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WO2025053849A1 - Reconstruction zonale multispectrale pour spect - Google Patents

Reconstruction zonale multispectrale pour spect Download PDF

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Publication number
WO2025053849A1
WO2025053849A1 PCT/US2023/032283 US2023032283W WO2025053849A1 WO 2025053849 A1 WO2025053849 A1 WO 2025053849A1 US 2023032283 W US2023032283 W US 2023032283W WO 2025053849 A1 WO2025053849 A1 WO 2025053849A1
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energy
spect
emissions
reconstruction
image
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Alexander Hans Vija
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Siemens Medical Solutions USA Inc
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Siemens Medical Solutions USA Inc
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    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T11/00—2D [Two Dimensional] image generation
    • G06T11/003—Reconstruction from projections, e.g. tomography
    • G06T11/006—Inverse problem, transformation from projection-space into object-space, e.g. transform methods, back-projection, algebraic methods
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computed tomography [CT]
    • A61B6/037—Emission tomography
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/48—Diagnostic techniques
    • A61B6/482—Diagnostic techniques involving multiple energy imaging
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/48—Diagnostic techniques
    • A61B6/483—Diagnostic techniques involving scattered radiation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/161—Applications in the field of nuclear medicine, e.g. in vivo counting
    • G01T1/164—Scintigraphy
    • G01T1/1641—Static instruments for imaging the distribution of radioactivity in one or two dimensions using one or several scintillating elements; Radio-isotope cameras
    • G01T1/1647—Processing of scintigraphic data
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
    • G01T1/2914—Measurement of spatial distribution of radiation
    • G01T1/2985—In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis)
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5258—Devices using data or image processing specially adapted for radiation diagnosis involving detection or reduction of artifacts or noise
    • A61B6/5282—Devices using data or image processing specially adapted for radiation diagnosis involving detection or reduction of artifacts or noise due to scatter
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2211/00—Image generation
    • G06T2211/40—Computed tomography
    • G06T2211/424—Iterative

Definitions

  • the present embodiments relate to Single Photon Computed Tomography (SPECT).
  • SPECT Single Photon Computed Tomography
  • the reconstruction of a SPECT image is often difficult because the data is characterized by small signal rates and low signal-to- noise ratio.
  • the count rate is limited by the amount of a radionuclide (i.e., radioactive substance or radiotracer) that can be administered without harming the patient.
  • a radionuclide i.e., radioactive substance or radiotracer
  • radionuclides typically alpha and beta emitting isotopes and their progeny (e.g., Tb-161 , Ho-166, Lu-177, I- 131 , Ac-225, Pb208, Pb212, At211 , 1-123, Ga-67 and Y-90) have complicated gamma energy spectra, including discrete or continuous energy spectra due to bremsstrahlung.
  • the most prominent emission peak with the highest photon yields per decay is used in acquisition and subsequent reconstruction for which the image formation is optimized.
  • PET is designed for 511 keV gamma from positron annihilation, and in SPECT different collimators are used for different emission energy ranges. For radionuclides with complicated spectra, this limits the efficiency and applicability of the imaging as emissions from other energies suitable for imaging are essentially discarded.
  • Multi-energy reconstruction may be used to benefit from the complicated energy spectra. Image blurring may still result due to degradation of resolution in the image formation process.
  • a SPECT image does not necessarily provide structural information. Thus, a SPECT image is often evaluated with the help of an adjacent structural image.
  • Computed tomography (CT) may be used for the structural image.
  • CT data may be used as part of the SPECT reconstruction, such as by reconstructing separately for different types of tissue or zones.
  • the zonal reconstruction may improve accuracy or resolution.
  • the preferred embodiments described below include methods, systems, instructions, and computer readable storage media for SPECT reconstruction.
  • Zonal reconstruction is provided intra-modally.
  • the zonal reconstruction may be combined with model-based multi-energy image formation. Rather than or in addition to using CT for structure, SPECT data from one energy may be used to provide structural information or zones for another energy. Multi-spectral, zonal reconstruction is used as an intra- modal imaging approach.
  • a hybrid energy detector may be used to detect emissions at multiple energies, allowing for solving of the image formation for multiple energy ranges, assisting lower energy image formation with higher energy formation.
  • a method for SPECT reconstruction is provided. SPECT emissions in a patient at first and second energies are detected. An image object is zonally reconstructed from the detected SPECT emissions. Zones of the zonal reconstruction for the second energy are determined from the SPECT emissions at the first energy. An image is generated from the image object.
  • the radionuclide is Lu-177, 1-131 , TI-201 , Tb161 , or progeny of Ac225, but other radionuclides may be used.
