Intraoperative 3D Navigation for Single or Multiple 125I-Seed Localization in Breast-Preserving Cancer Surgery.

Background Mammographic screening has led to the identification of more women with nonpalpable breast cancer, many of them to be treated with breast-preserving surgery. To accomplish radical tumor excision, adequate localization techniques such as radioactive seed localization (RSL) are required. For RSL, a radioactive I-125-seed is implanted central in the tumor to enable intraoperative localization using a -probe. In case of extensive tumor or multifocal carcinoma, multiple I-125-seeds can be used to delineate the involved area. Preoperative imaging is performed different from surgical positioning; therefore, exact I-125-seed depth remains unknown during surgery. Patients and Methods Twenty patients (mean age, 56.8 years) with 25 implanted I-125-seeds scheduled for RSL were included. Sixteen patients had 1 I-125-seed implanted in the primary lesion, 3 patients had 2 I-125-seeds, and 1 patient had 3 I-125-seeds. Freehand SPECT localized I-125-seeds by measuring -counts from different directions, all registered by an optical tracking system. A reconstruction and visualization algorithm enabled 3-dimensional (3D) navigation toward the I-125-seeds. Results Freehand SPECT visualized all I-125-seeds in primary tumors and provided preincision depth information. The deviation, mean (SD), between the freehand SPECT depth and the surgical depth estimation was 1.9 (2.1) mm (range, 0-7 mm). Three-dimensional freehand SPECT was especially useful identifying multiple implanted I-125-seeds because the conventional -probe has more difficulty discriminating I-125-seeds transcutaneous. Conclusions Freehand SPECT with 3D navigation is a valuable tool in RSL for both single and multiple implanted I-125-seeds in breast-preserving cancer surgery. Freehand SPECT provides continuous updating 3D imaging with information about depth and location of the I-125-seeds contributing to adequate excision of nonpalpable breast cancer.