Design Concepts and Performances of HEADTOME, a Multiring Hybrid Emission Tomograph for the Brain

Abstract

In order to meet an increasing clinical demand for a tomographic measurement of cerebral blood flow (CBF), a prototype HEADTOME was originally designed to measure a dynamic tomogram of inert gas clearance of the brain. To avoid the necessity for a cyclotron, we designed the prototype HEADTOME to include a hybrid capability for measuring both positron and single photon emissions. The prototype HEADTOME was a single-ring tomograph using 64 NaI detectors. Because of the primary demand for a dynamic study, high efficiency dominated other design characteristics. Therefore, a small-diameter detector ring was chosen to provide high efficiency. However, this caused difficulties in obtaining a uniformity of spatial resolution and slice thickness over the field of view (FOV) and in accurately correcting for scattered coincidences. These difficulties resulted in a different partial volume effect over the FOV and low accuracy.