Partial scan and reconstruction for positron emission tomography systems

Abstract

A method of performing a partial scan of a patient using a PET / CT system includes receiving a selection of a region of interest for a scan and performing a CT scan on the region of interest using the PET / CT system to acquire raw CT data. The raw CT data is reconstructed into one or more CT images. The PET / CT system is configured to limit data collection to the region of interest. A PET scan is performed using the PET / CT system to acquire raw PET data, the PET scan being limited to the region of interest. The raw PET data is reconstructed into one or more PET images of the region of interest.

Description

Technical Field

[0001] This disclosure generally relates to methods, systems, and apparatus for performing partial scans and reconstructions in positron emission tomography (PET) systems or combined computed tomography (CT) / PET systems. The techniques described herein can be applied, for example, to achieve axial field of view imaging. Background Technology

[0002] Nuclear medicine uses radiation emission to acquire images that reveal the function and physiology of organs, bones, or tissues in the body. Radiopharmaceuticals are introduced into the body via injection or ingestion. The radiopharmaceuticals are attracted to specific organs, bones, or tissues of interest. The radiopharmaceuticals cause gamma photons to be emitted from the body, which are then captured by a detector. The interaction of the gamma photons with the detector's scintillation crystal produces a flash of light. This light is detected by an array of optical sensors in the detector.

[0003] Positron emission tomography (PET) is a nuclear medicine imaging technique that uses positron-emitting radionuclides. PET is based on the coincidence detection of two gamma photons produced from positron-electron annihilation. These two gamma photons travel in generally opposite directions from the annihilation site and can be detected by two opposing detectors in a ring of detectors. An annihilation event is typically identified by the temporal coincidence in the detection of these two gamma photons. The opposing detectors identify the annihilation event along the response line (LOR) where it occurred.

[0004] PET can be combined with another imaging modality in a multimodal system. Such a multimodal imaging system may have diagnostic value. PET-CT multimodal imaging systems allow scans to be performed back-to-back or in the same coordinate system and at similar timing. The axial fields of view of individual modalities are typically brought as close together as possible to minimize the effects of patient motion and increase the spatial relevance of the corresponding datasets. PET-CT and multimodal systems typically combine the benefits of high local resolution modalities (e.g., CT imaging) with modalities with high functional sensitivity (e.g., PET) to spatially align detailed anatomical and functional information.

[0005] Historically, PET / CT systems were designed with an axial field of view (aFoV) matched to the organ of interest, such as the heart or brain. For larger imaging volumes, the patient would be scanned at different axial positions, either via step-and-shoot or continuous bed position. With the development towards longer aFoV systems, the expectation is that a CT dataset matching the aFoV of the PET tomograph must exist for attenuation and scattering correction. However, such long and detailed CT scans can expose patients to high doses of radiation.

[0006] Therefore, it is desirable to provide a way to minimize the dose to patients while still collecting enough data to cover the region / organ of interest. Summary of the Invention

[0007] Embodiments of the present invention address and overcome one or more of the aforementioned deficiencies and disadvantages by providing methods, systems, and apparatus related to performing partial scans and reconstructions in positron emission tomography (PET) systems or combined computed tomography (CT) / PET systems. More specifically, the techniques described herein minimize the CT dose to the patient by scanning the minimum extent required to cover the region of interest / organ and reconstructing only the volume defined by that region of interest.

[0008] According to some embodiments, a method for performing a partial scan of a patient using a PET / CT system includes: receiving a selection of a region of interest (ROI) for scanning; performing a CT scan on the ROI using the PET / CT system to obtain raw CT data; reconstructing one or more CT images from the raw CT data; configuring the PET / CT system to restrict data collection to the ROI; performing a PET scan restricted to the ROI using the PET / CT system to obtain raw PET data; and reconstructing one or more PET images from the ROI using the raw PET data.

[0009] According to other embodiments, a method for performing a partial scan of a patient using a PET / CT system includes: receiving a selection of a region of interest (ROI) for scanning; performing a CT scan on the ROI using the PET / CT system to obtain raw CT data; reconstructing one or more CT images from the raw CT data; identifying a restricted ring difference and one or more radial offset values ​​describing the ROI in the coordinate space of the PET / CT system; performing a PET scan using the PET / CT system to obtain raw PET data; and performing reconstruction of the raw PET data restricted to the ROI to generate one or more PET images.

[0010] According to other embodiments, a method for performing a partial scan of a patient using a PET / CT system includes: receiving a selection of a region of interest for scanning; performing a CT scan on the region of interest using the PET / CT system to obtain raw CT data; reconstructing one or more CT images from the raw CT data; performing a PET scan using the PET / CT system to obtain raw PET data; and performing reconstruction of the raw PET data limited to the region of interest to generate one or more PET images.

[0011] According to other embodiments, a system for performing partial scans of a patient includes one or more operator consoles, a CT subsystem, and a PET subsystem. The operator console is configured to receive selection of a region of interest (ROI) for scanning. The CT subsystem is configured to perform a CT scan on the ROI to obtain raw CT data and reconstruct one or more CT images from the raw CT data. The PET subsystem is configured to adjust one or more hardware components of the PET subsystem to limit data collection to the ROI and perform a PET scan limited to the ROI to obtain raw PET data. The raw PET data is reconstructed into one or more PET images of the ROI.

[0012] Additional features and advantages of the invention will become apparent from the following detailed description of illustrative embodiments with reference to the accompanying drawings. Attached Figure Description

[0013] The foregoing and other aspects of the invention will be best understood from the following detailed description when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, presently preferred embodiments are shown in the drawings; however, it is to be understood that the invention is not limited to the specific means disclosed. The drawings include the following figures: Figure 1This is a schematic side view of the PET / CT scanner of the present invention, showing the CT scanner and PET scanner disposed in a single gantry; Figure 2A An alternative embodiment is illustrated, wherein the X-ray CT and PET tomography detectors are positioned in separate gantry frames fixed relative to each other, and the patient bed is movable between the gantry frames; Figure 2B The illustration shows another alternative embodiment in which the X-ray and PET tomography detectors are arranged in separate gantry, wherein either gantry is movable relative to the other gantry, and wherein the patient bed is movable relative to each gantry. Figure 3 An example method for performing a partial scan of a patient using a PET / CT system, according to some embodiments, is shown; Figure 4 A second method for performing a partial scan of a patient using a PET / CT system, according to some embodiments, is shown; Figure 5 A third method for performing partial scans of a patient using a PET / CT system is shown; Figure 6 An example topogram interface is shown that has been used in some embodiments to select a region of interest; Figure 7A An example CT image of the region of interest is shown; and Figure 7B A PET image of an example region of interest is shown. Detailed Implementation

[0014] The following disclosure describes several embodiments of the invention relating to methods, systems, and apparatus for performing partial scans and reconstructions in a positron emission tomography (PET) system or a combined computed tomography (CT) / PET system. The techniques described herein can be applied, for example, to achieve long-axis field-of-view imaging. In short, CT localization images are acquired to help the user define a region of interest (ROI). A CT scan is then performed against the selected ROI using sufficient overscanning for attenuation and scattering correction. Various techniques can then be applied to perform a partial PET scan. In some embodiments, the partial scan is performed by collecting only data from PET detectors that cover the ROI and satisfy the desired ring difference. This can be achieved, for example, by disabling detectors falling outside the associated ROI or by programming the coincidence electronics to transmit only data from the response line (LOR) crossing the ROI. In other embodiments, the partial scan is performed by first acquiring data normally and then limiting histogramming to the LOR crossing the ROI. In other embodiments, both data acquisition and histogram formation are performed in a conventional manner, and the reconstruction of the resulting sine wave is limited to the region of interest. Utilizing each of the techniques discussed above, the patient dose from the CT scan will be significantly lower. Additionally, since less data needs to be collected and stored as images, the techniques discussed above save storage space, accelerate any subsequent processing, and speed up data transfer overall.

[0015] Figure 1 , 2A Figure 2B illustrates an example combined PET and X-ray CT tomography system 10 that can be used in some embodiments of the invention. This combined PET and X-ray CT tomography system, or PET / CT scanner 10, allows for the sequential acquisition of registered CT and PET images in a single device, thereby overcoming alignment problems caused by internal organ movement, changes in the scanner bed profile, and patient positioning for scanning.

