Abstract P1-01-20: Intra-operative sentinel node imaging with a portable gamma camera in breast cancer

Abstract

Abstract Introduction: Access to nuclear medicine department and sentinel node imaging remain an issue in number of hospitals. Preoperative Scintigrams are performed to confirm uptake of radioactivity and localisation of nodes in centres where facilities are available. Sentinella® (Oncovision, Valencia, Spain) is a recently introduced portable imaging gamma camera used intraoperatively to produce real time visual localisation of SLNs. Sentinella® was tested in a controlled laboratory environment and we report the first use of this technique in breast cancer patients from UK. Methods: In the laboratory setting our aim was to compare the sensitivity and spatial resolution of the Sentinella® and a conventional gamma camera (cGC) used for sentinel node imaging by comparing it with the performance of a GE multi-purpose rectangular (MPR) conventional single head gamma camera normally used for sentinel node imaging. A simulator containing seeds 10kBq, 100kBq, 500kBq of radiocolloid Tc, mimicking SLN, were used. Seeds were placed at several depths in the axilla, at 3cm, 5cm and 8cm from the skin. Sentinella was placed first at 10cm and then 1cm away from the axilla and images were recorded at 1min and at 2.5min for every position. The cGC was placed 20 cm away from the simulator. Results: 68 Sentinella® images and 34 cGC images obtained from the simulated axilla. Sentinella® resolution is comparable with the cGC for objects close to the camera i.e. ∼ 5 cm, but reduces rapidly as it's moved away from the camera. For distances up to about 7 cm the Sentinella® with the blue collimator is more sensitive than the cGC. Sentinella detects high radioactivity (500 kBq) faster than cGC (1 vs 2.5min). In cases of low radioactivity (10kBq) Sentinella® was equally accurate and faster than cGC, when placed close to the skin. Identification of different number of beads with varying radioactivity was similar in Sentinella and cGC. Sentinella scans of the axilla were obtained in 85 patients undergoing SLNB. All patients had a preoperative lymphoscintigram. Serial Sentinella scans were obtained after removal of every hot node. Sentinella scans correlated with all the lymphoscintigrams in the 85 cases studied. Serial decay in activity was seen with removal of every hot node. Extra nodes were picked up in 6/85 cases after the axilla was found silent using hand held gamma probe. In 2/85 cases extra nodes found had cancer that led to axillary clearance. Sentinella scans were extremely useful in differentiating between a hot sentinel node and signal from injection site in upper outer quadrants of small sized breasts. Conclusion: Sentinella is accurate and fast in detecting radioactivity in the axilla. The anatomical shape of its collimator allows the operator to place it close to the axilla thus increasing sensitivity in cases of low radioactivity. Our independent tests and initial patient data confirm the excellent sensitivity and specificity. It's major advantage is that it can be used by surgeons to scan for residual nodes before completion of the procedure. It can resolve the problem of centres that do not have nuclear medicine departments. This portable gamma camera can definitely replace the use of conventional lymphoscintigrams saving time and money both for patients and the Hospital. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-01-20.