Hybrid pet / ct detector and imaging system

Abstract

The application discloses a hybrid PET / CT detector and an imaging system, and relates to the technical field of medical imaging, and specifically discloses the detector which comprises a detection unit and a sealed shell covering the detection unit; the detection unit comprises a circuit board, a photoelectric converter and a plurality of scintillation crystals; the photoelectric converter is arranged on the circuit board; and the scintillation crystals are coupled to the photoelectric converter and form gaps; by adjusting the distribution of reflective materials and air in the gaps of the detection unit, the structure of the detection unit is changed, and the switching of CT scanning or PET scanning is completed. In the CT and PET detection process, the distribution of reflective materials and air in the detection unit is adjusted, the structure of the detection unit is changed, different readout modes of the rear-end circuit are combined, and the respective detection requirements are met.

Description

Technical Field

[0001] This invention relates to the field of medical imaging technology, and more particularly to a hybrid PET / CT detector and imaging system. Background Technology

[0002] CT (Computed Tomography) uses X-ray beams to scan a layer of the human body of a certain thickness. A detector receives the X-rays that pass through this layer, converts them into visible light, then converts them into electrical signals via photoelectric conversion, and finally into digital signals via an analog-to-digital converter. The scanned information is then used to calculate the X-ray attenuation or absorption coefficient of each voxel, which is arranged into a digital matrix. Based on the coefficients in the digital matrix, these are converted into small squares of varying gray levels from black to white, thus forming a CT image.

[0003] PET (Positron emission computed tomography) imaging utilizes the tracer principle and positron coincidence detection technology to display biological characteristics and biochemical metabolic processes such as functional changes, cell metabolism, molecular binding and information transmission in human tissues and organs at the cellular, subcellular and molecular levels. It can detect abnormalities before the appearance of clinical symptoms and signs and changes in tissue anatomy, which is beneficial for the early diagnosis of diseases.

[0004] Comparing CT and PET scans, their working principles are similar. When photons enter the detector material, the photoelectric effect, Compton effect, and electron-pair reaction occur, resulting in energy deposition within the detector material. The detector material then emits visible light, which is transmitted to a photoelectric device, converted into an electrical signal, and processed by backend circuitry to reconstruct the image. However, their focuses differ. For CT detectors, high resolution and high count rate are the primary requirements, while for PET detectors, high light collection and high temporal resolution are essential.

[0005] The CT detector is mounted opposite the X-ray tube, which is fixed to the gantry. During rotational scanning, their relative positions remain constant. The X-ray tube emits X-rays, which pass through the scanned object and are absorbed by the detector. Based on the intensity of the collected photons, the density distribution of the scanned object is reconstructed. CT detectors typically use ceramic scintillators encased in reflective material, with pixel sizes of 0.5-1mm. The output signal is integrated and read out in a single path. While semiconductor materials are also used for photon counting, these are expensive and technically challenging.

[0006] During PET scans, a positron-emitting radioactive reagent is injected into the subject, releasing positrons that annihilate and produce a pair of 511 keV photons. These photons are received by a ring-shaped array of detectors. Within a fixed coincidence time window, the coincidence photon pair is detected, and the annihilation location is reconstructed using the coincidence time difference to identify the positron emission point. Because the radioactive dose of the reagent is relatively small (compared to CT scans) and because it is necessary to measure the coincidence photon pair, the detectors are generally arranged in a ring to increase the 511 keV photon energy deposition ratio.

[0007] For PET and CT with their own independent detector architectures, positional fusion of CT and PET images is necessary. Due to the difference in detector positions, registration errors occur during image fusion, affecting image accuracy. When considering a shared detector, the current mainstream design is a stacked design, with an X-ray absorption region at the front and a gamma-ray absorption region at the rear. However, in multi-layer detector structures, the X-ray sensitive area at the front scatters and absorbs gamma rays, affecting the gamma-ray detection efficiency at the rear. Furthermore, because the gamma-ray sensitive area is at the rear, in PET applications, when detectors are arranged in a ring, there will be a large dead zone between two adjacent detector units (compared to a single PET detector), resulting in a decrease in sensitivity for the same crystal cost. Summary of the Invention

[0008] In view of the above problems, the present invention proposes a hybrid PET / CT detector and imaging system that overcomes or at least partially solves the above problems.

