Extravasation of a Therapeutic Dose of 131I-Metaiodobenzylguanidine: Prevention, Dosimetry

After the extravasation of a therapeutic dose of 131I-metaiodo-benzylguanidine that produced a radiation burn to a patient’s forearm, we instituted a catheter placement verification proto-col. Methods: Before therapy infusion, proper placement is verified by administering 37 MBq of 99mTc-pertechnetate through the catheter, and monitoring activity at the administra-tion 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 99mTc dose with probe monitoring of comparable sites in both upper extremities appears to be an effective pre-ventive measure. Key Words: radiopharmaceutical therapy; skin radiation injury; extravasation dosimetr