Abstract: In addition to the traditionally calculated photodetector sum signal or energy value, and X, Y position values, the second order moment of the photodetector signals is calculated from photodetector signals to obtain a value proportional to light spread out in the scintillation camera giving an indication of the depth of interaction "DOI". A position correction vector is selected according to the initially calculated position values and the second order moment value and is added to the initial position values to obtain more accurate scintillation event position values. The correction values can be calculated by interpolation using empirically determined or simulation determined values contained in a table. The method of correction using the second order value proportional to DOI can also be used to correct the first order moment value or energy value.

Abstract: For accurate position calculation of scintillation events in a gamma camera, photodetector signals are processed based on small groups of photodetectors surrounding the scintillations. Relative position correction and energy correction is carried out based on rough position values relative to the group of photodetectors, taking into consideration the number of the center photodetector and the sum of all photodetector signals in the group.

Abstract: A control circuit for a scintillation camera is provided in which only discrete scintillation events are processed. When a scintillation event arrives, all light intensity signals below a predetermined threshold, indicating that the signals below the thresholds are not likely to be involved in the event, are blocked from the sum signal. The valid event discrimination circuit disclosed considers the sum signal of light intensity signals originating from only those photodetectors whose output signals are above the threshold. Valid event discrimination is not adversely affected by signals coming from photodetectors not involved in the event after the threshold detection takes place.

Abstract: The position calculation system has position and energy calculators for each scintillation event. After correcting the position and energy values using tables, non-uniform random distribution variance values are added to the position and energy values with the variance added being a product of the random number and a constant precalibrated for the given position. The variance injected position and energy values have a more uniform resolution and substantially remove artifact characteristics in the scintillation camera's image.

Abstract: Digital intensity values from a planar array of photodetectors optically coupled to a scintillator in a digital electronic scintillation camera are compared to one another from most significant bit down to least significant bit in order to determine within the limits of precision of the digital values which photodetector has the maximum light intensity. Center photodetector determination is an important part of efficient position calculation in a scintillation camera.

Abstract: For accurate position calculation of scintillation events in a gamma camera, improved methods are disclosed calibrating gain of photodetectors. The camera system may comprise an array of LEDs optically coupled to a scintillator crystal in which signals from photodetectors also coupled to the crystal are separated into those resulting from test LED pulses and actual gamma ray induced scintillations. The LED induced signals may be used for camera calibration while the camera is in image collecting mode. Image clarity may also be improved by correcting roughly calculated positions as a function of the roughly calculated positions, and by eliminating events which do not exactly correspond to nuclear decay emissions as a function of the events' positions.