Adac Laboratories, Inc.

Peter Nellemann

Horace H Hines

Hugo Bertelsen

Donald R Wellnitz

Matthew J Murphy

Lingxiong Shao

Gerd Muehllehner

Edward M Goldberg

David Coles

Lingxion Shao

Jacobus Koster

Ian Farmer

A dual-purpose transmission source for use in a nuclear medicine imaging system is described. A Cs-137 point source is used to transmit radiation having a 662 keV photopeak to a corresponding detector during a transmission scan of an object. The Cs-137 source can be used in transmission scans for correcting either coincidence or single-photon emission data for non-uniform attenuation. When performing a transmission scan to correct single-photon emission data, a collimator may remain mounted to the detector, since a substantial portion of the transmitted radiation completely penetrates the radiation-absorbing material of the collimator to reach the detector.

Dual-purpose radiation transmission source for nuclear medicine imaging

A method of correcting for deadtime in an attenuation map generated by a nuclear medicine imaging system is provided. The imaging system includes a gamma ray detector that is rotatable about an object to be imaged. A region is defined on the imaging surface of the detector, such as the edge of the field of view of the detector, such that during a transmission scan of the object, the radiation shadow of the object is substantially less likely to fall upon the defined region than upon other regions of the imaging surface. A blank transmission scan is then performed, including recording the radiation intensity level detected in the region as a reference intensity level. A transmission scan of the object is then performed to acquire an attenuation map of the object, including recording a radiation intensity level detected in the first region during the transmission scan. A correction value is then determined as the ratio of the reference intensity level to the intensity level detected in the region during the transmission scan. The attenuation map is then corrected for deadtime based on the correction value.

Deadtime correction in a nuclear medicine imaging system

A nuclear camera system includes a pair of detectors orientated 180 degrees apart about an axis of rotation for detecting radiation emitted from an object, a pair of single-photon radiation point sources for transmitting radiation through the object, each to a different detector, and a gantry supporting the detectors and the radiation sources. The gantry provides rotation of the detectors and the radiation source about the axis of rotation, such that the angular positions of the radiation source about the axis of rotation remain fixed relative to the angular positions of the detectors. The camera system further includes a processing system coupled to control the dectors and the radiation sources and to selectably configure the detectors for either coincidence or single-photon emission imaging. The processing system controls the detectors to acquire coincidence emission data of the object and controls the single-photon point sources to acquire transmission data of the object, wherein the radiation from the point sources has a fanbeam illumination profile. The processing system corrects the acquired coincidence emission data for attenuation using the transmission data.

Dual-mode gamma camera system utilizing single-photon transmission

A correction system for correcting and maintaining the baseline offset signal value of a PMT channel of a scintillation detector at a predetermined value. The correction system utilizes an event driven mode wherein the correction is performed based on detected gamma interactions and this mode is utilized during periods of high count rate. Using the event driven correction mode, the system provides an output of far PMT channels based on a detected peak PMT channel. In a second mode, software driven correction, false triggers are inserted into the processing logic to initiate sampling of the baseline offset signal value and 'simulate' gamma interactions. The false triggers are used by the system to perform baseline correction. The second mode is used during periods of lower count rate. Under both modes, the system effectively samples the baseline offset values from a channel that detects substantially no light energy to sample the baseline offset amount. This sampled value is averaged and compensated for against an ideal reference value, Vm. This is performed independently for each channel.

Software and event driven baseline correction

A dual head nuclear camera system automatically switchable (and optimized) to perform either SPECT imaging or PET imaging that utilizes attenuation correction for nonuniform attenuation in SPECT or PET modes. The dual head detectors contain switchable triggering circuitry so that coincidence detection for PET imaging and non-coincidence detection for SPECT imaging is available. The system uses a variable integration technique with programmable integration interval; variable sized clusters for centroiding, use of dual integrators per PMT channel, the event detection and acquisition circuitry of the camera system is switchable for PET and SPECT imaging. In such a switchable SPECT/Pet dual head camera system, a mechanism and method is shown to perform transmission and emission scanning sessions with two line sources and two detectors wherein two sliding transmission detection windows are employed to differentiate between transmission and emission photons. Transmission and emission data can be collected simultaneously. This system provides that the dual transmission detection windows are each associated with a particular line source and move in synchronization. Further, the two line sources and the two detector windows all move in synchronization in the direction of the long axis of the object being scanned. In this configuration, the system can effectively reduce the amount of cross-talk detected by a detector.

Multi-head nuclear medicine camera for dual SPECT and PET imaging with

A gamma camera for a Positron Emission Tomography (PET) system comprises a single, continvous scintillation crystal having an imaging surface, and a first layer of septa disposed along the imaging surface between the object and the imaging surface. A gap is provided between the imaging surface and the first layer of septa to allow non stray radiation to reach the imaging surface. The septa may be arranged to have a long axis disposed at an acute angle away from perpendicular to an axis of rotation or made to move in relation to the imaging surface of the scintillation crystal to reduce cold spots on the image. Multiple layers of septa may be provided.

Gamma camera having partial septas and moving septas for positron

A multi-detector head nuclear camera system automatically switchable (and optimized) to perform either SPECT imaging or PET imaging. The camera system employs, in one embodiment, multi-detector configuration having dual head scintillation detectors but can be implemented with more than two detector heads. The detectors contain switchable triggering circuitry so that coincidence detection for PET imaging and non-coincidence detection for SPECT imaging is available. Using a variable integration technique with programmable integration interval, the event detection and acquisition circuitry of the camera system is switchable to detect events of different energy distribution and count rate which are optimized for PET and SPECT imaging. The system also includes dual integrators on each scintillation detector channel for collecting more than one event per detector at a time for PET or SPECT mode. In PET or SPECT mode, the system also employs variable PMT cluster sizing having smaller cluster sizes for PET imaging and relatively larger cluster sizes for SPECT. In PET or SPECT mode, the system also employs variable centroid shape and zonal triggering. Utilizing the above programmable settings, the camera system can be automatically configured to operate in either SPECT or PET imaging modes.

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Pleasanton, CA, United States of America

Peter Nellemann