Radiolabeled cell tracking and imaging

Abstract

A system and method includes acquiring positron emission tomography data of an object as a radiation source moves within the object, determining a plurality of positions within the object, each of the plurality of positions being associated with a respective time at which the radiation source was at the position, determining a respective time period associated with each of the plurality of positions, for each determined time period, determining a frame of positron emission tomography data associated with the determined time period, and for each frame of positron emission tomography data, generating an image based on the frame and a position associated with the time period with which the frame is associated.

Description

Background Technology

[0001] In traditional nuclear imaging, a radioactive tracer is first introduced into the patient's body. The tracer emits gamma rays (in the case of single-photon emission computed tomography (SPECT) imaging) or positrons; the positrons annihilate with electrons to produce gamma rays (in the case of positron emission tomography (PET) imaging). An external detector system detects the emitted gamma rays and reconstructs an image based on this.

[0002] For some medical applications, it is desirable to track the location of individual cells within the body. These applications could include tracking white blood cells to identify sites of infection, tracking therapeutic cells used for tissue regeneration and cancer immunotherapy, and tracking cells involved in other biological processes. To track cells using nuclear imaging, the cells are labeled with a radioactive tracer before being introduced into the body.

[0003] The imaging paradigm presented by radiolabeled cells is not suitable for PET imaging. When radiolabeled cells, containing a relatively small amount of radiotracer, move through the body, only a small amount of sparse data from PET conformation measurements is acquired. This sparse data is typically insufficient for conventional rear-projection algorithms used to reconstruct PET images. As a result, PET images reconstructed based on the acquired data are unsuitable for tracking radiolabeled cells. Improved PET imaging of radiolabeled cells moving within the body is desired. Attached Figure Description

[0004] Figure 1 This is a block diagram of a system for generating images based on a low-activity, low-capacity source, according to some embodiments.

[0005] Figure 2 This is a block diagram of a PET / CT system that acquires PET data and generates images based on the acquired PET data, according to some embodiments.

[0006] Figure 3 Includes a flowchart of a process for generating images based on a low-activity, low-capacity source, according to some embodiments;

[0007] Figure 4 The diagram illustrates the path of a low-volume radiation source within the body according to some embodiments;

[0008] Figure 5 The illustration shows, according to some embodiments, the framing of acquired PET data based on the determined location of a low-volume radiation source over time; and

[0009] Figure 6 The illustration shows the generation of a PET image based on a determined source location and a PET data frame associated with that determined source location, according to some embodiments. Detailed Implementation

[0010] The following description is provided to enable any person in the art to make and use the described embodiments, and illustrates the best mode contemplated for implementing the described embodiments. However, various modifications will remain apparent to those skilled in the art.

[0011] Some embodiments provide PET image generation based on PET data generated by low-volume, low-activity sources moving through the body. Generally, the location of the source within the body is determined at various time points. The PET data acquired during movement is then framed based on these time points. Given the source location associated with the time point represented in the frame, a PET image is generated based on each frame by applying a point-source image generation algorithm to the frame. According to some embodiments, the source's location at various time points can be determined based on known source motion, velocity, and behavioral information, anatomical information, and / or time-of-flight PET data. Therefore, in some embodiments, the location is determined automatically and does not require user input.

[0012] Therefore, embodiments can provide improved PET images at various locations, where a low-volume, low-activity source travels through the location during PET imaging.

[0013] Figure 1 This is a block diagram of system 10 according to some embodiments. System 10 can operatively generate multiple PET images 17 based on PET data 11. Generally, small volumes (e.g., each cell of a single cell or group of single cells) can be labeled with radioactive material (e.g., 1-10 Bq of radioactive 18-fluorodeoxyglucose (FDG)) and injected into the body. The body is then scanned over time using a PET scanner to generate PET data 11.

[0014] Path planning data 12 can represent the anatomical features of the body to which a small volume is injected. As described below, path planning data 12 can be used to help determine the path of the small volume within the body over time. Path planning data 12 can be acquired using a different imaging modality than that used to acquire PET data 11, or simultaneously with or at different times than the acquisition of PET data 11. Path planning data 12 may include assumptions about the body's anatomical features.

[0015] The carrier travel characteristics 13 may include theoretically and / or experimentally derived information associated with the expected movement of the volume through the body. The carrier travel characteristics 13 may specify the expected velocity of the volume through the body, which may be a function of the volume type, fluid characteristics, and anatomical features indicated by the pathway planning data 12. Together with the pathway planning data 12, the carrier travel characteristics 13 can help determine where the volume is located at various times after injection into the body.

