Extravasation of a therapeutic dose of 131I-metaiodobenzylguanidine: prevention, dosimetry, and mitigation.

UNLABELLED After the extravasation of a therapeutic dose of (131)I-metaiodobenzylguanidine that produced a radiation burn to a patient's forearm, we instituted a catheter placement verification protocol. METHODS Before therapy infusion, proper placement is verified by administering 37 MBq of (99m)Tc-pertechnetate through the catheter, and monitoring activity at the administration site and on the contralateral extremity. A dosimetric model describing both high-rate and low-rate dose components was developed and predicted that the basal epidermal layer received a radiation dose consistent with the observed moist desquamation radiation skin toxicity. RESULTS No extravasation incidents have occurred since the verification procedure was instituted. CONCLUSION To protect against radiation injury from extravasation of therapeutic radionuclides, test administration of a small (99m)Tc dose with probe monitoring of comparable sites in both upper extremities appears to be an effective preventive measure.