Abstract: A subject (10) is disposed adjacent a detector array (18) for the purposes of nuclear imaging. The subject (10) is injected with a radioactive isotope (14) and &ggr;-ray emissions indicative of nuclear decay are detected at the detector array (18). P-ASIC (60) preamplifier circuits are complex low-noise integrated circuits which dissipate a considerable amount of power (300-500 mW each). These components account for most of the dissipated power on the daughter cards (62). In order to facilitate the cooling of these electrical components, they are mounted on circuit boards (62) that are arranged parallel to each other extending perpendicularly away from the detector array (18). This provides channels between the boards through which cooling air is drawn by an array of fans (84).

Abstract: A subject (10) is disposed adjacent a detector array (18) for the purposes of nuclear imaging. The subject (10) is injected with a radioactive isotope (14) and &ggr;-ray emissions indicative of nuclear decay are detected at the detector array (18) these signals are processed and reconstructed into an image representation of the anatomy of the subject (10). A dual level arbitration system orders detected signals for ease of processing and efficiency of reconstruction. The first level of the arbiter monitors a group of individual detectors (22). It locks out any signal that arrives from its group of detectors if a previous signal is still being analyzed. This avoids paralyzation of the system. The second level of the arbiter consists of a plurality of memories, one for each group of individual detectors (22) that store an address and energy of each processed signal.

Abstract: A subject (10) is disposed adjacent a detector array (18) of a nuclear camera. The subject (10) is injected with a radioactive isotope (14) and &ggr;-ray emissions indicative of nuclear decay are detected at the detector array (18). Individual detectors (22) are monitored in groups of 64. When one of them detects a nuclear event, it produces an electrical spike that is filtered into a Gaussian with about a 1.2 &mgr;sec peaking time. A 10 bit analog to digital converter (44) 10 repeatedly digitizes the amplitude of the Gaussian pulse, e.g. at a 20 MHz clock rate. The 10 bit digitized pulse amplitudes are monitored by a 10 bit comparitor (46), which monitors consecutive values of the digitized signal, looking for the peak value, e.g. for the amplitude to stop rising. When the peak is detected, the most recent four digital pulse amplitudes contiguous to the peak are summed in a 12 bit accumulator (106) to generate a 12 bit peak amplitude value.

Abstract: Scatter errors are eliminated from a gamma camera image on a spatially dependent basis. A global scatter curve is obtained and normalized for each local area. Based on this local scatter curve and the local spectrum, a local correction factor is obtained. The correction factors are then used to remove scatter errors from the image. The method provides spatially-dependent correction based on measured scatter. It does not require the camera's zero-scatter response to be known and it does not require the fitting of spectra either by a polynomial or by a theoretical scatter function. It allows for rapid determination of scatter correction factors for each pixel in an image. It produces excellent results for both transmission and emission images.

Abstract: A gamma camera is calibrated at different photon energies to provide several different calibration arrays. The calibration arrays are used to correct the camera image according to the energy of the photons detected from the body to be examined. The calibration array obtained from the photons having an energy closest to the photons detected from the body may be used. Another alternative is to form an interpolation array based on two or more calibration arrays obtained with photons having energies bracketing those from the body.

Abstract: An imaging detector on a medical imager is provided with a proximity sensor for automatically maintaining a desired distance from the subject to be imaged. The proximity sensor is formed from three infrared beams at decreasing distances from the imaging detector. The imaging detector is moved toward the subject until the first two beams are interrupted. If the third beam is interrupted, the imaging detector is moved back from the subject until only the first beam is interrupted. Faults are detected by monitoring the order in which the beams are interrupted, whether the beams are interrupted when the imaging detector is fully retracted, and whether beams are present when no signal is applied to the beam emitters.