[0009] The present invention provides a hybrid PET / CT detector, the detector comprising: a detection unit and a sealed housing covering the detection unit; the detection unit includes a circuit board, a photoelectric converter and a plurality of scintillation crystals, the photoelectric converter being disposed on the circuit board and the scintillation crystals having gaps between them;

[0010] By adjusting the distribution of reflective material and air in the gaps inside the detection unit, the structure of the detection unit can be changed, enabling the switching between CT and PET scans.

[0011] Optionally, the hybrid PET / CT detector further includes a hydraulic device connected to the detection unit;

[0012] The sealed housing is provided with a reflective agent injection pipe and a compressed air injection pipe connected to the hydraulic device. By controlling the pressure of the hydraulic device, the distribution of reflective material and air inside the detection unit can be adjusted via the reflective agent injection pipe or the compressed air injection pipe, thereby changing the structure of the detection unit and enabling the switching between CT scan and PET scan.

[0013] Optionally, during a CT scan, the air in the detection unit is expelled by changing the pressure in the hydraulic device, and the reflective agent is injected through the reflective agent injection channel until the gap is completely filled. When photons interact with the scintillation crystal, the crystal generates visible light. Due to the obstruction of the reflective agent, the light can only be transmitted inside the crystal to the lower coupled photoelectric conversion device, where it is converted into an electrical signal. A single-channel readout method is used, and the back-end electronics acquire the data.

[0014] Optionally, during PET scanning, by changing the pressure in the hydraulic device, the reflective agent in the detection unit is discharged, and air is injected into the gaps inside the detection unit. The generated visible light can be freely transmitted between the crystals and enter the resistor network to achieve signal acquisition.

[0015] Optionally, a retractable reflective interlayer is formed inside the sealed housing; by controlling the reflective interlayer to insert into or move away from the gap in the detection unit, the structure of the detection unit can be changed, thus completing the switching between CT scan and PET scan.

[0016] Optionally, during CT scanning, a reflective interlayer is inserted into the gap to achieve spectral isolation of the crystal;

[0017] During PET scanning, the reflective interlayer is pulled out from the gap, enabling light sharing through air coupling.

[0018] Optionally, the inner surface of the sealed housing is coated with a reflective material;

[0019] The reflective material is composed of at least one of barium sulfate powder, titanium dioxide powder, and adhesive.

[0020] Optionally, the scintillation crystal has a cuboid structure and is coupled one-to-one to the photoelectric conversion device via optical adhesive, arranged in a fixed array.

[0021] Optionally, the cross-section of the scintillation crystal is less than 1*1mm, and the length is 10-20mm;

[0022] The slit size formed by the scintillation crystal is 0.1 to 0.2 mm.

[0023] The present invention also provides an imaging system comprising the hybrid PET / CT detector described in any of the preceding claims.

[0024] The hybrid PET / CT detector provided by this invention achieves spectral dispersion and transmission by controlling the pressure of compressed air and spectral dispersive material. In CT detection, the crystal unit is isolated and surrounded by spectral dispersive material to achieve individual detection, in order to meet the requirements of high count rate and high resolution. In PET detection, the crystal unit is arranged in a predetermined combination, the assembly is surrounded by fixed reflective material, and there is an air gap between the crystals in the assembly, in order to meet the requirements of high light collection and high time resolution.

[0025] Unlike multilayer detector designs, in CT and PET detection processes, the distribution of reflective material and air inside the detection unit is adjusted to change the structure of the detection unit. Combined with different readout methods of the back-end circuit, it meets the respective detection requirements.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below.

[0027] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 A schematic diagram of the lower component and photoelectric conversion array of a hybrid PET / CT detector provided in an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of the lower component and crystal arrangement of a hybrid PET / CT detector provided in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the upper component and crystal arrangement of a hybrid PET / CT detector according to an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the upper and lower component assembly of a hybrid PET / CT detector according to an embodiment of the present invention;

[0033] Figure 5 This is a cross-sectional view of the upper and lower component assembly of a hybrid PET / CT detector provided in an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of the signal acquisition mode of a hybrid PET / CT detector provided in an embodiment of the present invention;

[0035] Figure 7 This is a schematic diagram of a resistor network provided in an embodiment of the present invention;

[0036] Figure 8 This is a schematic diagram of the PET and CT image acquisition process provided in an embodiment of the present invention;

[0037] Figure 9 A schematic diagram of an upper reflective interlayer assembly provided in another embodiment of the present invention;

[0038] Figure 10 A schematic diagram of the lower crystal and light collection assembly provided in another embodiment of the present invention;

[0039] Figure 11 This is a schematic diagram of the upper and lower component assembly provided in another embodiment of the present invention;

[0040] Figure 12 A cross-sectional view of the upper and lower component assembly provided in another embodiment of the present invention;

[0041] Figure 13 A schematic diagram of the ET and CT image acquisition process provided in another embodiment of the present invention.

