A normalization correction device for axial large field of view PET detectors

Abstract

The application relates to a normalization correction device for an axial large-view PET detector, which is arranged on both sides of a PET detector ring and comprises a radioactive rod source clamping mechanism arranged at one end of a radioactive rod source rotating arm and used for fixing the radioactive rod source to the radioactive rod source rotating arm, a center shaft positioning plate with a center shaft hole arranged at the center of the center shaft positioning plate, a rotating shaft with one end fixedly connected with the center of the radioactive rod source rotating arm and the other end connected with a driving motor through the center shaft hole, the driving motor being used for driving the rotating shaft to rotate when the driving motor is turned on, and a positioning pin matched with the center shaft positioning plate and used for positioning the rotating shaft; the relative positions of the radioactive rod sources on both sides and the PET detector ring are adjusted, the radioactive rod sources on both sides are rotated to generate a unified circular track, and the PET detector with an axial large view of twice the length of the rod source can be completely covered.The device has the beneficial effects that the axial length of the PET detector with a large axial view is fully covered, all the detection units are uniformly irradiated, and the PET equipment can be quickly and accurately corrected.

Description

Technical Field

[0001] This invention relates to the field of medical imaging equipment technology, and in particular to a normalization correction device for an axial large field of view PET detector. Background Technology

[0002] In the field of nuclear medicine, PET (Positron Emission Tomography) is a non-invasive imaging technique that can visualize the function and metabolism of human organs. Clinically, this technique can guide cancer treatment. Its principle is as follows: malignant tumor tissue in a patient's body has a high metabolic rate, with a large accumulation of metabolic substances (such as glucose and proteins). Radioactive isotopes (such as F and C) can be used to label these metabolic substances, and then the PET imaging system uses three-dimensional imaging technology to accurately display the accumulation and activity of these metabolic substances, reflecting the activity of life metabolism. Therefore, PET provides a direct and timely method for the diagnosis and analysis of tumors.

[0003] Radioactive nuclides that label metabolic substances decay to produce positrons. These positrons then encounter and annihilate an electron in the organism, generating a pair of annihilated photons that shoot back-to-back. When these photons encounter a scintillation crystal in a detector, they create a point of light, which is detected by a SiPM (Silicon Photodetector), photomultiplier tube, or avalanche photodiode. The detector then sends out a time pulse, which is converted into a square wave by a pulse processor. After data classification by a coincidence circuit, the computer performs image reconstruction, producing cross-sectional, coronal, and sagittal images of various parts of the human body. This technology relies on the detection of concurrent events of photon pairs. Photons that arrive at the detector at different times (i.e., with a time difference of several nanoseconds or more) are considered background events and not included in the data. The raw data obtained by the PET system is a series of concurrent events determined by photon pairs. These concurrent events are arranged and combined from multiple angles and positions to generate three-dimensional sinograms, which are then reconstructed into a three-dimensional distribution of radioactive elements using a reconstruction algorithm.

[0004] To increase detection efficiency, medical PET scanners are typically ring-shaped detection systems containing tens of thousands of detector units. Due to variations in geometry and performance—such as crystal luminescence efficiency, crystal packaging, crystal-to-PMT (photomultiplier tube) coupling, electronic systems, and different incident angles of photon pairs—the detection efficiency of each detector unit is not uniform. Therefore, in actual detection, the output of a detector unit does not accurately reflect the intensity of the input photon beam. For example, the detector may output non-uniform detection results (sinograms). Even if all detector units are uniformly illuminated, this will inevitably introduce artifacts during reconstruction, leading to misdiagnosis of tumors by doctors. To accurately model the detection system and obtain satisfactory image quality, users must pre-calibrate the detector's detection efficiency; this is called normalization calibration. Before the PET system leaves the factory, a low-scattering source is used to correct the time-invariant portion of the normalization factor. In normalization calibration, a common practice is to use a rod source containing uniform radioactivity to rotate uniformly around the axis of the PET detector system to uniformly illuminate all detector units. The rod source must be long enough to ensure that the trajectory covers the required lateral field of view of the PET detector ring. Since the photon events detected by all detection units are statistically identical, the corresponding count response can be used as a measure of the detection unit's efficiency. Based on this, the normalization factor can be calculated. Because the radiation source is a rod source, scattering correction and attenuation correction can be ignored in data processing. These factors need to be calculated in advance and stored in a computer as files. When examining a patient, the normalization factor is directly applied to the measured value to achieve detector normalization correction.

