Radioiodine retention on percutaneous endoscopic gastrostomy tubes.

An 80-year-old male with recurrent thyroid cancer and a percutaneous endoscopic gastrostomy (PEG) tube in situ was referred for radioiodine therapy and was administered 5510 MBq I-131 sodium iodide intravenously. Sequential whole-body images taken over the subsequent 7 days for dosimetric evaluation revealed an area of persistent high uptake in the abdomen. Delayed imaging with single photon emission CT/CT at 15 days post administration revealed this uptake to be at the junction of the PEG tube with the anatomically normal stomach wall. We hypothesise that the PEG tube became contaminated by radioiodine secreted in the gastric mucosa during therapy and this radioactivity subsequently decayed with an increased effective half-life relative to the stomach, leading to the apparent hot spot.