Clinical evaluation of a novel intraoperative handheld gamma camera for sentinel lymph node biopsy

Objective: Preoperative lymphoscintigraphy (PLS) combined with intraoperative gamma probe (GP) localization is standard procedure for localizing the sentinel lymph nodes (SLN) in melanoma and breast cancer. In this study, we evaluated the ability of a novel intraoperative handheld gamma camera (IHGC) to image SLNs during surgery. Methods: The IHGC is a small-field-of-view camera optimized for real-time imaging of lymphatic drainage patterns. Unlike conventional cameras, the IHGC can acquire useful images in a few seconds in a free-running fashion and be moved manually around the patient to find a suitable view of the node. Thirty-nine melanoma and eleven breast cancer patients underwent a modified SLN biopsy protocol in which nodes localized with the GP were imaged with the IHGC. The IHGC was also used to localize additional nodes that could not be found with the GP. Results: The removal of 104 radioactive SLNs was confirmed exvivo by GP counting. Invivo, the relative node detection sensitivity was 88.5 (82.3, 94.6)% for the IHGC (used in conjunction with the GP) and 94.2 (89.7, 98.7)% for the GP alone, a difference not found to be statistically significant (McNemar test, p=0.24). Conclusion: Small radioactive SLNs can be visualized intraoperatively using the IHGC with exposure time of 20s or less, with no significant difference in node detection sensitivity compared to a GP. The IHGC is a useful complement to the GP, especially for SLNs that are difficult to locate with the GP alone.