Abstract: A method of tuning an imaging system can include the steps of receiving photons at photo-multiplier units that are part of an array, determining an energy level for each of the photo-multiplier units based on events over a specific photo-multiplier unit and determining a sum energy level for the array of photo-multiplier units based on the events over the specific photo-multiplier unit. The method can also include the step of comparing the energy level for each of the photo-multiplier units with the sum energy level for the array of photo-multiplier units to assist in determining a contribution matrix for the array of photo-multiplier units. The energy level determination steps and the comparison step can be repeated for each photo-multiplier unit in the array to determine the contribution matrix.

Abstract: An improved system and method for tuning individual sensors (e.g., photomultiplier tubes) of a multi-sensor imaging system such as e.g., a gamma camera having an array of photo-multiplier tubes is provided that produces a uniform response over the entire system. Individual sensors of a multi-sensor imaging system are tuned based explicitly or implicitly on gain characteristics of individual sensors of the multi-sensor imaging system so as to produce a uniform response over the system.

Abstract: Determining a scintillation event location bevent along an axis B of an array of photomultiplier tubes, each photomultiplier tube having a location bPMT and an output ZPMT. Determining a preliminary event location bprelim along the B axis as a centroid of the photomultiplier tube outputs. Determining a position-weighted characteristic (ZPMT·(bPMT?bprelim)2) of each of the photomultiplier tubes. Determining event location bevent along the B axis as a centroid of the outputs of those photomultiplier tubes characterized by a position-weighted characteristic less than or equal to a predetermined cutoff.

Abstract: Implementations of the present technology include error mitigation processes that determine gantry angle-dependent measures of detector deflections for a given class of systems using a first method, then determine gantry angle-independent deviations from the class measures using a second method on a specific system; then apply, to the specific system of the second method, the gantry angle-dependent class deflection results of the first method modified by the system-specific gantry angle independent deflections of the second method; and further include a system calibrated by such combinations of processes and computer program products for performing at least portions of the combination of processes.

Abstract: A method for measuring a SPECT collimator's hole orientation angles includes obtaining a set of stepped radiation line images of a line radiation source by scanning/stepping the line radiation source across a first collimator in a first direction; obtaining a second set of stepped radiation line images of the line radiation source across the first collimator in a second direction that is perpendicular to the first direction; and obtaining two sets of stepped radiation line images for a second collimator, wherein one of the two collimators is a reference collimator and the other is a collimator being measured. Calculating the collimator hole orientation angles requires determining offset distances along the two directions for each pair of lines between the reference collimator's line images and the measured collimator's line images by identifying and pairing the lines from the reference collimator line images and the measured collimator line images.

Abstract: An improved system and method for tuning individual sensors (e.g., photomultiplier tubes) of a multi-sensor imaging system such as e.g., a gamma camera having an array of photo-multiplier tubes is provided that produces a uniform response over the entire system. Individual sensors of a multi-sensor imaging system are tuned based explicitly or implicitly on gain characteristics of individual sensors of the multi-sensor imaging system so as to produce a uniform response over the system.

Abstract: In an imaging system employing a multifocal collimator, displaying an image. Framing an event stream into a first buffer. Mapping each first buffer bin to a bin of each of a normalization buffer and a count buffer. Normalization buffer and count buffer are the same dimension. First buffer bins correspond to normalization buffer bins and the count buffer bins such that geometric distortion from the multifocal collimator is substantially reduced. The value of each normalization buffer bin corresponds to the quantity of corresponding first buffer bins corresponding to that normalization buffer bin, and a value of each count buffer bin corresponds to total counts of the one or more of the first buffer bins corresponding to the each count buffer bin. Determining an updated image as the ratio of the values of count buffer bins to the normalization buffer bins. Displaying an image as a function of the updated image.

Abstract: Determining a scintillation event location bevent along an axis B of an array of photomultiplier tubes, each photomultiplier tube having a location bPMT and an output ZPMT. Determining a preliminary event location bprelim along the B axis as a centroid of the photomultiplier tube outputs. Determining a position-weighted characteristic (ZPMT·(bPMT?bprelim)2) of each of the photomultiplier tubes. Determining event location bevent along the B axis as a centroid of the outputs of those photomultiplier tubes characterized by a position-weighted characteristic less than or equal to a predetermined cutoff.

Abstract: A method of tuning an imaging system can include the steps of receiving photons at photo-multiplier units that are part of an array, determining an energy level for each of the photo-multiplier units based on events over a specific photo-multiplier unit and determining a sum energy level for the array of photo-multiplier units based on the events over the specific photo-multiplier unit. The method can also include the step of comparing the energy level for each of the photo-multiplier units with the sum energy level for the array of photo-multiplier units to assist in determining a contribution matrix for the array of photo-multiplier units. The energy level determination steps and the comparison step can be repeated for each photo-multiplier unit in the array to determine the contribution matrix.

