plurality of pixel units are encoded based on at least one characteristic of the scintillation pulses generated according to a corresponding impulse response function, the characteristic comprises a starting step, a magnification, a decay time and a decay time constant; if a given photon is incident to different encoded pixel units, the characteristics of the read scintillation pulses are different; and the encoding of the corresponding pixel units receiving the incident photons is determined according to the characteristics of the read scintillation pulses. The spatial resolution after decoding can be specific to the specific encoded pixel unit, and the photosensitive area of the entire photoelectric conversion device is no longer used as the basic unit of the spatial resolution pixel, so that the spatial resolution is greatly improved.

Description

Technical Field

[0001] This application relates to the field of photon detection, and more specifically, to a photon detection method, detector, and imaging device. Background Technology

[0002] Silicon photomultiplier (SiPM) is a type of low-light detection image sensor widely considered the future direction for ultra-low-light detectors. Typically, a SiPM consists of a large number of pixel units, each including a series-connected avalanche diode (APD) and a quenching resistor. When photons are incident on the SiPM, the corresponding avalanche diodes undergo an avalanche effect, generating scintillation pulses. These scintillation pulses are superimposed and output through a readout circuit connected to the SiPM. In practical applications, only the total number of photons received by the entire SiPM can usually be calculated. Using the entire photosensitive area of ​​a single SiPM as the smallest unit for imaging results leads to insufficient imaging resolution and imprecise positional information.

[0003] However, in some ultra-high-precision imaging applications, such as positron emission tomography (PET), autonomous driving, and night vision imaging, extremely high requirements are placed on the ability to resolve the specific location of photons. Current imaging resolution techniques are insufficient to meet these demands. To achieve higher resolution, existing technologies typically employ methods that reduce the size of the SiPM (Silicon Photomultiplier Device). While this method can improve imaging resolution to some extent, reducing the physical size of the photomultiplier device significantly increases the complexity of the back-end readout circuitry, introducing excessive noise and signal resolution bias. This not only degrades image quality but also leads to a sharp increase in cost as precision requirements rise. Therefore, it is necessary to propose a solution that can achieve higher-precision imaging without substantially altering the physical size of existing optoelectronic devices. Summary of the Invention

[0004] Therefore, the photon detection method, detector, and imaging device provided in this application can solve at least one problem existing in the prior art.

[0005] In a first aspect, a photon detection method is provided, comprising:

[0006] An incident photon is received using a photoelectric converter with multiple pixel units, thereby generating a scintillation pulse by the corresponding pixel unit receiving the incident photon. The multiple pixel units are encoded based on at least one feature of the scintillation pulse according to a corresponding pulse generation function, which is expressed by the following formula:

[0007]

[0008] Among them, A i Let i be the starting step of the i-th pixel unit. τ is the magnification factor of the i-th pixel unit, t is the decay time of the flash pulse, and τ is the magnification factor of the t i-th pixel unit. i The decay time constant of the i-th pixel unit is defined as follows: the feature includes the starting step, the magnification factor, the decay time, and the decay time constant. Each code corresponds to one or more pixel units, and the pixel units corresponding to different codes do not overlap.

[0009] The generated scintillation pulses are read out, wherein the characteristics of the read-out scintillation pulses are different when a given photon is incident on different coded pixel units;

[0010] Based on the characteristics of the readout scintillation pulse, the encoding of the corresponding pixel unit receiving the incident photon is determined.

[0011] According to one embodiment of the present invention, the encoded sequence has an encoding pattern of any one of arithmetic sequence, geometric sequence, prime number, and random number.

[0012] According to one embodiment of the present invention, each pixel unit includes a photosensitive module and a pulse generation module, wherein the photosensitive module receives incident photons and the pulse generation module generates a flashing pulse based on a pulse generation function.

[0013] According to one embodiment of the present invention, reading out the generated flicker pulse includes: using a single signal readout circuit to read out a single flicker pulse from the plurality of encoded pixel units arranged in parallel.

[0014] According to one embodiment of the present invention, reading out the generated flicker pulses includes: using multiple signal readout circuits to read out multiple flicker pulses from the multiple pixel units, wherein pixel units with the same encoding are connected in parallel to the same signal readout circuit.

