Detector for spect imaging system, spect probe, and imaging system and method

Abstract

A detector for an SPECT imaging system, an SPECT probe, and an imaging system and method. The detector comprises: an SiPM detector array (1-2), a CsI crystal array (1-1), and a preprocessing circuit board (1-3). The CsI crystal array (1-1) comprises a plurality of strip-shaped crystals (3-1); each strip-shaped crystal (3-1) comprises at least one crystal light exit surface (3-2); and one crystal light exit surface (3-2) of each strip-shaped crystal (3-1) is coupled to the SiPM detector array (1-2). An electrical signal of each SiPM detector pixel (2-3) in the SiPM detector array (1-2) is independently outputted by means of a detector base plate (2-4) in the SiPM detector array (1-2). The preprocessing circuit board (1-3) combines electrical signals of all SiPM detector pixels (2-3) and outputs a number of signals equal to or fewer than the number of the SiPM detector pixels (2-3).

Description

Detectors, SPECT probes, imaging systems, and methods for SPECT imaging systems

[0001] Cross-references to related applications

[0002] This application is based on and claims priority to CN application No. 202411674165.7, filed on November 21, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure pertains to the field of nuclear medicine, and particularly relates to a detector, SPECT probe, imaging system, and method for use in a SPECT imaging system. Background Technology

[0004] SPECT (Single-Photon Emission Computed Tomography) imaging is one of the important imaging technologies in the field of nuclear medicine, and it is widely used in clinical diagnosis, preclinical research, drug development and other fields. Summary of the Invention

[0005] According to one aspect of this disclosure, a detector for a SPECT imaging system is provided, comprising: a silicon photomultiplier tube (SiPM) detector array, a cesium iodide (CsI) crystal array, and a preprocessing circuit board. The CsI crystal array includes a plurality of strip-shaped CsI crystals, each strip-shaped CsI crystal including at least one light-emitting surface; one light-emitting surface of each strip-shaped CsI crystal is coupled to the SiPM detector array; the SiPM detector array includes: a detector substrate and a plurality of detector pixels on the detector substrate, wherein the SiPM detector array is configured to independently output the electrical signal of each detector pixel to the preprocessing circuit board via the detector substrate; the preprocessing circuit board is configured to synthesize and process the received electrical signals from all detector pixels to output a signal equal to or less than the number of detector pixels.

[0006] In some embodiments, the CsI crystal array employs a polycrystalline bulk structure.

[0007] In some embodiments, each strip-shaped CsI crystal further comprises a plurality of frosted surfaces; among the plurality of strip-shaped CsI crystals, a reflective material is filled between adjacent strip-shaped CsI crystals, wherein the reflective material is located between the frosted surfaces of adjacent strip-shaped CsI crystals.

[0008] In some embodiments, the CsI crystal array and the SiPM detector array are directly coupled using optical silicone oil; or, the CsI crystal array and the SiPM detector array are indirectly coupled through a photoconductor component.

[0009] In some embodiments, all detector pixels in the SiPM detector array are divided into multiple subarrays, and the electrical signals of the multiple subarrays are processed independently.

[0010] In some embodiments, the plurality of strip-shaped CsI crystals are coupled one-to-one with a plurality of detector pixels in the SiPM detector array.

[0011] According to another aspect of this disclosure, a detector for a SPECT imaging system is provided, comprising: a silicon photomultiplier tube (SiPM) detector array, a cesium iodide (CsI) crystal array, and a preprocessing circuit board; the CsI crystal array includes a plurality of strip-shaped CsI crystals; each strip-shaped CsI crystal includes a light-emitting surface and five frosted surfaces; the light-emitting surface of the strip-shaped CsI crystal is coupled to the SiPM detector array; the electrical signal of each detector pixel in the SiPM detector array is independently output through a detector substrate; the preprocessing circuit board integrates the electrical signals of all detector pixels and outputs a signal equal to or less than the number of detector pixels.

[0012] In some embodiments, the CsI crystal array employs a polycrystalline bulk structure.

[0013] In some embodiments, the detectors are freely spliced ​​and expanded in the direction of the detection surface to form SPECT probes of different shapes and sizes.

[0014] In some embodiments, the spaces between the strip-shaped CsI crystals are filled with a reflective material.

[0015] In some embodiments, the CsI crystal array and the SiPM detector array are directly coupled using optical silicone oil.

[0016] In some embodiments, the CsI crystal array and the SiPM detector array are indirectly coupled through a photoconductor assembly.

[0017] In some embodiments, the preprocessing circuit board employs multi-channel data processing technology.

[0018] In some embodiments, the preprocessing circuit employs a row-column weighted network or a centroid weighted network.

[0019] In some embodiments, all detector pixels in the SiPM detector array are divided into multiple subarrays, and the electrical signals of the multiple subarrays are processed independently.

[0020] In some embodiments, the plurality of strip-shaped CsI crystals are coupled one-to-one with a plurality of detector pixels in the SiPM detector array.

[0021] According to another aspect of this disclosure, this disclosure provides a SPECT probe comprising: one or more detectors as described above.

