Feasibility of MR Imaging–guided Breast Lumpectomy for Malignant Tumors in a 0.5-T Open-Configuration MR Imaging System1

Rationale and Objectives. The authors performed this study to develop the technology for and evaluate the utility of a 0.5-T vertical open-configuration magnetic resonance (MR) imaging system for imaging-guided breast lumpectomy of malignant tumors. Materials and Methods. Twenty women with breast cancer underwent MR imaging–guided lumpectomy in a 0.5-T vertical open-configuration MR system. During lumpectomy, preand postresection images were acquired with and without contrast material. Images were used both for tumor localization and to monitor resection. If residual enhancement was observed, additional resection was performed in an effort to secure negative pathologic margins. Results. The procedure evolved over time with technology innovations and improvements. Specifically, instruments were acquired that were compatible with MR imaging breast procedures, the echo time with the Dixon technique was modified to optimize image quality, contrast material injection was timed for maximum lesion enhancement, breath-hold image acquisition was instituted, and the biopsy cavity was filled with saline and the incision closed before image acquisition. Conclusion. All breast lesions were identified despite limited spatial resolution and fat-suppression techniques. The evolved techniques facilitated intraoperative margin evaluation and prompted additional surgical margin resection in five patients, sparing four from an additional surgical procedure. Intraoperative MR imaging has the potential to improve the complete pathologic excision of invasive breast cancer.