[0005] To ensure the accuracy of detector normalization calibration before PET equipment leaves the factory, the testing must guarantee that all detection units in the PET system are uniformly irradiated for an extended period, requiring high precision in the position of the radiation rod source. The rotation axis of the rod source must coincide with the axis of the PET detector ring, and the rotational trajectory of the radiation rod source must be completely coaxial with the detector ring. The rotation radius needs to be sufficiently large to ensure a close distance between the rod source and the detector. The vertical distance from different positions of the rod source to the detector ring must be consistent to ensure uniform irradiation of all detection units.

[0006] In order to cover the detector’s large axial field of view (field of view length greater than 500 mm), the length of the radiation rod source usually needs to exceed the detector’s axial field of view. The radioactivity of the solid rod source needs to be very uniform, the manufacturing process requires high precision, the manufacturing cost of long radiation rod sources is very high, and the weight of long radiation rod sources makes positioning and moving operations very difficult.

[0007] Currently, the radiation rod source used for normalization calibration of PET detectors is relatively short (generally less than 500mm) due to manufacturing process requirements and cost. For PET detectors with a large axial field of view of more than 500mm, the current radiation rod source calibration length cannot fully cover the axial length of the detector ring. Summary of the Invention

[0008] Technical problems to be solved

[0009] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a normalized correction device for an axial large field of view PET detector, which solves the technical problem that the correction length of the radiation rod source cannot fully cover the axial length of the detector ring.

[0010] Technical solution

[0011] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0012] This invention provides a normalization correction device for an axially large field-of-view PET detector, disposed on both sides of the PET detector ring, the device comprising:

[0013] Drive motor;

[0014] Radiation rod source rotating arm;

[0015] Radioactive rod source;

[0016] A radiation rod source clamping mechanism is located at one end of the radiation rod source rotating arm and is used to fix the radiation rod source to the radiation rod source rotating arm.

[0017] A central shaft positioning plate, with a central shaft hole at its center;

[0018] One end of the rotating shaft is fixedly connected to the center of the rotating arm of the radiation rod source, and the other end is connected to the drive motor through the central shaft hole. When the drive motor is turned on, it drives the rotating shaft to rotate.

[0019] The positioning pin is set on the PET detector ring, and the positioning pin cooperates with the central shaft positioning plate to position the rotating shaft;

[0020] By adjusting the relative positions of the two radiation rod sources and the PET detector ring, rotating the two radiation rod sources generates a uniform circular trajectory, which can completely cover the axial large field of view of the PET detector, which is twice the length of the rod source.

[0021] Optionally, the radiation rod source clamping mechanism includes:

[0022] A fixing plate is fixedly connected to the rotating arm of the radiation rod source, and fixing holes are provided on the fixing plate;

[0023] A radiation rod source fixing block is fixedly connected to the radiation rod source;

[0024] Adjust the knob;

[0025] An adjusting rod is provided with threads that mate with a fixed plate. One end of the adjusting rod is fixedly connected to an adjusting knob, and the other end is connected to a radiation rod source fixing block.

[0026] Optionally, the knob can be rotated to adjust the angle of the radiation rod source.

[0027] Optionally, the length of the radiation rod source is A, where A ≤ 500 mm.

[0028] Optionally, the axial field of view length of the PET detector is less than or equal to 2A.

[0029] Optionally, the length of the rotation axis can be adjusted to accommodate different sizes of axial field of view.

