Classifications

• • 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
  • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
  • A61B6/4266—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a plurality of detector units
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • 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
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  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/10—Safety means specially adapted therefor
  • A61B6/102—Protection against mechanical damage, e.g. anti-collision devices
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
  • A61B6/4291—Arrangements for detecting radiation specially adapted for radiation diagnosis the detector being combined with a grid or grating
• • 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
  • A61B6/44—Constructional features of apparatus for radiation diagnosis
  • A61B6/4429—Constructional features of apparatus for radiation diagnosis related to the mounting of source units and detector units
  • A61B6/4458—Constructional features of apparatus for radiation diagnosis related to the mounting of source units and detector units the source unit or the detector unit being attached to robotic arms
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/54—Control of apparatus or devices for 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
  • A61B6/54—Control of apparatus or devices for radiation diagnosis
  • A61B6/542—Control of apparatus or devices for radiation diagnosis involving control of exposure
  • A61B6/544—Control of apparatus or devices for radiation diagnosis involving control of exposure dependent on patient size
• • 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
  • A61B6/58—Testing, adjusting or calibrating thereof
  • A61B6/582—Calibration
  • A61B6/583—Calibration using calibration phantoms
  • A61B6/584—Calibration using calibration phantoms determining position of components of the apparatus or device using images of the phantom
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21K—HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
  • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
  • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
  • G21K1/025—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation
• • 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
  • A61B6/50—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications
  • A61B6/501—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications for diagnosis of the head, e.g. neuroimaging or craniography
• • 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
  • A61B6/50—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications
  • A61B6/502—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications for diagnosis of breast, i.e. mammography
• • 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
  • A61B6/50—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications
  • A61B6/508—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications for non-human patients
• • 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
  • A61B6/5205—Devices using data or image processing specially adapted for radiation diagnosis involving processing of raw data to produce diagnostic data
• • 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
  • A61B6/54—Control of apparatus or devices for radiation diagnosis
  • A61B6/545—Control of apparatus or devices for radiation diagnosis involving automatic set-up of acquisition parameters

Definitions

• PET positron emission tomography
• Positron emission tomography (PET) scanners typically include a cylindrical bore-type housing supporting several PET detector rings for detecting 51 1 keV gamma rays. These PET scanners have a field of view (FOV) with fixed axial and radial dimensions. Commercial PET scanners have been developed with increasingly large bore diameters, so as to accommodate larger patients. However, such designs increase the cost as the number of detectors increases with bore diameter.
• FOV field of view
• Commercial PET scanners have been developed with increasingly large bore diameters, so as to accommodate larger patients. However, such designs increase the cost as the number of detectors increases with bore diameter.
• the usual solution is to employ multi-stage imaging, in which the patient is stepped through the bore and imaged at several positions that overlap in the axial direction. These individual PET images are then“stitched” together at the axial overlaps to form a whole-body image (or other image with extended axial extent). This solution has disadvantages including potential for error at the stitched overlap regions, and increased imaging session time required to acquire the multiple
• the detectors can be sparsely populated around the circumference of each detector ring, so that each ring has a reduced number of PET detector modules so that more rings can be added to increase the axial FOV.
• Zhang et ah,“PET System With Crystal or Detector Unit Spacing”, WO 2015/019312 Al discloses embodiments of“sparse” designs, including embodiments in which the spacing(s) between adjacent detector rings can be adjusted for specific imaging tasks.
• an adjustable axial FOV is provided.
• Detector bars are arranged parallel to the axial axis of the bore of the PET scanner and populated along a circle surrounding the patient. The bars can shift in the axial direction relative to each other by the desired amount to achieve the desired axial FOV while keeping a central axial region into which all the bars extend, providing full detector coverage for this central axial region.
• the regions/organs of interest will be aligned with the central axial region to optimize the imaging for such regions/organs.
• a dual detector PET system includes two detector sets to image different portions of a patient and an adjustable detector ring having one set of detectors that can move in and out radially to form different size of transaxial rings to image patient of different sizes, while the other set of detectors can acquire data simultaneously if desired.
• a PET imaging device includes a plurality of PET detector modules; and a robotic gantry operatively connected to the PET detector modules.
• the robotic gantry is configured to control a position of each PET detector module along at least two of an axial axis, a radial axis, and a tangential axis of the corresponding PET detector module.