[0016] The time-specific localization component 14 estimates the position of the volume within the body over time based on PET data 11, path planning data 12, and vehicle travel characteristics 13. The time-specific localization component 14 can use PET data 11, path planning data 12, and vehicle travel characteristics 13 as boundary conditions for determining the three-dimensional position of the volume over time. In this respect, the PET data may include time-of-flight (TOF) information, which provides positional information in addition to that provided by non-TOF PET data.

[0017] The specific time positioning component 14 provides the framing component 15 with the three-dimensional location of the capacity at various times. The framing component 15 also receives PET data 11. The framing component 15 operates to generate a PET data frame associated with each of the plurality of three-dimensional locations. In some embodiments, the PET data frame associated with a three-dimensional location includes PET data acquired from a specific time before the time the capacity arrives at that location to a specific time after the time the capacity arrives at that location.

[0018] Image generation algorithm 16 receives frames associated with each location. 0-N ) and associated locations 0-N Using each frame (e.g., frame3) and the corresponding location (e.g., location3), image generation algorithm 16 generates a corresponding PET image (e.g., image3). Image generation algorithm 16 may include any suitable algorithm for generating PET images based on sparse PET data and the location of low-capacity sources within the PET data. According to some embodiments, image generation algorithm 16 is a point source algorithm known in the art.

[0019] Each functional component of System 10 and each other system described herein may be implemented in computer hardware, program code, and / or one or more computing systems that execute such program code, as known in the art. Each component may include any elements necessary for its operation, as well as additional elements for providing functionality beyond that described herein. A computing system implementing one or more components may include one or more processing units that execute processor-executable program code stored in a memory system.

[0020] Figure 2 The illustration shows a PET / CT system 100 performing one or more of the processes described herein. Embodiments are not limited to system 100.

[0021] In conventional PET imaging, a tracer compound comprising a radionuclide or radiolabeled cells is introduced into the patient's body via injection or ingestion. Radioactive decay produces positrons, which eventually encounter electrons and are annihilated. This annihilation produces two gamma photons traveling in approximately opposite directions. Therefore, an annihilation event, or cue, is identified when two detectors positioned on opposite sides of the body detect the arrival of these two opposing gamma photons within a specific coincidence time window.

[0022] Because the two gamma photons travel in approximately opposite directions, the positions of the two detectors determine the response line (LOR), along which an annihilation event occurs. Each annihilation event can be represented by raw (i.e., list mode) data specifying the three-dimensional location and time at which the event occurs. Time-of-Flight PET also measures the difference between the detection times of the two gamma photons generated by the annihilation event. This difference can be used to estimate a specific location along the LOR where the annihilation event occurs. As mentioned above, this TOF estimated location can be used to aid in the localization of low-capacity sources.

[0023] System 100 includes a rack 110 defining an aperture 112. As is known in the art, rack 110 houses a PET imaging assembly for acquiring PET image data and a CT imaging assembly for acquiring CT image data. As is known in the art, the CT imaging assembly may include one or more X-ray tubes and one or more corresponding X-ray detectors.

[0024] PET imaging assemblies can include any number or type of detectors (e.g., any configuration of silicon photomultiplier (SiPM) or photomultiplier tube (PMT) 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.

[0025] CT imaging components can generate projected images of tissues, indicating their relative X-ray attenuation coefficients. As is known in the art, three-dimensional CT images can be reconstructed based on these projected images. Three-dimensional CT images can include anatomical features used as path planning data to aid in the localization of low-volume sources, as described herein.

[0026] Injection system 118 can be operated to deliver a calibration injection of one or more cells labeled with a tracer compound including FDG, iodine, or other radiopharmaceuticals to a patient before and / or during a PET scan. In some embodiments, injection system 118 is integrated into rack 110. Injection system 118 may support a wired or wireless communication link with control system 120 for receiving information on specified dose, injection protocol, and scan delay.

[0027] Before, during, and after imaging, the bed 115 and base 116 operably move a patient lying on the bed 115 into and out of the port 112. In some embodiments, the bed 115 is configured to translate on the base 116, and in other embodiments, the base 116 is movable together with the bed 115 or alternatively movable from the bed 115.

[0028] Movement of the patient access port 112 allows for scanning of the patient using the CT and PET imaging elements of the gantry 110. According to some embodiments, during such scanning, the bed 115 and base 116 can provide continuous bed movement and / or step-and-shoot motion.

[0029] The control system 120 may include any general-purpose or special-purpose computing system. Therefore, the control system 120 includes one or more processing units 122 and a storage device 130 for storing program code. The processing unit 122 is configured to execute processor-executable program code to cause the system 120 to operate as described herein. The storage device 130 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).