[0030] Optionally, the length of the rotating arm of the radiation rod source can be adjusted to accommodate the normalization correction of the PET detector ring with different radii.

[0031] Optionally, image comparison can be used to achieve high-precision co-circulation of the scanning trajectory rings of the radiation rod sources at both ends of the PET detector, as well as high-precision coaxiality between the two scanning trajectory rings and the detector ring.

[0032] Beneficial effects

[0033] The beneficial effects of this invention are as follows: The normalization calibration device for PET detectors with a large axial field of view (axial field of view greater than 500mm) can achieve full axial length coverage of PET detectors with a large axial field of view. The rotation axis of the rod source coincides with the axis of the PET detector ring, the rotational circular trajectory of the radiation rod source is coaxial with the detector ring, the rotation radius is large enough and the distance to the detector is close, and the vertical distance of the rod source from different positions to the detector ring is consistent, ensuring that all detection units are uniformly irradiated, which facilitates accurate and rapid calibration of PET equipment before leaving the factory. Attached Figure Description

[0034] Figure 1 A diagram of a normalization correction device provided in an embodiment of the present invention;

[0035] Figure 2 This is a diagram of a radiation rod source clamping mechanism provided in an embodiment of the present invention;

[0036] Figure 3 This is an installation diagram of the normalization correction device provided in an embodiment of the present invention;

[0037] Figure 4 This is an installation diagram of the two-sided normalization correction device provided in an embodiment of the present invention;

[0038] Figure 5 The scanning trajectory diagram of the two-sided normalization correction device provided in the embodiment of the present invention.

[0039] Explanation of reference numerals in the attached figures

[0040] 01: Central axis positioning plate, 02: Drive motor, 03: Rotating shaft, 04: Radiation rod source rotating arm, 05: Radiation rod source clamping mechanism, 06: Radiation rod source, 07: Radiation rod source fixing block, 08: Adjusting rod, 09: Adjusting knob, 10: Fixing plate, 11: PET detector ring, 12: Positioning pin, 13: First scan image, 14: Second scan image, 15: Detector central axis, 16: Detector outline, 17: Image overlapping area. Detailed Implementation

[0041] To better explain and facilitate understanding of the present invention, it will be described in detail below with reference to the accompanying drawings and specific embodiments. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0042] This embodiment provides a normalization correction device for an axial large field-of-view PET detector, which is disposed on both sides of the PET detector ring. The device includes: a drive motor; and a rotating arm for the radiation rod source.

[0043] A radiation rod source; a radiation rod source clamping mechanism, located at one end of the radiation rod source rotating arm, for fixing the radiation rod source to the radiation rod source rotating arm; a central shaft positioning plate, with a central shaft hole at its center; a rotating shaft, one end of which is fixedly connected to the center of the radiation rod source rotating arm, and the other end connected to a drive motor through the central shaft hole, which drives the rotating shaft to rotate when the drive motor is turned on; a positioning pin is located on the PET detector ring, and the positioning pin cooperates with the central shaft positioning plate to position the rotating shaft; wherein, by adjusting the relative positions of the two radiation rod sources and the PET detector ring, rotating the two radiation rod sources generates a uniform circular trajectory, which can completely cover the axial large field of view of the PET detector, which is twice the length of the rod source.

[0044] The central axis positioning plate positions the rotating axis through the positioning pins on the detector ring, ensuring that the rotating axis of the rod source coincides with the axis of the PET detector ring. The rotating arm of the long radiation rod source ensures that the rotation radius is large enough and the distance to the detector is close enough.

[0045] Two sets of normalization correction devices are installed on both sides of the PET detector ring, driving the motors on both sides to rotate at the same speed for 1 minute. The trajectory images generated by the PET detector and the two side radiation rod sources are fused and compared. Based on the offset of the two trajectory images, the radiation rod source clamping structure is adjusted so that the axes of the two side radiation rod sources are completely coincident, the trajectory of the two side rotation scanning images is on the same ring, and the edge line of the rotation scanning image ring is parallel to the central axis of the PET ring detector, ensuring that the distance from the two side radiation rod sources to each row of ring detectors is consistent.

