[ RadSafe ] medical issues

Stabin, Michael michael.g.stabin at Vanderbilt.Edu
Mon Jan 26 15:04:04 CST 2009

Cs-137 is not administered as a radiopharmaceutical in nuclear medicine and cannot be used for imaging on a PET system, it does not emit positrons. Ge-68, Cs-137, and I think some gadolinium isotope sources, as well as CT sources, have been used in PET scanners to set up attenuation correction maps. As Bjorn noted, Cs-137 has been used in brachy implants.

If heart imaging is done with Tc-99m (cardiolite or other forms), it goes through 8 half-lives in two days, and there is very little residual activity or measurable exposure after 1-2 days. Tl-201 has a longer half-life (around 3 days), but there is biological clearance. BUT there are often longer lived contaminants in the product (Tl-200, Tl-202, Pb-203, about 1, 12, and 2.5 day half-lives) which can be measured for some days after the test. I had a student in a radiation detector course who seriously messed up our scintillation detector lab because of residual thallium activity a few days after a heart study. She thought it would all be gone, but there was plenty there for the detectors to see. She didn't mind being sent home early so the rest of the class could get their measurements!

Michael G. Stabin, PhD, CHP
Associate Professor of Radiology and Radiological Sciences
Department of Radiology and Radiological Sciences
Vanderbilt University
1161 21st Avenue South
Nashville, TN 37232-2675
Phone (615) 343-4628
Fax   (615) 322-3764
e-mail     michael.g.stabin at vanderbilt.edu
internet   www.doseinfo-radar.com
"I am realistic -- I expect miracles." - Wayne Dyer

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