[0030] Storage device 130 stores the program code of control program 131. One or more processing units 122 can execute control program 131 to control hardware components in conjunction with PET system interface 123, bed interface 125, and injection interface 127 to introduce a low-volume radiation source into the patient, place the patient in an aperture 112 surrounded by PET detectors of gantry 110, and detect coincidence events occurring within the patient. Detected events can be stored in memory 130 as PET data 133, which may include list pattern data and / or sine waves.

[0031] The control program 131 can also be operated to frame the PET data 133 based on the estimated position of the low-capacity source over time, and generate a PET image associated with each frame described herein. At this point, the time-specific positioning component 132 can be executed as described above to estimate the position over time based on the PET data 133, stored path planning data 134, and carrier travel characteristics 135.

[0032] One or more processing units 122 may also execute control program 131 to, in conjunction with CT system interface 124, cause radiation sources within gantry 110 to emit radiation from different projection angles into the body within aperture 112, and control corresponding detectors to acquire two-dimensional CT data. CT data can be acquired substantially simultaneously with PET data.

[0033] The generated PET and / or CT images can be transmitted to terminal 140 via terminal interface 126. Terminal 140 may include a display device and an input device coupled to system 120 to display the PET images. Terminal 140 may receive user input for controlling the display of data, operation of system 100, and / or the processing described herein. In some embodiments, terminal 140 is a standalone computing device, such as, but not limited to, a desktop computer, laptop computer, tablet computer, and smartphone.

[0034] Figure 3 This includes a flowchart of a process 300 for generating PET images according to some embodiments. Flowchart 300 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 hard disks, volatile or non-volatile random access memory, DVDs, flash drives, and magnetic tapes. Embodiments are not limited to the examples described below.

[0035] In S305, radiolabeled cells are initially injected into a subject (e.g., a patient). The radiolabeling of the cells can occur in any suitable manner, whether known or becoming known. The cells can include any suitable cell type, and the radiolabeling can include any suitable compound. In some embodiments, more than one radiolabeled cell is injected in S305.

[0036] Following injection, PET data of the subject is acquired at S310. As is known in the art, PET data can be acquired via conventional static PET scans after injection of radiolabeled cells. In some embodiments, the acquired PET data may include list-pattern PET data as described above. The PET data may be acquired by an imaging system separate from the system performing the remaining steps of process 300. For example, the PET data may initially be acquired in an imaging operating room, and the remaining steps of process 300 may be performed by a separate system at an independent location for hours, days, months, etc., after acquisition.

[0037] According to some embodiments, the data acquired by the PET scanner in S310 is formatted as a sinusoid. A sinusoid is a data array of angles relative to displacement for each LOR (Location of Observation). Each sinusoid stores the location of the LOR for each coincidence event, such that all LORs passing through a single point in the imaged object trace a sinusoidal curve in the sinusoid. Each sinusoid includes a row containing the LORs at a specific azimuth angle φ. Each such row corresponds to a one-dimensional parallel projection of the tracer compound distribution at different coordinates.

[0038] In S315, multiple locations of the injected cells over time are determined. As described above, these locations can be determined based on acquired PET data, path planning data (e.g., acquired via concurrent CT scans), and known vector travel characteristics. For example, the determination in S315 can be based on boundary conditions defined by TOF data (which provides an estimated annihilation location at a specific time) and travel characteristics and anatomical features based on a solution space constrained for a given time. Therefore, each location determined in S315 is associated with the time at which the cell appeared at that location.

[0039] Figure 4 The illustration shows the travel of a low-volume radiation source through body 400 over time. Path 410 indicates injection position xyz0 and associated injection time t0 (i.e., the time when the low-volume radiation source is located at position xyz0), as well as various other positions and associated times until path 410 ends at position xyz5, which is associated with time t5. As described above, six indicated positions of path 410 can be determined in S315, but the embodiment is not limited to any particular number of determined positions.

[0040] In S320, a corresponding time period is determined for each identified location. The corresponding time period determined for a specific location is a time period surrounding the time associated with that location (i.e., the time when the source is determined to be present at that location). The lengths of the time periods associated with the identified locations do not need to be equal. A location-determined time period can be determined so that sufficient PET data can be collected as the source approaches and moves away from that location. At this point, in S325, based on the time period associated with the location, frames of the acquired PET data are generated for each location.

[0041] Figure 5 S320 and S325 are illustrated according to some embodiments. Figure 5 This is a graph showing the received PET data (e.g., represented as counts acquired at a given time) changing over time. Each time from t1 to t5 is associated with a corresponding defined location xyz1 to xyz5. Each of times t1 to t5 is illustrated by two solid lines and a bracket, which indicates the corresponding time period determined in S320. As shown, the time period associated with a given time from t1 to t5 defines a portion of the PET data acquired during that time period. This portion is used to generate PET data frames for the corresponding time and location. For example, F1 is a frame of PET data corresponding to time t1 and location xyz1.