  • the emissions from such radionuclides may be detected with a multi-camera SPECT system where a first camera of the multi-camera SPECT system is configured to detect at a lower energy than a second camera of the multicamera SPECT system.
  • the SPECT emissions at the first energy are detected with physical collimation, and the SPECT emissions at the second energy are detected with Compton scattering detection.
  • the zonal reconstruction includes generating a zone map including the zones from a first reconstruction of the SPECT emissions at the first energy, forward projecting the SPECT emissions at the second energy separately for each of the zones, weighted summing of the forward projections, obtaining an update from a comparison of a result of the weighted summing to an object model, back projecting the update, and updating an estimate from the back projected update.
  • zonal reconstructing includes generating a zone map of the zones from the SPECT emissions at the first energy.
  • the first energy is lower than the second energy.
  • the SPECT emissions at the first energy spatially stabilize the zonal reconstruction from the SPECT emissions at the second energy where the second energy is a higher energy than the first energy.
  • the zonally reconstruction includes modeling scatter for the second energy.
  • the second energy is higher than the first energy.
  • the SPECT emissions at the second energy are segmented by the zones determined from the first energy.
  • the zones are determined with a greater spatial resolution than an image object of the SPECT emissions at the second energy.
  • an initial reconstruction of the SPECT emissions at the first energy is performed.
  • the zones are segmented from the initial reconstruction for the zonal reconstruction of the SPECT emissions at the second energy.
  • the zonal reconstruction includes iterative reconstruction with reconstruction for the SPECT emissions at both the first and second energies in sequence within each iteration.
  • the iterative reconstruction includes a loop sequencing from the first energy to the second energy in each iteration. The first energy is lower than the second energy, and each iteration has an objective function including the SPECT emissions at both the first and second energies.
  • the image may be generated using various information.
  • the image is generated from the image object of the SPECT emissions at the second energy.
  • the image is generated from the image object zonally reconstructed from the detected SPECT emissions at the second energy combined with another image object reconstructed from the detected SPECT emissions at the first energy.
  • the image is generated from the image object zonally reconstructed from the detected SPECT emissions at the second energy in combination with reconstructed from detected SPECT emissions at the first energy.
  • SPECT reconstruction In a second aspect, a method is provided for SPECT reconstruction. SPECT emissions from a patient are detected. The SPECT emissions are from a radionuclide with multiple energies. An image object is reconstructed with multi-spectral zonal reconstruction. The multi-spectral zonal reconstruction includes the multiple energies and zones from a first of the multiple energies. An image is generated from the image object.
  • reconstructing the image object includes iterative reconstruction where each iteration includes low energy to high energy successive projection operations.
  • the zones are from the first energy.
  • the first energy is a lower energy than a second energy.
  • the multi-spectral zonal reconstruction reconstructs for the second energy with the zones from the first energy.
  • a medical imaging system for SPECT intra-modal zonal reconstruction.
  • a detector arrangement is configured to detect emissions from the patient, the emissions are of different energies from a radiotracer.
  • a processor is configured to reconstruct an object representing the patient from the detected emissions for at least two energy windows of the distributed energies. The reconstruction for a lower of the at least two energy windows is segmented, and the reconstruction for a higher of the at least two energy windows is zonal based on the segmentation from the reconstruction for the lower of the at least two energy windows.
  • a display is configured to display an image of the reconstructed object.
  • the detector arrangement is a detector configured to detect with the at least two energy windows.
  • the detector arrangement is a physically collimated detector and a Compton scattering detector.
  • Figure 1 is a flow chart diagram of one embodiment of a method for SPECT reconstruction
  • Figure 2 illustrates examples of different detector arrangements for detection of emissions at different energies
  • Figure 3 illustrates an iterative zonal reconstruction according to one embodiment
  • Figure 4 illustrates a sequential loop for multi-spectral reconstruction according to one embodiment
  • Figure 5 is a block diagram of one embodiment of a system for SPECT reconstruction for radionuclides with complicated spectra or spectra with multiple peaks.
  • Intra-modality SPECT zonal reconstruction is provided. Multienergy or multi-spectral and zone techniques used together improve both the quantitative accuracy and quality of SPECT images. Extending SPECT processes to include multi-energy tracers instead of a single energy tracer may not be strait forward. Rather than requiring extra-model information, zone information may be obtained from SPECT emissions at one energy for use in zonal reconstruction for another energy.
  • Image formation was designed for specifically a gamma emission range or a specific energy (e.g., 511 k eV- PET).
  • a hybrid image formation spectral detector see fig 11. US published patent application US 2022-0330909
  • a combination of multi-spectral and zone techniques may be provided.