[0022] According to another aspect of this disclosure, a single-photon emission computed tomography imaging system is disclosed, comprising: a detector module for detecting photons, wherein the detector module includes the detectors as described above.

[0023] According to another aspect of this disclosure, a SPECT imaging method is disclosed, comprising: performing detection using a detector as described above, a SPECT probe as described above, or a single-photon emission computed tomography (SPECT) imaging system as described above.

[0024] In some embodiments, after gamma rays enter the strip-shaped cesium iodide (CsI) crystal, the CsI crystal converts the energy of the gamma rays into an optical signal. The optical signal passes through the coupling surface between the CsI crystal and the silicon photomultiplier tube (SiPM) detector array and enters the SiPM detector array. The SiPM detector array converts the optical signal into an electrical signal and outputs the electrical signal to a preprocessing circuit board. The preprocessing circuit board outputs the electrical signal to subsequent circuits for processing.

[0025] In some embodiments, the preprocessing circuit board employs multi-channel data processing technology, which includes input channels, signal amplification, analog-to-digital conversion (ADC), real-time processing, signal integration and analysis, data filtering and denoising, integrated output, and feedback mechanisms. Attached Figure Description

[0026] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. In the drawings, several embodiments of this disclosure are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein:

[0027] Figure 1 shows a schematic diagram of the detector structure according to an embodiment of the present disclosure;

[0028] Figure 2 shows a schematic side cross-sectional view of the detector according to an embodiment of the present disclosure;

[0029] Figure 3A schematically shows a bottom view of a polycrystalline bulk structure crystal array according to an embodiment of the present disclosure;

[0030] Figure 3B schematically shows a side view of the structure of a polycrystalline bulk crystal array according to an embodiment of the present disclosure, taken along line A-A' in Figure 3A;

[0031] Figure 3C schematically shows an enlarged view of the structure of a polycrystalline bulk crystal array according to an embodiment of the present disclosure at the circle in Figure 3B;

[0032] Figure 4A shows a schematic diagram of a detector according to an embodiment of the present disclosure being spliced ​​and expanded into a rectangular probe of size 8×10;

[0033] Figure 4B shows a schematic diagram of a detector spliced ​​and expanded into a polygonal probe according to an embodiment of the present disclosure;

[0034] Figure 5 shows a schematic diagram of signal segmentation processing for a large-scale detector array according to an embodiment of the present disclosure;

[0035] Figure 6 illustrates a row-column weighted network processing diagram according to an embodiment of the present disclosure;

[0036] Figure 7 illustrates a centroid-based weighted network processing diagram according to an embodiment of the present disclosure; and

[0037] Figure 8 shows a signal processing flowchart of a flickering event according to an embodiment of the present disclosure.

[0038] In this array, 1-1 is a CsI crystal array, 1-2 is a SiPM detector array, 1-3 is a preprocessing circuit board, 2-2 is the coupling surface between the crystal and the detector array, 2-3 is a SiPM detector pixel, 2-4 is a detector substrate, 3-1 is a strip crystal, 3-2 is the light-emitting surface of the crystal, 3-3 is the outer packaging of the crystal array, 3-4 is the filling between the crystal strips, 4-1 is a detector, 5-1 is subarray 1, 5-2 is subarray 2, 5-3 is subarray 3, and 5-4 is subarray 4. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this disclosure clearer, the disclosure will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0040] The terminology used in the embodiments of this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The singular forms “a,” “the,” and “the” as used in the embodiments of this disclosure and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0041] It should be understood that although the terms first, second, third, etc., may be used to describe... in the embodiments of this disclosure, these... should not be limited to these terms. These terms are only used to distinguish... For example, first... may also be referred to as second... without departing from the scope of the embodiments of this disclosure, and similarly, second... may also be referred to as first...

[0042] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0043] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0044] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0045] The inventors of this disclosure have discovered that detectors in SPECT imaging systems in related technologies generally include the following three main schemes: The first scheme is based on photomultiplier tubes (PMTs) and continuous crystals (generally sodium iodide (NaI)), using the Anger method or the centroid method to obtain the location of scintillation events. Due to the physical size limitations of PMT detectors and the large propagation range of scintillation photons in continuous crystals, the inherent spatial resolution is low. In addition, PMT detectors have disadvantages such as the safety hazard of operating at high voltage, large probe size due to their large physical size, and susceptibility to external magnetic fields. NaI crystals are hygroscopic and decay easily over long-term use, causing various inconveniences in use. This method is the probe scheme of traditional gamma cameras and SPECT. The second scheme is based on silicon photomultiplier tubes (SiPMs) and continuous crystals (generally NaI), using SiPMs instead of PMTs as photodetectors, solving the problems of high-voltage power supply, large size, and susceptibility to magnetic field interference of PMT detectors. However, SiPM also suffers from higher background noise and a higher number of dark markers compared to PMT, resulting in relatively low spatial and energy resolution. The third approach is based on cadmium-zinc-telluride (CZT) detectors. CZT detectors do not use scintillation crystals but directly convert the energy of gamma rays into electrical signals, resulting in a compact structure and high spatial and energy resolution. However, CZT detectors are typically used for high-energy quantitative detection; for low-energy gamma rays such as 99mTc (i.e., Technetium-99m), distortion can lead to relatively large quantitative errors. CZT detectors also suffer from severe "hole tailing" phenomenon, reducing detection efficiency. Furthermore, the cost of CZT detectors is currently much higher than that of SiPM and PMT. Considering these factors, a low-cost, high-resolution, and high-sensitivity SPECT detector can be developed.

