Live display of pet image data

Abstract

A system and method including: localization of a first frame of positron emission tomography data acquired by an imaging device to a first frame of Cartesian data; generation of a first Cartesian image volume based on the first frame of Cartesian data; display of the first Cartesian image volume; localization of a second frame of positron emission tomography data acquired by the imaging device to a second frame of Cartesian data; generation of a second Cartesian image volume based on the second frame of Cartesian data; and display of the combined Cartesian image volumes.

Description

Background Technology

[0001] In conventional positron emission tomography (PET) imaging, a radioactive isotope tracer is initially injected into the patient's body. Inside the body, the radioactive isotope tracer emits positrons, which annihilate with electrons to produce gamma rays. An external detector system detects the emitted gamma rays and records the associated annihilation events in a sine plot or as list-pattern data. A three-dimensional Cartesian image can then be reconstructed based on this sine plot / list-pattern data.

[0002] Reconstruction is time-consuming and resource-intensive. The reconstructed images are only usable for good viewing after the PET scan is complete. This delay limits the ability to use PET imaging in conjunction with interventional procedures. Furthermore, current techniques cannot provide adequate indication of time-tracer distribution. The system is expected to improve the timeliness and usefulness of images generated from PET data. Attached Figure Description

[0003] Figure 1 The illustration shows the process of generating a three-dimensional image volume from PET data according to some embodiments;

[0004] Figure 2 The illustration shows the location of an event from detector space to Cartesian coordinates according to some embodiments;

[0005] Figure 3 This is a block diagram of a PET / CT imaging system according to some embodiments;

[0006] Figure 4 Includes flowcharts illustrating the process of generating a three-dimensional image volume from PET data according to some embodiments;

[0007] Figure 5 Includes a flowchart of a process for generating a three-dimensional image volume from PET data acquired during continuous bed motion, according to some embodiments;

[0008] Figure 6 The illustration shows the execution of a PET scan according to some embodiments;

[0009] Figures 7A to 7H This includes a two-dimensional depiction of a three-dimensional image volume generated from PET data according to some embodiments;

[0010] Figure 8 Includes a flowchart, according to some embodiments, of the process of generating a weighted combination of past and current image volumes generated from PET data;

[0011] Figures 9A to 9DThis includes a two-dimensional depiction of a three-dimensional image volume generated from past and current image volumes generated from PET data, according to some embodiments; and

[0012] Figures 10A to 10D This includes a two-dimensional depiction of a three-dimensional image volume generated from past and current image volumes generated from PET data, according to some embodiments. Detailed Implementation

[0013] The following description is provided to enable any person skilled in the art to make and use the described embodiments, and illustrates the best mode of operation intended for implementing the described embodiments. However, various modifications will still be apparent to those skilled in the art.

[0014] Typically, some embodiments provide direct localization of PET data to a Cartesian spatial location to generate Cartesian image data for display. Additional PET data is acquired and also projected onto the Cartesian spatial location to generate additional Cartesian image data. This additional Cartesian image data is combined with the already displayed Cartesian image data, and the image is displayed based on this combined image data.

[0015] Therefore, some embodiments can provide near real-time images during PET scanning. Such images can allow for live intervention procedures based on simultaneously acquired PET data.

[0016] According to some embodiments, the additional PET data is acquired from a different body region than the region from which previous PET data was acquired. The combination of this additional Cartesian image data with the already displayed Cartesian image data thus allows for the display of the entire field of view of the moving scan, where the area of ​​the field of view is gradually “filled” as the scan progresses.

[0017] In some embodiments, the combination of Cartesian image data sets can be time-dependent. For example, in the above combination of currently displayed image data and newly generated Cartesian image data, the currently displayed image data may be less weighted compared to the newly generated Cartesian image data. As new PET data frames are acquired and the Cartesian image data generated therefrom is combined with the currently displayed image, this weighting is used to reduce the prominence of earlier acquired PET data in each subsequently displayed combined frame.

[0018] The combination of Cartesian image datasets can also, or alternatively, be spatially correlated. For example, the combination could give less weight to image data of certain regions (e.g., regions far outside the region of interest) than to image data of other regions.

[0019] Figure 1The illustration shows the generation of a 3D image volume from PET data according to some embodiments. Along the time axis t Moving forward, PET data 102 to 132 represent the frames of PET data acquired sequentially.

