Imaging Energy
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 |