  • This combination multi-energy and zone approach attempts to make sense of the data by comprehensively solving the image formation equation for multiple image formation’s optimized from the energy ranges, and assisting the lower energy image formation with the higher energy image formation, that typically doesn’t have good spatial resolution of yield.
  • a combination of zonal reconstruction from multiple energy emissions with multi-spectral reconstruction simultaneously addresses three important problems.
  • One is the inaccurate model of image formation process in iterative reconstruction, especially for radionuclides with complicated energy spectra (e.g., Lu-177, 1-123, Ga-67, and Y-90).
  • Another is the image blurring due to degradation of resolution in the image formation process.
  • SPECT image reconstruction is improved.
  • Zonal reconstruction provides more accurate segmentation of critical organs, and improved quantitative accuracy in the critical organs provides more accurate dosimetry.
  • the third is use of intra-modal emissions at one energy, such as a lower energy with greater spatial resolution, to provide the zones.
  • the requirement for a CT scan is removed. Resolution and quantitative accuracy are improved without requiring CT or other extra-modal information for spatial structure. Lower resolution from collimation (e.g., electric) at higher energies may be improved.
  • Single photon image reconstruction is provided with combined image formation methods operating at different emission energies.
  • Multiple image formation models are combined in one joint reconstruction as an extension of both extra-modal imaging (the extension is using intra modal for zones) and multi-emission imaging. This combination, for example, enables Compton reconstruction using zonal reconstruction of low energy emissions at better quality than possible without use of, e.g., electron kinematics.
  • Figure 1 shows one embodiment of a method for SPECT reconstruction.
  • Multi-energy image formation e.g., model-based multi-energy image formation
  • zonal reconstruction e.g., multiple energies are used, one for segmentation and the other for zonal reconstruction.
  • the segmentation of zones relies on SPECT data at one or more energies rather than extra modal information (e.g., ratherthan CT). Resolution enhancement and improved quantitative accuracy may be simultaneously achieved without requiring CT imaging.
  • the method of Figure 1 is implemented using the system of Figure 5, a processor, a computer, a SPECT imager, and/or another device.
  • a SPECT imager performs act 100.
  • a computer e.g., server, workstation, or processor
  • acts 110-120 such as a computer of the SPECT imager.
  • Additional, different, or fewer acts may be provided.
  • an act for acquiring CT data for a mu-map or attenuation is provided.
  • acts for modeling attenuation as well as or instead of scatter in the zonal reconstruction are provided.
  • motion correction is performed.
  • the generation of the image in act 120 is not performed, instead saving the image in memory and/or transmitting over a computer network.
  • act 100 SPECT data is obtained.
  • SPECT scanning is performed on a patient.
  • other functional imaging is performed, such as PET and/or Compton scattering.
  • the SPECT data is measurements of single photon emissions from a patient.
  • the SPECT data is obtained from scanning, from data transfer, or from memory.
  • a SPECT system provides the SPECT data directly by scanning or indirectly by transfer or loading.
  • the activity concentration in a patient having received a radiotracer or radiotracers may be determined as part of reconstruction by a SPECT system. After ingesting or injecting the radiotracer or tracers into the patient, the patient is positioned relative to a SPECT detector, and/or the SPECT detector is positioned relative to the patient. Emissions from the radiotracer or tracers within the patient are detected over time. The lateral position of a line or cone relative to the detector may be determined. The SPECT detector may be rotated or moved relative to the patient, allowing detection of emissions from different angles and/or locations in the patient.
  • the emissions are from a radionuclide with multiple energies.
  • the emissions are at different energies.
  • Energys at two, three, or more levels or windows are detected. The energies are for chosen ranges whether from a continuous energy spectrum, from different major peaks, and/or from different minor peaks.
  • the emissions are generated by two or more radiotracers, such as where impurity exists or by design. Each radiotracer causes emissions at a different energy, such as using Tc-99m M I Bl and 1-123 MIBG for cardiac imaging. Any combination of two or more radiotracers may be used for a given scan of a patient (i.e. , at a same time). In another embodiment, a radionuclide with different emission energies is used.
  • Lu-177 emits with energy peaks at 113kv and 208kv. Other peaks may not be included or may be included within the energy ranges set around the peaks being used.
  • Y-90 is used. The energy spectra of Y-90 are generally continuous rather than having specific peaks. The broad spectra may be approximated into quasi emission lines. Any two or more portions of the spectra may be used for multi-energy reconstruction.
  • I- 131 , Y90, Sm153, Re186, W188/Re188, Ho166, Lu177, Cu67, 1125, TI-201 , Tb161 , or progeny of Ac225, Ar211 , Ra223, Tb149 . . . are used as radionuclides with multiple energy emissions.