[0020] Generally, and as is known in the art, the radioactive decay of a PET tracer injected into the body produces a positron, which eventually encounters an electron and is annihilated. The annihilation produces two gamma photons traveling in roughly opposite directions. The annihilation event is identified when two detectors positioned on opposite sides of the body detect the arrival of the two opposing gamma photons within a specific coincidence time window.

[0021] Because the two gamma photons travel in roughly opposite directions, the positions of the two detectors determine the response line (LOR) along which the annihilation event occurred. Time-of-flight (TOF) PET additionally measures the difference in arrival times between the two gamma photons produced from each annihilation event. Modern PET scanners are capable of measuring the difference in arrival times of each photon with sufficient accuracy to provide an indication of the spatial location along the LOR where positron annihilation occurred.

[0022] Each frame of PET data 102 to 132 may include list-pattern data describing each overlapping event or LOR detected within a specific time period associated with that frame, along with TOF information for each event. Typically, when an event is detected, the LOR and TOF for each event are placed in a list-pattern stream, and a new data “frame” is created whenever the defined frame duration has elapsed.

[0023] In some embodiments, PET data 102 to 132 are stored in a data array called a sine plot. The sine plot indicates the angular contrast displacement for each LOR. Each sine plot stores the location of the LOR for each coincidence event, such that all LORs passing through a single point in the volume are depicted as a sine curve in the sine plot. Each sine plot includes data for a specific azimuth angle. A row of the LOR. Multiple events detected along the same LOR are histogrammed to preserve successive events.

[0024] like Figure 1 As depicted, each of frames 102 to 132 undergoes Cartesian localization to generate corresponding frames of Cartesian data 106 to 136. Localization from list-mode TOF PET data to Cartesian data can be performed according to any known or becoming known process. Figure 2 The illustration shows the location of an event from detector space to Cartesian coordinates according to some embodiments.

[0025] Figure 2 The diagram illustrates a detector ring 210 consisting of gamma photon detectors. It will be assumed that an annihilation event occurs along LOR 220, resulting in the generation of two gamma photons traveling in opposite directions, located at the detector coordinates. x a , y a and x b , y b The detector at the location detected the event. Based on the corresponding arrival time of the gamma photon at the detector, it can be determined that the annihilation event occurred within the TOF window 230 along the LOR 220. According to some embodiments, it is assumed that the annihilation event occurred at a voxel located along the LOR 220 and at the center of the TOF window 230.

[0026] The TOF list mode frame-to-Cartesian frame localization can include positioning each annihilation event to Cartesian coordinates. For example, the LOR of an annihilation event can be considered as spatially... and A pair of crystals located, and the spatial offset describing the annihilation event from the center of LOR. The TOF value. Then, the estimated spatial location of the annihilation event. It can be calculated as:

[0027] .

[0028] in L 3D There are two crystals a and b The distance between them

[0029] .

[0030] This can be repeated continuously for each LOR of a frame to accumulate a volumetric representation of the activity distribution as the LOR is processed. Each event can be corrected for attenuation by weighting its contribution to the Cartesian data using a correction factor derived from the CT for a given LOR.

[0031] The above process occurs for each subsequently acquired frame of PET data. However, as Figure 1As shown, the displayed Cartesian data 118 is a combination of the displayed Cartesian data 108 and the Cartesian data 116 generated based on PET data 112. Similarly, the displayed Cartesian data 128 is a combination of the displayed Cartesian data 128 and the Cartesian data 126 generated based on PET data 122. As described above, the techniques used to combine the Cartesian coordinate system can be varied in the embodiments to produce various results.

[0032] According to some embodiments, each frame of Cartesian data 106 to 136 can be considered as a histogram initialized to 0 at the frame start time. As new detector pairs of events are collected in the PET data frames, each event is located at a Cartesian coordinate along the LOR at the center of the TOF window. This Cartesian coordinate is incremented within the Cartesian frame (i.e., the histogram). At the frame end time, this Cartesian frame is combined with the currently displayed Cartesian volume and is displayed.

[0033] Combined Cartesian data can be displayed as navigable quantitative Cartesian volumes (i.e., manually selectable transaxial, sagittal, and coronal slices), as sagittal and coronal maximum intensity projection (MIP) views, or as a single rotated MIP.

[0034] Figure 3 This is a block diagram of a PET / CT imaging system 300 that performs one or more of the processes described herein. Embodiments are not limited to system 300.

[0035] System 300 includes a gantry 310 that defines an aperture 312. As is known in the art, gantry 310 houses a PET imaging assembly for acquiring PET image data and a CT imaging assembly for acquiring CT image data. The CT imaging assembly may include one or more X-ray tubes and one or more corresponding X-ray detectors, as is known in the art.