[0016] In this example, the PET / CT scanner 10 combines a CT scanner 12 with a PET scanner 14. The PET / CT scanner 10 includes both a PET scanner 14 and a CT scanner 12, both of which are commercially available and are in a physically known relationship to each other. Each of the X-ray CT scanner 12 and the PET scanner 14 is configured for use with a single patient bed 18, such that a patient can be placed on the bed 18 and moved to a position for either or both of the X-ray CT scan and the PET scan.

[0017] exist Figure 1 In the illustrated embodiment, the completed PET / CT scanner includes an X-ray CT detector 12 and a PET tomography detector 14 housed within a single gantry 16, wherein a patient bed 18 is movable to expose selected areas of the patient to either one or both scans. In commercial PET / CT scanners 10, the detector 14 can vary in axial length. Historically, the axial length of the detector 14 has varied from 16 cm to 26 cm. Currently, there is a need for a PET scanner 16B in which the axial FoV or length of the detector 14 is longer than that of standard scanners, such as 50 cm to 200 cm.

[0018] In the second example, such as Figure 2A As illustrated, X-ray CT and PET computed tomography detectors 12 and 14 are positioned in separate gantry frames 16A and 16B that are fixed relative to each other, and the patient bed 18 is movable between the gantry frames 16A and 16B. In a third example, as... Figure 2B As illustrated, X-ray and PET computed tomography detectors 12 and 14 are housed in separate gantry frames 16A' and 16B', each movable relative to the other, wherein the patient bed 18' is movable relative to each gantry frame 16A' and 16B', as indicated by arrow 20. Alternatively, one or both gantry frames 16A' and 16B' may be movable relative to the patient bed 18' and another of the gantry frames 16A' and 16B', as indicated by arrow 22. Figure 1 , 2A In each of the embodiments illustrated in Figure 2B, the patient is placed on a single patient bed 18 for any one or two scans, wherein any one or all of the scanning devices and the patient bed are moved to complete one or more of the required scans.

[0019] In some embodiments, the combined PET and X-ray CT computed tomography system may include an operator interface ( Figure 1 , 2A(as shown in 2B) to provide data processing and user interface functions. In other embodiments, data processing and user interface functions may be provided separately. For example, image reconstruction and other processing of scan data may be performed by separate computing systems. The PET and CT subsystems may be supported by respective operator consoles and / or computing systems. The operator console may communicate with the gantry controller and data acquisition system to control the operation of the combined PET and X-ray CT computed tomography system. The gantry controller may be integrated with the operator console to any desired extent. In some embodiments, the operator console is configured to process PET and CT scan data provided by the data acquisition system. In other embodiments, separate computing systems may be provided for such processing.

[0020] Figure 3 An example method 300 for performing a partial scan of a patient using a PET / CT system, according to some embodiments, is shown. Method 300 can be performed, for example, by... Figure 1 , 2A This is performed using a combined PET and X-ray CT computed tomography system as shown in 2B. In short, the PET detector is either axially disabled or disabled at the pair production stage to create a sub-scanner within the PET / CT system. This reduces the overall file size associated with the reconstructed images. Figure 3 The method 300 described in the text also generally provides more efficient data throughput and creates smaller list patterns and sine graph files during the data collection phase.

[0021] exist Figure 3 Beginning at step 305, the system receives a selection of a region of interest for scanning. Various techniques can be used to interact with the user and collect this selection. For example, in some embodiments, a combined PET / CT system is used to acquire a localization image of the patient's body. This localization image is presented to the user on an operator console, and the user's selection of the region of interest for scanning is received via the operator console. In one of these embodiments, a sequence of blocks extending axially along at least one side of the localization image is presented on the operator interface. Each block in the sequence corresponds to a portion of the localization image. Figure 6An example of this interface is presented. User selection of a region of interest includes selecting one or more blocks (e.g., by clicking on one or more blocks of interest). In another embodiment, user selection of a region of interest includes one or more shapes drawn by the user on one or more portions of the localized image. As another alternative, in some embodiments, machine learning is used to automatically perform the selection of the region of interest. For example, based on the type of research being performed, a machine learning model can analyze the image to locate the organ or tissue of interest, as well as the surrounding area needed to perform the desired research.

