Canon Medical Systems Corporation

Kabushiki Kaisha Toshiba

Toshiba Medical Systems Corporation

Xiaoli Li

Yi Qiang

Kent C Burr

Peng Peng

Wenyuan Qi

Li Yang

Evren Asma

Jeffrey Kolthammer

Daniel Gagnon

Manabu Teshigawara

Gin-Chung Wang

Huini Du

Masaki Miyahara

A positron emission tomography (PET) scanner is provided having a plurality of detector subsystems, including processing circuitry to determine, for each detector subsystem of the plurality of detector subsystems, a singles count loss correction factor of the detector subsystem; determine, for each detector subsystem pair of a plurality of pairs of the detector subsystems, a coincidence count loss correction factor for the detector subsystem pair; calculate a scanner coincidence count loss correction factor for the PET scanner based on the coincidence count loss correction factors determined for the plurality of pairs of the detector subsystems; and reconstruct an image based on the calculated scanner count loss correction factor and scan data acquired from a scan of a patient performed using the PET scanner.

Method for correction of correlated count losses

An apparatus for reconstructing a positron emission tomography (PET) image, comprising processing circuitry configured to extract, from raw data obtained from a PET scanner, energy data and timing data associated with a plurality of annihilation events, the extracted energy data and the extracted timing data for each annihilation event corresponding to interactions between each of a pair of gamma rays generated by each annihilation event and one or more gamma ray detectors of the PET scanner, classify each annihilation event based on respective extracted energy data and respective extracted timing data, determine, for each annihilation event and based on a calculated timing resolution of the annihilation event, a width of a time-of-flight kernel, and reconstruct, by processing circuitry, the PET image based on the obtained raw data from the PET scanner and the determined width of the time-of-flight kernel associated with each annihilation event.

Methods and systems for reconstructing a positron emission tomography image

A method is provided for count loss correction based on detector dead time in a radiation diagnosis apparatus. The method includes acquiring scan data from a scan of a patient performed using the radiation diagnosis apparatus; determining, from the acquired scan data, a first count rate occurring in a first energy window spanning a first energy range; determining, from the acquired scan data, a second count rate occurring in a second window spanning a second energy range, the second energy range being different from the first energy range; calculating a particular count loss correction factor based on the determined first count rate and the determined second count rate; and reconstructing an image based on the acquired scan data and the calculated particular count loss correction factor.

Method to detect energy-dependent count loss

A method is provided for determining a scatter fraction for a radiation diagnosis apparatus. The method includes acquiring an energy spectrum from list mode data obtained from a scan performed using the radiation diagnosis apparatus; determining, from the acquired list mode data, a first number of events occurring in a first energy window spanning a first energy range; determining, from the acquired list mode data, a second number of events occurring in a second window, the second energy window spanning a second energy range different from the first energy range; calculating a singles scatter fraction based on the determined first number of events and the determined second number of events; and reconstructing an image based on the acquired list mode data and the calculated singles scatter fraction.

Energy-based scatter fraction estimation and scatter correction

In a gamma-ray detector system, such as a PET detector, coincidence events between multiple detector elements can be caused by inter-detector scattering and/or energy escape of the multi-stage radiation background in the scintillator crystals. Because these types of coincidence events are more likely to happen between nearby elements, they can be measured, analyzed and ultimately used to identify arrangement errors of detector elements in a gamma-ray detector system.

Identifying arrangement errors of detector elements within a gamma-ray detector system

A method and apparatuses for a radiation detector apparatus, comprising a scintillator array comprising a plurality of scintillator crystals. The plurality of scintillator crystals includes a first scintillator crystal and a second scintillator crystal adjacent to the first scintillator crystal within the scintillator array. A photosensor array comprising a plurality of photosensors including a first photosensor configured to detect photons from the first scintillator crystal. A first separator positioned between the first scintillator crystal and the second scintillator crystal. First separator optically separates the first scintillator crystal and the second scintillator crystal such that the first photosensor detects photons from the first scintillator crystal and not from the second scintillator crystal.

Method and apparatus for improved photosensor light collection in a radiation detector

A method of normalizing detector elements in an imaging system is described herein. The method includes a line source that is easier to handle for a user, and decouples the normalization of the detector elements into a transaxial domain and an axial domain in order to isolate errors due to positioning of the line source. Additional simulations are performed to augment the real scanner normalization. A simulation of a simulated line source closely matching the real line source can be performed to isolate errors due to physical properties of the crystals and position of the crystals in the system, wherein the simulated detector crystals are otherwise modeled uniformly. A simulation of a simulated cylinder source can be performed to determine errors due to other effects stemming from gaps between the detector crystals.

