A dynamic PET acquisition method and system based on time window

Abstract

The present invention relates to a dynamic coincidence time window PET acquisition method and system. The method comprises: obtaining contour information of a target; generating a contour cylinder for each scanning bed based on the contour information; determining a coincidence time window for each bed based on the distance between the two farthest points on the surface of each contour cylinder in the PET field of view; acquiring PET data for each bed based on the coincidence time window; and reconstructing PET data for each bed based on the coincidence time window. The method advantageously sets a corresponding coincidence time window for image scanning of each bed, thereby reducing the noise impact of random events on imaging results, improving the signal-to-noise ratio of the data, and enhancing imaging quality.

Description

Technical Field

[0001] The present invention relates to the field of PET technology, and in particular to a PET acquisition method and system that dynamically matches a time window. Background Art

[0002] PET (Positron Emission Tomography) is a clinical diagnostic imaging technique in nuclear medicine. Its basic principle is to inject a tracer containing a positron-emitting radionuclide into a living organism. The technique then detects the energy, timing, and location of the 511keV gamma rays emitted in the opposite direction during positron annihilation. The technique then statistically reconstructs the location of the annihilation event to determine the enrichment location of the tracer nuclide. This three-dimensional imaging technique boasts high sensitivity, excellent accuracy, and the ability to perform functional imaging. It is widely used in the diagnosis of tumors, cardiovascular diseases, and neurological diseases. Small animal PET is also widely used in research areas such as pathology and the metabolic dynamics of novel drugs.

[0003] Data acquired by a PET system can be categorized as true events, scattered events, and random events based on their relationship to imaging. A true event is one in which two gamma photons following positron annihilation are directly detected by the PET system's detector and recorded as a coincident event. These events are considered "good" events, representing the annihilation point and positively impacting image quality. A scattered event is one in which one or both of the two gamma photons following positron annihilation are scattered within the PET field of view before being detected by the PET system's detector and recorded as a coincident event. These events appear as "slow" variables around the annihilation point, blurring the image and requiring scatter correction to remove their effects. A random event is one in which two unrelated gamma photons are detected within a time window within the PET field of view, rather than a gamma photon following positron annihilation. These events are recorded as a coincident event. Random events appear as background noise in the image and require random coincidence correction. The primary factor influencing random coincidence is the setting of the coincidence time window: a larger coincidence time window increases the number of random coincidence events. Figure 1 This is a schematic diagram of the true coincidence, scattered coincidence and random coincidence counts. Summary of the Invention

[0004] Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a PET acquisition method and system with dynamic time window compliance, which solves the technical problem of how to reduce the noise impact of random events on imaging results.

[0006] Technical Solution

[0007] In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] In a first aspect, the present invention provides a dynamic time-windowed PET acquisition method, comprising:

[0009] Obtain the contour information of the target being measured;

[0010] Generate a contour cylinder of each scanning bed position according to the contour information;

[0011] The compliance time window for each bed is determined based on the distance between the two farthest points on the surface of each contour cylinder in the PET field of view;

[0012] PET data were collected for each bed based on its coincident time window;

[0013] PET data of each bed is reconstructed based on the coincident time window of each bed.

[0014] Optionally, obtaining the contour information of the measured target includes:

[0015] Before performing a PET scan, the contour information of the target is obtained through the CT reconstructed image in the PET / CT system, the magnetic resonance reconstructed image in the PET / MR system, the image obtained by the optical camera on the PET rack, the image obtained by the surveillance camera in the scanning room, the image obtained by the scanning radar, the contour image obtained by other external detectors, or the image after fusion processing of the above images.

[0016] Optionally, generating a contour cylinder of each scanning bed position according to the contour information includes:

[0017] The farthest distance from the axis of the PET system in the contour information is used as the radius, and the longest distance of the target to be measured in the PET scanning field of view of the current bed is used as the length to generate a contour cylinder.

[0018] Optionally, the compliance time window is determined according to the following formula:

[0019] CW ij =2L ijmax / c+t e , including CW ij is the matching time window of this scan, L ijmax is the distance between the two farthest points on the surface of the contour cylinder in the PET field of view, c is the speed of light, t e For protective extension time.

[0020] Optionally, t e It is a fixed value or n times of the system time resolution, 1≤n≤10.

[0021] Optionally, the method further includes:

[0022] In the case that the contour information of the measured target cannot be obtained, the time window is opened to collect the corresponding data for a short time before the formal collection of each bed data;

[0023] Analyze the temporal spectrum distribution of short-term coincident data;

[0024] The matching time window for each bed was confirmed by removing the random count threshold method.

