System temperature stabilizing method and system based on CT (Computed Tomography) exposure condition

Abstract

The invention relates to a system temperature stabilization method and system based on a CT exposure condition. The method comprises the following steps: determining a bias voltage reduction value of each detector of different exposure types; pre-judging a CT exposure type; cT exposure is started, and the process of the common temperature adjusting mechanism is stopped; reducing the bias voltage of the detector according to the exposure type and the corresponding bias voltage reduction value of each detector; under the condition that a CT exposure ending signal is received, original detector bias voltage is recovered; and recovering the process of the common temperature regulation mechanism after a preset duration. The method has the beneficial effects that the temperature of the SiPM on the PET detector is stably controlled, the sensitivity of the SiPM to the environment temperature is effectively overcome, and the overall performance and stability of PET equipment are improved.

Description

Technical Field

[0001] The present invention relates to the field of PET technology, and in particular to a system temperature stabilization method and system based on CT exposure. Background Art

[0002] As the core component of PET detectors, SiPM is known for its insusceptibility to magnetic field interference, high spatial resolution and high temporal resolution. These characteristics significantly improve the performance of PET equipment in tumor localization and image reconstruction signal-to-noise ratio. However, SiPM's sensitivity to ambient temperature has become a challenge. Fluctuations in ambient temperature will directly affect key parameters of SiPM, such as breakdown voltage, gain, junction capacitance, dark counts and photon detection efficiency, and thus affect the overall performance of PET detectors.

[0003] During CT exposure, there are still leaked and scattered X-rays reaching the PET detector. Especially during preheating, there will be more scattered low-energy signals. A large number of low-energy rays reach the PET detector. The scintillator at the front end of the detector can completely absorb these low-energy rays, generating a large number of low-energy small signals, which will cause the power of the SiPM of the detector photoelectric conversion to increase significantly at this moment. After the CT exposure is over, the low-energy rays disappear and the SiPM power is reduced to normal. In this process, since the SiPM signal power increases instantaneously for a period of time, it breaks the original thermal balance. Therefore, after CT exposure, the temperature of the SiPM on the detector increases. As the CT exposure ends, the thermal balance is re-established and the SiPM temperature drops.

[0004] The temperature rise speed and continuous temperature rise time of the whole process are determined by the CT exposure setting. If ordinary temperature correction is used, the temperature detection frequency is required to be high, and the response speed cannot be met by adjusting the water temperature of the water cooling outlet. After the CT exposure scan, the patient needs to move to the PET position and then start the PET imaging scan. Summary of the invention

[0005] Technical issues to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a system temperature stabilization method and system based on CT exposure, which solves the technical problem of how to stably control the temperature of SiPM on a PET detector.

[0007] Technical Solution

[0008] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, the present invention provides a system temperature stabilization method based on CT exposure, comprising:

[0010] Determine each detector bias voltage reduction value for different exposure types;

[0011] Predict CT exposure type;

[0012] Start CT exposure and stop normal temperature control mechanism process;

[0013] reducing the detector bias voltage according to the exposure type and the corresponding bias reduction value of each detector;

[0014] When receiving the CT exposure end signal, the original detector bias is restored;

[0015] After a preset period of time, the normal temperature control mechanism process is restored.

[0016] Optionally, the exposure type includes preheating and normal scanning.

[0017] Optionally, determining each detector bias reduction value for different exposure types includes:

[0018] Generate a preheating bias value and a normal scanning bias value for each detector according to a preset calibration method;

[0019] The detector bias reduction values ​​for preheating and normal scanning are determined respectively according to the preheating bias value, the normal scanning bias value and the original detector bias.

[0020] Optionally, the preset scale method includes:

[0021] For each detector, bias voltage difference and count difference are obtained by preheating and normal scanning respectively;

[0022] Based on the bias voltage difference and the count difference, a linear fit is performed to obtain the bias voltage change difference of each detector during preheating and normal scanning.

[0023] Optionally, bias voltage difference and count difference are obtained for each detector by preheating and normal scanning. Including:

[0024] Apply a fixed bias voltage V to all SiPM chips 1 , by low threshold count scanning, the normal low threshold count sum C of each detector without CT exposure is obtained statistically 无CT1 , and the normal low threshold count sum C of each detector during CT exposure CT1 ;

[0025] Using C CT1 Minus C 无CT1 Get a fixed bias voltage V 1 The exposure count difference C 1 .