• a PET imaging device in another disclosed aspect, includes a plurality of PET detector modules; and a robotic gantry operatively connected to the PET detector modules.
• the robotic gantry is configured to control a position of each PET detector module along each of an axial axis, a radial axis, and a tangential axis of the corresponding radiation detector.
• a PET imaging device in another disclosed aspect, includes a plurality of PET detector modules and a plurality of radiation shields disposed in gaps between neighboring PET detector modules.
• a robotic gantry is configured to control a position of each radiation detector along at least two of an axial axis, a radial axis, and a tangential axis of the corresponding radiation detector.
• the robotic gantry is operatively connected to the radiation shields to selectively extend or retract individual radiation shields.
• a plurality of racks is connected to the robotic gantry and upon which the PET detector modules are mounted, each rack being oriented parallel with the axial direction of the bore and each PET detector module robotically movable in the axial direction along the rack supporting the PET detector module.
• PET positron emission tomography
• Another advantage resides in providing an imaging device with movable radiation detectors to increase or decrease an axial field of view of the imaging device with reduced loss of data coverage in the increased FOV configuration by way of oscillating the detector modules axially and/or tangentially to provide oversampling.
• Another advantage resides in providing an imaging device with an increased axial field of view and a reduced number of detectors.
• Another advantage resides in providing an imaging device with movable detectors that conform to a subject geometry of a patient.
• a given embodiment may provide none, one, two, more, or all of the foregoing advantages, and/or may provide other advantages as will become apparent to one of ordinary skill in the art upon reading and understanding the present disclosure.
• FIGETRES 1-3 diagrammatically show an image reconstruction system according to one aspect.
• FIGETRES 4 and 5 show exemplary flow chart operations of the system of FIGURES 1-3;
• FIGURES 6-1 1 show different example configurations of the system of
• FIGURES 1-3 are views of FIGS 1-3.
• the PET detector modules are mounted on racks, which are tracks that allow the PET detector modules to be moved longitudinally (i.e. axially, i.e. in the z-direction) along the length of the rack.
• each PET module is mounted to the rack via a robotic telescoping arm to provide for movement in the radial direction.
• each rack may be moved along the tangential (i.e. angular) direction.
• the flexibility also allows for non-uniform PET module positioning, for example in a cardiac scan the density of rings near to the heart location can be increased (up to having no gap between adjacent rings) relative to the peripheral rings.
• the PET modules can be moved during a PET imaging data acquisition. For example, if a larger axial FOV is achieved by way of spacing apart the neighboring PET rings, those rings could be moved during the acquisition so that there are no axial gaps in the final collected data set.
• a similar concept is "oversampling", in which detectors are moved back and forth during the acquisition to increase axial detector resolution; similar angular back and forth movement could be used to increase detector resolution in the tangential direction.
• different PET modules may comprise different detector types, e.g. a mix of TOF-PET modules and non-TOF-PET modules, and the configurability of the PET scanner leveraged to optimally position the mixture of PET module types.
• PET modules with larger density of dead pixels could be compensated by moving other PET modules with fewer dead pixels close by to compensate for the dead pixels.
• any PET scanner configuration for which the acquisition setup is less than ideal e.g. with gaps between rings or so forth
• the disclosed PET system may require different or additional configuration robotics as compared with the illustrative rack arrangement.
• detectors could additionally be provided with a tilt robotic adjustment, and two PET modules located between the breasts can be tilted to face the opposing breasts, thereby providing PET counts in those directions.
• two PET modules located between the breasts can be tilted to face the opposing breasts, thereby providing PET counts in those directions.
• the robotic controller tracks the current location (and angulation, in the case of tilting PET modules) of each PET detector module in order to accurately record the line of response (LOR) spatial trajectories.
• a detector is defined to have a nominal position (z, ,r, Q) where z is the default axial position, r is the default radial position, and Q is the default tangential (i.e. angular) position. This is updated in a particular PET module to a value (z + Az, r + Ar, q + DQ) where Az is the axial shift of the PET module along the rack, Ar is the radial shift of the PET module, and DQ is the tangential (angular) shift of the supporting rack.
• the LOR is then conventionally defined given the positions of the two involved detectors in three-dimensional space. Additionally, the sensitivity matrix used in PET image reconstruction may need to be adjusted, especially when the PET detector modules are configured to a non-uniform arrangement which may, for example, increase sensitivity near the center of the scanner versus the axial periphery by having a higher density of detector rings positioned at/near scanner center.