[0015] According to one embodiment of the present invention, the plurality of pixel units are configured into an coded pixel unit array, the coded pixel unit array having an encoding sequence encoded based on the coefficients of a pulse generation function, and determining the encoding of the corresponding pixel unit receiving the incident photon based on the characteristics of the readout scintillation pulse includes: using the characteristics of the readout scintillation pulse, decoding the coefficients used for encoding based on the encoding sequence to determine the actual encoded value of the corresponding pixel unit receiving the incident photon.

[0016] According to one embodiment of the present invention, the photon detection method further includes: applying a preset excitation to a plurality of pixel units of the photoelectric converter.

[0017] According to one embodiment of the present invention, before receiving the incident photon, the method further includes: receiving the incident high-energy particles using a scintillation crystal or scintillation crystal array coupled to the photoelectric converter to generate the incident photon.

[0018] According to a second aspect of the present invention, a detector is provided, comprising: a photoelectric converter having a plurality of pixel units configured to receive incident photons, thereby generating scintillation pulses by corresponding pixel units receiving the incident photons, wherein the plurality of pixel units are encoded by the method described above; a signal readout circuit configured to read out the generated scintillation pulses, wherein the characteristics of the readout scintillation pulses are different if a given photon is incident on different encoded pixel units; and a decoder configured to determine the encoding of the corresponding pixel unit receiving the incident photon based on the characteristics of the readout scintillation pulses.

[0019] According to one embodiment of the present invention, each pixel unit includes a photosensitive module and a pulse generation module, wherein the photosensitive module receives incident photons and the pulse generation module generates a flashing pulse based on a pulse generation function.

[0020] According to one embodiment of the present invention, the detector includes multiple signal readout circuits, and pixel units with the same encoding are connected in parallel to the same signal readout circuit.

[0021] According to one embodiment of the present invention, the detector further includes: a reconstruction module configured to reconstruct the readout scintillation pulses to obtain an incident photon intensity distribution map of each coded pixel unit of the photoelectric converter.

[0022] According to one embodiment of the present invention, the detector further includes an excitation circuit configured to apply a preset excitation to a plurality of pixel units of the photoelectric converter.

[0023] According to one embodiment of the present invention, the detector further includes: a scintillation crystal or scintillation crystal array coupled to the photoelectric converter, the scintillation crystal or the scintillation crystal array being configured to generate the incident photons in response to incident high-energy particles.

[0024] According to a third aspect of the invention, an imaging device is provided, the imaging device comprising a detector as described above.

[0025] According to one embodiment of the present invention, the imaging device is one or a combination of multiple devices selected from PET equipment, CT equipment, MRI equipment, radiation detection equipment, oil detection equipment, low light detection equipment, SPECT equipment, security inspection equipment, gamma camera, X-ray equipment, and DR equipment.

[0026] The photon detection method, detector, and imaging device provided in this application utilize encoded pixel units to receive incident photons. The corresponding pixel units receiving the incident photons generate scintillation pulses with different characteristics. The encoding of the corresponding pixel unit receiving the incident photons can be determined based on the characteristics of the readout scintillation pulses. Different encoded pixel units can acquire different scintillation pulse characteristics under the same photon stimulation. Based on the different encoding forms of the pixel units, the encoding of the pixel unit receiving the incident photons can be quickly determined through decoding. This allows for rapid and accurate reconstruction of photon positions through encoded pixel units without changing the physical dimensions of existing photoelectric conversion devices, thereby achieving higher spatial resolution imaging in a high-response and low-resource-consumption manner. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart of a photon detection method according to an embodiment of this application;

[0028] Figure 2 This is a schematic flowchart of a photon detection method according to another embodiment of this application;

[0029] Figure 3 This is a schematic diagram of the structure of a detector according to an embodiment of this application;

[0030] Figure 4 This is a schematic diagram of the detector according to another embodiment of this application;

[0031] Figure 5 This is a schematic diagram of the structure of an coded pixel unit array according to an embodiment of this application;

[0032] Figure 6 This is a schematic diagram of the structure of an coded pixel unit array according to another embodiment of this application;

[0033] Figure 7 This is an application connection diagram of a detector according to one embodiment of this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention. Specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0035] Figure 1 A photon detection method according to an embodiment of this application is illustrated. The photon detection method includes the following steps:

[0036] S1: Encode the pixel unit according to the coefficients of the pulse generation function, where the pulse generation function is represented by the following equation (1):

[0037]

[0038] Where A is the initial step and τ is the decay time constant. Let t be the magnification factor, t be the pulse time, and i represent the i-th pixel unit. The encoding coefficient is one of the following: the starting step, the decay time constant, or the magnification factor. When encoding is based on this coefficient, for example, when encoding is based on the decay time constant, the other constants A of all pixel units are... They can be the same, but the decay time constant τ is different for different codes. Each code corresponds to one or more pixel units, and the pixel units corresponding to different codes do not overlap.