[0046] SiPMs can achieve millimeter-level dimensions, far smaller than the typically centimeter-level dimensions of PMTs, especially in the height direction. Detector modules using SiPMs are significantly smaller than those using PMTs. SiPM bias voltages are typically in the 30V–70V range, much lower than the approximately 1000V high-voltage supply of PMTs, resulting in simpler circuit design and a higher safety factor. In other aspects, they are comparable to or superior (e.g., gain, immunity to magnetic interference), making them excellent photodetectors. Currently, SiPM detectors are widely used in positron emission tomography (PET) systems, demonstrating superior performance.

[0047] SiPM is an array of avalanche photodiodes (APDs) operating in Geiger mode. Each SiPM detector typically contains several thousand APD units, and the gain of a SiPM is typically 10 compared to a standalone APD detector. 6 Level, far exceeding APD's 10 2 As the price of SiPM decreases, APD detectors are generally not used in nuclear medicine imaging equipment in recent years.

[0048] SiPMs are widely used in PET systems but less so in SPECT systems. One reason is the widespread use of NaI crystals in SPECT. The hygroscopic nature of NaI crystals necessitates their use in large, continuous crystal blocks sealed within an enclosure to minimize the influence of moisture. NaI crystals are generally not used in small crystal strips, and directly replacing PMTs with SiPMs does not significantly improve probe performance. LYSO / LSO crystals (Lutetium Yttrium Oxy Orthosilicate / Lutetium Oxy Orthosilicate, lutetium silicate crystals) widely used in PET systems are unsuitable for SPECT systems due to their inherent fluorescence effect, coupled with the relatively high background noise of SiPMs.

[0049] However, the inventors of this disclosure have made a groundbreaking discovery: the emission peak of CsI crystal (cesium iodide crystal) matches that of SiPM better than that of NaI. The overall conversion efficiency of CsI-matched SiPM is comparable to, or even better than, that of NaI-matched PMT. CsI crystal has very low hygroscopicity, is easy to process, and can be fabricated into smaller sizes (millimeter-scale). CsI crystal combined with a SiPM detector represents a superior SPECT probe solution.

[0050] The detector disclosed herein, through improvements to the CsI crystal shape, the coupling relationship between the crystal and the SiPM detector pixels, and the overall structure, ultimately achieves significant progress compared to traditional SPECT detectors in terms of spatial resolution and system sensitivity.

[0051] The optional embodiments of this disclosure are described in detail below with reference to the accompanying drawings.

[0052] This disclosure seeks to achieve a better solution in terms of spatial resolution, energy resolution, and cost.

[0053] In some embodiments of this disclosure, a detector for a SPECT imaging system is provided, comprising: a silicon photomultiplier tube (SiPM) detector array, a cesium iodide (CsI) crystal array, and a preprocessing circuit board. The CsI crystal array includes multiple strip-shaped CsI crystals, each strip-shaped CsI crystal including at least one light-emitting surface. One light-emitting surface of each strip-shaped CsI crystal is coupled to the SiPM detector array. The SiPM detector array includes: a detector substrate and multiple detector pixels on the detector substrate. The SiPM detector array is configured to independently output the electrical signal of each detector pixel to the preprocessing circuit board via the detector substrate. The preprocessing circuit board is configured to synthesize and process the received electrical signals from all detector pixels to output a signal equal to or less than the number of detector pixels.

[0054] This provides a detector for SPECT imaging systems. In this detector, the CsI crystal array employs multiple strip-shaped CsI crystals, with the light-emitting surfaces of these strip-shaped CsI crystals coupled to a SiPM detector array. Thus, the electrical signal of each detector pixel in the SiPM detector array is independently output through the detector substrate within the SiPM detector array, and the preprocessing circuit board synthesizes the electrical signals of all detector pixels, outputting a signal equal to or less than the number of detector pixels. This improves the spatial resolution of the detector and the system sensitivity while reducing cost.

[0055] For example, in terms of spatial resolution, traditional SPECT detectors have a maximum resolution of about 6mm, while this disclosure designs the CsI crystal into multiple vertical strip-shaped CsI crystals. This strip structure can achieve a size of 3mm×3mm, enabling it to reach a resolution of 3mm, which significantly improves the spatial resolution of SPECT, making the image clearer and the details more obvious.

[0056] Furthermore, regarding system sensitivity, the detector disclosed herein, due to its unique structural design, can process multiple events occurring simultaneously. Therefore, after injecting a smaller amount of drug, the detector disclosed herein can collect more counts within the same time frame compared to traditional detectors, significantly improving system sensitivity and image quality. It also reduces the drug injection dosage, minimizing side effects on the human body.