• PET scanner configuration for a particular imaging task can be variously chosen.
• the configuration is chosen manually, e.g. adding annular gaps between neighboring PET rings (or axial offsets between angularly neighboring racks) sized to achieve a desired axial FOV, setting radial positions of the PET modules to a minimum practical radial position for a patient of a certain girth, or so forth.
• IMRT Intensity-modulated radiation therapy
• the radiation sources configuration is chosen, the resulting dose (or fluence) distribution in the target modeled taking into account radiation absorption using an attenuation map, and the sources configuration updated to improve matching between the modeled dose or fluence distribution and dose optimization goals.
• the PET modules configuration can be chosen, the resulting counts distribution in the target modeled taking into account radiation absorption using an attenuation map, and the PET modules configuration updated to improve matching between the modeled counts distribution and dose optimization goals.
• the disclosed PET scanner configuration could in general be different for each bed position.
• the disclosed system contains multiple racks distributed along the frame of the gantry that surrounds the patient (and bed or pallet on which the patient lies).
• the racks are parallel to each other and they are all parallel to the axial axis of the gantry.
• the racks are sufficiently long for the maximal AFOV to be achieved.
• each rack can have multiple segmented pieces, and the segments can have offset in the plane perpendicular to the racks; racks or segments of racks can be in different orientations relative to each other and they don’t have to be parallel to each other, etc.
• the disclosed detectors can be designed as plug-in components with associated assembly peripherals.
• the detectors can be plugged into the racks and their positions on the racks can be independently controlled and is programmable by the system.
• the system can include a mechanism to allow the detector to move closer to or retract from an object of interest either by moving the racks or rack segments or by moving the PET detector modules.
• the system can also allow the detector to reorient to point to an object of interest.
• the PET detector modules includes a mechanism to move and reorient the detector as controlled by the system.
• the PET detector modules can include a collision detection and prevention mechanism.
• one or more pressure sensors (not shown) can be disposed at corners of the PET detector modules.
• One or more electronic processors can analyze pressure signals obtained by the pressure sensors to determine if a collision between PET detector modules (or between one of the PET detectors and a patient to be imaged) is occurring. The processors can then control the PET detector modules to move away from each other avoid a collision.
• each rack includes five detectors, and the detectors are pushed together to align all the detectors on all of the racks, the system configuration is the same as a conventional PET system with about 16 cm AFOV (assuming the detector assembly has dimension of 3.2 cm x 3.2 cm).
• the neighboring PET detector modules 18 can be positioned so that there is a pre-determined gap along the rack (along an axial direction).
• all the detectors on one rack can be moved together, but the detectors on different racks can be moved by different amounts.
• the previous two examples can be implemented in the disclosed PET system to increase the AFOV of image acquisition. These two example embodiments can be implemented to further increase the AFOV of the disclosed PET system. Since the pre-determined gaps between the detectors on the racks is programmable, the disclosed PET system has the flexibility of adjusting the gap as desired. For imaging of small organs/objects, the gap can be set to zero so that maximal sensitivity can be obtained using the same number of detector areas.
• the number of detectors on each rack can be different.
• one third of the racks of the gantry can have, for example, seven detectors (-22.4 cm), and the remaining portion of the racks can have, for example, four detectors each (-12.8 cm).
• the racks with seven detectors can provide an effective AFOV of 22.4 cm.
• the detectors on the four-detector racks can be shifted according to the intended application for optimal performance.
• the total number of detector area is the same as a system with five detectors on each rack (or a system with five fully populated rings), the effective AFOV of which, however, is increased from 16.4 cm to 22.4 cm.
• the configurable design of the disclosed PET system can allow the manufacturing of low-cost, high-performing, and scalable systems. For example, if each rack has three detectors, it is equivalent to a three-ring system with AFOV of 9.6 cm. ETsing the disclosed configurable design, the effective AFOV can be extended to that of five virtual rings, i.e., 16 cm.
• the three-ring system described above can be easily upgraded to a four-ring, a five-ring system, etc. by adding one or two detectors to each rack. This flexibility will significantly help customers with different upgrading needs.
• the position of the detectors can be controlled individually and optimized collectively for the intended applications using an optimization program (similar to that in radiation therapy in which the multi-leaf collimators openings, delivery length at each angle, etc. are optimized).
