Singles transmission in positron emission tomography using /sup 137/Cs

A singles transmission method of attenuation correction in PET has been developed, using a single-photon emitter, /sup 137/Cs, with an energy of 662 keV. The singles method can achieve a factor of ten in speed over the standard coincidence method, with comparable statistical quality and can enable post-injection transmission studies to be performed using energy discrimination to reject emission activity in the field-of-view. In order to compensate for the higher energy of the /sup 137/Cs source, the transmission images are segmented into tissue and lung compartments, and 511 keV attenuation coefficients are used. Segmentation also compensates for increased scatter with the singles method compared to the standard coincidence method, which takes advantage of a colinearity position gate.