The use of planar high-purity Ge detectors for in vivo measurement of low-energy photon emitters.

Multiple planar high-purity Ge detectors have been used for the past year to detect, localize and quantify several radionuclides in radiation workers. The advantages of these detectors over NaI(Tl), phoswich, and arrays of planar Ge detectors attached to a single cryostat are illustrated by the results of the measurements of 238Pu, 239Pu, 241Am, 210Pb, 144Ce, 125I, U and 154Eu in exposed radiation workers. The main advantages are a more positive identification of radionuclides, greater sensitivity, and less interference from higher energy gamma rays that might be present in the body. The increased sensitivity of these planar detectors over that of other types of detectors is due to better resolution which provides a better photopeak-to-background ratio and a much better background prediction capability. Good resolution is especially useful for measuring low-energy X or gamma rays in the presence of high-energy gamma emitters.