• the detectors are designed as swappable plug-in components, they can be shared among multiple systems as needed. For example, one or more detectors can (temporarily) be removed from an available three-ring system and use them on another three- ring system to achieve maximum effectiveness of a six-ring system. If the other system is a combined PET/CT system, removal of the PET detector modules 18 from the system does not impact the performance of the CT part of the system.
• the detectors can be turned or rotated to point to organs of interest and or move to and from the organs of interest to improve the sensitivity, reduce background activity impact, and improve the quality of the acquired data.
• the disclosed detector configuration can change during the scan via an optimization program. For example, for a multi-frame whole-body scan using step-and-shoot bed motion, the detectors can be positioned differently at the head, head/neck frames, torso, and lower body acquisition frame. This potentially reduces the total acquisition time and improve the clinical workflow and patient throughput.
• the disclosed racks are not necessarily implemented as racks in the system design if other alternatives are desired.
• a two-dimensional (2D) surface surrounding the patient can be designed as the base for detectors to be mounted/plugged.
• the position of the detectors on a 2D surface can be programmable.
• the detectors can also include the mechanism to reorient or move toward or away from the patient.
• the disclosed PET system can be transformed into a mammography PET scanner, forming the rings of PET detector modules 18 around patients breasts, with few extra detectors positioned to the sides and to the back of the patient for extra projection views to allow for complete tomographic data.
• the disclosed PET system can be transformed into brain PET scanner by forming the rings around patient head.
• the disclosed PET system can also be reconfigured into pre- clinical small animal scanner.
• an angle of a detector can be optimized by positioning the detectors closer to the patient’s body. To do so, the thickness of the detector crystals can be reduced in order to minimize the effect of depth-of-interaction (DOI). This potentially reduces the cost of goods for the production while the effective sensitivity of the PET camera would still be large due to optimized solid angle.
• DOE depth-of-interaction
• the detectors can have different configurations, or can be positioned closer to the patient with a smaller crystal size, for optimization optimized for higher spatial resolution.
• an illustrative positron emission tomography (PET) imaging system or device 10 receives a patient (not shown) into an examination region 11 for PET imaging.
• the imaging system 10 is described herein as a PET scanner, the imaging system can be any other suitable imaging modality (e.g., a gamma camera for a single photon emission computed tomography (SPECT) imaging device, a hybrid SPECT/PET imaging device, and so forth).
• the PET scanner 10 is controlled by a PET controller 12, e.g. a computer or other electronic device including a microprocessor, microcontroller, or the like.
• the PET scanner 10 employs a robotic gantry that is controlled by a robotic controller 14.
• the PET scanner 10 is shown in FIGETRE 1 in side-sectional view, and is seen to include a plurality of PET detector modules 18 supported by a robotic gantry 20 which in this illustrative embodiment includes a plurality of supporting racks 24.
• Each PET detector module 18 includes an array of radiation detector pixels comprising suitable radiation detector devices (details not shown), such as scintillator crystals of a material that absorbs 51 1 keV gamma rays and generates a scintillation with each 51 1 keV absorption coupled with photomultiplier tube (PMT), digital or analog silicon photomultiplier (SiPM), or other detectors arranged to detect the scintillations generated in the scintillator crystals.
• suitable radiation detector devices such as scintillator crystals of a material that absorbs 51 1 keV gamma rays and generates a scintillation with each 51 1 keV absorption coupled with photomultiplier tube (PMT), digital or analog silicon photomulti
• the detailed configuration may be various, e.g. a one-to-one arrangement in which each detector pixel comprises a corresponding scintillator crystal and SiPM or other detector, or a distributed arrangement such as a large area scintillator crystal optically coupled with a plurality of PMTs, SiPMs, or so forth and employing Anger logic to localize each 51 1 keV detection event, or so forth.
• FIGETRES 2 and 3 illustratively show the PET imaging system 10 in more detail.
• the PET imaging device 10 includes a plurality of PET detector modules 18 arranged to obtain PET imaging data of a patient in the examination region 16.
• the plurality of PET detector modules 18 can be identical to each other.
• At least one of the PET detector modules 18 is different from another one of the PET detector modules according to: a material used to construct the radiation detectors of the PET detector module, one of the PET detector modules comprising time-of-flight detectors and another of the PET detector modules comprising non-time of flight radiation detectors, one of the PET detector modules includes time-of-flight PET detector modules having a different time-of flight-resolution than another one of the PET detector modules comprising time-of-flight PET detector modules; one of the PET detector modules including crystals of at least one of a different size and length than crystals of another one of the PET detector modules; and/or so forth.