  • Other isotopes or combinations of isotopes may be used.
  • Raw SPECT data or preprocessed data is provided for reconstruction.
  • the reconstruction may use a system matrix or projection operators to describe the properties of the SPECT imaging system to iteratively improve a data model of an image object representing the SPECT data.
  • the image object may then be displayed using volume rendering or other imaging techniques.
  • the image object which is defined in an object space, is a reconstruction of the SPECT data measured in a data space.
  • the object space is the space in which the result of the image reconstruction is defined and which corresponds, for example, to the 3D volume (i.e. , field-of-view or “FOV”) that is scanned.
  • FOV field-of-view
  • the SPECT detector or gamma camera may be capable of detecting the different energies.
  • a detector has an operational range of energies that includes multiple energy peaks of a radionuclide.
  • a Cadmium zinc Telluride (CZT) detector has a sufficient thickness to detect over a range of energies.
  • the CZT or other type of detector detects over 40-1000, 40-3000, or 30-3000 keV ranges. Other ranges may be possible.
  • the detector arrangement provides for detection at different energies.
  • Figure 2 shows four examples. Below or at about 400 keV, 511 keV, or another level keV, the detector 200 operates with physical collimation from a collimator 202, such as a parallel hole collimator. “About” is used for +/-10%. Other values are possible based on material and state of the art. Rather than rely on any form of coincidence, individual emissions progressing through the collimator 202 at a given direction are detected by the detector 200.
  • the collimator 202 in front of the detector 200 limits the direction of photons detected by the SPECT detector 200, so each detected emission is associated with an energy and line or cone of possible locations from which the emission occurred.
  • an object 204 with a known edge or pattern relative to the detector 200 forms an encoded aperture by moving the object 204 relative to the detector 200.
  • electronic collimation is used.
  • Coincidence processing such as in positron emission tomography, is provided.
  • a ring 206 of detectors detects a pair of emissions in coincidence with each other.
  • Compton scattering detection may be used.
  • coincidence is provided by a catcher detector 210 detecting scatter from an event detected by the scatter detector 208.
  • Compton scattering detection may alternatively use electron tracking in a solid detector for both scatter and catcher detection.
  • a hybrid detector arrangement is used.
  • a multi-camera SPECT system is used.
  • One camera is configured to detect at one energy (e.g., lower energy (LE) window), and the other camera is configured to detect at a different energy (e.g., higher energy window).
  • one head or camera is optimized for, e.g., LE SPECT, and the other head or camera is optimized for mid-energy (ME) SPECT.
  • the gammas from the higher peak become a scatter correction only problem, while the image of the LE SPECT gets converted to become spatial or structure information to improve the ME SPECT.
  • a physical collimator 202 is used for one or more lower energy windows, and Compton scattering detection is used for one or more higher energy windows.
  • Separate detectors 200, 208, 210 may be used.
  • the scatter and/or catcher detectors 208, 210 may be used with a collimator to detect the lower energy events.
  • An intrinsic single layer Compton imaging or multi-layer detector may also detect lower energy events.
  • a three-dimensional tile-able gamma ray detector such as disclosed in US 2022/0354443A, is used to detect in multiple energy ranges.
  • the sensor layout for a direct converter detector such as disclosed in US 2022/0342091 A1 , may be used.
  • a multi-modal Compton and single photon emission computed tomography medical imaging system such as disclosed in US 2022/0330909A1 , may be used for detecting emissions in different energy windows.
  • an image processor zonally reconstructs an image object from the detected emissions. Any reconstruction in SPECT using zones for different anatomy or spatial structure may be used. Examples include the extra-modal zonal reconstructions disclosed in US Patent Nos. 8,577,103; 8,675,936; or 9,171 ,353. Instead of using CT or other “extra” (not SPECT) data for segmentation to identify zones, SPECT data (detected emissions) at one or more energies are used for segmentation. For example, lower energy emissions may have a greater spatial resolution, so reconstruction of the detected SPECT emissions at the lower energy window is used instead of CT to identify the zones.
  • the zonal reconstruction uses emissions at one energy (i.e., energy window or range) to reconstruct an image object from emissions at a different energy.
  • the detected emissions at two energies are used in the zonal reconstruction, which is multi-energy or multi-spectral reconstruction in that sense, but without using the emissions at the energy for identifying the zones in the projections or optimization.
  • the detected emissions for a 511 keV emission window are used to generate a zone map for tumors to improve Lu 177 imaging with zonal reconstruction.
  • the energies used for the zone map are not used in the reconstruction of the image object other than the use of zones. Separate reconstruction is used where the initial reconstruction is provided for segmenting.
  • the SPECT data at different energies are used together so that the resulting image object is matched to the SPECT data at the different energies.
