METHODS

The annular single-crystalbrain camera (ASPECT) is a digitalSPECT systemwith a single-crystalsodiumiodide thalliumNal (Tl) ring detector and collimatorsystem de signedto view the patient'sheadfrom threeanglessimul taneously. The ring is rotated concentrically to the detector for three-dimensionalreconstructionover a 21.4 cm (di ameter) by 10.7 cm (length) field of view. We evaluated the systemclinicallyby imaginga Hoffmanbrainphantom and seven subjects, of whom two were normalcontrols, threehadpreviouscerebralinfarctionandtwo haddemen tia. The ASPECT system producedtomographicimages of highspatialresolution. In normalsubjects, the separa tion of stnata from thalamiby the posteriorlimbsof the internalcapsuleswasmuchcleareronASPECTimages than on rotatinggamma camera images. The highspatial resolution obtained with the ASPECT system translates into superioranatomicalrepresentationof the braincorn pared to the standard rotating gamma camera.