[0039] S2: Photons are detected using encoded pixel units / pixel unit arrays to generate scintillation pulse signals. The characteristics of the scintillation pulses read out are different when photons are incident on different encoded pixel units.

[0040] S3: Determine the position of the pixel unit corresponding to each photon based on the characteristics of the read-out flash pulse signal.

[0041] In this embodiment, the photoelectric converter can be a silicon photomultiplier (SiPM) or other devices capable of generating flicker pulses, such as photoelectric conversion devices characterized by energy amplitude. Each SiPM pixel includes multiple basic pixel units capable of receiving photons and generating flicker pulses. Each pixel unit may include a photosensitive module and a pulse generation module, and multiple pixel units may be arranged into a pixel unit array. In some embodiments, the photosensitive module is typically an avalanche diode (APD) or other single-photon sensing element. In some embodiments, the pulse generation module is typically a quench resistor, a quench circuit, or a transistor, which can convert instantaneous current into flicker pulses for output.

[0042] In the embodiments of this application, the characteristics of the scintillation pulses read out after incident photons are incident on pixel units with different codes are different. In other words, pixel units with different codes can read out different scintillation pulse characteristics under the same photon stimulation. For example, a pixel unit array with different responses to different codes can be set in the SiPM. The scintillation pulse generated by each pixel unit after receiving the incident photon is an electroscintillation pulse. Therefore, the electroscintillation pulse characteristics output by different coded pixel units are not exactly the same or completely different.

[0043] In one exemplary embodiment, the encoded sequence has an encoding pattern of any one of the following: arithmetic sequence (such as ordinal number), geometric sequence, prime number, or random number.

[0044] In one embodiment, the encoded sequence is encoded using the decay time constant of the pulse generation function.

[0045] Assuming the pulse generation function is a decaying pulse function, it can be expressed by the following equation (1):

[0046]

[0047] Where t is the decay time, which is, for example, a constant A (A can be 0 or other constants) for all pixel units in the coded pixel unit group. They are the same, but the decay time constant τ is different for different codes.

[0048] For ease of understanding, it is exemplarily assumed that the pixel unit array is a 3×3 array, and that it is encoded according to the order number and the decay time constant τ. In this example, the decay time constants τ of the 9 groups of encoded pixel units are 1, 2, 3, 4, 5, 6, 7, 8, and 9, respectively. Assuming that two photons hit the device during one normal working time of all pixel units, and two pixel units generate pulses, the characteristic of the scintillation pulse obtained by the readout circuit is that the decay time constant τ = 1.5. Then, the actual encoded value of the corresponding pixel unit receiving the incident photon can be determined by decoding the decay time constant based on the encoding sequence using the characteristic of the readout scintillation pulse. Specifically, the actual encoded value of the received photon can be determined by decoding the coefficients to be decoded according to the encoding sequence table and the corresponding decoding method. For example, in this embodiment, decoding can be performed according to the following equation (2):

[0049]

[0050] Based on the encoding sequence table encoded according to the arithmetic progression (ordinal number) and the decay time constant, it can be determined by equation (2) that the encoded pixel unit with a decay time constant τ of 1 and the encoded pixel unit with a decay time constant τ of 2 generated flicker pulses. Therefore, the spatial resolution after decoding can be specified down to the specific encoded pixel unit, instead of using the photosensitive area of ​​the entire photoelectric conversion device as the basic unit of the spatial resolution pixel, thus achieving a significant improvement in spatial resolution.

[0051] In one embodiment, the encoded sequence is encoded using the amplification factor of the pulse generation function.

[0052] Assuming the pulse generation function is a decaying pulse function, it can be expressed by the following equation (3):

[0053]

[0054] For example, the coefficients A and τ are the same for all coded pixel unit groups, but the magnification factor varies between different codes. no the same.

