Normalization correction device for axial large-view PET detector

Abstract

The invention relates to a normalized correction device for an axial large-view PET detector, which is arranged on two sides of a PET detector ring, and comprises a radiation rod source clamping mechanism, a radiation rod source rotating arm, a radiation rod source rotating arm, a radiation rod source rotating arm, a radiation rod source rotating arm, a radiation rod source rotating arm, a radiation rod source rotating arm and a radiation rod source rotating arm, and is characterized in that the radiation rod source clamping mechanism is arranged at one end of the radiation rod source rotating arm; a central shaft hole is formed in the center of the central shaft positioning plate; one end of the rotating shaft is fixedly connected with the center of the radiation rod source rotating arm, and the other end of the rotating shaft is connected with the driving motor through a central shaft hole; the positioning pin is matched with the central shaft positioning plate for positioning the rotating shaft; the relative positions of the radiation rod sources on the two sides and the PET detector ring are adjusted, the radiation rod sources on the two sides are rotated to generate a unified circular track, and the axial large-view PET detector with the two-time rod source length can be completely covered. The beneficial effects are that the full coverage of the axial length of the PET detector with the large axial visual field is realized, all detection units are ensured to be uniformly irradiated, and the PET equipment is accurately and rapidly corrected.

Description

Technical Field

[0001] The invention relates to the technical field of medical imaging equipment, and in particular to a normalization correction device for an axial large-viewing-field PET detector. Background Art

[0002] In the field of nuclear medicine, PET (positron emission tomography) is an imaging technology that can non-invasively display the function and metabolism of human organs. In clinical practice, this technology can be used to guide cancer treatment. The principle is that the malignant tumor tissue in the patient's body has vigorous metabolism, and metabolites (such as glucose, protein, etc.) are more concentrated. Metabolites can be labeled with radioactive nuclides (such as F, C, etc.), and then the PET imaging system can be used to accurately display the aggregation and activity of metabolites through three-dimensional imaging technology to reflect the activity of life metabolism. It can be seen that PET provides a direct and timely method to diagnose and analyze tumors.

[0003] The radioactive nuclides that label the metabolites produce positrons through decay. The positrons will encounter and annihilate an electron in the organism, generating a pair of annihilation photons that shoot in two back-to-back directions. When they encounter the scintillation crystal material in the detector, they will cause a little light, which will be detected by the light detector SiPM or photomultiplier tube and avalanche photodiode. The detector will then send out a time pulse, and the pulse processor will convert the pulse into a square wave. After the coincidence circuit classifies the data, the computer will reconstruct the image, and then obtain the images of the cross-section, coronal section and sagittal section of various parts of the human body. This technology relies on the detection of concurrent events of a pair of photons. Photons that arrive at the detector non-simultaneously (i.e., the time difference is more than a few nanoseconds) will be regarded as background events and not considered. 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 at multiple angles and positions to produce three-dimensional sinograms, which are then restored to the three-dimensional distribution of radioactive elements through reconstruction algorithms.

[0004] In order to increase the detection efficiency, medical PET is usually a ring-shaped detection system containing tens of thousands of detection units. Affected by the geometric position and performance differences, such as crystal luminescence efficiency, crystal packaging, crystal and PMT (photomultiplier tube) coupling, electronic system, different incident angles of photon pairs, etc., the detection efficiency of the detection unit is not consistent. Therefore, in the actual detection process, the output of the detection unit cannot accurately reflect the intensity of the input photon beam. For example, the detector will output non-uniform detection results sinograms. Even if all detection units are uniformly irradiated, this will inevitably introduce artifacts in the reconstruction process, leading to doctors' misjudgment of tumors. In order to accurately model the detection system and obtain satisfactory image quality, users must calibrate the detection efficiency of the detector in advance, which is called normalization correction. Before the PET system leaves the factory, a low-scattering source is used to calibrate the part of the normalization factor that does not change with time. In the normalization correction, the usual practice is to use a rod source containing uniform radioactivity to rotate at a uniform speed around the axis of the PET detection system to uniformly irradiate all detection 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. The photon events detected by all detection units are statistically the same, so the corresponding counting response can be used as a measure of the efficiency of the detection unit, based on which the normalization factor can be calculated. Since the radiation source is a rod source, scatter correction and attenuation correction can be ignored in data processing. These factors need to be calculated in advance and stored in the computer in the form of files. When examining the patient, the normalization factor is directly applied to the measurement value to achieve the normalization correction of the detector.

