Transferring innovative freehand SPECT to the operating room: First experiences with sentinel lymph node biopsy in malignant melanoma

Abstract Purpose The purpose of this study was to report on the first experiences with freehand single-photon emission-computed tomography (freehand SPECT) in sentinel lymph node biopsy (SLNB) in patients with malignant melanoma. Freehand SPECT is a novel imaging modality combining gamma probes, surgical navigation systems, and emission tomography algorithms, designed to overcome some of the limitations of conventional gamma probes. Methods In this study 20 patients with malignant melanoma underwent conventional planar scintigraphy prior to surgery. In the operating room, the number and location of separable SLNs were detected first by a pre-incisional scan with freehand SPECT to render a 3D-image of the target site and afterwards by a scan with a conventional gamma probe. After SLNB another scan was performed to document the removal of all targeted SLNs. Results Planar scintigraphy identified 40 SLNs in 26 nodal basins. Pre-incisional freehand SPECT mapped 38 of these nodes as well as one additional node in one patient (95.0% node based sensitivity). The results of freehand SPECT were identical to those of planar scintigraphy in 25 basins, while it missed one basin (96.2% basin based sensitivity). In comparison, the gamma probe failed to detect 7 nodes in 4 basins (82.5% node based sensitivity and 84.6% basin based sensitivity). After resection freehand SPECT detected 9 remaining radioactive spots, two of whichwere resected as they matched the position of SLNs detected on preoperative planar scintigraphy. Conclusions Freehand SPECT provides a real-time, intraoperative 3D-image of the radioactive labelled SLNs, facilitating their detection and resection.