[0055] For ease of understanding, let's assume, for example, that the pixel unit array is a 3×3 array, and that the numbers follow a sequential order, with the magnification factor as the basis. Encoding is performed. In this example, the magnification factor of the 9 groups of encoded pixel units is... The numbers are 1, 2, 3, 4, 5, 6, 7, 8, and 9. Assume that during one normal operating time for all pixel units, a total of two photons strike the device, generating pulses in two pixel units. The characteristics of the flicker pulses obtained by the readout circuit, specifically the amplification factor... Then, by utilizing the characteristics of the readout scintillation pulse, the actual encoded value of the corresponding pixel unit receiving the incident photon can be determined by decoding the encoded sequence for the amplification factor. More specifically, the actual encoded value of the received photon can be determined by decoding the coefficients to be decoded according to the encoded sequence table and the corresponding decoding method. For example, in this embodiment, decoding can be performed according to the following equation (4):

[0056]

[0057] Based on the encoding sequence table of arithmetic progression (ordinal number) coded according to the magnification factor, the magnification factor can be determined by equation (4). Encoded pixel unit of 1 and magnification factor A flicker pulse was generated for each 2-encoded pixel unit. Therefore, the spatial resolution after decoding can be specified down to the specific coded pixel unit, instead of using the entire photosensitive area of ​​the photoelectric conversion device as the basic unit of spatial resolution pixels, thus achieving a significant improvement in spatial resolution.

[0058] In one embodiment, the encoded sequence is encoded using the starting step of the pulse generation function. Different starting steps are set for the pulse generation functions of different encoded pixel units, and encoding is performed using these steps.

[0059] Assuming the pulse generation function is a decaying pulse function, it can be expressed by the following equation (6):

[0060]

[0061] For example, the pulse amplification factor of pixel units in all coded pixel unit groups. It is the same as the decay time constant τ, but the starting step A is different for different codes.

[0062] For ease of understanding, let's assume, for example, that the pixel unit array is a 3×3 array, and that encoding follows a sequential number pattern, starting with a step A. In this example, the starting steps A of the 9 groups of encoded pixel units are 1, 2, 3, 4, 5, 6, 7, 8, and 9. Assume that during one normal operating time for all pixel units, a total of 2 photons strike the device, resulting in two pixel units generating pulses. The readout circuit obtains a signal A of 1.5. Based on the encoding sequence table using arithmetic progression (sequential number) and amplification factor encoding, it can be determined that the encoded pixel unit with starting step A of 1 and the encoded pixel unit with starting step A of 2 generated flicker pulses. Therefore, the decoded spatial resolution can be specified down to the specific encoded pixel unit, rather than using the entire photosensitive area of ​​the photoelectric conversion device as the basic unit of spatial resolution pixels, thus achieving a significant improvement in spatial resolution.

[0063] In this application embodiment, the specific implementation means of the coefficients encoded by the aforementioned pulse generation function are not limited, as long as it allows multiple pixel units in this application embodiment to be encoded based on the coefficients of the pulse generation function. For example, the enable amplification factor and / or delay time can be achieved by integrating an amplifier and / or a delay unit in the pixel unit; and / or, the enable coefficients such as the decay time constant and the starting step can be achieved by adjusting the material parameters of the pixel unit, such as the resistance value and capacitance value of the pulse generation module.

[0064] In the embodiments of this application, the pixel unit array of the photoelectric converter can be encoded based on the coefficients of the pulse generation function, and the pixel unit encoding that receives incident photons can be quickly determined based on the encoded sequence and possibly related decoding methods. This enables the rapid sensing of photon signals with encoded subpixels without changing the physical size of the existing photoelectric converter, thereby achieving higher spatial resolution imaging in a high-response and low-resource-consumption manner.

[0065] like Figure 2 As shown in the embodiments, a preset excitation can be applied to the pixel unit, causing the pixel unit to generate a scintillation pulse accordingly when receiving incident photons. Specifically, the photon detection method of this application may further include the following steps:

[0066] S12: Apply a preset excitation, such as a bias voltage, to the pixel unit / pixel unit array so that the pixel unit generates a scintillation pulse in response to the incident photon.

[0067] Furthermore, the photon detection method of this application may also include the following steps:

[0068] S0: A scintillation crystal coupled to a pixel unit / pixel unit array is used to convert rays into visible photons.

