A dynamic SPECT camera, comprising: an overall structure, which defines proximal and distal ends with respect to a body of a patient; an assembly array of a plurality of movable assemblies arranged on the overall structure each said movable assembly comprising a plurality of detecting units, each detecting unit including a single-pixel detector configured for detecting impinging radioactive emissions, and a dedicated collimator with a solid collection angle for each pixel of at least 0.005 steradians or greater, for a fast collection rate, attached to the single-pixel detector at the proximal ends thereof; a timing mechanism, in communication with each detecting unit; a parallel readout unit coupled to receive impinging radioactive emissions data from the pixels of the pixilated detecting units, the timing mechanism being configured for enabling time-binning of the radioactive emissions impinging upon each single pixel detector to time periods not greater than substantially 30 seconds; an assembly motion provider, configured for providing the assembly with individual assembly motion with respect to the overall structure, during a simultaneous acquisition of radioactive-emission data for a tomographic image by the assemblies, each scanning the same region of interest of said body from a different viewing position; and a position-tracker, configured for providing information on the position and orientation of each said detecting unit substantially at all times during the individual motion, with respect to the overall structure, wherein the dynamic SPECT camera is configured for using said movable assembly array for acquiring a tomographic reconstruction image of a region of interest of at least about 15 X 15 X 15 cubic centimeters, during an acquisition time of 300 seconds, at a spatial resolution of at least 10 X 10 X 10 cubic millimeter. an overall structure, which defines proximal and distal ends with respect to a body of a patient; an assembly array of a plurality of movable assemblies arranged on the overall structure each said movable assembly comprising a plurality of detecting units, each detecting unit including a single-pixel detector configured for detecting impinging radioactive emissions, and a dedicated collimator with a solid collection angle for each pixel of at least 0.005 steradians or greater, for a fast collection rate, attached to the single-pixel detector at the proximal ends thereof; a timing mechanism, in communication with each detecting unit; a parallel readout unit coupled to receive impinging radioactive emissions data from the pixels of the pixilated detecting units, the timing mechanism being configured for enabling time-binning of the radioactive emissions impinging upon each single pixel detector to time periods not greater than substantially 30 seconds; an assembly motion provider, configured for providing the assembly with individual assembly motion with respect to the overall structure, during a simultaneous acquisition of radioactive-emission data for a tomographic image by the assemblies, each scanning the same region of interest of said body from a different viewing position; and a position-tracker, configured for providing information on the position and orientation of each said detecting unit substantially at all times during the individual motion, with respect to the overall structure, wherein the dynamic SPECT camera is configured for using said movable assembly array for acquiring a tomographic reconstruction image of a region of interest of at least about 15 X 15 X 15 cubic centimeters, during an acquisition time of 300 seconds, at a spatial resolution of at least 10 X 10 X 10 cubic millimeter.