[0025] Optionally, the compliance time window for each bed is confirmed based on the random count threshold removal method, including:

[0026] The counting threshold N for removing random coincidences is calculated according to the following formula:

[0027] N = k × (PB) + B, where k is the threshold coefficient, P is the peak count based on the short-term distribution of the data time spectrum, and B is the baseline count based on the mean of the edge counts based on the short-term distribution of the data time spectrum;

[0028] The coincidence time window is determined based on the range of the short-term coincidence data time spectrum that reaches a count threshold N for removing random coincidences.

[0029] In a second aspect, the present invention provides a dynamic time-windowed PET acquisition system, comprising:

[0030] Acquisition module, acquires the contour information of the target being measured;

[0031] A generation module generates a contour cylinder of each scanning bed according to the contour information;

[0032] A determination module determines the compliance time window for each bed based on the distance between the two farthest points on the surface of each contour cylinder in the PET field of view;

[0033] The acquisition module collects PET data for each bed based on the time window of each bed;

[0034] The reconstruction module reconstructs the PET data of each bed based on the matching time window of each bed.

[0035] 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 dynamically matching a time window to a PET acquisition method described in any one of the first aspects above is implemented.

[0036] 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 PET acquisition method according to any one of the first aspects above is implemented.

[0037] Beneficial effects

[0038] The beneficial effects of the present invention are as follows: a PET acquisition method of the present invention that dynamically meets the time window is designed to dynamically set a scanning mode that meets the time window, evaluates the contour range of the target to be measured through CT images or images of optical probes, and then plans the scanning contour range of each bed, and sets a corresponding time window for the image scan of each bed, thereby reducing the noise impact of random events on the imaging results, improving the signal-to-noise ratio of the data, and improving the imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the true coincidence, scattered coincidence and random coincidence counting provided by the present invention;

[0040] Figure 2 A schematic flow chart of a dynamic time-windowed PET acquisition method provided by an embodiment of the present invention;

[0041] Figure 3 A schematic diagram of the dynamic time window acquisition mode flow provided by an embodiment of the present invention;

[0042] Figure 4 Comparison of NECR results between the dynamic time window acquisition mode provided by the embodiment of the present invention and the traditional acquisition mode;

[0043] Figure 5 The embodiment of the present invention provides a coincident time window confirmed according to the time spectrum distribution.

[0044] Description of Reference Numerals

[0045] 1: True coincidence count; 2: Scattered coincidence count; 3: Random coincidence count. DETAILED DESCRIPTION

[0046] To better explain the present invention and facilitate understanding, the present invention is described in detail below with reference to the accompanying drawings and through specific embodiments. Although exemplary embodiments of the present invention are shown in the 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. Rather, 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.

[0047] First, refer to Figure 2 This embodiment provides a dynamic time-windowed PET acquisition method, including:

[0048] S1, obtain the contour information of the target to be measured.

[0049] S2, generating a contour cylinder of each scanning bed according to the contour information.

[0050] S3, determining the compliance time window for each bed according to the distance between the two farthest points on the surface of each contour cylinder in the PET field of view.

[0051] S4, collecting PET data for each bed based on the matching time window of each bed.

[0052] S5, reconstructing PET data for each bed based on the coincident time window of each bed.

[0053] Data acquisition and reconstruction are performed within the planned time window, and random coincidence correction of image reconstruction for each bed is performed according to the corresponding time window setting.

[0054] Optionally, obtaining the contour information of the measured target includes:

[0055] Before performing a PET scan, the contour information of the target is obtained through the CT reconstructed image in the PET / CT system, the magnetic resonance reconstructed image in the PET / MR system, the image obtained by the optical camera on the PET rack, the image obtained by the surveillance camera in the scanning room, the image obtained by the scanning radar, the contour image obtained by other external detectors, or the image after fusion processing of the above images.

[0056] Optionally, generating a contour cylinder of each scanning bed position according to the contour information includes:

[0057] The farthest distance from the axis of the PET system in the contour information is used as the radius, and the longest distance of the target to be measured in the PET scanning field of view of the current bed is used as the length to generate a contour cylinder.

[0058] Attached is the diagram of the cylindrical profile section Figure 3 ,In the figure, the middle black line is the central axis of the system, the ,black shadow block is the overall contour section of the measured ,target, and the rectangle is the cross section of the obtained cylindrical ,contour.