[0036] PET imaging assemblies can include any number or type of detectors (e.g., silicon photomultipliers (SiPMs)) in any configuration, as is known in the art. The detectors are associated with slice thickness (spatial resolution), enabling the assembly to independently image two slices separated by a distance greater than or equal to the slice thickness. Slice thickness (e.g., 2.0 mm) corresponds to the detector resolution.

[0037] Injection system 318 can be operated to deliver calibrated injections of rubidium, fluorodeoxyglucose (FDG), iodine, or other radioisotopes to a patient before and / or during a PET scan. In some embodiments, injection system 318 is incorporated into bench 310. Injection system 318 may support a wired or wireless communication link with control system 320 for receiving information specifying dosage, injection protocol, and scan delay.

[0038] The bed 315 and the base 316 are operable to move a patient lying on the bed 315 into and out of the aperture 312 before, during, and after imaging. In some embodiments, the bed 315 is configured to translate on the base 316, and in other embodiments, the base 316 may move with the bed 315 or alternatively move from the bed 315.

[0039] The movement of the patient into and out of the opening 312 allows for scanning of the patient using CT and PET imaging elements of the gantry 310. This scanning can be performed based on scanning parameters such as scan range and corresponding scan speed. According to some embodiments, the bed 315 and the base 316 can provide continuous bed movement and / or step-and-shoot movement during such scanning.

[0040] The control system 320 may include any general-purpose or special-purpose computing system. Therefore, the control system 320 includes one or more processing units 322 configured to execute processor-executable program code to cause the system 320 to operate as described herein, and a storage device 330 for storing the program code. The storage device 330 may include one or more fixed disks, solid-state random access memory, and / or removable media (e.g., thumb drives) mounted in a corresponding interface (e.g., a USB port).

[0041] Storage device 330 stores the program code of control program 331. One or more processing units 322 can execute control program 331 to control hardware components in conjunction with PET system interface 323, bed interface 325, and injection interface 327 to inject a radioactive isotope into a patient, move the patient through orifice 312 to pass through the PET detector of bench 310, and detect annihilation events occurring within the patient. Detected events can be stored in memory 330 as PET data 333, which may include list pattern data and / or sine waves.

[0042] One or more processing units 322 may also execute control program 331 to coordinate with CT system interface 324 to cause radiation sources within gantry 310 to emit radiation toward the body within aperture 312 from different projection angles, and to control corresponding detectors to acquire two-dimensional CT data. The CT data may be acquired substantially simultaneously with the PET data described above, and may be stored as CT data 334. This CT data 334 may be used for attenuation correction of the simultaneously acquired PET data 333, as is known in the art. In this respect, control program 331 may also be executed to reconstruct three-dimensional slices from the PET scan data 333 using any known or becoming known reconstruction algorithm.

[0043] One or more processing units 322 may execute a Cartesian localization procedure 332 to help generate a Cartesian image volume 335 based on the corresponding frame of the PET data 333. The Cartesian image volume 335 may include a combination of image volumes as described herein.

[0044] PET images, CT images, and / or image volumes 335 can be transmitted to terminal 340 via terminal interface 326. Terminal 340 may include display devices and input devices coupled to system 320. Terminal 340 may display PET images, CT images, and / or image volumes 335. Terminal 340 may receive user input for controlling the display of data, operation of system 300, and / or the processing described herein. In some embodiments, terminal 340 is a separate computing device, such as, but not limited to, a desktop computer, laptop computer, tablet computer, and smartphone.

[0045] Each component of system 300 may include other elements necessary for its operation, as well as additional elements for providing functionality beyond that described herein. Each functional component described herein may be implemented in computer hardware, program code, and / or one or more computing systems that execute such program code, as is known in the art. Such computing systems may include one or more processing units that execute processor-executable program code stored in a memory system.

[0046] Figure 4 This includes a flowchart of a process 400 for generating a three-dimensional image volume from PET data according to some embodiments. Flowchart 400 and other processes described herein can be performed using any suitable combination of hardware and software. The software program code embodying these processes can be stored by any non-transitory tangible medium, including fixed disks, volatile or non-volatile random access memory, DVDs, flash drives, and magnetic tapes. Embodiments are not limited to the examples described below.