• a robotic gantry 20 is operatively connected to the plurality of PET detector modules 18.
• the robotic gantry 20 configured to control a position of each PET detector module 18 along an axial axis z and/or a radial axis r (FIGETRE 2) and/or a tangential axis 0 (FIGURE 3) of the corresponding radiation detector.
• the robotic gantry 20 is configured to independently control a position of each PET detector module 18 along two or more of the axial axis z, the radial axis r, and the a tangential axis Q of the corresponding radiation detector.
• each PET detector module 18 comprises a one- or two- dimensional array of PET detector pixels supported on a common substrate or housing to move together as a unit.
• the robotic gantry 20 operates to move the PET detector modules 18, or at least groups of the PET detector modules 18, independently of one another, thereby permitting the plurality of PET detector modules 18 to be arranged in any of a wide range of different configurations.
• the PET detector modules 18 of the PET imaging system 10 are arranged around a bore that, in the illustrative example, is a horizontal cylindrical bore having a defined bore axis 22, which is parallel to the axial axis z of the PET detector modules 18.
• a plurality of racks 24 are disposed around the bore axis 22.
• Each PET detector module 18 is mounted to one of the racks 24.
• Each rack 24 is oriented parallel with the bore axis 22.
• Each PET detector module 18 is robotically movable in the axial direction (i.e. parallel with the bore axis 22, or equivalently along the axial axis z of the PET detector module 18) along the rack 24 supporting the PET detector module 18.
• upper and lower racks 24 (and supported PET detector modules 18) are shown on opposing sides of the bore axis 22 (the racks are mirror images of each other, but for clarity, some reference characters are included only for the“top” rack and other reference characters are included only for the“bottom” rack).
• FIGURE 3 which shows an end view of the PET scanner 10
• a telescoping arm 26 is connected to, and supports, each PET detector module 18.
• the telescoping arms 26 are operable to move the supported PET detector modules 18 along the radial axis r of the radiation detector, i.e. toward or away from the imaging subject disposed in the bore of the PET scanner 10 (or, equivalently, toward or away from the bore axis 22).
• the robotic gantry 20 further includes a plurality of rack support arcs or rings 28 each at least partially encircling the bore 22 of the imaging device 10.
• rack support arcs or rings 28 each at least partially encircling the bore 22 of the imaging device 10.
• only one rack support ring 28 is visible, but typically multiple such support rings 28 are provided, e.g. one at each of the two opposite ends of the racks 24 and optionally one or more additional intermediate rack support rings in-between to provide additional support.
• a single rack support ring may be provided which extends the full axial length of the PET scanner 10, so that this single rack support ring is a cylinder axially coextensive with the racks 28.
• the one or more rack support arcs or rings 28 include robotic links operable to move each rack 24 along a tangential axis Q transverse to the rack (see FIGURE 3), thereby moving the connected PET detector modules 18 along the tangential direction t (see FIGURE 3).
• the PET imaging device 10 also optionally includes a plurality of radiation shields 32 disposed in gaps between axially neighboring PET detector modules 18. While not illustrated, it is similarly contemplated to include radiation shields disposed in gaps between tangentially neighboring PET detector modules 18.
• the robotic gantry 20 is operatively connected to the radiation shields 32 by telescoping arms 33 to selectively extend or retract individual radiation shields 32.
• the pair of radiation shields 32 disposed at the ends of the robotic gantry 20 are extended past the PET detector modules 18 to provide radiation shielding, e.g. to reduce the detection of spurious out-of-axial FOV radiation, while the radiation shields 32 disposed between radiation detectors are retracted such that the PET detector modules 18 extend past the radiation shields.
• the PET detector modules 18 can include a collision detection and prevention mechanism including one or more pressure sensors 34.
• one or more pressure sensors 34 can be disposed at corners of the PET detector modules 18.
• the PET controller 12 can analyze pressure signals obtained by the pressure sensors 34 to determine if a collision between neighboring PET detector modules (or between one of the PET detector modules and a patient to be imaged) is occurring. The PET controller 12 can then control the PET detector modules 18 to move away from each other avoid a collision.
• the robotic controller 14 comprises an electronic processor programmed to: determine a desired change in position along at least one of the axial axis z, the radial axis r, and the tangential axis Q of the corresponding PET detector modules 18; and move the corresponding radiation detector along the determined change.