[0069] High-energy rays include common X-rays, gamma rays, neutron rays, proton rays, etc. After being converted into visible photons by a scintillation crystal, high-energy rays are incident on the pixel unit / pixel unit array described in the above embodiment, and are further converted into scintillation pulse signals. By decoding, the position of the high-energy rays can be determined, thereby improving the spatial resolution of high-energy rays.

[0070] In this embodiment, the identification of coded subpixel-level flicker pulses can be achieved by reading out the flicker pulse characteristics. In this embodiment, the incident photon incident on different coded pixel units can cover at least one of the following situations: a single photon incident on different coded pixel units within a specified time, or one or more photons incident on various different coded pixel units simultaneously.

[0071] In the embodiments of this application, the coded photon detection method can be used to realize coded subpixel level multiphoton detection, and further determine the subpixel level coded positions of these incident photons, and to determine the intensity of the incident photons at the coded positions of each pixel unit.

[0072] Accordingly, this application provides an optoelectronic converter employing the above-described photon detection method. Those skilled in the art will understand that the features of the optoelectronic converter provided according to this embodiment or other embodiments can be combined with the photon detection method provided in previous embodiments or other embodiments to obtain new embodiments, and vice versa.

[0073] For example, Figure 3 An coded detector according to an embodiment of this application is illustrated. The detector includes a photoelectric converter 100 having a plurality of coded pixel units 110, a signal readout circuit 200, and a decoder 300. The photoelectric converter 100 is configured to receive incident photons, thereby generating scintillation pulses by corresponding pixel units receiving the incident photons. The signal readout circuit 200 is configured to read out the generated scintillation pulses, wherein the characteristics of the readout scintillation pulses differ when the incident photons are incident on different coded pixel units. The aforementioned "different characteristics of the readout scintillation pulses" includes: first, different pixel units have different properties, so when incident photons are incident on different pixel units, the characteristics of the scintillation pulses generated by each pixel unit are different, therefore the characteristics of the readout scintillation pulses are different; second, different coded pixel units have the same properties, so when incident photons are incident on different coded pixel units, the characteristics of the scintillation pulses generated by each pixel unit are the same, but the characteristics of the scintillation pulses read out for different coded pixel units are different, for example, different readout circuits can be used for reading; or a combination of the above solutions. The decoder 300 can be configured to determine the encoding of the corresponding pixel unit receiving the incident photon based on the characteristics of the readout scintillation pulse.

[0074] The photoelectric converter 100 can be a silicon photomultiplier (SiPM). The SiPM can be formed as a pixel array including a plurality of pixel units 110. Each pixel unit 110 may include a photosensitive module and a pulse generation module. In embodiments of this application, the photosensitive modules of each pixel unit can be configured identically, for example, each photosensitive module may have the same sensing area. In different embodiments, the pulse generation modules of each pixel unit can be configured identically, differently, or not entirely identically according to the teachings of the present invention. For example, the pulse generation modules of each coded pixel unit can be configured to generate different or not entirely identical flicker pulse characteristics upon receiving incident photons, preferably based on different coefficients of the pulse generation function, which will be further described below.

[0075] exist Figure 4 In the illustrated embodiment, the detector may further include an excitation circuit 500, such as a bias voltage excitation circuit, which may be configured to apply a bias voltage to a plurality of pixel units 110 of the photoelectric converter 100.

[0076] Furthermore, the detector may also include a scintillation crystal / scintillation crystal array 400 coupled to the photoelectric converter 100, which can be configured to generate incident photons in response to incident high-energy particles.

[0077] Figure 5 and Figure 6 Schematic diagrams of different coded pixel unit arrays are shown. In some embodiments, multiple pixel units are configured into a rectangular or square coded pixel unit array, and each coded pixel unit has the same number and size.

[0078] For example, in Figure 5 In the illustrated embodiment, multiple pixel units can be constructed into a 2M×2N (M and N are both natural numbers) rectangular or square coded pixel unit array. Figure 5 In the illustrated embodiment, the coded pixel unit array is encoded in a 2×2 pattern (shown by gray squares in the figure), and pixel units with the same encoding can be referred to as coded pixel unit groups. Accordingly, Figure 5 The array of encoded pixel units shown can include M×N groups of encoded pixel units. Figure 5 The arrangement of pixel units is shown only schematically; the number of squares in the figure does not represent the actual number of encoded pixel units.

