Resolution performance of a prototype detector for small animal imaging

Full text: A gamma camera is being developed for high resolution imaging of small animals, based on a detector developed by the Jefferson Lab Detector Group. The detector is housed in tungsten and composed of a position sensitive photomultiplier tube (Hamamatsu R3941), a 29x29 array of CsI(TI) crystals each 1.7 x 1.7 x 5mm spaced 2mm apart, and a 25mm (length) x 1mm (diameter) parallel hole collimator. Intrinsic resolution was measured using a highly collimated 99Tcm point source. The point source was moved across the field of view in 0.2mm increments. The mean intrinsic full width at half maximum (FWHM) for source to crystal surface distances of 5 and 30mm, was 1.6 and 1.8mm respectively. An extrinsic measurement was made using a 0.1 mm diameter 99Tcm line source using the same acquisition parameters. The mean extrinsic FHWM for line source to collimator distances of 10 and 30mm, was 2.7 and 3.8mm respectively. Single photon emission computed tomography (SPECT) studies were performed using the same line source and a miniature Derenzo resolution phantom, both at 30mm radius of rotation with 60 angles (6 degree increments) and reconstructed using iterative reconstruction. Reconstructed resolution was 3.4 mm FWHM and the 1.5mm diameter rods (6mm separation) were easily resolved. This detector demonstrates high intrinsic and extrinsic spatial resolution when compared with current clinical SPECT systems and should be suitable for high resolution imaging of small animals. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc