Abstract: An electronic gain control is disclosed for the photomultipliers of a gamma camera which assures that all photomultipliers in the camera have uniform gain for any given ganuna event. A specific dynode in the photomultiplier is isolated from the line resistive voltage divider string in the photomultiplier which places each dynode under incremental voltages. A voltage is then applied to the isolated dynode which can vary anywhere from the voltage the isolated dynode would have had if inserted in the voltage divider string to the voltage that the immediately preceding or immediately succeeding dynode in the string has whereby the photomultiplier's gain is controlled. The applied voltage to the isolated dynode is developed electronically by a voltage to frequency converter coupled by an opto-isolator to a gain voltage divider circuit which cycles the applied voltage between two different voltage potentials tapped from the voltage divider string.

Abstract: An electronic gain control for the photomultipliers of a gamma camera assures that all photomultipliers in the camera have uniform gain for any given gamma event. A specific dynode in the photomultiplier is isolated from the line resistive voltage divider string in the photomultiplier which places each dynode under incremental voltages. A voltage is then applied to the isolated dynode which can vary anywhere from the voltage the isolated dynode would have had if inserted in the voltage divider string to the voltage that the immediately preceding or immediately succeeding dynode in the string has whereby the photomultiplier's gain is controlled. The voltage applied to the isolated dynode is established for each photomultiplier in the camera by individual gain signals developed and stored during calibration of the camera for each radio active isotope whereby all photomultipliers have uniform gain for each isotope.

Abstract: An X-ray collimator is provided to permit diagnostic medical imaging of two or more radioactive isotopes emitting spectrically close gamma rays. The collimator includes a filter plate at one or both ends of the collimator's tubular passageways with the filter plate having a plurality of openings extending therethrough which are aligned and coincident with the tubular passageways. The openings in the filter provide a thin filtering edge adjacent the collimator passageway ends which interact with and remove substantially most of the unwanted secondary and scattered radiation produced by photons striking septa within the collimator's passageways.

Abstract: A transfer system is provided to effect collimator change out for a medical nuclear camera. The system includes a rectangular lead collimator frame into which the collimator is mounted. The collimator frame has an outer peripheral edge and an inner peripheral edge, the peripheral edges defining the collimator thickness. A transfer cart has a C-shaped transfer frame carrying top, bottom and side supports. The top and bottom supports have spring biased locking discs protruding therefrom which are adapted to contact and lock into contact grooves formed into the collimator frame's outer peripheral edge at its top and bottom thus encapsulating the collimator frame within the transfer cart frame for movement of the camera to storage and vise-versa. An especially configured storage rack is provided which has vertically extending, rack modules for storage/retrieval of the collimators.