  • the emissions at the energy used to identify the zone are also used in the reconstruction of the image object as part of the projection and optimization of the zonal reconstruction.
  • Examples of multi-spectral or multi-energy reconstruction are in US Patent Nos. 10,126,439 (reconstruction with multiple photopeaks in quantitative SPECT); or 10,395,353 (multi-modality multi-energy SPECT reconstruction).
  • Zonal reconstruction is used in combination with the multi-energy or spectral reconstruction but with detected photon emissions being used to define the zones instead of or in addition to another modality.
  • the image processor reconstructs the image object with multi-spectral zonal reconstruction.
  • the multi-spectral zonal reconstruction includes the multiple energies and zones from one or more of the multiple energies.
  • the image processor determines the zones from the SPECT data at an energy.
  • a zone map of the zones is determined from the emissions at the energy, such as a lower energy window for the radionuclide.
  • the SPECT data at the energy for determining the zones spatially stabilizes the zonal reconstruction from the SPECT data at one or more energies, such as higher energy windows.
  • lower energy photons of an isotope are used to make an image to “stabilize” the higher energy of the same isotope.
  • the low energy peak is imaged, and the resulting image is segmented to identify zones.
  • the higher energy photon emissions are treated as a scattering correction problem for reconstruction.
  • This reconstruction of the higher energy gammas uses the zones or segments from the lower peak energy at higher resolution, improving the spatial resolution of the higher energy collimation (physical or electric) of the higher energy emissions.
  • the zones represent locations within the examined object and are derived from SPECT data at one or more energies.
  • the spatial resolution for some energies may be greater than others, so that better spatial resolution is used for zonal reconstruction of the other energies.
  • the zonal reconstruction may improve the image quality and/or reduce the acquisition time of the SPECT imaging process by considering the zonal information in the reconstruction.
  • the SPECT emissions at the energy or energies are reconstructed into an image object.
  • This image object is then segmented, such as with thresholding, pattern matching, random walker, model fitting, and/or artificial intelligence.
  • the segmentation separates regions or zones, which can then be used in zonal reconstruction.
  • Each zone is a three-dimensional (3D) region of similar anatomy.
  • bone tissue is segmented from non- bone tissue.
  • the reconstructed image object may be a full or final image object from reconstruction or may be an image object generated in an iteration during reconstruction.
  • a SPECT image of an examined object is reconstructed by considering the spatial or spatial- temporal structure of the object when approximating the SPECT image according to the acquired SPECT data.
  • the structure of the object allows separating the object into multiple zones. Each organ or type of tissue is assigned to a separate zone. The volume within each of those zones is treated separately and equally in the reconstruction. Rather than equal treatment, the independence of the zones may be used for different treatment for different zones. Different amounts of signal are allocated to the zones according to the zone's contribution to the functional feature observed.
  • Zonal reconstruction may impose a separation in anatomical zones of the reconstructed image object, but the zones do not modify the merit function of the applied reconstruction algorithm.
  • Figure 3 shows an example.
  • the different zones 330 of the zone map 300 are separately forward projected 320 from the estimate 310 and renormalized as part of the iterative reconstruction.
  • the result of multi-modal reconstructions may be increased resolution as compared to reconstruction with the functional information without zones 330, even with attenuation correction.
  • Attenuation and/or collimator-detector response function are modeled.
  • One model handles the scatter, attenuation, and/or collimator-response function differently for different energies, providing separate models for separate energy windows.
  • Any type of scatter model may be used. Model-based scatter estimation is provided by modeling the physics of scatter in the patient. A Monte-Carlo simulation or other simulation may be used. Other physics or types of modeling of scatter may be used. The scatter may be modeled differently for different energies. Photons with different energies may scatter differently.
  • the image formation models for different energies are used for separate reconstructions at the different energies.
  • the resulting image objects are then combined 332.
  • the combination for the multiple photopeaks may be performed within or as part of reconstruction. Reconstruction is performed iteratively, so the combination for the multiple photopeaks is performed within the iteration loop of the reconstruction, such as combining back projected feedback 350 of the different photopeaks for updating 360 the volume based on comparison 340. An update is obtained from a comparison 340 of a result of the weighted summing 332 to SPECT data.
  • Reconstruction using photon counts from multiple photopeaks in a combined way may increase the signal-to-noise ratio and improve image quality and quantitative accuracy for SPECT imaging.
  • the image volume is projected 320 and back projected 350 with photopeak specific system matrix or projection operators (e.g., projection operators modeling attenuation correction, scatter correction, point response function, and/or sensitivity).
  • the residuals, negradients (for conjugate-gradient method), or an analog resulting from back projection 350 of the multiple photopeaks are combined.