[0026] Similarly, the fixed bias voltage V is added to all SiPM chips. 2 Each detector CT exposure time low threshold count C CT2 ;

[0027] Using C CT2 Minus C 无CT1 Get a fixed bias voltage V 2 The exposure count difference C 2 .

[0028] Optionally, a linear fit is performed based on the bias voltage difference and the count difference, including:

[0029] V is obtained based on the linear fitting of bias voltage difference and count difference 2 -V 1 =a(C 1 -C 2 )+b, where a and b are obtained by fitting, and the count difference C 1 -C 2 = Bias value V when 0 2 -V 1 =b.

[0030] Optionally, the preset duration is 20 seconds.

[0031] In a second aspect, the present invention provides a system temperature stabilization system based on CT exposure, comprising:

[0032] A determination module determines a bias reduction value of each detector for different exposure types;

[0033] Prediction module, predicting CT exposure type;

[0034] The temperature control process stops the module, starts CT exposure and stops the normal temperature control mechanism process;

[0035] A bias voltage adjustment module, which reduces the detector bias voltage according to the exposure type and the corresponding bias voltage reduction value of each detector;

[0036] The bias voltage recovery module restores the original detector bias voltage upon receiving the CT exposure end signal;

[0037] The temperature control process recovery module restores the normal temperature control mechanism process after a preset period of time.

[0038] In a third aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed, the method for stabilizing system temperature based on CT exposure as described in any one of the first aspects above is implemented.

[0039] In a fourth aspect, the present invention provides a storage device comprising a storage medium and a processor, wherein the storage medium stores a computer program, and when the program is executed by the processor, the method for stabilizing system temperature based on CT exposure as described in any one of the first aspects above is implemented.

[0040] Beneficial Effects

[0041] The beneficial effects of the present invention are as follows: the system temperature stabilization method based on CT exposure of the present invention dynamically adjusts the working bias voltage of SiPM through the CT exposure process, reduces SiPM power fluctuations, thereby reducing temperature fluctuations, and restores the SiPM working bias voltage after the CT exposure is completed. By predicting CT exposure, voltage reduction measures are taken in advance, effectively avoiding the immediate impact of a large number of small signals on SiPM performance. During the CT exposure process, there is no need for a complex temperature compensation algorithm to reduce SiPM power. At the end of CT exposure, SiPM can return to a normal state, and temperature fluctuations are greatly reduced. The method of controlling temperature fluctuations from the source is incomparable to simply relying on a temperature compensation mechanism. The present invention predicts the CT exposure mechanism, combines scale evaluation, and reduces the bias voltage and SiPM power in advance, thereby achieving stable control of the SiPM temperature on the PET detector, effectively overcoming the sensitivity of SiPM to ambient temperature, and improving the overall performance and stability of the PET device. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of a CT exposure process processing flow provided by an embodiment of the present invention;

[0043] Figure 2 A schematic diagram of the low threshold count difference of CT preheating with different bias voltages provided in an embodiment of the present invention;

[0044] Figure 3 A relationship diagram between a detector CT preheating count difference and a bias voltage difference provided in an embodiment of the present invention;

[0045] Figure 4 A graph showing the average temperature change of the detector before and after CT exposure before and after the voltage reduction provided by the embodiment of the present invention;

[0046] Figure 5 A comparison chart of the maximum temperature values ​​after CT preheating before and after the pressure reduction provided by the embodiment of the present invention;

[0047] Figure 6 This is a comparison diagram of the maximum temperature of the PET detector in the CT plain scan before and after the pressure reduction provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0049] The power of the SiPM of the PET system detector is greatly increased during CT exposure. During CT exposure, the temperature of the SiPM will continue to rise. After the CT exposure is over, the SiPM will cool down to its original temperature. It takes some time to completely cool down to a temperature close to the original temperature (without affecting the scan results). It is possible that the patient has already moved from the CT position to the PET position at this time. If the whole process is very fast without any processing and temperature adjustment, it will slightly affect the patient's scan.