[0022] Continue to refer to Figure 3 At step 310, the PET / CT system performs a CT scan on the region of interest to acquire raw CT data, and at step 315, the raw CT data is reconstructed into one or more CT images. At step 320, the PET / CT system is configured to restrict data collection to the region of interest identified in step 305. In some embodiments, a subset of PET detectors outside the region of interest is identified. This identification can be performed automatically by the PET / CT system, or the detectors can be identified manually by the operator. Once these detectors have been identified, the PET / CT system can disable them during data acquisition. Alternatively, in other embodiments, a response line is determined for each coincidence event. The coincidence electronics within the PET / CT system are then configured to process only a subset of the coincidence events that have a corresponding LOR traversing the region of interest.

[0023] Once the PET / CT system has been configured, at step 325, a PET scan limited to the region of interest is performed to obtain raw PET data. In some embodiments, the PET / CT system is configured to satisfy a ring difference selected by the user during the scan. As is generally understood in the art, the term "ring difference" refers to the maximum extent of axial coincidence in 3D. In other words, the ring difference specifies how many rings away the rebinning algorithm will accept coincidence events. Limiting this ring difference reduces randomness and scattering that occurs during the scan, thereby making the image sharper. However, a small ring difference also reduces the overall number of counts acquired. The ring difference can be specified, for example, as a parameter via the operator console of the combined PET and X-ray CT computed tomography system.

[0024] return Figure 3At step 330, the raw PET data is reconstructed into one or more PET images of the region of interest. The CT and PET images can then be displayed using any techniques known in the art. For example, in some embodiments, the CT and PET images are displayed side-by-side on a graphical user interface (GUI) presented on the operator interface of the PET / CT system. In other embodiments, the GUI displays one type of image (i.e., CT or PET), and the GUI includes one or more interface elements (e.g., buttons) that allow the user to selectively switch between image types.

[0025] Figure 4 A second method 400 for performing partial scans of a patient using a PET / CT system, according to some embodiments, is illustrated. This process can be understood as “virtual histogramization.” In short, the PET / CT system remains in its native state; however, histogramization is limited to creating a sine curve that matches only the sub-scanner covering the region of interest. As is generally understood in the art, during data collection, the PET scanner bins overlapping events into the data array based on the detected coordinates of the events in space. The sine curve is a matrix into which all the overlaps found from the PET scan are histogramized. Each sine curve includes 2D, 3D, and 4D representations of the events from the data stream collected from the scanner. Each element in the matrix corresponds to the number of valid LORs recorded by a certain pair of opposing detectors. The sine curve is conceptually a line integral of the emitted data, in which it is offset along a specific radial direction. s The data for the angle φ is mapped to row and column positions. Using virtual histogramting, the matrix is ​​truncated so that it includes only values ​​corresponding to the region of interest. s And the elements of φ. Therefore, each region is essentially a "sub-scanner" of the entire PET scanner.

[0026] Steps 405-415 of method 400 are similar to those discussed above. Figure 3 Steps 305-315 are performed in this manner. In short, the user selects the region of interest, and the PET / CT system acquires and reconstructs CT images of that region. (Compared to...) Figure 3 Similar to method 300, the user can interact with the localization image to identify the region of interest. At step 420, the axial region of interest is identified in the coordinate space of the PET / CT system. This identification includes a radial offset value and a restricted loop difference value (where the restriction is based on the LOR traversing the region to be reconstructed). At step 425, the PET / CT scanner performs a PET scan to obtain raw PET data.

[0027] Next, at step 430, the PET / CT system creates a sinusoidal plot confined to the region of interest by histogramling the raw PET data using radial offset values ​​and restricted ring aberrations. This can be achieved in several ways. For example, in some embodiments, a lookup table is used to identify the region for reconstruction when creating the sinusoidal plot. This lookup operation can be confined based on the radial offset values ​​and restricted ring aberrations, as well as other factors associated with the region of interest, such as its axial length. Finally, at step 435, the sinusoidal plot is reconstructed into one or more PET images of the region of interest.