[0042] Among them, 10-detection unit, 11-circuit board, 12-photoelectric converter, 13-scintillation crystal, 20-sealed shell, 21-compressed air injection pipe, 22-reflective agent injection pipe, 23-reflective interlayer, 24-telescopic device. Detailed Implementation

[0043] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0047] This invention provides a hybrid PET / CT detector, such as... Figures 1-5 , Figures 9-12 As shown, the hybrid PET / CT detector of this embodiment may include: a detection unit 10 and a sealed housing 20 covering the detection unit 10. The detection unit 10 includes a circuit board 11, a photoelectric converter 12 and a plurality of scintillation crystals 13. The photoelectric converter 12 is disposed on the circuit board 11, and the scintillation crystals 13 are coupled to the photoelectric converter 12 and form gaps.

[0048] Optionally, the scintillation crystal 13 can be a cuboid structure with a cross-section smaller than 1*1mm and a length of 10-20mm. The scintillation crystal 13 is coupled one-to-one to the photoelectric converter 12 via optical adhesive and arranged in a fixed array. The circuit board 11 can be a PCB board, and the photoelectric conversion device is soldered onto the circuit board 11 with solder joints at the bottom for electrical connection. The scintillation crystal 13 can be a high-density scintillator such as LYSO, LSO, or GSO. The scintillation crystal 13 can be arranged in a fixed number with a fixed gap in the middle, the gap size being 0.1-0.2mm. After the crystals are arranged, a sealing shell 20 is installed on the outside. The sealing shell 20 is fixed to the circuit board 11 by adhesive or screws to achieve complete sealing between the detection unit 10 and the detection unit 20. The inner surface of the sealing shell 20 is coated with a reflective material; the reflective material is composed of at least one of barium sulfate powder, titanium dioxide powder, and adhesive.

[0049] As shown above, in this embodiment of the hybrid PET / CT detector, the detection unit 10 has a gap inside. By adjusting the distribution of reflective material and air in the gap inside the detection unit 10, the structure of the detection unit 10 can be changed, thus completing the switching between CT scan and PET scan.

[0050] In some embodiments, the hybrid PET / CT detector also includes a hydraulic device (not shown in the figures) connected to the detection unit 10, such as... Figures 1-5As shown, the sealed housing 20 is provided with a reflective agent injection pipe 22 and a compressed air injection pipe 21 connected to the hydraulic device. By controlling the pressure of the hydraulic device, the distribution of reflective material and air inside the detection unit 10 is adjusted via the reflective agent injection pipe 22 or the compressed air injection pipe 21, thereby changing the structure of the detection unit 10 and completing a CT scan or PET scan. Figure 3 As shown, the upper part of the sealed housing 20 has an opening to connect to the compressed air inlet pipe 21, and the surrounding openings are connected to the reflective agent injection pipe 22. The end of the pipe is a hydraulic device, and the injection and discharge of air and reflective agent are completed by controlling the hydraulic device.

[0051] like Figure 6 As shown, the hybrid PET / CT detector in this embodiment can be divided into two sampling modes: CT mode and PET mode.

[0052] In CT mode: a single-channel readout method is used, with each photoelectric converter 12 output signal processed independently. At low doses, a single-photon counting mode is employed. After signal amplification and shaping, the signal passes through a threshold comparator. Signals exceeding the threshold are recorded as the effective photon count. Multiple thresholds can be set to meet energy spectrum counting requirements. At high doses, due to the short signal intervals, overlap may occur. An integration method is used, integrating the signal within milliseconds before acquisition and recording as intensity information. The acquired data is transmitted to the backend reconstruction system for image reconstruction.