[0050] For the common temperature stabilization adjustment mechanism, the PET system frequently detects the temperature status of the SiPM at the detector end. If it recognizes that there is a temperature rise, it will stabilize the water temperature and suppress the temperature rise by lowering the outlet temperature of the water cooling. However, the mechanism of adjusting the water cooling temperature after identifying the temperature rise can only adjust the overall temperature of all SiPMs. If the temperature rise amplitudes between SiPMs are different and there are large differences, the temperature stability of the detector with a large deviation from the average temperature of a single detector will not be good. In addition, the water temperature adjustment responds relatively slowly to the temperature change of the probe, and the time from the start to the end of the CT exposure is short. After the exposure, the SiPM will enter the cooling stage, so it is not very suitable to stabilize the CT exposure effect by adjusting the water temperature.

[0051] In order to overcome this limitation, another control strategy is proposed: after the CT exposure command is issued, it is generally necessary to manually press a button to actually issue the exposure command. By using the time difference, PET can predict the need for CT exposure, reduce the voltage of SiPM on all detectors, reduce the power of SiPM during CT exposure, and reduce the temperature rise of SiPM during CT exposure. The PET system can obtain the CT exposure end signal and then restore the SiPM bias. Based on this method, the system can actively and significantly reduce the corresponding voltage of SiPM in advance, thereby significantly reducing the temperature rise of the detector during CT exposure. The temperature rise caused by CT exposure has a certain distribution, which is clearly defined in advance through the scale. Using different voltage changes at different positions can make the temperature curve smoother and more stable. This method not only improves the overall performance of the PET scanning system, but also ensures the continued high standards of image quality, further enhancing the reliability of the system and user experience.

[0052] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. 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 described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0053] In a first aspect, the present embodiment provides a method for stabilizing system temperature under CT exposure conditions, including: determining a bias reduction value for each detector under different exposure types; predicting the CT exposure type; starting CT exposure and stopping a normal temperature control mechanism process; reducing the detector bias according to the exposure type and the corresponding bias reduction value for each detector; restoring the original detector bias upon receiving a CT exposure end signal; and restoring the normal temperature control mechanism process after a preset time.

[0054] Figure 1 It is the CT exposure process. First, the line scale is used to confirm the bias reduction value of each detector. The PET system predicts the information and exposure type of the CT to be exposed through communication, stops the normal temperature control mechanism process, and reduces the detector bias according to the exposure type. Wait for the CT exposure end signal to be received, restore the original detector bias, and delay for a period of time to resume the normal temperature control mechanism process.

[0055] There are two types of CT exposure: warm-up and normal scanning. During warm-up, the tube is in a fixed position, while during normal scanning, the tube is not fixed. The specific PET system has 4 ring detectors, from Figure 5 and Figure 6 According to the PET system, there are 4 rings of detectors divided into four areas. From the four areas, we can see that no matter what kind of exposure, the ring farthest from the CT is relatively least affected.

[0056] During preheating, the tube is exposed at a fixed position, which is above the PET / CT system, so the position most affected by scattering is below the PET system.

[0057] During normal scanning, the tube rotates, so the scattering received by the detector itself is relatively uniform. Due to the heat dissipation characteristics of the system itself, there is a slight difference in flow resistance at different distribution positions, showing that the heat dissipation at the bottom of the system is better than that at the top.

[0058] Therefore, during CT exposure, the system needs to identify the exposure type and provide different bias voltages to stabilize the system temperature changes.

[0059] Scale method:

[0060] Apply a fixed bias voltage V to all SiPM chips 1 , by low threshold count scanning, the normal low threshold count sum C of each detector without CT exposure is obtained statistically 无CT1 When CT is exposed, the normal low threshold count sum C of each detector during exposure is obtained in the same way. CT1 , using C CT1 Minus C 无CT1 Get a fixed bias voltage V 1 The exposure count difference C 1 .

[0061] Apply a fixed bias voltage V to all SiPM chips 2 In the same way, the low threshold count C of each detector during CT exposure is obtained. CT2 , using C CT2 Minus C 无CT1 Get a fixed bias voltage V 2 The exposure count difference C 2 .

[0062] like Figure 2 The figure shows the low threshold count difference of each detector at different bias voltages during CT preheating. If the count difference remains unchanged or changes slightly, the corresponding SiPM power change will also be small, and the resulting temperature change will also be small.

