Wilson, Charles

Radioactive seed localization (RSL) using 125 I is widely employed for the surgical resection of nonpalpable breast lesions due to its precision and scheduling flexibility. Although clinical experience supports its safety, quantifying radiation dose to surrounding healthy breast tissue remains important for establishing conservative operational guidelines, including acceptable implant duration prior to surgery. In this study, cumulative dose to healthy breast tissue from an implanted 125 I localization seed was evaluated using two independent computational approaches: a simplified hemispherical breast model implemented in MATLAB and a Monte Carlo simulation developed in Mathematica. Both models incorporated dosimetric parameters from AAPM Task Group 43, including the dose-rate constant, radial dose function, and two-dimensional anisotropy function, along with tissue properties consistent with International Commission on Radiological Protection recommendations. Results from both models demonstrated that cumulative dose decreases rapidly with increasing distance from the seed and increases slowly with implantation time due to the low dose rate and long half-life of 125 I. At a distance of 1 cm, cumulative dose reached approximately 3–4 cGy after 5 d and approximately 50 cGy only after extended implantation times exceeding 200 d. Agreement between the MATLAB and Monte Carlo models was within expected limits given differences in deterministic and stochastic modeling approaches. These findings indicate that radiation dose to healthy breast tissue from RSL remains well below thresholds associated with deterministic effects for clinically relevant implantation times. The results support the use of a conservative “no later than” removal date while reaffirming the radiological safety and practical advantages of 125 I seed localization in breast cancer surgery.

This paper summarizes the presentations and panel discussion provided at Plenary Panel #2 on the first day of the 16 th World Congress of the International Radiation Protection Association (IRPA) jointly organized with the 69th Annual Meeting of the Health Physics Society (HPS) in Orlando/Florida in July 2024. International organizations that play a key role in radiation protection and are close in contact with IRPA by official agreements or even MoU’s (Memorandum of Understanding) presented highlights of their projects in radiation protection as well as results. Topical issues on their current work program as seen in a list of statements, including future efforts, were presented and discussed. The needs of practitioners were stressed for recognition by the representatives of the international organizations to be included in their projects. Requested and presented topics were: • Key challenges for radiation protection practitioners in the next 10 y. • Potential effects of emerging science on radiation protection. • Challenges for implementation of IAEA Safety Standards in low- and middle-income countries. • Challenges in occupational radiation protection. • Broadening the process of optimization. • Impact of emerging technologies on radiation protection. • Ensuring radiation protection workforce for the future.