Radioactive Seed Localization or Wire-guided Localization of Nonpalpable Invasive and In Situ Breast Cancer: A Randomized, Multicenter, Open-label Trial.

OBJECTIVE: To compare the rate of positive resection margins between radioactive seed localization (RSL) and wire-guided localization (WGL) after breast conserving surgery (BCS). BACKGROUND: WGL is the current standard for localization of nonpalpable breast lesions in BCS, but there are several difficulties related to the method. METHODS: From January 1, 2014 to February 4, 2016, patients with nonpalpable invasive breast cancer or DCIS visible on ultrasound were enrolled in this randomized, multicenter, open-label clinical trial, and randomly assigned to RSL or WGL. The primary outcome was margin status after BCS. Secondary outcomes were duration of the surgical procedure, weight of surgical specimen, and patients' pain perception. Analyses were performed by intention-to-treat (ITT) and per protocol. RESULTS: Out of 444 eligible patients, 413 lesions representing 409 patients were randomized; 207 to RSL and 206 to WGL. Twenty-three did not meet inclusion criteria, chose to withdraw, or had a change in surgical management and were excluded. The remaining 390 lesions constituted the ITT population. Here, resection margins were positive in 23 cases (11.8%) in the RSL group compared with 26 cases (13.3%) in the WGL group (P = 0.65). The per-protocol analysis revealed no difference in margin status (P = 0.62). There were no significant differences in the duration of the surgical procedure (P = 0.12), weight of the surgical specimen (P = 0.54) or the patients' pain perception (P = 0.28). CONCLUSION: RSL offers a major logistic advantage, as localization can be done several days before surgery without any increase in positive resection margins compared with WGL.

Technical Note: DoseMapper: A validated GUI-based exact numerical modeling method of shielding in PET/CT facilities.

PURPOSE: To provide a faster and more intuitive way of designing shielding for PET facilities, while still relying on the principles of the AAPM 108 Taskforce guidelines, as well as illustrating the calculation output using dose maps that are easily evaluated. METHODS: A graphical user interface was developed, implementing an inverse AAPM method, wherein radiation sources and shield barriers are manually defined. Simulations are calculated using a user-defined control mesh grid. DoseMapper simulations were verified against manual calculations using the AAPM guidelines, as well as compared with in situ dose rate measurements using four different dosemeters. RESULTS: DoseMapper simulations were virtually identical to manual calculations using AAPM guidelines, with a maximum relative error of <0.01%. Comparison with in situ measurements showed that DoseMapper-simulated dose rates in all instances are higher than what can be measured, ensuring that no unintended hotspots can be overlooked in the shielding design. CONCLUSIONS: DoseMapper is an easy to use implementation of the AAPM 108 Taskforce principles that allows for a rapid iterative design process of shielding in PET facilities, and the resulting maps of dose rate and annual accumulated dose serve as clear documentation for the design.