[0057] In some embodiments, the CsI crystal array employs a polycrystalline bulk structure.

[0058] In some embodiments, each strip-shaped CsI crystal further comprises a plurality of frosted surfaces; among the plurality of strip-shaped CsI crystals, a reflective material is filled between adjacent strip-shaped CsI crystals, wherein the reflective material is located between the frosted surfaces of adjacent strip-shaped CsI crystals.

[0059] In some embodiments, the CsI crystal array and the SiPM detector array are directly coupled using optical silicone oil; or, the CsI crystal array and the SiPM detector array are indirectly coupled through a photoconductor component.

[0060] In some embodiments, all detector pixels in the SiPM detector array are divided into multiple subarrays, and the electrical signals of the multiple subarrays are processed independently.

[0061] In some embodiments, the plurality of strip-shaped CsI crystals are coupled one-to-one with a plurality of detector pixels in the SiPM detector array.

[0062] In some embodiments, this disclosure also provides a detector for a SPECT imaging system, the detector comprising: a silicon photomultiplier tube (SiPM) detector array, a cesium iodide (CsI) crystal array, and a preprocessing circuit board; the CsI crystal array comprises a plurality of strip-shaped CsI crystals; each strip-shaped CsI crystal comprises a light-emitting surface and five frosted surfaces; the light-emitting surface of the strip-shaped CsI crystal is coupled to the SiPM detector array; the electrical signal of each detector pixel in the SiPM detector array is independently output through a detector substrate in the SiPM detector array; the preprocessing circuit board integrates the electrical signals of all detector pixels and outputs a signal equal to or less than the number of detector pixels.

[0063] This provides a detector for SPECT imaging systems. In this detector, the CsI crystal array employs multiple strip-shaped CsI crystals, with the light-emitting surfaces of these strip-shaped CsI crystals coupled to a SiPM detector array. Thus, the electrical signal of each detector pixel in the SiPM detector array is independently output through the detector substrate within the SiPM detector array, and the preprocessing circuit board synthesizes the electrical signals of all detector pixels, outputting a signal equal to or less than the number of detector pixels. This improves the spatial resolution and system sensitivity of the detector while reducing cost.

[0064] In some embodiments, this disclosure proposes a detector for a SPECT imaging system, comprising: a silicon photomultiplier tube (SiPM) detector array, a cesium iodide (CsI) crystal array, and a preprocessing circuit board. The CsI crystal array includes multiple strip-shaped CsI crystals; each strip-shaped CsI crystal has one light-emitting surface and five frosted surfaces; the light-emitting surface of the strip-shaped CsI crystal is coupled to the SiPM detector; the electrical signal of each detector pixel in the SiPM detector array is independently output through a detector substrate in the SiPM detector array; the preprocessing circuit board integrates the electrical signals of all detector pixels and outputs a signal fewer than the number of detector pixels. Here, a detector pixel is the smallest unit of a detector capable of independent operation. This can improve the spatial resolution and system sensitivity of the detector, and reduce costs.

[0065] In some embodiments, the CsI crystal array employs a polycrystalline bulk structure.

[0066] In some embodiments, the detectors can be freely spliced ​​and expanded in the direction of the detection surface to form SPECT probes of different shapes and sizes.

[0067] In some embodiments, the spaces between the strip-shaped CsI crystals are filled with a reflective material.

[0068] In some embodiments, the CsI crystal array and the SiPM detector array are directly coupled using optical silicone oil.

[0069] In some embodiments, the CsI crystal array and the SiPM detector array are indirectly coupled through a photoconductor assembly.

[0070] In some embodiments, the preprocessing circuit board employs multi-channel data processing technology.

[0071] Multichannel data processing is a technique that simultaneously processes data from multiple signal sources (such as SiPM detector arrays), enabling efficient data acquisition, processing, and analysis. This technique is suitable for applications requiring rapid response and high data throughput, such as medical imaging and particle physics experiments.

[0072] The input channels and preprocessing circuit board are equipped with multiple input channels, each corresponding to the output signal of a SiPM detector. This ensures that the signal from each detector is acquired independently, avoiding signal interference.

[0073] Signal amplification: The input signal of each channel is amplified by a preamplifier circuit to improve the signal-to-noise ratio and ensure the accuracy of subsequent processing.

[0074] Analog-to-digital converter (ADC) converts amplified analog signals into digital signals for subsequent digital signal processing.

[0075] Real-time processing and multi-channel data processing technology allow for real-time analysis and processing of signals output from multiple detectors, improving processing speed through parallel processing.

[0076] Signal integration and analysis: The preprocessing circuit board integrates the signals from each channel and uses algorithms (such as the row and column method and the centroid method) to calculate the location and intensity of the event.

[0077] Data filtering and denoising involves applying filtering techniques to remove background noise, enhance the effective components of the signal, and improve the signal's usability.

[0078] The integrated output allows the processed data to be output to subsequent molding circuits and data recording systems with equal or fewer signals, reducing the amount of data and lowering the system load.

[0079] The feedback mechanism allows the preprocessing circuit board to adjust processing parameters (such as gain and time constant) based on real-time analysis results to optimize signal processing performance.

