For imaging distant radiation sources, a collimator is rotated about its own axis while that axis moves about a fixed axis pointing toward the overall field of view of the collimator. Radiation from the source will be transmitted through the collimator during each of its revolutions about its axis. The angular position of the collimator about its axis, and the angular position of the collimator axis about the fixed axis, at the time of each such transmission, define a response plane. Computerized data reduction is used to find the intersection of the response planes, which will be a line pointing precisely at the source. For multiple sources, there will be a corresponding number of intersections.

This device comprises a chamber (4) with a pinhole, the walls of the chamber acting as shielding (6) that absorbs radiation. The chamber contains means of forming images of the sources, due to radiation, and the area in which the sources are located, due to visible light from this area. A part (36) of the shielding in which the pinhole (32) is located, is free to move and is fixed to an optical system (34) capable of providing sharp images in visible light over the required field depth by replacing the pinhole for the formation of the image of the area, and vice versa for formation of the image of the sources. Application to localizing gamma radiation sources.

Distant radiation sources are imaged using a collimator having a multiplicity of portions, the transmissivities of the portions to radiation reaching the collimator from a given source being different from portion-to-portion for a given orientation of the collimator; these transmissivities are varied over time, and radiation passing through each portion is detected for successive values of its transmissivity.

A radiation detector includes slit collimator. A radiation detector receives radiation which has been received in each of the slits. The aspect ratio of the detector is approximately three, and each semiconductor radiation detector has a transverse dimension which is less than that of its respective slit. A reconstruction processor generates an image indicative of the radiation received by the detectors. The detector may be rotated about a fixed axis. Alternately, the detector may be translated in coordination with its rotation to provide a substantially square field of view.

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 .gamma.-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. These memories pass a token around among themselves, and if they possess the token, as well as data, they load that data onto a data collection bus, which transfers it to an event archive (44) for storage until enough data is collected to be reconstructed into an image of the subject (10).