A special cut-off gamma camera for high-resolution SPECT of the head

A modern system for single photon emission computerized tomography has been modified in order to optimize examinations of the head. By cutting off part of the detector housing and collimators at one edge, it is possible to rotate the camera close to the skull while still covering the entire brain and the skull base. The minimum radius of revolution used in 32 patients was thereby reduced from about 20 cm to 12.7 +/- 0.8 cm. This, combined with an adjustment of the 64 X 64 matrix to a 26- by 26-cm field of view, resulted in an improvement of the spatial resolution from about 19 mm to 12.6 +/- 0.3 mm with a low-energy, all-purpose collimator, and to 10.4 +/- 0.3 mm (FWHM) with a low-energy, high-resolution collimator. The improved spatial resolution offers several clinical advantages in studies of the brain, the cerebrospinal fluid space, and the skull base.