[0053] In PET mode: After arranging the crystals as described above, the photoelectric converter 12 inputs to the resistor network, as shown in the resistor network... Figure 7 As shown, the example is a 4x4 distribution. The resistor network can combine multiple inputs into four outputs. Depending on the location of the input point, the four responses are different. After being acquired by an analog-to-digital converter, the energy values ​​are output. After acquiring the four energy values, the incident point position information is restored. The summed signals are acquired to determine the photon arrival time information. The data is transmitted to the back-end reconstruction system for image reconstruction.

[0054] The signal processing flow of the hybrid PET / CT detector in this embodiment is divided into X-ray and gamma-ray processing. In X-ray processing, photon counting is used at low count rates, and multiple thresholds can be set. At high count rates, signal integration mode is used. In gamma-ray processing, a resistor network is used at the energy end to output four energy information channels, calculate and restore the position information, sum all input signals at the time end, and output time information after threshold discrimination.

[0055] Both the air end and the reflector end are hydraulically controlled, allowing for adjustments to the pressure distribution, such as... Figure 8As shown, during a CT scan, after the patient injects the medication, the air in the detection unit 10 is expelled by changing the pressure in the hydraulic device, and the reflective agent is injected into the detection unit 10 through the reflective agent injection channel 22 until the gap is completely filled. When the photons interact with the scintillation crystal 13, the scintillation crystal 13 generates visible light. Due to the obstruction of the reflective agent, the light can only be transmitted inside the crystal to the lower coupled photoelectric converter 12, which converts it into an electrical signal. The data is acquired by the back-end electronics using a single-channel readout method.

[0056] During PET scanning, by changing the pressure in the hydraulic device, the reflective agent in the detection unit 10 is expelled, and air is injected into the internal gaps of the detection unit 10. The generated visible light can freely propagate between the scintillation crystals 13 and enter the resistor network for signal acquisition. The detector can be selected as a 4*4 structure, with each photoelectric converter connected to each input of the resistor network.

[0057] The hybrid PET / CT detector in this embodiment separates the crystals during CT scans, providing one-to-one signal output. This achieves high spatial resolution and a high count rate. The threshold discrimination counting mode and integral acquisition mode have simple circuit structures, eliminating the need for full-energy counting and reducing channel complexity. During PET scans, the crystals are separated by air, and a resistor network is used for output acquisition. Compared to single-channel output, this improves light collection and reduces the impact of scattering counts, resulting in higher temporal resolution and sensitivity.

[0058] The above embodiments mention a solution that achieves different light-splitting effects by injecting a reflective agent. Another solution is to change the reflective layer using a mechanical structure.

[0059] In some embodiments, such as Figures 9-12 As shown, a retractable reflective interlayer 23 is formed within the sealed housing 20, and multiple reflective interlayers 23 can be provided. By controlling the reflective interlayer 23 to insert into or move away from the gap within the detection unit 10, the structure of the detection unit 10 can be changed, thus completing the switching between CT scanning and PET scanning. Optionally, a mechanical telescopic device 24 connected to the reflective interlayer 23 can be provided on the upper part of the sealed housing 20. The mechanical telescopic device 24 can realize the vertical extension and retraction of the reflective interlayer 23, and can be a structure of a servo motor with a screw. The reflective interlayer 23 can be a white reflector made of barium sulfate or titanium dioxide.

[0060] The hybrid PET / CT detector in this embodiment, by incorporating a retractable reflective interlayer 23, enables rapid switching between beam splitting and transmission. Combined with... Figure 13 Based on the hybrid PET / CT detector of this embodiment: during CT scanning, the reflective interlayer 23 is inserted into the gap to achieve crystalline beam separation; during PET scanning, the reflective interlayer 23 is pulled out from the gap to achieve air-coupled light sharing.

[0061] This invention combines X-ray and gamma-ray detection by distributing reflective material and air within the detection unit 10. Unlike multilayer designs, it uses a single absorption layer material for detection. Furthermore, the distribution of the dispersive material can be flexibly adjusted to meet the acquisition requirements of CT and PET scans. Based on this embodiment, the hybrid PET / CT detector inherently aligns the acquired CT and PET images, eliminating registration errors. The detection efficiency of gamma rays and X-rays is independent, simplifying the system and reducing the overall detector cost.