[0059] Optionally, the compliance time window is determined according to the following formula:

[0060] CW ij =2L ijmax / c+t e , including CW ij is the matching time window of this scan, L ijmax is the distance between the two farthest points on the surface of the contour cylinder in the PET field of view, c is the speed of light, t e For protective extension time.

[0061] Optionally, t eIt is a fixed value or n times of the system time resolution, 1≤n≤10.

[0062] Optionally, the method further includes:

[0063] In the case that the contour information of the measured target cannot be obtained, the time window is opened to collect the corresponding data for a short time before the formal collection of each bed data;

[0064] Analyze the temporal spectrum distribution of short-term coincident data;

[0065] The matching time window for each bed was confirmed by removing the random count threshold method.

[0066] Optionally, the compliance time window for each bed is confirmed based on the random count threshold removal method, including:

[0067] The counting threshold N for removing random coincidences is calculated according to the following formula:

[0068] N = k × (PB) + B, where k is the threshold coefficient and ranges from 0.01 to 0.5, P is the peak count based on the short-term distribution of the data time spectrum, and B is the baseline count based on the mean of the edge counts based on the short-term distribution of the data time spectrum;

[0069] The coincidence time window is determined based on the range of the short-term coincidence data time spectrum that reaches a count threshold N for removing random coincidences.

[0070] For PET systems that are not easy to process the contour information of the scanned object, the range adjustment of the coincident time window can also be carried out by collecting coincident data for a short time under the setting of a larger time window, analyzing the coincident time distribution, and blocking out the random coincident parts according to the shape of the coincident time spectrum distribution.

[0071] By dynamically setting the coincidence time window, the coincidence time window is minimized, reducing the noise disturbance caused by random coincidences without reducing true and scattered coincidences, thereby improving image quality. This improvement is particularly evident in scanning small objects such as the head.

[0072] Random coincidence counts are a noise component in PET systems. Reducing the system's coincidence time window setting can improve the system's image signal-to-noise ratio and image quality. However, to maintain the system's detection field of view, traditional PET systems set the coincidence time window to a fixed value, which can introduce unnecessary random coincidence noise when scanning smaller targets. The present invention designs a PET data acquisition mode with dynamic time window settings. This mode ensures that the acquisition results of the true coincidence data of the measured object are not lost, while reducing the noise counts caused by random coincidence counts, improving the signal-to-noise ratio of the coincidence data and image quality.

[0073] The following uses a system noise equivalent count rate (NECR) evaluation as an example to further introduce a dynamic time-windowed PET acquisition method of the present application:

[0074] The noise-equivalent count rate (NECR) reflects the ratio of the absolute number of photons captured by a PET device to the square of the number of true coincidence events (T). This reflects the ratio of the system's "useful" signal to the total signal. It also reflects the system's ability to discriminate between true coincidence events (T) and exclude "dirty" data such as scattered events (S) and accidental coincidence events (R). The NECR (Non-Noise-Equivalent Count Rate) ultimately reflects the image's signal-to-noise ratio (SNR). PET systems have a low SNR, and the SNR is more important than the resolution. Therefore, the system's SNR is the most important determinant of PET imaging quality, and the NECR most directly reflects the system's SNR.

[0075] The NER test phantom is a 20cm diameter, 70cm long plastic cylinder. During testing, the cylinder is placed within the PET system, with its central axis aligned with the system's central axis. A line source is inserted through a through-hole slightly below the cylinder, and the entire plastic cylinder acts as a scattering phantom.

[0076] Under the fixed time window system acquisition setting, the time window is set to 4ns, and then the data acquisition of the NECR test is carried out.

[0077] In a dynamic time window PET acquisition system, a CT scan of the phantom is performed to confirm that the maximum distance of the cylindrical contour surface in the PET field of view is 22 cm. Considering the system's time resolution of 300 ps, ​​using twice the system's time resolution as a protective expansion time, the system's time window can be set to:

[0078] CW ij =2L ijmax / c+t e =2×22 / 30+0.3×2≈2.10(ns)

[0079] The NECR test was performed under the new time window setting.

[0080] Comparing the NECR results under the two time window settings, it can be seen that the system NECR result under the dynamic time window setting is better, and a better image signal-to-noise ratio can be obtained, especially in high activity conditions. Figure 4 .

