Abstract: A method for correcting energy values of pulses from a nuclear medicine camera for errors due to Analog to Digital conversion shift includes determining a relationship between a subset of samples selected from a set of samples from the pulse, the relationship being expressed in the form of a code. A conversion table is accessed which provides a list of codes and corresponding conversion factors. The conversion factor for the closest code to that of the subset of samples is selected from the table and applied to an integration of the set of samples to correct the energy value of the pulse.

Abstract: A method of reconstructing time-of-flight (TOF) images includes obtaining a profile of a subject to be imaged in an examination region (14) of an imaging system (10), Events associated with radiation emitted from the subject are detected and converted to electronic data. Electronic data attributable to radiation events located outside the profile are removed and images are reconstructed from the remaining electronic data.

Abstract: A method for correcting energy values of pulses from a nuclear medicine camera for errors due to Analog to Digital conversion shift includes determining a relationship between a subset of samples selected from a set of samples from the pulse, the relationship being expressed in the form of a code. A conversion table is accessed which provides a list of codes and corresponding conversion factors. The conversion factor for the closest code to that of the subset of samples is selected from the table and applied to an integration of the set of samples to correct the energy value of the pulse.

Abstract: A method of reconstructing time-of-flight (TOF) images includes obtaining a profile of a subject to be imaged in an examination region (14) of an imaging system (10), Events associated with radiation emitted from the subject are detected and converted to electronic data. Electronic data attributable to radiation events located outside the profile are removed and images are reconstructed from the remaining electronic data.

Abstract: A method of generating a filter (40) for a nuclear medicine system (20) where the filter selects valid detected radiation events for image processing. A dataset (60) is provided that is indicative of a plurality of emitted radiation events occurring over a predetermined period of time. Signals representative of the response of a detector to the dataset of the plurality of emitted radiation events are generated. A pattern is determined (66) based on a correlation of a plurality of signals resulting from the response of the detector to a plurality of single radiation events in the dataset. A filter is generated (74) based on the correlation pattern. A method and apparatus of using the generated filter is also disclosed.

Abstract: A nuclear medicine imaging system includes the capability to correct for the deadtime, including the capability to correct for spatial variations in deadtime across the imaging surface of a detector. The imaging system includes one or more radiation detectors, each using a large, monolithic scintillation crystal. Each detector has deadtime associated with it. A given detector is used to acquire an energy profile of a patient based on emission radiation. The detector includes a number of timing channels. The energy profile is used to select a zone influence map indicating the extent of spatial overlap in response between the various timing channels. Emission data of the patient is then acquired during an emission scan. During acquisition of the emission data, a rate meter assigned to each timing channel samples the number of counts associated with each timing channel to acquire deadtime data.

Abstract: An event detector method and apparatus are described. One embodiment includes a first detector that includes a plurality of zones. Each zone includes a plurality of detector devices, wherein each zone generates a zone trigger signal when an event is detected by a detector device in the zone. The embodiment further includes a first energy source coupled to the first detector, wherein when the first energy source is active, events occur that are detectable by the first detector. A calibration circuit is coupled to the first detector, to perform timing calibration of zone trigger signals of zones of the first detector with respect to timing of a reference zone trigger signal of the predetermined reference zone of the first detector, wherein the zone trigger signals and the reference zone trigger signal are generated when an event is detected.

Abstract: A method and apparatus for selectively integrating PMT channel signals in a gamma camera system are described. A trigger word is decoded to determine which of multiple PMT channels are affected by a given scintillation event. When two scintillation events overlap both spatially and temporally, only those channels which are affected by both events stop integrating in response to the second event. Pre-pulse pile-up is corrected by removing the tail of a preceding pulse from a current pulse using an approximation of the tail of the preceding pulse based upon the instantaneous energy of the current pulse and the current countrate. Extrapolation of the tail of the current pulse may also be performed in essentially the same manner.

Abstract: A technique for correcting for random coincidences in a gamma camera system is provided. The system includes a pair of scintillation detectors coupled to a processing system and is configured to detect radiation coincidences. Each detector generates trigger pulses in response to scintillation events to generate a plurality of event-based trigger pulses. Each detector includes a pulse generator, which generates a plurality of artificial trigger pulses. When an artificial trigger pulse in one detector occurs in coincidence with an event-based trigger pulse in the other detector, data is registered by the corresponding detectors, and the artificial trigger pulse is associated with a predetermined energy level. The data processing system examines the data to identify singles events that were registered as a result of artificial trigger pulses and prevents such singles events from contributing to the coincidence images. Instead, such singles events are used to generate a singles image for each detector.

Abstract: A method and apparatus for selectively integrating PMT channel signals in a gamma camera system are described. A trigger word is decoded to determine which of multiple PMT channels are affected by a given scintillation event. When two scintillation events overlap both spatially and temporally, only those channels which are affected by both events stop integrating in response to the second event. Pre-pulse pile-up is corrected by removing the tail of a preceding pulse from a current pulse using an approximation of the tail of the preceding pulse based upon the instantaneous energy of the current pulse and the current countrate. Extrapolation of the tail of the current pulse may also be performed in essentially the same manner.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A circuit for performing digital dynamic compression wherein the circuit is readily modifiable to accept different compression procedures and the input and output signals are in digital form. The system utilizes a memory unit (e.g., a random access memory or other form of programmable memory, such as EEPROM) to contain a procedure utilized to transform digital input channel signal to an offset digital value which is determined based on the total energy of a gamma interaction. This offset digital value is then subtracted from the digital input channel data to arrive at the output dynamically compressed value. However, given sufficient memory size, the memory circuit may be implemented to directly output the compressed value. Since a programmable memory look up table is utilized to contain the dynamic compression procedure, different dynamic compression procedures may be readily loaded into the memory from a computer system.

Abstract: A system including circuitry within a gamma camera system for generating spatially variant photomultiplier cluster based on a peak photomultiplier and for generating spatially variant weights for photomultipliers of the cluster depending on a cluster type signal. The system includes a first memory circuit addressed by a peak photomultiplier address signal and responsive thereto which generates (1) a unique photomultiplier cluster in geometry and size for the peak photomultiplier and (2) a cluster type. A resolution input signal (high/low) changes the size of the cluster. The first memory is programmable. A second memory responsive to photomultiplier addresses of the cluster and the cluster type, generates weight values for each photomultiplier. The second memory is programmable. The second memory allows weights for individual photomultipliers to be altered based on the geometry and size (e.g., type) of the cluster generated by the first memory.