[0005] In order to ensure the correctness of the detector normalization calibration before the PET equipment leaves the factory, it is necessary to ensure that all detection units in the PET system can be evenly irradiated for a long time during the test, and the position accuracy of the radiation rod source is required to be high. The rotation axis of the rod source is required to coincide with the axis of the PET detector ring, and the rotation circle trajectory of the radiation rod source is completely coaxial with the detector ring. The rotation radius needs to be large enough to ensure that the rod source is close to the detector, and the vertical distance from the rod source to the detector ring at different positions is consistent to ensure that all detection units are evenly irradiated.

[0006] In order to cover the large axial field of view of the detector (field of view length greater than 500mm), the length of the radiation rod source usually needs to exceed the axial field of view of the detector. The radioactivity of the solid rod source needs to be very uniform, and the manufacturing process requirements are high. The production cost of a longer radiation rod source is very high, and the longer radiation rod source is heavier, making positioning and moving operations very difficult.

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

[0008] Technical issues to be solved

[0009] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a normalization correction device for an axial large-field-of-view PET detector, which solves the current 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] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0012] The present invention provides a normalization correction device for an axial large-viewing-field PET detector, which is arranged on both sides of a PET detector ring. The device comprises:

[0013] Drive motor;

[0014] Rotating arm of the radiation rod source;

[0015] Radioactive rod source;

[0016] The radiation rod source clamping mechanism is arranged 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 axis positioning plate, wherein a central axis hole is arranged at the center of the central axis positioning plate;

[0018] A rotating shaft, one end of which is fixedly connected to the center of the rotating arm of the radiation rod source, and the other end of which is connected to the driving motor through the central shaft hole, and drives the rotating shaft to rotate when the driving motor is turned on;

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

[0020] Among them, by adjusting the relative positions of the radiation rod sources on both sides and the PET detector ring, the radiation rod sources on both sides are rotated to generate a unified circular trajectory, which can completely cover the PET detector with a large axial field of view that is twice the length of the rod source.

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

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

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

[0024] Adjustment knob;

[0025] The adjusting rod is provided with a thread matched with the fixing plate, one end of the adjusting rod is fixedly connected with the adjusting knob, and the other end is connected with the radiation rod source fixing block.

[0026] Optionally, the adjustment knob is turned 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 is adjustable to accommodate axial fields of view of different sizes.

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

[0031] Optionally, an image comparison method is used to achieve high-precision alignment of the scanning trajectory circles of the radiation rod sources at both ends of the PET detector, as well as high-precision coaxiality of the two scanning trajectory circles with the detector circle.

[0032] Beneficial Effects

[0033] The beneficial effects of the present invention are as follows: the normalization correction device for a PET detector with a large axial field of view of the present invention can achieve full coverage of the axial length of the PET detector with a large axial field of view for a PET device detector with a large axial field of view (axial field of view greater than 500 mm), the rotation axis of the rod source coincides with the axis of the PET detector ring, the rotation circular track of the radiation rod source is coaxial with the detector circular ring, the rotation radius is large enough to be close to the detector, the vertical distances of different positions of the rod source from the detector circular ring are consistent, ensuring that all detection units are evenly irradiated, and conveniently and accurately and quickly calibrating the PET device before leaving the factory. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0036] Figure 3 An installation diagram of a normalization correction device provided by an embodiment of the present invention;

[0037] Figure 4 Installation diagram of the bilateral normalization correction device provided by an embodiment of the present invention;

[0038] Figure 5 Scanning trajectory diagram of the bilateral normalization correction device provided in an embodiment of the present invention.

[0039] Description of Reference Numerals

[0040] 01: Central axis positioning plate, 02: Driving motor, 03: Rotating axis, 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 contour, 17: Image overlap area. DETAILED DESCRIPTION

[0041] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below in conjunction with the accompanying drawings through specific embodiments. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a clearer and more thorough understanding of the present invention and to be able to fully convey the scope of the present invention to those skilled in the art.