  • the image volume is updated by adding the conjugate gradient resulting from the combined negradients.
  • the conjugate gradient is multiplied by an optimal step size based on the combined negradients. This reconstruction scheme combines multiple photopeaks in one image volume for quantitative SPECT.
  • the combination is of image objects from different energies postreconstruction.
  • the reconstruction includes forward projections 320 for zones 330. For each zone 330, forward projections 320 are performed for different energies using different image formation models. Part of the image formation models includes scatter correction in act 116. Any scatter correction may be used, such as energy window-based scatter correction. In one embodiment, model-based scatter correction is used. The scatter correction is performed as part of the forward projection 320 from the image or object space to the data space. The scatter correction model is used in applying the image formation process to the activity distribution. The resulting projection data model has reduced scatter.
  • a scatter response function is combined with the activity distribution of the patient to form a modelbased scatter source.
  • the SRF is represented by scatter kernels.
  • the scatter kernels for the given SPECT system are used.
  • the interaction of scatter resulting from different sources with a detector and collimator are simulated.
  • Monte Carlo or other stochastic simulation may be used.
  • the simulation is performed for all systems of a given type, such as all SPECT systems using a same combination of collimator and detector.
  • the simulation is for that combination, such as based at least in part of the size, shape, and/or material characteristics of the collimator and detector.
  • the simulation is not performed by the SPECT system, but by a computer, workstation, or server. Alternatively, the SPECT system performs the simulation.
  • the results of the simulation are scatter kernels for the collimator and detector combination.
  • the scatter kernels model the common physics in the image formation process for scatter.
  • the simulation is for a given radiotracer.
  • the simulation provides for the source or sources to emit at the energy level for the selected photon energy.
  • the simulation provides scatter kernels for different energy levels for the multi-energy image formation model.
  • the forward projection of the activity distribution from the multienergy image formation is combined with the model of scatter to reduce the scatter in the resulting projection data model for each zone.
  • the image object or activity distribution for a given zone i e. , zonal object
  • the image object for forward projecting is at a given resolution.
  • the resolution may be a resolution of the SPECT data of one energy to increase SPECT resolution for another energy. In alternative embodiments, other resolutions are used. For modeling scatter, a different resolution is used.
  • the image object for the zone is resampled, such as down-sampled or up-sampled.
  • the scatter kernels are based on the energy resolution of the SPECT system, fitting the physics of the different energy windows.
  • the resampling matches the image object resolution to the energy and spatial resolution of the SPECT system as represented by the scatter kernels. Different resampling of reconstructed images is provided for different models in multi-energy modeling.
  • the resampling matches the image object resolution to the SPECT system resolution rather than the resolution used for forward projection of the zonal image object.
  • the zonal objects are used at one resolution for forward projecting the zonal objects and at one or more other resolutions for modeling scatter. Resampling is provided for each of the energies being used in the multi-energy reconstruction.
  • the voxel size of reconstructed images is set to be the same as the voxel size of input zone map. In the model of image formation process for primary photons, the voxel size of reconstructed images is not changed.
  • Figure 4 shows an example implementation of multi-energy zonal reconstruction. This example includes or does not include the scatter correction of act 116.
  • a loop of three operations 400, 410, 420 for three energy windows is provided.
  • the loop may include two, three, four, or more operations.
  • the loop represents iterative reconstruction with reconstruction for the photon emissions at the different (e.g., three) energies E1 , E2, E3 in sequence within each iteration.
  • each iteration includes low energy to high energy successive projection (forward and backward) operations 400, 410, 420.
  • the image object of an operation (e.g., 400) from one energy may be used to form zones for zonal-based forward projection in other operations (e.g., 410, 420) of other energies in the loop.
  • Each iteration of the loop has an objective function including the photon emissions at the different energies.
  • the objective function is given by:
  • the spatial resolution may be very poor, but high statistics, while at the low energy with better spatial resolution the statistics is poor. In which case, one would use the lower energy to bound the region and high energy to estimate the uptake within the boundary. Cross terms can further be introduced to tailor the minimization efficiency, yet not to bias the result.
  • the same operations 400, 410, 420 are repeated.
  • the operations may change for different iterations. For example, after a given number of iterations or other change criterion is meet, zones are not updated. The same zones continue to be used for later iterations.
  • the image processor generates an image from the image object.
  • the output of the reconstruction is used for imaging.
  • the reconstruction outputs an image object or volume representing the patient from a last iteration. This final image object is used for generating the image.
  • the image object is a three-dimensional representation of the detected emissions of the patient.