Method and system for PET detector efficiency normalization

A circuit for receiving signals from a photodetector array arranged to detect signals generated by a crystal includes a plurality of summing circuits having weighting circuits, the summing circuits being configured to produce outputs corresponding to a total energy of the signals, a position of the signals in a first dimension of the photodetector array, a position of the signals in a second dimension of the photodetector array, and a radius of a charge distribution of the signals.

Summing circuit for positron emission tomography diagnostic apparatus

A method and system for providing improved timing calibration information for use with apparatuses performing Time of Flight Positron Emission Tomography scans. Relative timing offset, including timing walk, within a set of processing units in the scanner are obtained and corrected using a stationary limited extent positron-emitting source, and timing offset between the set of processing units is calibrated using an internal radiation source, for performing calibration.

Timing calibration using internal radiation and external radiation source in time of flight positron emission tomography

A method and apparatus are provided for nonlinear energy correction of a gamma-ray detector using a calibration spectrum acquired from the background radiation of lutetium isotope 176 (Lu-176) present in scintillators in the gamma-ray detector. Further, by periodically acquiring Lu-176 spectra using the background radiation from the scintillators, the nonlinear energy correction can be monitored to detect when changes in the gamma-ray detector cause the detector to go out of calibration, and then use a newly acquired Lu-176 spectrum to update the calibration of the nonlinear energy correction as needed. The detector calibration is performed by comparing a reference histogram to a calibration histogram generated using the nonlinear energy correction, and adjusting the parameters of the nonlinear energy correction until the two histograms match. Alternatively, the detector calibration is performed by comparing reference and calibration values for specific spectral features, rather than for the whole Lu-176 spectrum.

Method and apparatus to use a broad-spectrum energy source to correct a nonlinear energy response of a gamma-ray detector

A method and apparatus are provided for positron emission imaging to calibrate energy measurements of a pixilated gamma-ray detector using energy calibration based on a calibration with a distribution energy signature (i.e., having more spectral features than just a single full-energy peak). The energy calibration can be performed using a deep learning (DL) network or a physics-based model. Using the DL network, a calibration spectrum is applied to either generate the measured-signal values of known energy values (e.g., spectral peaks for spectra of various radioactive isotopes) or the parameters of an energy-calibration function/model.

A method and apparatus are provided for positron emission imaging to calibrate timing of a pixelated gamma detector using multi-channel events. The apparatus can include processing circuitry configured to obtain calibration data representing a time and a position at which gamma rays are detected at a plurality of detector elements, and determine which gamma-ray detections of the calibration data correspond to multi-channel detections in which energy of a respective gamma ray is shared and detected by two or more of the plurality of detector elements. Additionally, the processing circuitry can be configured to determine a timing calibration of the plurality of detector elements by optimizing an objective representing agreement between time data of the multi-channel detections in the calibration data and the timing calibration.

Method and apparatus to calibrate timing of a detector using multi-channel events

A method and apparatus are provided for positron emission imaging to calibrate energy measurements of a pixilated gamma-ray detector using energy sharing events between channels of the detector. Due to conservation of energy, when the energy of a single gamma ray shared among multiple channels, the sum of measured energies across the respective channel must equal the original energy of the incident gamma ray. Further, the fractions of the original energy distributed to the respective channels can span the entire range of zero to the original energy. Thus, a single gamma-ray source (e.g., cesium isotope 137) can be used to continuously calibrate the nonlinear energy response of the detector over an entire range of interest.

Method and apparatus to use a single energy source to determine energy correction for a gamma detector

A method and apparatus are provided for positron emission imaging to correct a position at which a gamma ray was detected, when the gamma ray is scattered during detection. When Compton scattering occurs during detection of a gamma ray, the energy of the gamma ray deposited in multiple crystals in an array of detector elements. The corrected position is determined as a weighted sum of the position of the multiple crystals, each weighted by an inverse of the energy measured at the respective crystal. Further, the inverse-energy weight can be raised to a power p. A minimum energy threshold can be applied to determine the multiple crystals at which the gamma ray energy is deposited. The corrected position can be a floating position or can be rounded to a nearest crystal or to a nearest virtual sub-crystal.

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Vernon Hills, IL, United States of America

Xiaoli Li