Precise Localization of Sentinel Lymph Nodes and Estimation of Their Depth Using a Prototype Intraoperative Mini -Camera in Patients with Breast Cancer

Abstract

The aim of this study was to evaluate the ability of a prototype intraoperative mini γ-camera, the CarolIReS, with a 50 × 50 mm field of view, to precisely localize sentinel lymph nodes (SLNs) and to determine their depth in a series of patients with infiltrative breast cancer requiring SLN excision. Methods: With the use of phantoms, the broadness of the signal of an acquired projection was shown to linearly depend on its distance from the collimator. A preclinical ex vivo study of 25 excised SLNs demonstrated that SLN size did not influence depth estimation. The minimum activity threshold for successful use of the proposed method was determined. After a preoperative radioisotope injection and lymphoscintigraphy, the SLN was localized in a series of 11 patients using both the mini γ-camera and a γ-probe. During surgery, a ruler was used to measure the depth of all SLNs before their excision. Results: Using the measured linear dependence of image broadness, we found that the expected SLN anatomic depth was compatible with its measured depth during surgery. Conclusion: This study showed that the mini γ-camera efficiently estimated the location of SLNs in 3 dimensions.