[0028] Figure 5 A third method 500 for performing a partial scan of a patient using a PET / CT system is illustrated. In short, the PET / CT system is left in its native state; however, the reconstructed volume is limited. Reconstruction of PET data in sonograms is performed after acquisition to estimate the distribution of the in vivo tracer in the patient's anatomy. Steps 505-515 are respectively performed in a manner similar to... Figure 3 and 4 The process is performed in the manner described in steps 305-315 and 405-415. At step 520, the PET / CT system performs a PET scan to acquire raw PET data. At step 525, the PET / CT system creates a sine wave by histogramizing the raw PET data. Next, at step 525, the PET / CT system identifies one or more portions of the sine wave corresponding to the region of interest. Then, at step 530, the portions of the sine wave are reconstructed into one or more PET images of the region of interest.

[0029] In some embodiments, as an alternative to using sine waves to perform reconstruction, reconstruction is performed directly on the data stream collected from the PET / CT scanner. This is referred to as “list-mode reconstruction.” Because the crystal pairs of the volume of interest are known, the methods discussed above for limiting the acquired or processed data can be similarly applied to list-mode reconstruction.

[0030] Figure 6 An example localization image interface is shown, which is used in some embodiments to select a region of interest. The frame extends along the side of the localization image. Figure 6 As shown, when certain boxes are selected, they change color to indicate that the corresponding anatomical region should be designated as the region of interest. In this example, the patient's central region is selected. Figure 7A and 7B The CT and PET images of this area are shown.

[0031] The embodiments of this disclosure can be implemented using any combination of hardware and software. Furthermore, the embodiments of this disclosure can be included in an article of manufacture having, for example, a computer-readable non-transitory medium (e.g., one or more computer program products). This medium embodies, for example, computer-readable program code for providing and facilitating the embodiments of this disclosure. This article of manufacture can be included as part of a computer system or sold separately.

[0032] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, wherein the true scope and spirit are indicated by the following claims.

[0033] As used herein, an executable application includes code or machine-readable instructions for regulating a processor to perform predetermined functions, such as those of an operating system, context data acquisition system, or other information processing system, for example, predetermined functions in response to user commands or input. An executable procedure is a piece of code or machine-readable instructions, subroutines, or other distinct code portions or part of an executable application for performing one or more specific procedures. These procedures may include receiving input data and / or parameters, performing operations on the received input data, and / or performing functions in response to received input parameters, and providing the obtained output data and / or parameters.

[0034] As used herein, a graphical user interface (GUI) includes one or more display images generated by a display processor and enabling user interaction with the processor or other devices, as well as associated data acquisition and processing functions. The GUI also includes an executable process or executable application. The executable process or executable application modulates the display processor to generate signals representing the GUI display images. These signals are supplied to a display device, which displays the images for the user to view. Under the control of the executable process or executable application, the processor manipulates the GUI display images in response to signals received from input devices. In this way, the user can interact with the display images using input devices, thereby enabling user interaction with the processor or other devices.

[0035] The functions and process steps described herein may be executed automatically, or in whole or in part, in response to user commands. Automatically executed activities (including steps) are performed in response to one or more executable instructions or device operations without direct user initiation. Furthermore, although some method steps are described as separate steps for ease of understanding, any such steps should not be interpreted as necessarily being distinct or dependent on a specific order in their execution.

[0036] The systems and processes shown in the figures are not exclusive. Other systems, processes, and menus can be derived from the principles of the invention to achieve the same purpose. Although the invention has been described with reference to specific embodiments, it is to be understood that the embodiments and variations shown and described herein are for illustrative purposes only. Modifications to the present design can be made by those skilled in the art without departing from the scope of the invention. As described herein, various systems, subsystems, agents, managers, and processes can be implemented using hardware components, software components, and / or combinations thereof. The elements of the claims herein should not be construed in accordance with 35 USC 112(f) unless the element is expressly stated using the phrase “means for…”.

