1. A high-resolution radioisotopic imaging system for imaging a source field with sub-cubic centimeter resolution, comprising: inner electronic collimator detector means spaced radially outwardly from a radioisotopic source field of radio-isotopic atoms, each atom radioactively decaying to substantially simultaneously emit a plurality of gamma rays, said inner detector means being operative for detecting and scattering gamma rays impinging thereon; outer electronic collimator detector means spaced radially outwardly from the inner detector means, and operative for detecting and substantially fully absorbing the gamma rays scattered form the inner detector means; said inner and outer detector means being operative, when a first gamma ray is simultaneously detected by the inner and outer detector means, for specifying a first emission probability field in space; said inner and outer detector means being operative, when a second gamma ray is simultaneously detected by the inner and outer detector means, for specifying a second emission probability field in space; and said inner and outer detector means being so arranged relative to one another that the first and second emission probability fields intersect each other in space and form a reduced zone in space for imaging the source field with sub cubic centimeter resolution.