[0080] In some embodiments, the detector's detection surface is spliced ​​in different shapes through modular design to form SPECT probes of different shapes and sizes. The splicing method can be a modular plug-in method or a modular splicing method.

[0081] In some embodiments, the preprocessing circuit employs a row-column weighted network or a centroid weighted network.

[0082] In some embodiments, all detector pixels in the SiPM detector array are divided into multiple subarrays (also referred to as small arrays), and the electrical signals of the multiple subarrays are processed independently.

[0083] In some embodiments, the plurality of strip-shaped CsI crystals are coupled one-to-one with a plurality of detector pixels in the SiPM detector array.

[0084] In the detectors of the above embodiments, in addition to improving spatial resolution and system sensitivity, significant progress has also been made in spatial uniformity and count rate characteristics, as detailed below:

[0085] Regarding spatial uniformity, traditional SPECT detectors rely solely on computation to obtain resolution, resulting in better resolution near the center of the field of view but poor resolution at the edges, causing some areas of the image to appear blurry. This disclosure, however, couples multiple CsI crystal strips (i.e., strip-shaped CsI crystals) one-to-one with multiple SiPM detector pixels, allowing for direct and intuitive digital resolution without computation. This eliminates errors caused by computation during use, and the resolution remains consistent across both the central and edge regions of the field of view, significantly improving image uniformity. Furthermore, this disclosure designs the crystals, detectors, and preprocessing circuit board to be of the same size, resulting in virtually no gaps between detectors when they are assembled into a probe, significantly enhancing the spatial uniformity of the probe.

[0086] Regarding count rate characteristics, this application significantly improves the maximum count rate. The count rate, which is the number of effective gamma photon events recorded by the detector per unit time, directly affects the scan time and system efficiency. Traditional SPECT detectors, due to the non-one-to-one correspondence between the crystal and SiPM detector pixels, can only process one event at a time. If two photons arrive almost simultaneously, the system may be unable to distinguish them, leading to count loss and a low maximum count rate. After a certain drug activity is achieved, count blockage occurs, resulting in a longer scan time. Furthermore, the limitation of the maximum count rate prevents the scan time from being shortened. In contrast, this application, due to the one-to-one correspondence between the crystal and SiPM detector pixels, can process multiple events simultaneously, resulting in a significantly improved maximum count rate and thus a significantly shorter scan time.

[0087] In other embodiments, in this detector, a strip CsI crystal can be coupled to multiple detector pixels, or multiple strip CsI crystals can be coupled to a single detector pixel.

[0088] In some embodiments of this disclosure, a SPECT probe is also provided, comprising one or more detectors as described above.

[0089] For example, multiple detectors can be freely spliced ​​and expanded in the direction of the detection surface to form SPECT probes of different shapes and sizes.

[0090] For example, multiple detectors can be spliced ​​together in different shapes through modular design to form SPECT probes of different shapes and sizes. The splicing method can be a modular plug-in method or a modular splicing method.

[0091] Compared to probes fabricated using traditional SPECT detectors, the detectors disclosed in this invention, when assembled into a probe, can reduce the detection dead zone and significantly improve patient comfort. Specifically: Traditional SPECT detection dead zones are at least 6-8 cm in size, while this invention designs the crystal, detector, and preprocessing circuit board to be the same size. Therefore, when the detectors are assembled into a probe, the edges of the detectors are tightly attached to the probe shell and shielding structure, thus significantly reducing the detection dead zone to less than 3 cm. Due to the reduced detection dead zone, the probe can be placed much closer to the human body during examination. According to the definition of spatial resolution in SPECT systems, the system's spatial resolution is inversely proportional to the distance between the scanned object and the probe. In other words, the closer the scanned object is to the probe, the closer the scanning result is to the system's theoretically optimal resolution, resulting in better image quality and more accurate diagnosis. Furthermore, when performing scans of organs such as the heart, patients usually need to raise their arms to bring the probe closer to their body. Due to the improved construction of the SPECT detector disclosed in this invention, the SiPM probe has significantly smaller dimensions in terms of both the probe dead zone and the probe thickness. During the scan, patients can raise their arms to a lesser extent, greatly improving comfort.

[0092] Furthermore, compared to traditional SPECT probes, the detector disclosed herein is significantly lighter after being assembled into a probe. Traditional SPECT probes can weigh over 100 kg, while the overall weight of the probe in this disclosure is only about 50 kg due to improvements in structure and materials, greatly reducing the difficulty of equipment installation and maintenance.

[0093] In some embodiments of this disclosure, a single-photon emission computed tomography (SPCT) imaging system is also provided, comprising: a detector module for detecting photons, wherein the detector module includes the detectors described above.

[0094] In some embodiments of this disclosure, this disclosure also provides a SPECT imaging method, including: performing detection using the detector as described above, or the SPECT probe as described above, or the single-photon emission computed tomography imaging system as described above.

