Determination of radionuclide concentrations with positron CT scanning (PETT): concise communication.

A series of experiments was undertaken to evaluate the response of a positron emission transverse tomograph (PETT) to measured radionuclide concentrations similar to those encountered in human studies. The correlation between the response of the imaging system (mean PETT number/min), and the concentration of the radioactivity producing the output data, was linear with a computed sensitivity of 2720 PETT number/min, per micronCi/ml, per picture element, for a radionuclide (100% beta+) contained in either of two phantoms and imaged with a reduction of 1.5 cm. It was concluded that the output data are essentially independent of the imaged object's physical dimensions for the range of 18-28-cm diam and faithfully reflect the regional radioactivity concentration within the object, provided valid attenuation correction is achieved and the sampled area is not compromised by the imaging system's limitations of spatial resolution.