Radiation Safety With Use of I-125 Seeds for Localization of Nonpalpable Breast Lesions

Rationale and Objectives: To describe radiation safety procedures for limiting exposures during localizing placement of iodine-125 (I-125) seeds in nonpalpable breast lesions. Radiation safety tasks included seed receipt, assay, sterilization, transfer, and placement; surgical localization and retrieval; and extraction of seeds by pathologists. Additional regulatory aspects included institutional review board approval, physician credentialing, off-label use, and governmental licensing. Materials and Methods: Titanium seeds were assayed to ensure strength (1.85-5.55 MBq). Radiologists credentialed in mammography placed seeds with an 18-gauge needle under ultrasound or mammographic guidance. Surgeons located seeds with a hand-held, solid-state radiation detector. I-125 seeds were extracted from excised tissue and secured by pathologists. Results: After the investigational phase, state permission was obtained for the institution's Radiation Safety Committee to oversee the clinical application of the procedure. In more than 300 procedures, all seeds and targeted lesions were removed successfully; more than 98% of patients had seeds removed within 24 hours. Mean diameter of excised specimens was about 4 cm, for a maximum dose to residual breast tissue of 2 cGy (approximately that of a two-view mammogram). Badge monitoring showed no loss of seeds and no increase in physician or technologist exposure. Radiation safety precautions facilitated safe handling. Conclusion: Clinically, the procedure has been accepted as routine, with standardized steps for safe and secure handling of radioactive seeds. Compared with conventional methods, use of I-125 seeds offers an improved method for localizing before surgical excision and has essentially replaced wire localization in our tertiary-care academic medical center.