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

[0043] A radiation rod source; a radiation rod source clamping mechanism, which is arranged 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; a central axis positioning plate, the center of which is provided with a central axis hole; a rotating shaft, one end of which is fixedly connected to the center of the radiation rod source rotating arm, and the other end is connected to a driving motor through the central axis hole, and drives the rotating shaft to rotate when the driving motor is turned on; a positioning pin is arranged on a PET detector ring, and the positioning pin cooperates with the central axis positioning plate to position the rotating shaft; wherein, by adjusting the relative positions of the radiation rod sources on both sides and the PET detector ring, the radiation rod sources on both sides are rotated to generate a unified circular trajectory, which can completely cover the PET detector with a large axial field of view that is twice the length of the rod source.

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

[0045] Two sets of normalization correction devices are installed on both sides of the PET detector ring, and the motors on both sides are driven to rotate at the same speed for 1 minute. The trajectory images generated by the rotational irradiation of the PET detector and the radiation rod sources on both sides are fused and compared. According to the offset size of the two trajectory images, the clamping structure of the radiation rod source is adjusted to make the axes of the radiation rod sources on both sides completely coincide, the rotational scanning image trajectories on both sides are on the same circle, and the edge line of the rotational scanning image ring is parallel to the central axis of the PET ring detector, ensuring that the distances from the radiation rod sources on both sides to each column of the ring-mounted detectors are consistent.

[0046] After the positions of the scanning image rings on both sides are adjusted, the motors on both sides are driven to rotate at a uniform 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 correction of the PET equipment.

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

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

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

[0050] Adjustment knob;

[0051] The adjusting rod is provided with a thread matched with the fixing plate, one end of the adjusting rod is fixedly connected with the adjusting knob, and the other end is connected with the radiation rod source fixing block.

[0052] Among them, the adjustment knob has a scale so that the angle of the radiation rod source can be adjusted more accurately according to the scale.

[0053] Optionally, the adjustment knob is turned to adjust the angle of the radiation rod source.

[0054] The angle of the radiation rod source can be adjusted by turning the adjustment knob with high adjustment accuracy. The radiation rod source clamping mechanism can realize the fixation of the radiation rod source and the precise adjustment of its direction, ensuring that the radiation rod source is parallel to the central axis of the PET annular detector and that the vertical distances between the different positions of the rod source and the detector ring are consistent.

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

[0056] The radiation rod sources on both sides (single rod source length 500mm) can cover the axial field of view (field of view length 1000mm) of the detector ring.

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

[0058] The images generated by the detector for the rod sources on both sides have overlapping parts. The two normalized correction factors of the overlapping parts of the images can be compared to verify the accuracy of the normalized factors.

[0059] Optionally, the length of the rotation axis is adjustable to accommodate axial fields of view of different sizes.

[0060] The normalization correction device can change the length of the rotating axis to perform multiple scanning circular trajectory image fusion to meet the normalization correction of PET detectors with different axial fields of view.

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

[0062] Optionally, an image comparison method is used to achieve high-precision alignment of the scanning trajectory circles of the radiation rod sources at both ends of the PET detector, as well as high-precision coaxiality of the two scanning trajectory circles with the detector circle.

[0063] The normalization correction device for a PET detector with a large axial field of view provided in this embodiment can use a short-length radiation rod source to perform normalization correction on a PET detector with a large axial field of view, thereby avoiding the difficulty of manufacturing a long radiation rod source and reducing the procurement cost. In addition, it can be applied to normalization correction of PET detectors with axial fields of view of different sizes. It can be applied to normalization correction of PET detector rings with different radii. The image comparison method can achieve high-precision coaxiality between the rotating image track ring of the radiation rod source and the detector ring, and the normalization accuracy is high. The accuracy of the normalization factor can be verified. It has a simple structure, high adjustment accuracy, and good feasibility.