[0042] In S330, an image is generated from each frame of PET data based on the position associated with the frame. As described above, the point source algorithm can generate an image based on sparse PET data and the position of the radiation source. Therefore, S330 may include inputting the PET data frame (e.g., frame F1) and the corresponding position (e.g., xyz1) generated in S325 into the point source algorithm.

[0043] Figure 6 The diagram illustrates step S330 according to some embodiments. As shown, the point source algorithm receives frames F1 to F5 of PET data and corresponding position data xyz1 to xyz5. Using each frame and the corresponding position, the point source algorithm generates corresponding 3D PET images I1 to I5.

[0044] In S335, multiple images can be displayed. Each image represents activity at locations around the position corresponding to that image, and thus represents a three-dimensional region along the path of the source. According to some embodiments, the images can be displayed in a time-delayed and / or "fly-through" sequence.

[0045] Those skilled in the art will understand that various adaptations and modifications can be made to the above embodiments without departing from the claims. Therefore, it should be understood that the claims may be implemented in ways different from those specifically described herein.

Claims

1. A system for generating an image of an object, comprising: Imaging equipment, used for: Acquire positron emission tomography data associated with objects including moving radiation sources; Processing system, used for: Multiple locations are determined based on the anatomical features of the object and the travel characteristics of the radiation source, each of which is associated with a corresponding time when the radiation source is located at that location, wherein the multiple locations are determined without user input of the multiple locations; Determine the corresponding time period associated with each of the multiple locations; For each defined time period, determine the frames of positron emission tomography data associated with that time period; For each frame of positron emission tomography (PET) data, an image is generated based on that frame and the location associated with that time period; and Display image; The radiation source is radioactively labeled cells.

2. The system according to claim 1, wherein, The generation of the image involves performing a point source algorithm on frames of positron emission tomography data and locations associated with time periods that are linked to those frames.

3. The system of claim 1, wherein determining multiple locations within the object comprises: Multiple locations were determined based on the object's anatomical features, the trajectory characteristics of the radiation source, and positron emission tomography (PET) data. The positron emission tomography (PET) data includes time-of-flight positron emission tomography (TOF PET) data.

4. The system according to claim 1, wherein, The generation of the image involves performing a point source algorithm on frames of positron emission tomography data and locations associated with time periods that are linked to those frames.

5. A method for generating an image of an object, comprising: Inject the radiation source into the object; Positron emission tomography (PET) data of the object is acquired as the radiation source moves within the object. Multiple locations are determined based on the anatomical features of the object and the travel characteristics of the radiation source, each of which is associated with the corresponding time when the radiation source is located at that location. Determine the corresponding time period associated with each of the multiple locations; For each defined time period, determine the frames of positron emission tomography data associated with that time period; and For each frame of positron emission tomography data, an image is generated based on that frame and the location associated with a time period that is related to that frame; The radiation source is radioactively labeled cells.

6. The method of claim 5, wherein generating the image comprises performing a point source algorithm on a frame of positron emission tomography data and a location associated with a time period, the time period being associated with the frame.

7. The method of claim 5, wherein determining a plurality of locations within the object comprises: Multiple locations were determined based on the object's anatomical features, the trajectory characteristics of the radiation source, and positron emission tomography (PET) data. The positron emission tomography (PET) data includes time-of-flight positron emission tomography (TOF PET) data.

8. The method of claim 5, wherein generating the image comprises performing a point source algorithm on a frame of positron emission tomography data and a location associated with a time period, the time period being associated with the frame.

9. A computing system, comprising: Memory that stores process steps that can be executed by the processor; Processing unit, used to execute processor-executable process steps, to: Positron emission tomography (PET) data of the object is acquired as the radiation source moves within the object. Multiple locations are determined based on the anatomical features of the object and the travel characteristics of the radiation source, each of which is associated with the corresponding time when the radiation source is located at that location; Determine the corresponding time period associated with each of the multiple locations; For each defined time period, determine the frames of positron emission tomography data associated with that time period; and For each frame of positron emission tomography data, an image is generated based on that frame and the location associated with that time period, which is associated with that frame; The radiation source is radioactively labeled cells.

10. The system according to claim 9, wherein, The generation of the image involves performing a point source algorithm on frames of positron emission tomography data and locations associated with time periods that are linked to those frames.

11. The system of claim 9, wherein determining a plurality of locations within an object comprises: Multiple locations were determined based on the object's anatomical features, the trajectory characteristics of the radiation source, and positron emission tomography (PET) data. The positron emission tomography (PET) data includes time-of-flight positron emission tomography (TOF PET) data.

12. The system of claim 11, wherein the generation of the image comprises performing a point source algorithm on frames of positron emission tomography data and locations associated with time periods, the time periods being associated with the frames.

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