[0079] In another embodiment, the number and size of each coded pixel unit in the coded pixel unit array may be different. In a preferred embodiment, encoding can be performed approximately according to the distance (radius) from the center of the coded pixel unit array.

[0080] For example, Figure 6An alternative embodiment of the coded pixel unit array is shown. Figure 6 In the illustrated embodiment, multiple pixel units can be constructed into a rectangular or square coded pixel unit array. In this embodiment, the number of pixel units with the same encoding increases with the distance from the array center. More specifically, the pixel units in each ring around the array center from the inside out are uniformly encoded, thus forming a coded pixel unit group, for example in... Figure 6 In the embodiments, the alternation of gray and white rings represents multiple groups of coded pixel units. Figure 6 The encoding format shown can sometimes be advantageous, for example, by reconstructing an incident photon intensity distribution map that is roughly based on the radius distance.

[0081] In some embodiments, various readout methods can be selected to implement the coded photon detection method according to the embodiments of this application. For example, multiple pixel units of the photoelectric converter can be connected to the same signal readout circuit.

[0082] Specifically, Figure 7 The illustrated embodiment shows the module connection structure of the corresponding coded detector. For example... Figure 7 As shown, the detector may include a photoelectric converter with multiple encoded pixel units, a single signal readout circuit 570, and a decoder 580. Figure 7 In the illustrated embodiment, the detector may further include an excitation circuit 510, such as a bias voltage excitation circuit, which may be configured to apply a bias voltage to a plurality of pixel units of the photoelectric converter.

[0083] like Figure 7 As shown, different encoded pixel units, i.e., different encoded pixel unit groups 520, 530, 540, 550, and 560, can be connected in parallel to the single signal readout circuit 570.

[0084] In another embodiment, pixel units with the same encoding can be connected to the same signal readout circuit, while pixel units with different encodings can be connected to different modules.

[0085] exist Figure 7 In the illustrated embodiment, since pixel units with the same encoding are connected in parallel to their respective signal readout circuits, if a given photon is incident on pixel units with different encodings, the characteristics of the generated flicker pulses can be different. Alternatively, when the characteristics of the generated flicker pulses are the same, different readout methods can be used to make the read-out flicker pulses different. Thus, when the flicker pulses of different encoded pixel units are read out by their respective signal readout circuits, the encoding of the pixel unit receiving the photon can be determined by the decoding method described in the embodiments of this application.

[0086] When pixel units with the same encoding are constructed in parallel and connected to the same signal readout circuit, different readout methods can be used to make the readout flicker pulses different even if the characteristics of the flicker pulses are the same.

[0087] In a further embodiment, reconstruction can be performed based on the readout scintillation pulses. For example, after obtaining the encoding of the corresponding pixel unit of the incident photon through the aforementioned method steps, as well as the actual encoding value as described, encoded photon detection reconstruction can be performed through a separate reconstruction step. Advantageously, the relevant values ​​determined in the previous steps, such as the coefficients of the pulse function corresponding to the encoding value, can be advantageously used for reconstruction, thereby effectively improving reconstruction efficiency and reducing resource consumption.

[0088] In this embodiment of the application, a preset reconstruction algorithm can be used to reconstruct the incident photon intensity distribution map of each encoded pixel unit based on the readout scintillation pulse of each encoded pixel unit.

[0089] In the embodiments of this application, as described above, the preset reconstruction algorithm may include one or more of the following algorithms: Filtered Back Projection (FBP), Maximum Likelihood Expectation Maximization (MLEM), Ordered Subset Expectation Maximization (OSEM), Maximum A posteriori estimation (MAP), etc. The aforementioned derived algorithms refer to variations of the algorithm obtained by combining, simplifying, transforming, and / or normalizing operations without departing from the aforementioned preset reconstruction algorithm.

[0090] In this embodiment, the Filtered Backprojection (FBP) algorithm is based on Fourier transform theory. Before backprojection, the projections at each acquired projection angle are convolved to improve the shape artifacts caused by the point spread function, resulting in better reconstructed image quality. Specifically, the projection reconstruction process involves first performing a one-dimensional Fourier transform on the projection data obtained from the photoelectric converter, then convolving it with a filter function to obtain convolved and filtered projection data in each direction. Then, these data are backprojected along each direction, i.e., evenly distributed to each corresponding pixel unit along their original path, and overlapped to obtain the photon intensity value (photon intensity map) of each unit. Optionally, the filter function can be either the RS filter function or the SL filter function. In this embodiment, the Filtered Backprojection (FBP) algorithm can be implemented iteratively.