[0095] In some embodiments, after gamma rays enter the strip-shaped cesium iodide (CsI) crystal, the CsI crystal converts the energy of the gamma rays into an optical signal. The optical signal passes through the coupling surface between the CsI crystal and the silicon photomultiplier tube (SiPM) detector array and enters the SiPM detector array. The SiPM detector array converts the optical signal into an electrical signal and outputs the electrical signal to a preprocessing circuit board. The preprocessing circuit board outputs the electrical signal to subsequent circuits for processing.

[0096] In some embodiments, the preprocessing circuit board employs multi-channel data processing technology, which includes input channels, signal amplification, analog-to-digital conversion (ADC), real-time processing, signal integration and analysis, data filtering and denoising, integrated output, and feedback mechanisms.

[0097] In some embodiments, the signal processing method of the detector includes steps such as amplifying the preprocessed signal, data conversion, position discrimination, and energy calculation.

[0098] In some embodiments, the signal processing method for the detector further includes independent energy correction and energy window discrimination steps for the signal of each SiPM corresponding channel.

[0099] Energy correction is performed individually on the signal corresponding to each SiPM detector pixel, making the measurement of X-ray energy by each detector pixel more accurate. This improves the accuracy of energy information in the image, reduces image blurring and distortion, and enhances the spatial resolution and contrast of the image. It also helps to more clearly display the boundary between lesion tissue and normal tissue, thereby more accurately identifying minute lesions.

[0100] The SPECT imaging method provided in this disclosure further includes, after performing independent energy correction and energy discrimination on the signal of the channel corresponding to each SiPM detector pixel, identifying true events, removing noise events, and packaging the information of true events and uploading it to the data acquisition computer.

[0101] As shown in Figure 1, this disclosure provides a detector for a single-photon emission computed tomography (SPECT) imaging system. Its core consists of a polycrystalline bulk cesium iodide (CsI) crystal array (1-1) and a silicon photomultiplier (SiPM) array (1-2), along with a preprocessing circuit (1-3), to provide signals to subsequent analog-to-digital conversion and digital signal processing circuit modules for processing. This detector effectively improves the inherent resolution of the SPECT system and significantly enhances its performance.

[0102] As shown in Figures 3A to 3C, CsI crystals are processed into long strips (3-1). The light-emitting surface of the crystal strip is polished (3-2), while the other five surfaces are frosted. Multiple strip-shaped crystals form a polycrystalline block structure crystal array, with reflective material used to fill and bond the crystal strips (3-4). Except for the light-emitting surface coupled to the detector, the other five surfaces of the crystal array are covered with reflective material. An opaque material is then used to encase the reflective material, forming the crystal array, and finally, an opaque material is used as the outermost layer (3-3). The light-emitting surface is generally square or rectangular and is polished. The sides are rectangular and generally frosted. The sides of multiple crystals are bonded together using reflective material, with the light-emitting surfaces on the same plane. The crystal strips are arranged in rows and columns to form a large crystal block.

[0103] A multi-pixel SiPM array consists of multiple SiPM detector pixels soldered to a detector substrate. These multiple SiPM detector pixels are typically arranged in a row-column aligned manner.

[0104] The light-emitting surface of the CsI crystal array (2-1) is coupled to the SiPM detector array (2-3). The CsI crystal array and the SiPM detector array can be directly coupled using materials such as optical silicone oil (2-2), or they can be coupled after adding components such as photoguides. When the light-emitting surface of the CsI crystal array is directly coupled to the SiPM detector array, the CsI crystal strips are coupled to the SiPM detector in a 1:1 ratio. That is, multiple CsI crystal strips are coupled to multiple SiPM detector pixels in a one-to-one correspondence.

[0105] After gamma rays enter the CsI crystal, the crystal converts the energy of the gamma rays into an optical signal. The optical signal passes through the coupling surface and enters the SiPM detector. The SiPM detector converts the optical signal into an electrical signal, which is then output to the subsequent circuitry for processing after passing through the preprocessing circuit.

[0106] In some embodiments, during direct coupling, no optical guide is added between the crystal array and the SiPM array. High-transmittance materials (typically optical grease or optical adhesive) are used for coupling, and the coupling surface is kept as thin as possible to reduce light loss between the coupling surfaces and improve energy resolution. The light-emitting surfaces of the crystal strips correspond one-to-one with the SiPM detection surfaces. That is, multiple light-emitting surfaces of the crystal strips correspond one-to-one with multiple SiPM detection surfaces. This simplifies the design of the position calculation circuit and improves the accuracy of event localization.

[0107] In other embodiments, a light guide can be added between the crystal array and the SiPM array, for example, to distribute the optical signal generated in one crystal strip to multiple SiPM detector pixels for reception. This approach allows for the use of small-sized crystal strips to match large-sized SiPM detectors, improving the inherent spatial resolution of the probe. Currently, SiPMs can be made in sizes ranging from 2.5mm × 2.5mm to 4mm × 4mm, preferably ≤3mm × 3mm, and more preferably 3mm × 3mm.