• the at least one electronic processor 12, 14, 40 is operatively connected with one or more non-transitory storage media 46 (such as a magnetic disk, RAID, or other magnetic storage medium; a solid state drive, flash drive, electronically erasable read-only memory (EEROM) or other electronic memory; an optical disk or other optical storage; various combinations thereof; or so forth) which stores instructions which are readable and executable by the at least one electronic processor 12, 14, 40 to perform operations disclosed herein such as performing a detector configuration update method or process 100, 200 (see FIGETRES 4 and 5) to configure the PET imaging device 10 for a received imaging subject geometry and/or for a received imaging task, and to perform an imaging data acquisition and image reconstruction process 48 which includes detecting coincidence events each comprising a pair of 511 keV detection events detected by PET detector modules 18 within a coincidence time window, and reconstructing the coincidence events to generate a reconstructed PET image.
• non-transitory storage media 46 such as a magnetic disk, RAID, or other magnetic storage medium; a solid state drive, flash drive
• the image reconstruction may employ any suitable image reconstruction algorithm, e.g. maximum likelihood-expectation maximization (MLEM), ordered subsets expectation maximization (OSEM), or so forth, and may incorporate scatter correction, edge preserving regularization, and/or other techniques for enhancing image quality as are known in the art.
• MLEM maximum likelihood-expectation maximization
• OSEM ordered subsets expectation maximization
• the image reconstruction may leverage the TOF information in the image reconstruction.
• an illustrative embodiment of a detector configuration update method 100 is diagrammatically shown as a flowchart.
• the PET detector modules 18 are configured, or controlled by the at least one electronic processor (i.e. robotic controller 14), to acquire phantom data of a subject in both a desired configuration and an undesired configuration of the radiation detectors.
• the at least one electronic processor 40 is programmed to apply a machine-learned transform to the acquired phantom or patient data to adjust the PET detector modules 18 from the undesired configuration to the desired configuration of the PET detector modules 18.
• the at least one electronic processor 40 is programmed to determine a configuration of the PET detector modules 18.
• the configuration of the PET detector modules 18 is determined for a received imaging subject geometry (e.g., one or more breasts).
• the at least one electronic processor 40 is programmed to determine the detector configuration including axial positions of the PET detector modules 18 to encompass the received imaging subject geometry radial positions of the radiation detectors determined based on a girth of the received imaging subject geometry.
• the at least one electronic processor 40 is programmed to determine the detector configuration comprising positioning of the PET detector modules 18 conformably with at least one surface of the received imaging subject geometry.
• the at least one electronic processor 40 is programmed to acquire imaging data with the configuration of the PET detector modules 18. To do so, the at least one electronic processor 40 is programmed to operate the robotic gantry 20 to arrange the plurality of PET detector modules 18 in the determined detector configuration. With the plurality of PET detector modules 18 arranged in the determined detector configuration, the at least one electronic processor 12, 14, 40 is programmed to control the robotic gantry 20 to acquire imaging data using the PET detector modules and reconstruct the imaging data to generate a reconstructed image. In some examples, the at least one electronic processor 12, 14, 40 is further programmed to, during the acquisition of imaging data, operate the robotic gantry 20 to oscillate the PET detector modules 18 in at least one of the axial direction and the tangential directions, so as to perform oversampling.
• the PET detector modules 18 are disposed in a predefined range along at least one of the two directions (z, r, and Q).
• the PET detector modules 18 can be controlled by the robotic gantry 20 to move the PET detector modules to a different location, either continuously or in multiple steps for data acquisition. When a scan is done, PET detector modules 18 can resume an original position.
• the illustrative robotic gantry 20 of FIGETRES 1 -3 is an illustrative example. Different and/or additional configuration robotics are also contemplated. It will be appreciated that not all three of the axial (z), radial (r), and tangential (t) degrees of freedom may be provided. For example, a robotic gantry providing the axial (z) and radial (r) degrees of freedom, but not the tangential (t) degree of freedom, can be useful in accommodating patients of different heights (corresponding to axial“length” when the patient is lying in a prone or supine position along the bore axis 22) and different girths.
• a robotic gantry providing the axial (z) and tangential (Q) degrees of freedom, but not the radial (r) degree of freedom, can be useful in accommodating patients of different heights and also employing fewer PET detector modules by providing for gaps between adjacent detector modules along the circumferential direction.