Claims

1. A method for performing a partial scan of a patient using a positron emission tomography (PET) / computed tomography (CT) system, the method comprising: Receive the selection of a region of interest for scanning, wherein the selection of the region of interest is based on a constrained ring difference and one or more radial offset values ​​that describe the region of interest in the coordinate space of the PET / CT system; The PET / CT system is used to perform a CT scan on the region of interest to obtain raw CT data; The raw CT data is reconstructed into one or more CT images; The PET / CT system is used to perform PET scans to obtain raw PET data; and Reconstruction of the original PET data, confined to the region of interest, is performed to generate one or more PET images, wherein the reconstruction is performed through the following steps: A sine plot constrained to the region of interest is created by histogramting the raw PET data using the radial offset value and the constrained ring difference; and The sine curve is reconstructed into a PET image.

2. The method according to claim 1, further comprising: Use a combination PET / CT system to acquire localized images of the patient's body; The positioning image is presented to the user on the operator's console. The selection of the region of interest for scanning is received via the operator's console.

3. The method according to claim 2, further comprising: A sequence of blocks extending axially along at least one side of the positioning image is presented on the operator's console. Each block in the sequence corresponds to a portion of the localization image; The selection of the region of interest includes the selection of one or more blocks.

4. The method of claim 2, wherein the selection of the region of interest includes one or more shapes drawn by a user on one or more portions of the positioning image.

5. The method of claim 1, wherein the PET / CT system comprises a plurality of PET detectors, and wherein the method further comprises: A subset of the PET detector located outside the region of interest; Configure the PET / CT system such that the subset of PET detectors is disabled during the acquisition of the raw PET data.

6. The method of claim 1, further comprising: Receive the selection of the restricted ring difference associated with the PET / CT system; The PET / CT system is configured to satisfy the constrained ring difference during the PET scan.

7. A method for performing a partial scan of a patient using a positron emission tomography (PET) / computed tomography (CT) system, the method comprising: Receive the selection of the region of interest for scanning; The PET / CT system is used to perform a CT scan on the region of interest to obtain raw CT data; The raw CT data is reconstructed into one or more CT images; Based on the one or more CT images, identify the constrained ring aberration and one or more radial offset values ​​describing the region of interest in the coordinate space of the PET / CT system; The PET / CT system is used to perform PET scans to obtain raw PET data; and Reconstruction of the original PET data, confined to the region of interest, is performed to generate one or more PET images, wherein the reconstruction is performed through the following steps: A sine plot constrained to the region of interest is created by histogramting the raw PET data using the radial offset value and the constrained ring difference; and The sine curve is reconstructed into a PET image.

8. The method of claim 7, further comprising: Use a combination PET / CT system to acquire localized images of the patient's body; The positioning image is presented to the user on the operator's console. The selection of the region of interest for scanning is received via the operator's console.

9. The method of claim 8, further comprising: A sequence of blocks extending axially along at least one side of the positioning image is presented on the operator's console. Each block in the sequence corresponds to a portion of the localization image; The selection of the region of interest includes the selection of one or more blocks.

10. The method of claim 7, wherein the reconstruction of the original PET data is a list-mode reconstruction directly applied to the original PET data.

11. A system for performing a partial scan of a patient, the system comprising: One or more operator consoles are configured to receive selection of a region of interest for scanning, wherein the selection of the region of interest is based on a constrained ring difference that identifies the region of interest in the coordinate space of the system and one or more radial offset values; The computed tomography (CT) subsystem is configured as follows: Perform a CT scan on the region of interest to obtain raw CT data, and Reconstructing the original CT data into one or more CT images; and The positron emission tomography (PET) subsystem is configured as follows: Perform a PET scan to obtain raw PET data including multiple coincidence events, and Reconstruction of the original PET data, confined to the region of interest, is performed to generate one or more PET images, wherein the reconstruction is performed through the following steps: A sine plot constrained to the region of interest is created by histogramting the raw PET data using the radial offset value and the constrained ring difference; and The sine curve is reconstructed into a PET image.

12. The system of claim 11, wherein the PET subsystem comprises a plurality of PET detectors, and the PET subsystem is further configured to: A subset of the PET detector located outside the region of interest; The subset of PET detectors is disabled during the acquisition of the raw PET data.

Images