  • the image object is rendered or otherwise used to generate an image. For example, a multi-planar reconstruction or single slice image of a plane is generated. The intersection of one or more planes with the image object is visualized. As another example, a surface or projection rendering is performed for three-dimensional imaging. Other imaging may be used.
  • One image is generated.
  • a sequence of images is generated. For example, image objects from different time periods are used to generate a sequence of images representing the patient over time.
  • the image of the functional information from the zonal reconstruction is displayed alone.
  • an anatomical image is displayed with the functional image.
  • the functional image is overlaid on a CT image.
  • the overlay may be colored for display on a gray scale CT image. Other combinations may be used.
  • the image may be an alphanumeric text of a specific uptake value for a location.
  • a graph, chart, or other representation of uptake at multiple locations may be output.
  • the spatial image representing distribution of uptake may use color or brightness modulation to represent a level of uptake by location.
  • the image object used for imaging is reconstructed from emissions at one or more energies.
  • the image object is zonally reconstructed from emissions at one energy window based on zones determined from reconstruction of emissions at a different energy window.
  • multiple image objects are separately zonally reconstructed from the different energy windows.
  • the image object used for imaging is a combination (e.g., average or weighted average) of the image objects from the different energies (i.e. , post reconstruction combination).
  • the image object is zonally reconstructed from the detected emissions at the different energy windows. The combination is within the reconstruction.
  • the emissions at the different energies are combined in the reconstruction, such as with a shared objective function.
  • Figure 5 shows one embodiment of a medical imaging system 500 for SPECT intra-modal zonal reconstruction.
  • the system 500 may implement multi-energy zonal reconstruction where the zones are intra-modal (i.e. , from the SPECT emissions).
  • the method of Figures 1 , 3, and/or 4 or another method is implemented.
  • the system 500 is a SPECT imaging system or scanner and includes a detector arrangement 510, reconstruction processor 520, a memory 530, and a display 540. Additional, different, or fewer components may be provided. For example, a PET or Compton imaging system is provided instead of the SPECT imaging system.
  • the reconstruction processor 520, memory 530, and/or display 540 are part of the SPECT imaging system. In alternative embodiments, the reconstruction processor 520, memory 530, and/or display 540 are provided as a workstation, server, or computer separate from the detector arrangement 510.
  • the memory 530 is part of a computer or workstation with the reconstruction processor 520 or is a remote database, such as a picture archiving and communications system (PACS).
  • PACS picture archiving and communications system
  • the detector arrangement 510 includes one or more detectors for detecting emitted radiation from within the patient.
  • a gamma camera is used to detect.
  • the detector detects photon emissions.
  • the photon is emitted from a tracer or radiopharmaceutical.
  • the detector detects the photon.
  • a given detector may detect a sequence of events from the same or different locations of the patient.
  • the tracer includes a radionuclide with a complex energy spectrum. Multiple energy peaks or a region of substantially continuous energy are provided. A combination of radionuclides may be provided to generate the emissions at different energies. The radionuclide emits energies at or near the different energy peaks or within a continuous energy region.
  • the detector arrangement 510 includes one or more detectors for detecting in two or more different energy windows.
  • the detector arrangements of Figure 2 or other detector arrangements may be used.
  • one detector detects emissions at different energy windows, such as using a CZT detector.
  • a combination of detectors for physical collimation and Compton scattering is provided.
  • a multi-camera system has one detector with physical collimation for a relatively lower energy range (e.g., LE detector) and another detector with electrical or physical collimation for detecting at a relatively higher energy range (e.g., ME detector).
  • the reconstruction processor 520 is a general processor, central processing unit, control processor, graphics processor, digital signal processor, application specific integrated circuit, field programmable gate array, artificial intelligence processor, digital circuit, analog circuit, timing circuit, combinations thereof, or other now known or later developed device for reconstructing a patient volume from detected emissions.
  • the reconstruction processor 520 is a single device or multiple devices operating in serial, parallel, or separately.
  • the reconstruction processor 520 is specifically designed or provided for reconstruction but may be a main or general processor of a computer, such as a laptop or desktop computer, or may be a processor for handling tasks in a larger system.
  • the reconstruction processor 520 may perform other functions than zonal reconstruction.
  • the reconstruction processor 520 is configurable.
  • the reconstruction processor 520 is configured by software, firmware and/or hardware. Different software, firmware, and/or instructions are loaded or stored in memory 530 for configuring the reconstruction processor 520.
  • the reconstruction processor 520 is configured to reconstruct an object representing the patient from the detected emissions.
  • the reconstruction may be performed for at least two energy windows of the distributed energies of the radionuclide.