[0064] The following is a further description of a normalization correction device for an axial large field of view PET detector of the present invention in combination with a specific embodiment:

[0065] Assemble the central axis positioning plate 01, driving motor 02, rotating shaft 03, radiation rod source rotating arm 04, radiation rod source fixing block 07, adjusting rod 08, adjusting knob 09, fixing plate 10 and other components according to Figure 1 and Figure 2 Assemble together.

[0066] The two sets of assembled components are fixed to the two sides of the PET detector ring 11 respectively, and fixed by the positioning pins 12 on the side of the detector ring. Figure 3 and Figure 4 shown.

[0067] Place the radiation rod source 06 in the radiation rod source clamping mechanism 05, start the motor to rotate for 1 minute, fuse and compare the trajectory images generated by the rotational irradiation of the PET detector and the radiation rod sources on both sides, and adjust the angle of the radiation rod source 06 according to the image generated by the rotation of the PET detector 11 scanning rod source, so that the axis of the radiation rod source on both sides completely coincides with the central axis of the detector 15, and the rotation scanning image trajectories on both sides are on the same circle, such as Figure 5 To ensure that the vertical distances between the different positions of the radiation rod source 06 and the detector ring 11 are consistent, the radiation rod source rotating image track ring is coaxial with the detector ring 11 and is located within the detector outline 16 .

[0068] After the circular trajectory of the scanning images on both sides is adjusted, the driving motors 02 on both sides are driven to rotate synchronously and uniformly for a sufficient time, respectively, to obtain the first scanning image 13 and the second scanning image 14 of the rod sources on both sides, with an image overlap area 17 between them, to ensure that the correction length of the radioactive rod source fully covers the axial length of the detector ring. The PET detector 11 detects and collects the positrons generated by the radioactive rod source, obtains the normalization factor of each detector, and completes the normalization correction of the PET device.

[0069] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention should also include these modifications and variations.

[0070] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify 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 in that: Arranged on both sides of the PET detector ring, the device includes: Drive motor; Rotating arm of the radiation rod source; Radioactive rod source; The radiation rod source clamping mechanism is arranged 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; A central axis positioning plate, wherein a central axis hole is arranged at the center of the central axis positioning plate; A rotating shaft, one end of which is fixedly connected to the center of the rotating arm of the radiation rod source, and the other end of which is connected to the driving motor through the central shaft hole, and drives the rotating shaft to rotate when the driving motor is turned on; The positioning pin is arranged on the PET detector ring, and the positioning pin cooperates with the central axis positioning plate to position the rotating axis; Among them, by adjusting the relative positions of the radiation rod sources on both sides and the PET detector ring, the radiation rod sources on both sides are rotated to generate a unified circular trajectory, which can completely cover the PET detector with a large axial field of view that is twice the length of the rod source.

2. A normalization correction device for an axial large field of view PET detector according to claim 1, characterized in that: The radiation rod source clamping mechanism comprises: A fixing plate, fixedly connected to the rotating arm of the radiation rod source, and provided with fixing holes; A radiation rod source fixing block, fixedly connected to the radiation rod source; Adjustment knob; The adjusting rod is provided with a thread matched with the fixing plate, one end of the adjusting rod is fixedly connected with the adjusting knob, and the other end is connected with the radiation rod source fixing block.

3. A normalization correction device for an axial large field of view PET detector according to claim 2, characterized in that: Turn the adjustment knob to adjust the angle of the radiation rod source.

4. The normalization correction device for an axial large field of view PET detector according to claim 3, characterized in that: The length of the radiation rod source is A, and A≤500mm.

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

6. The normalization correction device for an axial large field of view PET detector according to claim 5, characterized in that: The length of the rotating axis can be adjusted to accommodate different sizes of axial fields of view.

7. The normalization correction device for an axial large field of view PET detector according to claim 6, characterized in that: The length of the rotating arm of the radiation rod source can be adjusted to adapt to the normalization correction of PET detector rings with different radii.

8. The normalization correction device for an axial large field of view PET detector according to claim 7, characterized in that: The image comparison method is used to achieve high-precision alignment of the scanning trajectory circles of the radiation rod sources at both ends of the PET detector, as well as high-precision coaxiality of the two scanning trajectory circles with the detector circle.

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