[0046] After the positions of the two scanning image rings are adjusted, the motors on both sides are driven to rotate at a constant speed for a sufficient time. The PET detector detects and collects the positrons generated by the radiation rod source, obtains the normalization factor of each detector, and completes the normalization calibration of the PET equipment.

[0047] Optionally, the radiation rod source clamping mechanism includes:

[0048] A fixing plate is fixedly connected to the rotating arm of the radiation rod source, and fixing holes are provided on the fixing plate;

[0049] A radiation rod source fixing block is fixedly connected to the radiation rod source;

[0050] Adjust the knob;

[0051] An adjusting rod is provided with threads that mate with a fixed plate. One end of the adjusting rod is fixedly connected to an adjusting knob, and the other end is connected to a radiation rod source fixing block.

[0052] The adjustment knob has a scale, allowing for more precise adjustment of the angle of the radiation rod source.

[0053] Optionally, the knob can be rotated to adjust the angle of the radiation rod source.

[0054] The angle of the radiation source can be adjusted by rotating the adjustment knob, with high precision. The radiation source clamping mechanism can fix the radiation source and precisely adjust its direction, ensuring that the radiation source is parallel to the central axis of the PET ring detector and that the vertical distance between different positions of the source and the detector ring is consistent.

[0055] Optionally, the length of the radiation rod source is A, where A ≤ 500 mm.

[0056] The two radiation rod sources (each rod is 500mm long) can cover the detector ring with an axial field of view (1000mm long).

[0057] Optionally, the axial field of view length of the PET detector is less than or equal to 2A.

[0058] The detector generates images from the two rod sources that overlap. The accuracy of the normalization factor can be verified by comparing the two normalization correction factors of the overlapping image.

[0059] Optionally, the length of the rotation axis can be adjusted to accommodate different sizes of axial field of view.

[0060] The normalization correction device can change the length of the rotation axis to perform multiple scans of circular trajectory images for image fusion, thus adapting to the normalization correction of PET detectors with different axial field of view sizes.

[0061] Optionally, the length of the rotating arm of the radiation rod source can be adjusted to accommodate the normalization correction of the PET detector ring with different radii.

[0062] Optionally, image comparison can be used to achieve high-precision co-circulation of the scanning trajectory rings of the radiation rod sources at both ends of the PET detector, as well as high-precision coaxiality between the two scanning trajectory rings and the detector ring.

[0063] This embodiment provides a normalization calibration device for PET detectors with large axial fields of view. It allows for the normalization calibration of PET detectors with large axial fields of view using a short radiation rod source, avoiding the manufacturing difficulties and reducing procurement costs associated with long radiation rod sources. Furthermore, it is applicable to the normalization calibration of PET detectors with different axial field of view sizes and to the normalization calibration of PET detector rings with different radii. Using image comparison, high-precision coaxiality between the rotating image track ring of the radiation rod source and the detector ring can be achieved, resulting in high normalization accuracy. The accuracy of the normalization factor can be verified. The device has a simple structure, high adjustment accuracy, and good feasibility.

[0064] The following describes a normalization correction device for an axially large field-of-view PET detector, using specific embodiments as an example:

[0065] The components, including the central shaft positioning plate 01, drive motor 02, rotating shaft 03, radiation rod source rotating arm 04, radiation rod source fixing block 07, adjusting rod 08, adjusting knob 09, and fixing plate 10, are arranged according to... Figure 1 and Figure 2 Assembled together.

[0066] The two assembled components are then fixed to both sides of the PET detector ring 11 using the positioning pins 12 on the side of the detector ring. Figure 3 and Figure 4 As shown.