[0081] In a second aspect, this embodiment provides a dynamic time-windowed PET acquisition system, comprising: an acquisition module for acquiring contour information of a target; a generation module for generating a contour cylinder for each scanning bed based on the contour information; a determination module for determining the time-windowed PET acquisition for each bed based on the distance between the two farthest points on the surface of each contour cylinder in the PET field of view; an acquisition module for acquiring PET data for each bed based on the time-windowed PET acquisition for each bed; and a reconstruction module for reconstructing PET data for each bed based on the time-windowed PET acquisition for each bed. The dynamic time-windowed PET acquisition system provided in this embodiment, because it is used to implement the steps of the dynamic time-windowed PET acquisition method provided in the first aspect of the present invention, possesses all the technical effects of the dynamic time-windowed PET acquisition method, and thus will not be further elaborated herein.

[0082] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the dynamic time-windowed PET acquisition method described in any one of the first aspects above.

[0083] In a fourth aspect, an embodiment of 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 dynamic time-windowed PET acquisition method described in any one of the first aspects above is implemented.

[0084] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. 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 magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0085] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of the claims and their equivalents, the present invention shall also include such modifications and variations.

[0086] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on 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 dynamic time-windowed PET acquisition method, characterized in that: include: Obtain the contour information of the target being measured; Generate the contour cylinder of each scanning bed based on the contour information, including: The farthest distance from the axis of the PET system in the contour information is used as the radius, and the longest distance of the target to be measured in the PET scanning field of view of the current bed is used as the length to generate a contour cylinder; The compliance time window for each bed is determined based on the distance between the two farthest points on the surface of each contour cylinder in the PET field of view; PET data were collected for each bed based on its coincident time window; PET data of each bed is reconstructed based on the coincident time window of each bed.

2. The dynamic time-windowed PET acquisition method according to claim 1, characterized in that: Obtain the contour information of the measured target, including: Before performing a PET scan, the contour information of the target is obtained through the CT reconstructed image in the PET / CT system, the magnetic resonance reconstructed image in the PET / MR system, the image obtained by the optical camera on the PET rack, the image obtained by the surveillance camera in the scanning room, the image obtained by the scanning radar, the contour image obtained by other external detectors, or the image after fusion processing of the above images.

3. The dynamic time-windowed PET acquisition method according to claim 2, characterized in that: The compliance time window is determined according to the following formula: CW ij =2L ijmax / c+t e , including CW ij is the matching time window of this scan, L ijmax is the distance between the two farthest points on the surface of the contour cylinder in the PET field of view, c is the speed of light, t e For protective extension time.

4. The dynamic time-windowed PET acquisition method according to claim 3, characterized in that: t e It is a fixed value or n times of the system time resolution, 1≤n≤10.

5. The dynamic time-windowed PET acquisition method according to claim 4, characterized in that: The method further comprises: In the case that the contour information of the measured target cannot be obtained, the time window is opened to collect the corresponding data for a short time before the formal collection of each bed data; Analyze the temporal spectrum distribution of short-term coincident data; The matching time window for each bed was confirmed by removing the random count threshold method.

6. The dynamic time-windowed PET acquisition method according to claim 5, characterized in that: The eligible time window for each bed was confirmed by removing the random count threshold method, including: The counting threshold N for removing random coincidences is calculated according to the following formula: N = k × (PB) + B, where k is the threshold coefficient, P is the peak count based on the short-term compliance with the data time spectrum distribution, and B is the baseline count based on the mean of the edge counts based on the short-term compliance with the data time spectrum; The coincidence time window is determined based on the range of the short-term coincidence data time spectrum that reaches a count threshold N for removing random coincidences.

7. A dynamic time-windowed PET acquisition system, characterized in that: include: Acquisition module, acquires the contour information of the target being measured; The generation module generates the contour cylinder of each scanning bed according to the contour information, including: The farthest distance from the axis of the PET system in the contour information is used as the radius, and the longest distance of the target to be measured in the PET scanning field of view of the current bed is used as the length to generate a contour cylinder; A determination module determines the compliance time window for each bed based on the distance between the two farthest points on the surface of each contour cylinder in the PET field of view; The acquisition module collects PET data for each bed based on the time window of each bed; The reconstruction module reconstructs the PET data of each bed based on the matching time window of each bed.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the dynamic time-windowed PET acquisition method according to any one of claims 1 to 6 is implemented.

9. 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 dynamic time-windowed PET acquisition method according to any one of claims 1 to 6 is implemented.

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