A 65-year-old man with prostate cancer underwent a bone scan for evaluation of metastatic disease and left second and third metatarsal fractures using 15.89 mCi Tc-99m MDP. He was status post insertion of one hundred thirteen 0.97-mCi prostatic TheraSeed palladium-103 implants (110 mCi). Although 20 to 23 keV characteristic radiographs are the most significant in terms of treatment dose, higher-energy gamma emissions of low abundance (297 keV equals; 0.011percnt;, 362 keV equals; 0.060percnt;, 498 keV equals; 0.011percnt;) are responsible for scatter seen in the pelvis on a Tc-99m MDP bone scan. Because the palladium-103 half-life is 16.97 days, this interference will persist for weeks after seed implantation.
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