[0067] Place the radiation rod source 06 in the radiation rod source clamping mechanism 05, start the motor to rotate for 1 minute, and fuse and compare the trajectory images generated by the PET detector and the two sides of the rotating radiation rod source. Adjust the angle of the radiation rod source 06 according to the image generated by the PET detector 11 scanning the rotating rod source, so that the axes of the two sides of the radiation rod source are completely aligned with the central axis 15 of the detector, and the trajectories of the rotating scanning images on both sides are on the same circle. Figure 5 As shown. Ensure that the vertical distance between the radiation rod source 06 and the detector ring 11 is consistent at different positions. The rotating image track ring of the radiation rod source is coaxial with the detector ring 11 and located within the detector contour 16.

[0068] After the circular trajectories of the scanning images on both sides are adjusted, the drive motors 02 on both sides are driven to rotate synchronously and uniformly for a sufficient time to obtain the first scanning image 13 and the second scanning image 14 of the rod source on both sides. There is an image overlap region 17 between the two to ensure that the correction length of the radiation rod source fully covers the axial length of the detector ring. The PET detector 11 detects and collects the positrons generated by the radiation rod source, obtains the normalization factor of each detector, and completes the normalization correction of the PET equipment.

[0069] 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, then this invention should also include these modifications and variations.

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A normalization correction device for an axial large field of view PET detector, characterized by, The device is arranged on both sides of the PET detector ring, and comprises: a driving motor; a radioactive rod source rotating arm; a radioactive rod source; a radioactive rod source clamping mechanism arranged at one end of the radioactive rod source rotating arm and used for fixing the radioactive rod source to the radioactive rod source rotating arm; a center shaft positioning plate, the center of the center shaft positioning plate being provided with a center shaft hole; a rotating shaft, one end of the rotating shaft being fixedly connected with the center of the radioactive rod source rotating arm, and the other end of the rotating shaft being connected with the driving motor through the center shaft hole, the driving motor being capable of driving the rotating shaft to rotate when the driving motor is turned on; a positioning pin arranged on the PET detector ring, the positioning pin being used for positioning the rotating shaft in cooperation with the center shaft positioning plate; wherein, by adjusting the relative positions of the radioactive rod sources on both sides and the PET detector ring, the radioactive rod sources on both sides are rotated to generate a unified circular track, and the PET detector can completely cover an axial large field of view with a length of two times the radioactive rod source.

2. The normalization correction device for an axially large field of view PET detector according to claim 1, wherein, The radioactive rod source clamping mechanism comprises: a fixed plate, the fixed plate being fixedly connected with the radioactive rod source rotating arm, the fixed plate being provided with a fixed hole; a radioactive rod source fixing block, the radioactive rod source fixing block being fixedly connected with the radioactive rod source; an adjusting knob; an adjusting rod, the adjusting rod being provided with a thread matched with the fixed plate, one end of the adjusting rod being fixedly connected with the adjusting knob, and the other end of the adjusting rod being connected with the radioactive rod source fixing block.

3. The normalization correction device for an axially large field of view PET detector according to claim 2, wherein, The adjusting knob is rotated to adjust the angle of the radioactive rod source.

4. The normalization correction device for an axially large field of view PET detector according to claim 3, wherein, The length of the radioactive rod source is A, and A≤500 mm.

5. The normalization correction device for an axially large field of view PET detector according to claim 4, wherein, The axial field of view of the PET detector is less than or equal to 2A.

6. The normalization correction device for an axially large field of view PET detector according to claim 5, wherein, The length of the rotating shaft is adjustable to adapt to different sizes of the axial field of view.

7. The normalization correction device for an axially large field of view PET probe according to claim 6, wherein, The length of the radioactive rod source rotating arm is adjustable to adapt to different radii of the PET detector circular ring normalization correction.

8. The normalization correction device for an axially large field of view PET probe according to claim 7, wherein, The image comparison method is adopted to realize high-precision circular ring of the scanning track of the radioactive rod sources at both ends of the PET detector and high-precision coaxiality of the two scanning track circular rings and the detector circular ring.

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