• the robotics for positioning the PET detector modules could optionally be provided with a tilt robotic adjustment (not shown).
• two PET modules can be placed between the breasts, with one tilted to face the left breast and the other tilted to face the right breast, thereby providing PET counts in those directions.
• imaging data can be collected for both breasts simultaneously.
• the robotic controller 14 tracks the current location (and angulation, in the case of tilting PET detector modules) of each PET detector module 18 in order to accurately record the line of response (LOR) spatial trajectories of coincidence events.
• a PET detector module is defined to have a default position and a given detector on that module then has a nominal position (z, r, Q ) where z is the default axial position, r is the default radial position, and Q is the default tangential (i.e. angular) position of the detector.
• each 51 1 keV detection event in PET detector module coordinates is transformed to a location in PET imaging device coordinates by shifting the location of the 51 1 keV detection event in PET detector module coordinates in accord with the position of the PET detector module along the axial axis (z), the radial axis (r), and the tangential axis (t) of the PET detector module containing that radiation detector.
• the LOR is then defined as connecting the locations of the pair of 51 1 keV detection events in PET imaging device coordinates.
• the sensitivity matrix used in PET image reconstruction 48 may need to be adjusted, especially when the PET detector modules are configured to a non-uniform arrangement which may, for example, increase sensitivity near the center of the PET scanner 10 versus the axial periphery by having a higher density of PET detector modules positioned at or near scanner center.
• the at least one electronic processor 40 is programmed to repeat the determination of the detector configuration, the operating of the robotic gantry 20 to arrange the plurality of PET detector modules 18 in the determined detector configuration, and the acquisition of imaging data for a plurality of bed positions to perform multi-station imaging.
• the at least one electronic processor 40 is programmed to model a counts distribution of the acquired imaging data using an attenuation map and a dose distribution.
• the at least one electronic processor 40 is programmed to update the configuration of the PET detector modules 18 with the counts distribution and the dose distribution.
• the PET detector modules 18 are configurable in many suitable desired configurations.
• the PET detector modules 18 can be configured as tiles, and designed as plug-in components.
• the PET detector modules 18 can be plugged into the racks 24 to face the patient, and can also be move to and from the patient and reorient to the regions of interest for optimized imaging.
• the imaging system 10 can include optimization software to compute the optimal position/orientation of each PET detector module 18 according to the imaging task. For example, for a system with PET detector modules 18 equivalent to a conventional five- ring system with AFOV of 16.4 cm, if the imaging task needs an effective AFOV greater than 16.4 cm, the system can program AFOV extension and move the PET detector modules 18 accordingly to achieve the desired AFOV.
• FIGETRES 6A-6C show different possible configurations of the PET detector modules 18.
• FIGETRE 6A shows configurable PET detector modules 18 on each of the racks (not shown in FIGETRE 6A) positioned next to each other, and detectors on different racks are aligned with the axial axis of the detectors. This configuration has an AFOV of 16.4 cm.
• the PET detector modules 18 can be moved to increase the AFOV to 19.6 cm for cardiac scans (as shown in FIGETRE 6B), or to 22.8 cm (as shown in FIGETRE 6C) in, for example, pulmonary or head and neck scans.
• FIGETRE 7 shows the PET detector modules 18 in a conventional three ring system (shown on the“left” side of FIGETRE 7) can be manipulated to have the AFOV of a conventional five-ring system (as shown on the“right” side of the FIGETRE 7).
• Data simulated from a real acquisition showed the reconfigurable system had 35% the total counts as a conventional five-ring system.
• the reconstructed images showed higher noise level but no degradation to the image quality otherwise.
• FIGETRE 8 shows two other configurations of the PET detector modules 18 to extend the AFOV of the imaging system 10 from 16.4 cm to 22.8 cm.
• a gap can be formed between individual PET detector modules 18 to achieve the desired AFOV.
• the gap can be set to 3.2 cm, and the shift in the gaps can be 1.6 cm to achieve the AFOV of 22.8 cm.
• the racks 24 can include different numbers of PET detector modules 18.
• the top and bottom racks 24 can include seven PET detector modules 18, while the middle racks 24 can include four radiation detectors to achieve the AFOV of 22.8 cm.
• FIGURES 9A-9D show other examples of detector configurations to achieve an AFOV 22.8 cm.
• FIGURE 9A shows a middle rack 24 having only three PET detector modules 18 to achieve a 20% reduction of detectors to achieve the AFOV of 22.8 cm.