[0091] In the embodiments of this application, the Maximum Likelihood Expectation Maximization (MLEM) method first performs calculations using maximum likelihood theory, and then solves the problem based on the maximum expectation value in order to find an estimated solution with maximum likelihood. In one specific embodiment, it can be assumed that the photons detected by the photoelectric converter satisfy an independent Poisson distribution. Based on this Poisson distribution model, the likelihood function of the observed data (i.e., the readout electroscintillation pulses) is set, and the maximum expectation value is obtained through an iterative method.

[0092] In this embodiment, the Ordered Subset Expectation Maximization (OSEM) method is also an iterative image reconstruction algorithm based on the maximum likelihood expectation method. It divides the electroscintigraphy pulses into L subsets, where L is a natural number. Each time data from one subset is used, all pixels (each pixel corresponding to a pixel unit) are updated once. One iteration consists of using all subsets in turn. OSEM includes two steps: determining the expression for calculating the conditional expectation value of the likelihood function; and deriving the pixel update value that maximizes the conditional expectation value of the likelihood function using the derivative extremum method. The likelihood function value obtained from each pixel update is greater than or equal to the previous value, and the pixel values ​​eventually converge to the point where the likelihood function reaches its maximum.

[0093] In this embodiment, the maximum a posteriori (MAP) estimation method is implemented similarly to the maximum likelihood method, except that the maximum likelihood function introduces the prior distribution of the parameter to be estimated (i.e., the number of photons / photon intensity received by each pixel unit). In this embodiment, the maximum a posteriori (MAP) estimation method can also be implemented iteratively.

[0094] In some embodiments, the preset reconstruction algorithm may be a combination of the above-mentioned algorithms.

[0095] As an alternative embodiment, the steps and sub-steps described above for determining the encoding of the corresponding pixel unit of the incident photon, and the actual encoded value as described, can be combined with the reconstruction step. Accordingly, the encoded sequence (matrix), as well as the related decoding and other algorithms for determining the encoding, and the actual encoded value as described (such as the aforementioned prime number factorization algorithm and the intersection and / or merging algorithm for determining the actual encoded value) can be combined in the analytical or iterative reconstruction algorithm.

[0096] Therefore, different encoded pixel units can acquire different scintillation pulse characteristics under the same photon stimulation. Moreover, based on different encoding forms of pixel units, photon signals can be rapidly sensed at the encoded subpixel level, thereby achieving higher spatial resolution imaging in a high-response and low-resource-consumption manner.

[0097] In some embodiments, an imaging device having a coded detector as described in the embodiments of this application may also be provided. Preferably, the imaging device is one or a combination of multiple devices utilizing the principle of high-energy ray conversion, such as PET devices, CT devices, MRI devices, radiation detection devices, oil detection devices, low-light detection devices, SPECT devices, security inspection devices, gamma cameras, X-ray devices, DR devices, etc., as well as other photoelectric conversion application devices.

[0098] Those skilled in the art will understand that the apparatus and devices described in the embodiments of this application can be combined with the features of the methods described in the embodiments of this application, and vice versa.

[0099] This document describes several embodiments, but for the sake of brevity, the descriptions of the embodiments are not exhaustive, and identical or similar features or parts between the embodiments may be omitted. In this document, "one embodiment," "some embodiments," "example," "specific example," or "some examples" refers to at least one embodiment or example applicable to this application, but not all embodiments. The above terms do not necessarily mean referring to the same embodiment or example. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

[0100] The exemplary systems and methods of this application have been specifically shown and described with reference to the above embodiments, which are merely examples of the best mode for implementing the systems and methods. Those skilled in the art will understand that various changes can be made to the embodiments of the systems and methods described herein without departing from the spirit and scope of the invention as defined in the appended claims when implementing the systems and / or methods. For example, multiple photosensitive modules or multiple pulse generation modules may be provided in the same pixel unit, or different arrangements and combinations of the number, connection, etc., of different components may be used according to the teachings of the present invention.

