Canon Medical Systems Corporation

Yi Qiang

Xiaoli Li

Kent C Burr

Wenyuan Qi

Evren Asma

Peng Peng

Jeffrey Kolthammer

Li Yang

Xiaohui Zhan

Yujie Lu

Xiaochun Lai

Vishnu Balaraman

Ehod Elran

Zhou Yu

Manabu Teshigawara

Liang Cai

Chung Chan

Huini Du

Kevin Christopher Zimmerman

Karthikayan Balakrishnan

Steve F Ross

Zhihong Ye

Masaki Miyahara

Nikolay Markov

Cameron Clarke

An apparatus and a method for detection of defective pixels for a photon-counting detector-based computed tomography (CT) system is disclosed. In particular, the apparatus and the method disclosed herein, detect detector pixels that have intermittent behavior using on-the-fly defective pixel screening based on various criteria during an object scan. The defective pixels are discarded using a defective pixel map before image reconstruction.

Method for detecting and handling detector pixels with intermittent behavior for a small pixelated photon counting computed tomography (CT) system

An apparatus and method are provided to correct for time-walk errors during photon detections (e.g., detecting gamma rays). A time-walk correction is determined using measurements of energy (or charge) that apply different time windows, enabling corrections accounting for variations in the ratio between fast and slow components in the detected pulse. For example, one time window can be used to integrate the leading end of the pulse, thereby predominantly measuring the fast component, while a second window is used to integrate a trailing end of the pulse to predominantly measure the slow component. Alternatively or additionally, low-pass and high-pass filters may select the slow and fast components, respectively. The time-walk correction is a function of multiple measurements representing different components (e.g., fast and slow) of the pulse shape.

Time-walk correction using multiple energy measurements

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

A PET scanner includes gamma-ray detector rings that form a bore through which an imaging subject is translated, a length of the bore defining an axial length of the PET scanner, the gamma-ray detector rings being movable along the axial length, the gamma-ray detector rings including gamma-ray detector modules therein, and processing circuitry configured to receive PET data associated with a plurality of transaxial slices of the imaging subject, the PET data including a first set of spatial information and timing information corresponding to a first data acquisition period for the gamma-ray detector modules in a first axial position and a second set of spatial information and timing information corresponding to a second data acquisition period for the gamma-ray detector modules in a second axial position, and reconstruct a PET image based on the first set of spatial and timing information and the second set of spatial and timing information.

Pet reconstruction for adjustable pet system

An apparatus for calibrating a detector, including acquiring an energy spectrum obtained from a scan using an X-ray tube as a source of radiation, estimating calibration parameters, such as a gain and an offset, for each of several channels of the detector by applying the acquired first energy spectrum to inputs of a trained neural network that outputs the calibration parameters, and calibrating each of the plurality of channels using the estimation parameters. The neural network is trained to produce target output calibration parameters, using two or more measurements selected from isotope peak positions, K-edge absorption features, or K-edge emission peaks.

PCCT energy calibration from X-ray tube spectra using a neural network

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

Existing, low quality images can be restored using reconstruction or a combination of post-reconstruction techniques to generate a real patient phantom. The real patient phantom (RPP) can then be simulated in Monte Carlo simulations of a higher performance system and a lower performance system. Alternatively, the RPP can be simulated in the higher performance system, and a real scan can be performed by an existing, lower performance system. The higher performance system can be differentiated from the lower performance system in a variety of ways, including a higher resolution time of flight measurement capability, a greater sensitivity, smaller detector crystals, or less scattering. A neural network can be trained using the images produce by the higher performance system as the target, and the images produced by the lower performance system as the input. After training, the trained neural network can be used to output input images taken in a lower performance system with higher performance system characteristics.

Neural network for improved performance of medical imaging systems

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 guided pairing method includes generating a singles list by detecting a plurality of singles at a plurality of detector elements in a detector array, the plurality of singles falling within a plurality of detection windows; for each detection window of the plurality of detection windows in the singles list having exactly two singles of the plurality of singles, determining the line of responses (LORs) for each of the two singles of the plurality of singles; for each detection window of the plurality of detection windows in the singles list having more than two singles of the plurality of singles, determining all coincidences possible based on the more than two singles; generating a weight for said each coincidence of the coincidences based on the determined LORs for said each of the two singles of the plurality of singles; and pairing the more than two singles based on the generated weight for said each coincidence of the coincidences.

Method and apparatus for guided pairing of multi-coincidences for time of flight positron emission tomography

A method of grouping detection events in an imaging apparatus is described herein. The detection events can include primary detection events and secondary scattered events, which are frequently discarded due to the secondary scattered events, thus reducing sensitivity of the dataset for eventual image reconstruction. The method includes cell modules cascaded with identical parametrized cells, in a pipeline fashion, having the last cell in the chain circle back to the first cell. A rotating data pointer indicates the location of the first entry in the cell pipeline. The described method enables the grouping of multiple samples of detector data in real time with no loss of information, based on a time and location of the detected event. The method can be implemented in an FPGA as a hardware-based real time process.

Method and apparatus for using a parameterized cell based circular sorting algorithm

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.

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Vernon Hills, IL, United States of America

Yi Qiang