[0108] As shown in Figures 4A and 4B, the detector base plate (or detector base plate circuit board) and preprocessing circuit board do not exceed the size of the light-emitting surface of the crystal array. The detectors can be freely spliced ​​and expanded along the detection surface direction to form SPECT probes of different shapes and sizes. Figure 4A shows the detectors spliced ​​and expanded into an 8×10 rectangular probe in eight rows of ten detectors each. This rectangular probe is a common structure used in SPECT systems. Figure 4B shows a method of splicing the detectors into irregular polygons, similar to the traditional gamma camera method. The detectors in this scheme have the ability to be arbitrarily spliced. Figures 4A and 4B only show two examples; in actual system development, the same detector can be used in different systems, saving development time and costs.

[0109] In the SiPM detector array, the electrical signal of each detector pixel is output independently through the detector base circuit board. The preprocessing circuit board combines the signals and outputs a signal equal to or less than the number of detector pixels.

[0110] As shown in Figure 5, for large-scale detector arrays, during circuit processing, the large-scale array can be divided into several smaller subarrays for independent processing. The signal output from the SiPM detector is fed into the weight network in the preprocessing circuit. Depending on the size of the detector array, all detector pixels in a detector array can be divided into several smaller arrays for independent processing. Generally, the processing size does not exceed 8×8 arrays. Figure 5 shows a 16×16 detector module, which is divided into four subarrays during signal processing, each with a size of 8×8. The signals of each subarray are processed independently without intersecting with those of other subarrays. This processing can reduce the impact of the high background noise of the SiPM and improve energy resolution and position calculation accuracy.

[0111] Figure 6 shows a typical diagram of a weighted network. In this network, the signal is divided into row X and Y signals for separate processing. SiPM1, SiPM2, SiPM3, and SiPM4 are in the same row of the detector array. The output signals of the detectors in the same row are connected together after being coupled by a resistor or capacitor, defined as the summation signal of one row of detectors. This signal is then fed into the weighted network in the Y direction. The output signals at the two ends of the Y-direction weighted network are defined as YA and YB, respectively. When a flickering event occurs in different rows, the signals generated at the YA and YB ends have different outputs. By acquiring and calculating the outputs of YA and YB, the row information of the flickering event location can be reconstructed. SiPM1, SiPM5, SiPM9, and SiPM13 are in the same column of the detector array. The output signals of the detectors in the same column are connected together after being coupled by resistors or capacitors, and are defined as the sum of the signals of a column of detectors. This sum is then fed into a weighted network in the X-direction. The output signals at the two ends of the weighted network in the X-direction are defined as XA and XB, respectively. When a scintillation event occurs in different columns, the signals generated at the XA and XB ends will have different outputs. By collecting and calculating the outputs of XA and XB, the column information of the location where the scintillation event occurred can be reconstructed. Knowing the row and column information of the scintillation event in the detector array, the specific location of the photon incident scintillation event can be determined.

[0112] Figure 7 shows another typical weighted network with four outputs, defined as A, B, C, and D. When a scintillation event occurs, the signal output from the SiPM detector is distributed within the weighted network, with different weights assigned to signals at different access points at the four outputs. By sampling and calculating the signals at the four network outputs, the specific location of the photon incident scintillation event can be determined.

[0113] The output signals of the readout network in Figure 6 or 7 all need to be processed by the preamplifier circuit and the shaping circuit.

[0114] Figure 8 shows a signal processing flowchart for a scintillation event according to an embodiment of this disclosure. As shown in Figure 8, after gamma rays enter the scintillation crystal, energy conversion occurs, transforming them into visible light of a specific wavelength. The visible light propagates along the scintillation crystal, is detected by the SiPM detector, and converted into an electrical signal. The electrical signal output by the SiPM is directly proportional to the number of photons. The electrical signal output by the SiPM detector is input into a weighted network for processing and synthesis, reducing the number of output channels, typically to four channels. The output signal of the weighted network needs to undergo amplification, analog-to-digital conversion, and other processing. Energy discrimination is performed within the FPGA. Since each SiPM detector in the probe operates independently, to improve the accuracy of energy discrimination, independent energy correction and energy window discrimination are required for the signal of each corresponding channel of the SiPM detector to identify true events, remove noisy events, improve the signal-to-noise ratio, and thus improve image quality. After energy discrimination, the location of the event on the probe is calculated. The location and energy information of the filtered events are packaged and uploaded to the data acquisition computer for further processing.

[0115] This disclosure presents a novel SPECT imaging system probe constructed by coupling a large-area SiPM detector array with a polycrystalline bulk array of CsI crystals, unlike traditional SPECT probes which use large NaI crystals coupled with photomultiplier tubes. This disclosure solves the inherent problems of low resolution, large probe size, hygroscopic crystals causing maintenance difficulties, and the need for high-voltage power supply in traditional SPECT probes. Furthermore, through modular structural design and position determination methods, it improves the maintainability and upgradeability of the probe, reducing the development cycle and cost of new products.

[0116] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0117] The units described in the embodiments of this disclosure can be implemented in software or hardware. The names of the units are not, in some cases, intended to limit the specific unit.

[0118] The preferred embodiments of this disclosure have been described above to make the spirit of this disclosure clearer and easier to understand, and are not intended to limit this disclosure. Any modifications, substitutions, or improvements made within the spirit and principles of this disclosure should be included within the scope of protection outlined in the appended claims.