Claims

1. A photon detection method, characterized in that, include: An incident photon is received using a photoelectric converter with multiple pixel units, thereby generating a scintillation pulse by the corresponding pixel unit receiving the incident photon. The multiple pixel units are encoded based on at least one feature of the scintillation pulse according to a corresponding pulse generation function, which is expressed by the following formula: ； Among them, A i Let i be the starting step of the i-th pixel unit. τ is the magnification factor of the i-th pixel unit, t is the decay time of the flash pulse, and τ is the magnification factor of the t i-th pixel unit. i The decay time constant of the i-th pixel unit is defined as follows: the feature includes the starting step, the magnification factor, the decay time, and the decay time constant. Each code corresponds to one or more pixel units, and the pixel units corresponding to different codes do not overlap. The generated scintillation pulses are read out, wherein the characteristics of the read-out scintillation pulses are different when a given photon is incident on different coded pixel units; Based on the characteristics of the readout scintillation pulse, the encoding of the corresponding pixel unit receiving the incident photon is determined.

2. The photon detection method according to claim 1, characterized in that, The encoded sequence has an encoding pattern that can be any one of the following: arithmetic sequence, geometric sequence, all prime numbers, or random number.

3. The photon detection method according to claim 1, characterized in that, Each pixel unit includes a photosensitive module and a pulse generation module. The photosensitive module receives incident photons, and the pulse generation module generates a flashing pulse based on a pulse generation function.

4. The photon detection method according to claim 1, characterized in that, Read out the generated flicker pulses, including: A single signal readout circuit is used to read out a single flash pulse from the multiple encoded pixel units arranged in parallel.

5. The photon detection method according to claim 1, characterized in that, Read out the generated flicker pulses, including: Multiple signal readout circuits are used to read out multiple flash pulses from the multiple pixel units, wherein pixel units with the same code are connected in parallel to the same signal readout circuit.

6. The photon detection method according to claim 1, characterized in that, The plurality of pixel units are constructed into an array of coded pixel units, which has a coded sequence encoded based on the coefficients of a pulse generation function. Based on the characteristics of the readout scintillation pulse, the encoding of the corresponding pixel unit receiving the incident photon is determined, including: By utilizing the characteristics of the readout scintillation pulse, the coefficients used for encoding are decoded based on the encoding sequence to determine the actual encoded value of the corresponding pixel unit receiving the incident photon.

7. The photon detection method according to claim 1, characterized in that, Also includes: A preset excitation is applied to multiple pixel units of the photoelectric converter.

8. The photon detection method according to claim 1, characterized in that, Before receiving the incident photon, the method further includes: The incident high-energy particles are received using a scintillation crystal or scintillation crystal array coupled to the photoelectric converter to generate the incident photons.

9. A detector, characterized in that, include: A photoelectric converter having multiple pixel units is configured to receive incident photons, thereby generating scintillation pulses by the corresponding pixel units receiving the incident photons, wherein the multiple pixel units are encoded by the method of claim 1; A signal readout circuit is configured to read out the generated scintillation pulses, wherein the characteristics of the readout scintillation pulses are different when a given photon is incident on different coded pixel units; The decoder is configured to determine the encoding of the corresponding pixel unit receiving the incident photon based on the characteristics of the read-out scintillation pulse.

10. The detector according to claim 9, characterized in that, Each pixel unit includes a photosensitive module and a pulse generation module. The photosensitive module receives incident photons, and the pulse generation module generates a flashing pulse based on a pulse generation function.

11. The detector according to claim 9, characterized in that, The detector includes multiple signal readout circuits, and pixel units with the same encoding are connected in parallel to the same signal readout circuit.

12. The detector according to claim 9, characterized in that, The detector also includes: The reconstruction module is configured to reconstruct the readout scintillation pulses to obtain the incident photon intensity distribution map of each coded pixel unit of the photoelectric converter.

13. The detector according to claim 9, characterized in that, The detector also includes: The excitation circuit is configured to apply a preset excitation to a plurality of pixel units of the photoelectric converter.

14. The detector according to claim 9, characterized in that, The detector also includes: A scintillation crystal or scintillation crystal array coupled to the photoelectric converter, the scintillation crystal or scintillation crystal array being configured to generate the incident photons in response to incident high-energy particles.

15. An imaging device, characterized in that, Includes the detector according to any one of claims 9 to 14.

16. The imaging device according to claim 15, characterized in that, The imaging device is one or a combination of multiple devices selected from PET, CT, MRI, SPECT, and X-ray.

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