Angled-collimator SPECT (A-SPECT): an improved approach to cranial single photon emission tomography

A special 30 degree slant-hole collimator has been developed for rotating camera single photon emission computerized tomography (SPECT) that allows the camera to remain close to the patient's head throughout a standard 360 degrees circular rotation. Compared with SPECT using parallel-hole collimation, angled-collimator SPECT (A-SPECT) yielded approximately a 30% increase in resolution without significant losses in sensitivity. The full width at half maximum in reconstructed transaxial images of Tc-99m line sources was 1.2 cm for the A-SPECT system compared with 1.6 cm for conventional SPECT, and A-SPECT yielded substantial improvements in modulation transfer function for the line source. A-SPECT images of phantoms and of patients with paranasal sinus disease were consistently superior in resolution to those of conventional SPECT. The findings suggest that A-SPECT will improve the quality of cranial images obtained with rotating camera SPECT systems.