[0063] Each detector uses V 1 、V 2 , C 1 and C 2 The relationship between the bias voltage difference and the count difference of each detector can be obtained through linear fitting: V 差值 =aC 差值 +b, a and b are obtained by fitting. Let the count difference C 差值 = Bias value V when 0 差值 =b.

[0064] like Figure 3 As shown, the bias voltage difference and count difference obtained when a detector is tested with preheat exposure are given. After linear fitting, the bias voltage change difference is obtained.

[0065] Due to the slight difference in distribution between the two exposure processes, two calibration processes can be used to generate two bias voltages V for each detector. 预热 and V 扫描 , different bias values ​​are used corresponding to different exposure processes, and these two scale bias values ​​are lower than the original bias values.

[0066] The purpose itself is not to require that the CT scan can be performed normally during exposure, but to ensure that the temperature of the detector is as small as possible when the PET scan starts after the CT exposure is completed and before the CT exposure.

[0067] The system control process is to obtain the CT exposure type before CT exposure and set the scale corresponding voltage for each detector; at the end of exposure, the original bias voltage is added back; the ordinary temperature adjustment mechanism is not used during exposure.

[0068] The blood pressure was lowered after CT exposure. Figure 4It is the change of the average temperature of the system detector before and after the voltage reduction. The first temperature change peak in the figure is the CT preheating exposure, and the second and third peaks are the temperature changes caused by the CT axial scanning exposure. By comparison, the first peak CT preheating has the greatest impact on the temperature change. When the bias reduction stabilization method corresponding to the exposure is used, the peak with the largest average temperature change is less than 0.1℃. After the exposure stops, the temperature drops to less than half of the highest temperature after 20s.

[0069] Figure 5 and Figure 6 It captures the temperature distribution of each detector at the highest temperature during CT exposure. It compares the temperature change amplitude of each detector before and after voltage reduction when the temperature is the highest. The distribution shows that the temperature change can be greatly reduced by reducing the bias voltage. The impact of CT preheating on temperature is still large, but since the PET scan will not be performed quickly after preheating, the patient can enter the scanning room and get on the bed at this time. The moving bed only takes about 20 seconds for the temperature impact to drop by half. At this time, starting the PET scan will not affect the image effect. If it is a normal CT exposure, the basic maximum temperature change is also controlled at 0.1℃, which will not affect the scan at all.

[0070] When the CT exposure is finished, the system receives the signal and quickly restores the bias setting, and after a short delay, resumes the normal temperature adjustment mechanism.

[0071] One of the methods to stabilize the gain of SiPM is to adjust the bias voltage. This solution also uses the method of reducing the bias voltage. The difference between the two methods is that the bias voltage for stabilizing the gain increases with the temperature, and the bias voltage is increased to ensure the gain of SiPM itself. The purpose of this solution is not to stabilize the gain of SiPM itself, but to reduce the power of SiPM during CT exposure and reduce the temperature rise of SiPM during exposure. The temperature rise is small, and it will return to the original temperature state faster when the exposure ends. When the PET scan actually starts, the temperature is closer to the original state.

[0072] The purpose is not to require normal scanning during CT exposure, but to ensure that the temperature of the detector is as small as possible when the PET scan starts after the CT exposure ends. By reducing the SiPM bias, the power of the SiPM during exposure is reduced to stabilize the temperature of the detector. When the exposure ends, the original bias is added back. From the end of the CT exposure to the time when the patient is moved to the PET position via the bed to start scanning, it usually takes at least 20 seconds to restore the temperature.

[0073] This embodiment proposes a system temperature stabilization method based on CT exposure. By predicting CT exposure, the SiPM bias voltage is adjusted in time. The temperature change response is a slow-frequency process. By predicting in advance, the temperature stability of the detector is improved, and the temperature fluctuation control accuracy is improved by an order of magnitude. It ensures that the gain of the PET detector remains stable and reduces the impact of CT exposure.

[0074] Second, as Figure 3 As shown, this embodiment provides a system temperature stabilization system based on CT exposure, including: a determination module, determining the bias reduction value of each detector under different exposure types; a pre-judgment module, pre-judgment of the CT exposure type; a temperature control process stop module, starting CT exposure and stopping the ordinary temperature control mechanism process; a bias adjustment module, reducing the detector bias according to the exposure type and the corresponding bias reduction value of each detector; a bias recovery module, restoring the original detector bias when receiving the CT exposure end signal; a temperature control process recovery module, restoring the ordinary temperature control mechanism process after a preset time. According to the system temperature stabilization system based on CT exposure provided by this embodiment, since it is used to implement the steps of a system temperature stabilization method based on CT exposure provided by the first aspect of the present invention, the system temperature stabilization system based on CT exposure has all the technical effects of the system temperature stabilization method based on CT exposure, which will not be repeated here.

[0075] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed, the method for stabilizing system temperature based on CT exposure as described in any one of the first aspects above is implemented.

[0076] In a fourth aspect, an embodiment of the present invention provides a storage device, including a storage medium and a processor, wherein the storage medium stores a computer program, and when the program is executed by the processor, the method for stabilizing system temperature based on CT exposure as described in any one of the first aspects above is implemented.

[0077] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0078] 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.

[0079] 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 system temperature stabilization method based on CT exposure, characterized in that: include: Determine each detector bias voltage reduction value for different exposure types; Predict CT exposure type; Start CT exposure and stop normal temperature control mechanism process; reducing the detector bias voltage according to the exposure type and the corresponding bias reduction value of each detector; When receiving the CT exposure end signal, the original detector bias is restored; After a preset period of time, the normal temperature control mechanism process is restored.

2. The system temperature stabilization method based on CT exposure according to claim 1, characterized in that: The exposure types include preheating and normal scanning.

3. The system temperature stabilization method based on CT exposure according to claim 2, characterized in that: Determine the bias reduction value for each detector for different exposure types, including: Generate a preheating bias value and a normal scanning bias value for each detector according to a preset calibration method; The detector bias reduction values ​​for preheating and normal scanning are determined respectively according to the preheating bias value, the normal scanning bias value and the original detector bias.

4. The method for stabilizing system temperature under CT exposure according to claim 3, characterized in that: The preset scale method comprises: For each detector, bias voltage difference and count difference are obtained by preheating and normal scanning respectively; Based on the bias voltage difference and the count difference, a linear fit is performed to obtain the bias voltage change difference of each detector during preheating and normal scanning.

5. The method for stabilizing system temperature under CT exposure according to claim 4, characterized in that: For each detector, the bias voltage difference and count difference are obtained by preheating and normal scanning. Including: Apply a fixed bias voltage V1 to all SiPM chips, and perform low threshold count scanning to obtain the normal low threshold count sum C of each detector without CT exposure. 无CT1 , and the normal low threshold count sum C of each detector during CT exposure CT1 ; Using C CT1 Minus C 无CT1 The exposure count difference C1 under the fixed bias voltage V1 is obtained. Similarly, the low threshold count C of each detector during CT exposure is obtained when a fixed bias voltage V2 is applied to all SiPM chips. CT2 ; Using C CT2 Minus C 无CT1 The exposure count difference C2 under the fixed bias voltage V2 is obtained.

6. The method for stabilizing system temperature under CT exposure according to claim 5, characterized in that: Linear fit based on bias voltage difference and count difference, including: Based on the linear fitting of the bias voltage difference and the count difference, V2-V1=a(C1-C2)+b is obtained, where a and b are obtained through fitting, and the bias voltage value V2-V1=b when the count difference C1-C2=0 is set.

7. The method for stabilizing system temperature under CT exposure according to claim 6, characterized in that: The preset duration is 20 seconds.

8. A system temperature stabilization system based on CT exposure, characterized in that: include: A determination module determines a bias reduction value of each detector for different exposure types; Prediction module, predicting CT exposure type; The temperature control process stops the module, starts CT exposure and stops the normal temperature control mechanism process; A bias voltage adjustment module, which reduces the detector bias voltage according to the exposure type and the corresponding bias voltage reduction value of each detector; The bias voltage recovery module restores the original detector bias voltage upon receiving the CT exposure end signal; The temperature control process recovery module restores the normal temperature control mechanism process after a preset period of time.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the system temperature stabilization method based on CT exposure described in any one of claims 1 to 7 is implemented.

10. A storage device comprising a storage medium and a processor, wherein the storage medium stores a computer program, wherein: When the processor executes the computer program, the system temperature stabilization method based on CT exposure described in any one of claims 1 to 7 is implemented.

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