[0047] At S405, the first frame of PET data is initially acquired. Following the injection of a radioisotope tracer into the body volume (e.g., the patient), PET data can be acquired via conventional static PET scanning, as is known in the art. According to some embodiments, the data acquired by the PET scanner is list-pattern data as described above.

[0048] Next, at S410, the PET data is localized into Cartesian coordinate space to generate a frame of Cartesian data. As described above, the localization of a specific event into three-dimensional Cartesian space is based on the location of the detector that absorbed the coincident gamma photons of that event, and the TOF data of that event. The frame of Cartesian data may include a histogram such that the value associated with a specific Cartesian coordinate can be directly related to the number of PET events localized to that coordinate.

[0049] At S415, the Cartesian image data is displayed based on the Cartesian data frame. As mentioned above, this image data can be displayed using any known or becoming known technique for displaying three-dimensional image data. At S420, the next frame of PET data is acquired. As will be described in more detail below, the next frame of PET data may represent an imaging region different from the imaging region of the previous PET frame (i.e., a different region of the body). At S425, the next frame of PET data is positioned in Cartesian coordinate space to generate the next frame of Cartesian data, as described above regarding S410.

[0050] Next, at S430, combined Cartesian image data is generated based on the Cartesian image data displayed at S415 and the Cartesian data generated at S425. The combination at S430 can simply involve generating image data based on the Cartesian data generated at S425 and adding the generated image data to the Cartesian image data displayed at S415. In some embodiments, the combination of image data can be weighted, wherein the weight associated with a particular image data value depends on the acquisition time, Cartesian coordinates, and / or tracer decay rate.

[0051] At S435, the combined Cartesian image data is displayed. Then, at S440, it is determined whether the scan is complete. If not, the process returns to S420 and continues as described above. Specifically, at S420, the next frame of PET data is acquired, and at S425, it is positioned in Cartesian coordinate space to generate the next frame of Cartesian data.

[0052] At S430, combined Cartesian image data is generated based on the most recently displayed Cartesian image data and the most recently generated frame of Cartesian data. At S435, the new combination of Cartesian image data is displayed. The process continues to S440 and loops through S420, S425, S430, S435, and S440 until the scan is then determined to be complete.

[0053] According to some embodiments of process 400, each subsequently displayed image includes image data of each previously displayed image. As described below, in some embodiments, as more and more image data is generated and displayed, the image data of previously displayed images may gradually fade or eventually be completely removed.

[0054] Figure 5 This includes a flowchart of a process for generating a three-dimensional image volume from PET data acquired during continuous bed motion, according to some embodiments.

[0055] At S505, a first frame of PET data is initially acquired from a first portion of the field of view. The PET data may be acquired at S505 during continuous bed movement (e.g., 1 mm / s), as is known in the art, where the field of view is the entire area of ​​the body passing the detector during the scan. At S510, the PET data is localized in Cartesian coordinate space to generate a frame of Cartesian data, and at S515, Cartesian image data is displayed based on the frame of Cartesian data.

[0056] At S420, the next frame of PET data is acquired from the second portion of this field of view. Due to the continuous bed motion, the second portion may differ from the first portion from which the first PET data was acquired. In some embodiments, the first and second portions may overlap spatially.

[0057] Figure 6 The illustration depicts the acquisition of PET data during continuous bed movement according to some embodiments. Arrows indicate the passage of time during PET data acquisition, which pertains to a portion of body 600 from which PET data is acquired during this passage of time. In the illustrated example, PET data acquisition begins when the lower portion of body 600 is moved past the PET detector (by moving bed 315 through orifice 312), and continues until the head has been moved past the detector. Each frame of PET data used in process 500 may include data acquired within a specified time period during the movement.

[0058] At S525, the next frame of PET data representing the second part of the field of view is positioned in Cartesian coordinate space to generate the next frame of Cartesian data. Next, at S530, combined Cartesian image data is generated based on the frames of the Cartesian image data displayed at S515 and the Cartesian data generated at S525. Since the image data represents different parts of the entire axial field of view, the combination at S530 can simply include generating image data based on the Cartesian data generated at S525 and adding the generated image data to the Cartesian image data displayed at S515.

[0059] At S535, the combined Cartesian image data is displayed, and the process returns to S520 to continue as described above until the scan is complete. During this loop, Cartesian image data representing the continuation of the field of view is continuously added to the displayed image data, thus “completing” the image of that field of view. According to some embodiments, an isotope-related decay correction function is applied on-the-fly to the newly generated image data before combining the image data with the currently displayed image data. The isotope-related decay correction function increases the intensity of pixel values ​​based on the associated acquisition time of the pixel values ​​to compensate for isotope decay.