Abstract: A method and system of correcting misalignment effects in reconstructed images of a nuclear medical imaging apparatus includes calculating misalignments of a detector to accommodate for deflections (e.g., gravity induced deflections) of a detector (e.g., a cantilevered detector mounted for rotation movement about a patient) from a fixed coordinate system used for image data acquisition.

Abstract: A method and apparatus for acquiring total uniformity for a scintillation imaging apparatus are provided. A generic energy (Z) map is first obtained. The generic Zmap is then corrected for linearity by use of a dot pattern. The listmode data is used to construct an energy histogram matrix. A twin Zmap is then obtained by optimizing the lower and upper boundaries of the energy window for each pixel in relation to the average energy over the Center Field of View.

Abstract: A method and system for calibrating a scintillation camera includes steps of constructing a pair of generic linearity coefficient (LC) matrices from a representative detector based on measurement of non-linearity; and transforming the pair of generic LC matrices according to measured pinhole locations from a lead mask to generate detector specific LC matrices.

Abstract: In some preferred embodiments, an apparatus is provided that facilitates correction, such as, e.g., linearity correction, in imaging devices, such as, e.g., scintillation cameras. In preferred embodiments, a mask is implemented that can produce images for locating the actual position of a nuclear event based on its apparent position with high accuracy and reliability. In the preferred embodiments, the mask includes a non-uniform array of apertures that can achieve this goal.

Abstract: Point source responses of pinhole apertures in a non-uniform grid mask used to spatially calibrate a gamma camera can be modeled as a two-dimensional Gaussian model function. Pinhole data from each pinhole location are added together to generate a complete Gaussian model of the flood image from the mask. The Gaussian model then is subjected to global and PMT-based pattern matching with an actual input flood image obtained using the mask, to obtain a transformed Gaussian model that is more accurately aligned with actual pinhole locations of the mask. The transformed Gaussian model then can be used in a peak detection process for calibration images, which are used to develop LC coefficients for the camera.

Abstract: Point source responses of pinhole apertures in a non-uniform grid mask used to spatially calibrate a gamma camera can be modeled as a two-dimensional Gaussian function with a set of seven parameters. The Gaussian parameters can be measured using a surface-fitting algorithm that seeks minimum error in the least squares sense. The process is repeated for data from each pinhole location and the data are added together to generate a complete model of the flood image from the mask, which then can be used in a peak detection process for clinical images.

Abstract: A radiographic imaging device includes one or more sensors, a scintillation crystal including an emission face, a first set of channels of a first channel depth in the emission face, and a second set of channels of a second channel depth different from the first channel depth in the emission face. Channels of the first and second sets are in a substantially parallel, spaced apart relationship along a first direction, and the second set of channels extend along a second direction non-parallel with the first direction. The scintillation crystal exhibits an anisotropic light spreading function to compensate for differences in sensor spacing along the first and second directions.

Abstract: A radiographic imaging device includes one or more sensors, a scintillation crystal including an emission face, a first set of channels of a first channel depth in the emission face, and a second set of channels of a second channel depth different from the first channel depth in the emission face. Channels of the first and second sets are in a substantially parallel, spaced apart relationship along a first direction, and the second set of channels extend along a second direction non-parallel with the first direction. The scintillation crystal exhibits an anisotropic light spreading function to compensate for differences in sensor spacing along the first and second directions.

Abstract: An anisotropic imaging method and apparatus for determining the location of a radiation event. The method includes the steps of obtaining a sensor reading in response to a radiation event and applying an anisotropic transfer function to the sensor reading. The anistropic transfer function adjusts the sensor reading by using a different transfer curve depending upon whether a spatial coordinate of the detected radiation event in the X-axis direction or a spatial coordinate in the Y-axis direction is being calculated.

Abstract: An anisotropic imaging method and apparatus for determining the location of a radiation event. The method includes the steps of obtaining a sensor reading in response to a radiation event and applying an anisotropic transfer function to the sensor reading. The anisotropic transfer function adjusts the sensor reading by using a different transfer curve depending upon whether a spatial coordinate of the detected radiation event in the X-axis direction or a spatial coordinate in the Y-axis direction is being calculated.

Abstract: Signal processing circuitry for use in medical imaging includes a flash analog-to-digital converter (FADC) for digitizing signals from a sensor; a memory for storing a plurality of digitized signals prior to a current event; and a processor for generating an adjustment signal from the plurality of digitized signals to adjust a first signal corresponding to the current event. In a fast time scale event processing, the signal processing circuitry generates an adjustment signal in near real-time corresponding to an analog error which is computed and updated from signals just prior to an event. In an alternative embodiment, the signal processing circuitry includes an FADC which generates the plurality of signals from a plurality of pseudo-event signals; and a digital-to-analog converter (DAC) is used for generating the pseudo-event signals between a previous event and the current event.