• FIGURE 9B shows a middle rack 24 having only two PET detector modules 18 to achieve a 30% reduction of detectors to achieve the AFOV of 22.8 cm.
• FIGURE 9C shows a first middle rack 24 having only three PET detector modules 18, and a second middle rack having only two radiation detectors to achieve a 33% reduction of detectors to achieve the AFOV of 22.8 cm.
• FIGURE 9D shows alternating racks 24 having two and three PET detector modules 18 to achieve a 50% reduction of detectors to achieve the AFOV of 22.8 cm.
• the optimization program can reconfigure/position the PET detector modules 18 in different ways. Since the optimization program can reorient or move the PET detector modules 18 towards or away from the patient, the performance can further improved as compared to brutal force cost reduction through reducing the amount of detectors. In other words, the sensitivity decreases due to the reduction of detectors can be fully or partially compensated by the optimization program.
• FIGURE 10 shows potential programmable configurations for imaging large and small objects.
• a portion of the PET detector modules 18 move in radially to get closer to the patient for better sensitivity and resolution, but can program the rest of the detectors to form additional rings or partial rings according to the configuration program, to extent the effective AFOV to further improve image sensitivity.
• a large AFOV is desired to image large objects
• a smaller a FOV is desired to image smaller objects (as shown in the central left portion of FIGURE 10).
• FIGURE 1 1 shows a PET system 10 optimized for mammography studies. As shown in FIGURE 1 1 shows that individual PET detector modules 18 can be positioned to image individual breasts (e.g., detectors are positioned to conform to the geometry of the breasts).
• the system 10 shown in FIGURE 1 1 can be configured for optimized brain imaging in which a portion of the detectors can be configured to form a small rings as a conventional dedicated brain PET scanner, then some detectors can be configured to face the brain from the top of the head and some face the brain from the chin, based on the available space between patient chin and torso.
• the above-described examples can be optimized based on patient size, imaging protocol, CT information, etc. to optimize the position, orientation, etc. of each PET detector module 18.
• the PET detector modules 18 are positioned based on the programmed optimized position/orientation prior to or during the scans.
• a CT surview image is used to define the patient dimension and location in the imaging space.
• the optimization program can determine which PET detector modules 18 can be moved closer to the patient to form a ring or partial ring of smaller radius to surround the patient for optimal imaging.
• a system is configured as a conventional PET/CT system with AFOV of 16.4 cm for cardiac scans.
• CT image (e.g., surview) shows that the patient heart has a dimension of 15 cm in the axial direction. Imaging using conventional configuration with AFOV of 16.4 will lead to significantly higher noise level near the ends of the AFOV, also correction of scatter is challenging.
• the system can be configured to have an AFOV of 19.6 cm to allow high quality cardiac scan in one frame. Such optimization can be realized by moving the PET detector modules 18 to form a desired geometry, or by introducing gaps between PET detector modules 18 on the racks while the gap size and pattern are obtained from the optimization program.
• a CT image (e.g., surview image) shows that the patient heart has a dimension of 15 cm in the axial direction. Imaging using the conventional configuration with AFOV of 16.4 leads to significantly higher noise level near the ends of the AFOV.
• the system can be configured to have an AFOV of 19.6 cm to allow high quality cardiac scan in one frame. Such optimization can be realized by moving the PET detector modules 18 to form a desired geometry, or by introducing gaps between radiation detectors on the racks while the gap size and pattern are obtained from the optimization program.
• the optimization program can include an optimization program described in co-pending Application Serial No.
• the plug-and-play configuration of the PET detector modules 18 allows for easy upgrade and maintenance, e.g., from conventional three-ring system to a five-ring system by adding two detectors on each rack in a plug-and-play model. This allows for detector sharing between scanners, maximization performance/cost for sites with multiple systems, and minimizing costs for maintenance etc.
• the dynamic configuration of the PET detector modules PET detector modules 18 allows for a change to compensate for the speed ramping-up and ramping-down sensitivity change during a continue-couch-motion scan.
• This configuration can change during a whole- body scan to allocate better sensitivity for regions of interest, e.g. tumor area.
• the dynamic configuration can allow for a change during a whole-body scan to allocate less sensitivity (e.g., enlarged crystal axial distance) to less important region in the image to allow fast scans, (e.g. a leg area without a tumor). This potentially reduces the total acquisition and improve the clinical workflow and patient throughput.

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