[0060] Figures 7A to 7H This includes two-dimensional depictions of three-dimensional images generated by process 500 according to some embodiments. Although only eight images are shown, it should be understood that a whole-body PET scan can generate hundreds of PET data frames, which can be mapped to corresponding frames in Cartesian data.

[0061] Figure 7A It can depict the first Cartesian image data generated from the first frame based on PET data. Figure 7B This allows for the depiction of another frame generated based on PET data and added to it. Figure 7A The first Cartesian image data of the Cartesian image. Figure 7B Additional image data can inhabit with Figure 7A Some of the image data are in the same Cartesian region. At this point, during process 500, the positioning of the PET data to the Cartesian data takes into account the bed movement along the z-axis. For example, the z-position in the whole-body field of view where the PET data is acquired is used to determine the z-coordinate of the Cartesian data from which it is positioned.

[0062] As shown, as additional PET data frames are acquired and positioned in Cartesian space, the displayed image “grows” in the z-direction of the scan. As described above, the intensity of image pixels corresponding to later acquired frames can be increased based on anticipated tracer decay to normalize the intensity within the displayed image. Also as described above, the continuously changing displayed image can include, for example, manually selectable transverse, sagittal and coronal slices, sagittal and coronal MIP views, or a single rotated MIP.

[0063] Figure 8 This includes a flowchart of process 800, which generates a weighted combination of past and current image volumes from PET data according to some embodiments. Steps S805 to S825 can be performed similarly to steps S405 to S425 of process 400. Thus, at S825, the Cartesian image data generated based on the acquired PET data frame is currently displayed, and the next frame of the Cartesian data has been positioned based on the next acquired PET data frame.

[0064] Next, at S830, combined Cartesian image data is generated based on the currently displayed image data and the newly generated (i.e., "next") frame of the Cartesian data. As described in detail below, the generation at S830 applies different weights to the displayed image data and the newly generated Cartesian image data from the next frame of the Cartesian data.

[0065] In the following description of S830 according to some embodiments, the combined image is represented as g t The currently displayed image is represented as g t-1 And the newly generated Cartesian image data is represented as f t The combined image generated at S830 g t It is newly generated Descartes image data f t With the currently displayed image g t-1 The sum of a small fraction makes g t = αf t + βg t-1 . α ( x , y , z , t () controls image data f t A weighting factor for the degree of contribution to the global volume.β ( x , y , z , t () is a combination of images that determine events from successive events. g t The persistence parameter that is removed as quickly as possible.

[0066] For example, if β If = 1, then all previous image data is accumulated in the combined image. If β =0, then the combined image only includes the most recently generated Cartesian image data. f t . α and β The parameters can remain constant, or they can vary spatially and / or temporally to account for known tracer distributions, tracer decay, specific clinical protocols (e.g., myocardial blood flow studies), and well-characterized biological processes. Optimal parameters can be calculated through analysis or via deep learning methods.

[0067] At S835, the combined image is displayed, and then the process loops from S840 to S820 as described above until the scan is complete.

[0068] Figures 9A to 9D This includes a two-dimensional depiction of a three-dimensional image volume generated at S830 and displayed at S835 according to some embodiments. Figures 9A to 9D The illustration shows one of them. β The implementation of =1. Therefore, each contiguous image includes all image data from the previously combined images, as well as the newly generated Cartesian image data. At this point, Figures 9A to 9D The implementation method is similar to Figures 7A to 7H The implementation method described in the text.

[0069] Figures 10A to 10D This includes a two-dimensional depiction of the three-dimensional image volume generated at S830 and displayed at S835 according to some embodiments. Specifically, Figures 10A to 10D The illustration shows one of them. β The implementation uses a resolution of 0.9. Therefore, each concatenated image includes 90% of the image data from the previously combined image, plus the newly generated Cartesian image data. Because... β In the application of sequential images, the extent to which specific image data appears in a combined image depends on the number of combined images that have been generated since that specific image data was generated. For example, for α =.1 and β=0.9, the third combined image can be generated as 0.9((0.9 xImage1)+Image2) + Image3 = 0.81Image1 + 0.9Image2 +Image3.