Claims

1. A detector for a SPECT imaging system, comprising: The silicon photomultiplier tube (SiPM) detector array, cesium iodide (CsI) crystal array, and preprocessing circuit board, among which... The CsI crystal array comprises multiple strip-shaped CsI crystals, and each strip-shaped CsI crystal comprises at least one light-emitting surface; One light-emitting surface of each strip-shaped CsI crystal is coupled to the SiPM detector array; The SiPM detector array includes: a detector base plate and a plurality of detector pixels on the detector base plate, wherein the SiPM detector array is configured to output the electrical signal of each detector pixel independently to the preprocessing circuit board through the detector base plate; The preprocessing circuit board is configured to integrate and process the electrical signals received from all detector pixels to output a signal equal to or less than the number of detector pixels.

2. The detector according to claim 1, wherein, The CsI crystal array adopts a polycrystalline bulk structure.

3. The detector according to any one of claims 1 to 2, wherein, Each strip-shaped CsI crystal also contains multiple frosted surfaces; In the plurality of strip-shaped CsI crystals, a reflective material is filled between adjacent strip-shaped CsI crystals, wherein the reflective material is located between the frosted surfaces of adjacent strip-shaped CsI crystals.

4. The detector according to any one of claims 1 to 3, wherein, The CsI crystal array and the SiPM detector array are directly coupled using optical silicone oil; or... The CsI crystal array and the SiPM detector array are indirectly coupled through a photoconductor assembly.

5. The detector according to any one of claims 1 to 4, wherein, All detector pixels in the SiPM detector array are divided into multiple subarrays, and the electrical signals of the multiple subarrays are processed independently.

6. The detector according to any one of claims 1 to 5, wherein, The plurality of strip-shaped CsI crystals are coupled one-to-one with the plurality of detector pixels in the SiPM detector array.

7. A detector for a SPECT imaging system, comprising: The silicon photomultiplier tube (SiPM) detector array, cesium iodide (CsI) crystal array, and preprocessing circuit board, among which... The CsI crystal array comprises multiple strip-shaped CsI crystals; The strip-shaped CsI crystal comprises one light-emitting surface and five frosted surfaces; The light-emitting surface of the strip-shaped CsI crystal is coupled to the SiPM detector array; The electrical signal of each detector pixel in the SiPM detector array is output independently through the detector base plate; The preprocessing circuit board integrates the electrical signals of all detector pixels and outputs a signal equal to or less than the number of detector pixels.

8. The detector according to claim 7, wherein, The CsI crystal array adopts a polycrystalline bulk structure.

9. The detector according to claim 7 or 8, wherein, The detectors are freely spliced ​​and expanded in the direction of the detection surface to form SPECT probes of different shapes and sizes.

10. The detector according to any one of claims 7 to 9, wherein, The space between the strip-shaped CsI crystals is filled with a reflective material.

11. The detector according to any one of claims 7 to 10, wherein, The CsI crystal array and the SiPM detector array are directly coupled using optical silicone oil.

12. The detector according to any one of claims 7 to 10, wherein, The CsI crystal array and the SiPM detector array are indirectly coupled through a photoconductor assembly.

13. The detector according to any one of claims 7 to 12, wherein, The preprocessing circuit board employs multi-channel data processing technology.

14. The detector according to any one of claims 7 to 13, wherein, The preprocessing circuit employs a row-column weighted network or a centroid weighted network.

15. The detector according to any one of claims 7 to 14, wherein, All detector pixels in the SiPM detector array are divided into multiple subarrays, and the electrical signals of the multiple subarrays are processed independently.

16. The detector according to any one of claims 7 to 15, wherein, The plurality of strip-shaped CsI crystals are coupled one-to-one with the plurality of detector pixels in the SiPM detector array.

17. A SPECT probe, comprising: One or more detectors as described in any one of claims 1 to 16.

18. A single-photon emission computed tomography (SPCT) imaging system, comprising: A detector module for detecting photons, wherein the detector module includes the detector as described in any one of claims 1 to 16.

19. A SPECT imaging method, comprising: The detection is performed using the detector as described in any one of claims 1 to 16, the SPECT probe as described in claim 17, or the single-photon emission computed tomography imaging system as described in claim 18.

20. The SPECT imaging method according to claim 19, wherein, When gamma rays are incident on the strip-shaped cesium iodide (CsI) crystal, the CsI crystal converts the energy of the gamma rays into an optical signal. The optical signal passes through the coupling surface between the CsI crystal and the silicon photomultiplier tube (SiPM) detector array and enters the SiPM detector array. The SiPM detector array converts the optical signal into an electrical signal and outputs the electrical signal to a preprocessing circuit board. The preprocessing circuit board then outputs the electrical signal to subsequent circuits for processing.

21. The SPECT imaging method according to claim 20, wherein, The preprocessing circuit board employs multi-channel data processing technology, which includes input channels, signal amplification, analog-to-digital conversion (ADC), real-time processing, signal integration and analysis, data filtering and denoising, integrated output, and feedback mechanisms.

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