PCR-I-High Resolution Positron Tomograph Using Analog Coding

PCR-I has been designed and built to demonstrate the concept of analog coding to provide high resolution positron tomographic images without interpolative motion. The instrument uses 360 bismuth germanate (BGO) detectors coupled through a lucite light pipe to 90 phototubes. The measured resolution at the center is 4.8 mm. A straightforward extension of the concept will lead to a tomograph capable of obtaining resolution below 3 mm for low energy positron emitters. The sensitivity of PCR-I is 46 000/s for a 20 cm diameter phantom uniformly filled with 1 μCi/cc of a positron emitter. Parameters related to dead time and random and prompt scatter coincidences have been studied. Phantom measurements demonstrate the resolution and uniformity of PCR-I. Animal studies carried out to date include 18F in rat skeleton, ¹¹C-palmitate and ¹¹C-labeled red cells in dog heart and blood flow, and blood volume in monkey brain using C¹⁵O₂ and C¹⁵O.