[0070] The foregoing diagrams illustrate the logical architecture and processes according to some embodiments, and actual implementations may include additional or different components and / or steps arranged in other ways. Furthermore, each component or device described herein may be implemented by any number of devices communicating via any number of other public and / or private networks. Two or more such computing devices may be positioned remotely from each other and may communicate with each other via any known means of communication through one or more networks and / or private connections. Each component or device may include any number of hardware and / or software elements suitable for providing the functionality described herein as well as any other functionality. For example, any computing device used in an implementation of a system according to some embodiments may include a processor to execute program code causing the computing device to operate as described herein.

[0071] All systems and processes discussed herein can be embodied in program code stored on one or more non-transitory computer-readable media. Such media may include, for example, hard disks, DVD-ROMs, flash drives, magnetic tapes, and solid-state random access memory (RAM) or read-only memory (ROM) storage units. Embodiments are not limited to any particular combination of hardware and software.

[0072] Those skilled in the art will appreciate that various adaptations and modifications can be configured to the embodiments described above without departing from the claims. Therefore, it is to be understood that the claims can be practiced in ways other than those specifically described herein.

Claims

1. A system for live display of positron emission tomography (PET) data, comprising: Imaging equipment, used for: Acquire frames of positron emission tomography data, each frame including data representing multiple detected annihilation events; Processing system, used for: Receive the first frame of positron emission tomography data from the imaging device; The first Cartesian image volume is generated by directly locating each annihilation event in the first frame of positron emission tomography data to Cartesian coordinates. Display the volume of the first Cartesian image; While displaying the volume of the first Cartesian image: Receive a second frame of positron emission tomography data from the imaging device; The second Cartesian image volume is generated by directly locating each annihilation event in the second frame of positron emission tomography data to Cartesian coordinates. as well as A combined Cartesian image volume is generated based on the first and second Cartesian image volumes. as well as Display the volume of the combined Cartesian image.

2. The system of claim 1, wherein the first Cartesian image volume comprises a first portion of the field of view, and wherein the second Cartesian image volume comprises a second portion of the field of view.

3. The system of claim 2, wherein the generation of the combined Cartesian image volume comprises: Modifying the volume of the second Cartesian image based on the decay profile of the radioactive isotope, and adding the modified second Cartesian image volume to the first Cartesian image volume.

4. The system of claim 1, wherein the generation of the combined Cartesian image volume comprises: The application of weights to the first Cartesian image volume, and the addition of the weighted first Cartesian image volume to the second Cartesian image volume.

5. The system of claim 4, wherein the weights are time-varying.

6. The system of claim 5, wherein the weights are spatially variable.

7. The system of claim 6, wherein the generation of the combined Cartesian image volume comprises: Modification of the second Cartesian image volume based on the decay profile of radioactive isotopes, and addition of a weighted first Cartesian image volume to the modified second Cartesian image volume.

8. A method for live display of positron emission tomography (PET) data, comprising: Receive the first frame of positron emission tomography data, including data representing the first plurality of detected annihilation events; The first Cartesian image volume is generated by directly locating each annihilation event in the first frame of positron emission tomography data to Cartesian coordinates. Display the volume of the first Cartesian image; While displaying the volume of the first Cartesian image: The second frame of positron emission tomography data received includes data representing a second plurality of detected annihilation events; The second Cartesian image volume is generated by directly locating each annihilation event in the second frame of positron emission tomography data to Cartesian coordinates. as well as A combined Cartesian image volume is generated based on the first and second Cartesian image volumes. as well as Display the volume of the combined Cartesian image.

9. The method of claim 8, wherein the first Cartesian image volume comprises a first portion of the field of view, and wherein the second Cartesian image volume comprises a second portion of the field of view.

10. The method of claim 9, wherein generating the combined Cartesian image volume comprises: The second Cartesian image volume is modified based on the decay profile of the radioactive isotope, and the modified second Cartesian image volume is added to the first Cartesian image volume.

11. The method of claim 8, wherein generating the combined Cartesian image volume comprises: Weights are applied to the first Cartesian image volume, and the weighted first Cartesian image volume is added to the second Cartesian image volume.

12. The method of claim 11, wherein the weights are time-varying.

13. The method of claim 12, wherein the weights are spatially variable.

14. The method of claim 13, wherein generating the combined Cartesian image volume comprises: The volume of the second Cartesian image is modified based on the decay profile of the radioactive isotope, and the weighted volume of the first Cartesian image is added to the modified volume of the second Cartesian image.

15. A computing system, comprising: processor; as well as A memory that stores instructions, which, when executed by the processor, cause the computing system to perform the method according to any one of claims 8 to 14.

Images