  • the reconstruction also includes zonal reconstruction where the zones are intra-modal (i.e. , from detected emissions). Detected emissions at one or more energies are reconstructed or projected to image space for spatial segmenting. For example, the emissions at a lower energy window are used to form an image object or patient representation for segmenting the zones. These zones are then used for zonal reconstruction.
  • the emissions from the higher energy window or windows are zonally reconstructed using the zones from the lower energy emissions.
  • the reconstruction is multi-spectral or multi-energy, so an image object is zonally reconstructed from the emissions of both or multiple energy windows, including or not the energy window used to identify the zones.
  • the reconstruction processor 520 is configured to forward project a zonal image at a first resolution with multi-energy projectors and to model scatter with the zonal image at a second resolution different than the first resolution.
  • the zonal images are resampled (i.e., sampled differently) for the primary multi-energy projection and the model of scatter.
  • the resolution of the zonal images is a resolution of the image object from reconstruction of the lower energy emissions
  • the resolution for modeling scatter is a system or scatter kernel resolution.
  • the reconstruction processor 520 may be configured to alter the reconstruction.
  • the reconstruction is iterative. A different reconstruction process may be used for later iterations than for earlier iterations.
  • the memory 530 is a random-access memory, graphics processing memory, video random access memory, system memory, cache memory, hard drive, optical media, magnetic media, flash drive, buffer, database, combinations thereof, or other now known or later developed memory device for storing data.
  • the memory 530 stores detected emissions (e.g., PET, Compton, or SPECT detected event data), zone information, segmentation information, energy information, and/or reconstruction information.
  • the memory 530 stores data as processed, such as storing an updated image object, zonal image objects, renormalization coefficients, scatter kernels, projection operators or system matrix, zonal data models, combined data models, zone functions, resampled image objects, and/or other information.
  • the memory 530 or other memory is a non-transitory computer readable storage medium storing data representing instructions executable by the programmed reconstruction processor 520 for SPECT reconstruction.
  • the instructions for implementing the processes, methods and/or techniques discussed herein are provided on computer-readable storage media or memories, such as a cache, buffer, RAM, removable media, hard drive, or other computer readable storage media.
  • Computer readable storage media include various types of volatile and nonvolatile storage media. The functions, acts or tasks illustrated in the figures or described herein are executed in response to one or more sets of instructions stored in or on computer readable storage media.
  • processing strategies may include multiprocessing, multitasking, parallel processing, and the like.
  • the instructions are stored on a removable media device for reading by local or remote systems.
  • the instructions are stored in a remote location for transfer through a computer network or over telephone lines.
  • the instructions are stored within a given computer, CPU, GPU, or system.
  • the display 540 is a monitor, LCD, plasma, touch screen, printer, or another device for displaying an image for viewing by a user.
  • the display 540 shows one or more images representing function, such as uptake or activity concentration.
  • the image is a quantitative or qualitative SPECT image of the reconstructed object.
  • the image may be a volume rendering, a multi-planar reconstruction, a cross-section, and/or another image from a final image object.
  • the image represents a distribution of the radionuclide in the patient based on detected emissions from the SPECT system 500.

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Abstract

Pour une reconstruction SPECT, une reconstruction zonale est fournie de façon intra-modale. Au lieu, ou en plus, d'utiliser un CT pour la structure, des données SPECT provenant d'une énergie peuvent être utilisées pour fournir des informations ou des zones structurales pour une autre énergie. La reconstruction zonale peut être combinée à une formation d'image multi-énergie basée sur un modèle. Une reconstruction zonale multispectrale est utilisée en tant qu'approche d'imagerie intra-modale.
PCT/US2023/032283 2023-09-08 2023-09-08 Reconstruction zonale multispectrale pour spect Pending WO2025053849A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130248719A1 (en) * 2012-03-23 2013-09-26 General Electric Company Systems and methods for attenuation compensation in nuclear medicine imaging based on emission data
US20170164835A1 (en) * 2014-06-10 2017-06-15 Ithera Medical Gmbh Device and method for hybrid optoacoustic tomography and ultrasonography
US20180061031A1 (en) * 2016-08-31 2018-03-01 Siemens Medical Solutions Usa, Inc. Model-Based Scatter in Multi-Modality Multi-Energy SPECT Reconstruction

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130248719A1 (en) * 2012-03-23 2013-09-26 General Electric Company Systems and methods for attenuation compensation in nuclear medicine imaging based on emission data
US20170164835A1 (en) * 2014-06-10 2017-06-15 Ithera Medical Gmbh Device and method for hybrid optoacoustic tomography and ultrasonography
US20180061031A1 (en) * 2016-08-31 2018-03-01 Siemens Medical Solutions Usa, Inc. Model-Based Scatter in Multi-Modality Multi-Energy SPECT Reconstruction

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