Radiation dosimetry of two new tellurium- 123m-labeled adrenal-imaging agents: concise communication.

The absorbed radiation doses to humans from 23-(isopropyl[123mTe]telluro)-24-nor-5 alpha-cholan-3 beta-ol (Te-123m-23-ITC) and 24-(isopropyl[123mTe]telluro)-chol-5-en-3 beta-ol(Te-123m-24-ITC) have been calculated, based on rat biological data, to assess the relative radiation risks to humans from these two new adrenal-imaging agents. The estimated radiation doses to several critical organs have been compared with dose estimates for a variety of other radiolabeled steroids that have been designed as adrenal-imaging agents. Dose estimates to selected organs from Te-123m-23-ITC are as follows (rad/mCi): adrenals 98; ovaries 8.0; liver 1.6. Similar estimated values for Te-123m-24-ITC are: adrenals 210; ovaries 13; liver 2.0. The radiation dose estimates for these two agents are comparable to the calculated radiation doses from 6 beta-[(methyl[75Se]seleno)methyl]-19-nor-cholest-5(10)-en-3 beta-ol (Scintidren) and 19-[131I]iodocholest-5-en-3 beta-ol (NP-59), two agents currently in clinical use for the diagnosis of adrenal disease.