[0062] A single detector can detect both CTX and PET gamma rays. It features an innovative mechanical structure and a variable state of the beam-splitting material. Under different test conditions, the split crystal enables optical path transmission to meet the requirements of high resolution and high counting in CT detection as well as the requirements of high light collection and time resolution in PET detection.

[0063] The present invention also provides an imaging system comprising the hybrid PET / CT detector described in any of the preceding claims.

[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A hybrid PET / CT detector, characterized in that, The detector includes: a detection unit and a sealed housing covering the detection unit; the detection unit includes a circuit board, a photoelectric converter and a plurality of scintillation crystals, the photoelectric converter is disposed on the circuit board, the scintillation crystals are coupled to the photoelectric converter, and there are gaps between the scintillation crystals; The hybrid PET / CT detector also includes a hydraulic device connected to the detection unit. The sealed housing is provided with a reflective agent injection pipe and a compressed air injection pipe connected to the hydraulic device. By controlling the pressure of the hydraulic device, the distribution of reflective material and air in the gaps inside the detection unit can be adjusted via the reflective agent injection pipe or the compressed air injection pipe, thereby changing the structure of the detection unit and enabling the switching between CT scan and PET scan.

2. The hybrid PET / CT detector according to claim 1, characterized in that, During a CT scan, the air in the detection unit is expelled by changing the pressure in the hydraulic device, and the reflective agent is injected through the reflective agent injection pipe until the gap is completely filled. When photons interact with the scintillation crystal, the crystal generates visible light. Due to the obstruction of the reflective agent, the light can only be transmitted inside the crystal to the lower coupled photoelectric converter, where it is converted into an electrical signal. A single-channel readout method is used, and the back-end electronics acquire the data.

3. The hybrid PET / CT detector according to claim 1, characterized in that, During PET scanning, by changing the pressure in the hydraulic device, the reflective agent in the detection unit is discharged, and air is injected into the gaps inside the detection unit. The generated visible light can be freely transmitted between the crystals and enter the resistor network to achieve signal acquisition.

4. The hybrid PET / CT detector according to any one of claims 1-3, characterized in that, The inner surface of the sealed housing is coated with a reflective material; The reflective material is composed of at least one of barium sulfate powder, titanium dioxide powder, and adhesive.

5. The hybrid PET / CT detector according to any one of claims 1-3, characterized in that, The scintillation crystal has a cuboid structure and is coupled one-to-one to the photoelectric converter via optical adhesive, arranged in a fixed array.

6. The hybrid PET / CT detector according to claim 5, characterized in that, The cross-section of the scintillation crystal is less than 1 mm × 1 mm, and the length is 10~20 mm; The slit size formed by the scintillation crystal is 0.1~0.2 mm.

7. A hybrid PET / CT detector, characterized in that, The detector includes: a detection unit and a sealed housing covering the detection unit; the detection unit includes a circuit board, a photoelectric converter and a plurality of scintillation crystals, the photoelectric converter is disposed on the circuit board, the scintillation crystals are coupled to the photoelectric converter, and there are gaps between the scintillation crystals; A retractable reflective interlayer is formed inside the sealed outer shell; by controlling the reflective interlayer to insert into or move away from the gap in the detection unit, the structure of the detection unit can be changed, thus completing the switching between CT scan and PET scan.

8. The hybrid PET / CT detector according to claim 7, characterized in that, During CT scanning, a reflective interlayer is inserted into the gap to achieve optical separation of the crystal. During PET scanning, the reflective interlayer is pulled out from the gap, enabling light sharing through air coupling.

9. The hybrid PET / CT detector according to any one of claims 7-8, characterized in that, The inner surface of the sealed housing is coated with a reflective material; The reflective material is composed of at least one of barium sulfate powder, titanium dioxide powder, and adhesive.

10. The hybrid PET / CT detector according to any one of claims 7-8, characterized in that, The scintillation crystal has a cuboid structure and is coupled one-to-one to the photoelectric converter via optical adhesive, arranged in a fixed array.

11. The hybrid PET / CT detector according to claim 10, characterized in that, The cross-section of the scintillation crystal is less than 1 mm × 1 mm, and the length is 10~20 mm; The slit size formed by the scintillation crystal is 0.1~0.2 mm.

12. An imaging system, characterized in that, The imaging system includes the hybrid PET / CT detector as described in any one of claims 1-11.

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