From an imaging standpoint, the ideal imaging energy range is 100250 keV. Our imaging equipment has been tailored to function best in this range. Image quality is suboptimal above or below it, as illustrated in the figure below. Despite this limitation, there are certain radioisotopes that are commonly used clinically whose gamma ray energies are below 100 keV or above 250 keV. For example, on the low end, Tl201 and Xe133 emit photons with energies of about 70-80 keV, while on the high end, Ga67 and I131 emit photons of 300 and 364.5 keV, respectively. Use of these higher energies compromises image quality since greater collimation is required, decreasing both sensitivity and resolution. Commonly used radioisotopes considered ideal from an energy standpoint include Tc99m, In111, and I123.
|Stephen Karesh, PhD.||
Last Updated: August 14, 1996