Author: Ted Bartley, Steven Brown, Steven Chinn, Mike Hopkins, Stanley Leong, Jerimy C. Polf, Luke Rothermel, Scott Sawyer, Benjamin L. Viglianti 👨🔬
Affiliation: University of California School of Medicine, University of Michigan, H3D, inc, University Hospitals, M3D, Inc, M3D Imaging, California Pacific Medical Center 🌍
Purpose: In a collaboration between surgical oncologists and medical physicists, a new intra-operative gamma camera for imagining sentinel lymph nodes (SLN) during radio-guided SLN biopsy procedures has been developed. Previously developed intra-operative gamma cameras had limited spatial resolution, sensitivity, and long imaging times, which has left surgeons with only a hand-held Gieger probe for intra-operative SLN localization. Here we characterize and discuss the use of this new mobile gamma camera for intra-operative imaging and localization to help surgeons identify and localize SLNs more quickly.
Methods: We characterize the sensitivity, imaging time, and spatial resolution of a new mobile gamma camera to identify SLNs as a function of distance to the primary radiotracer injection site. Six (n=6) surgical oncologists then used the new camera and a previous generation intra-operative camera to image and identity a simulated SLN (20 µCi; 99mTc), located 2 cm from a primary radiotracer injection site (900 µCi; 99mTc).
Results: The new mobile gamma camera produced images in 10 seconds of weak activity vials (20 µCi) within 0.6 mm of larger activity (500 µCi) vials with a spatial resolution of 0.4 cm. The location of the test vial activity in the images was within 0.2 mm of the actual location. Finally, all (n=6) of the surgeons immediately identified the weak SLN location next to a hot injection site or large lymph node in a tissue phantom with the new mobile gamma imager, while none (n=0) identified the SLN using the previous generation camera.
Conclusion: The new mobile gamma camera could localize SLNs within 0.6 cm of a site of high radiotracer activity and could easily image and identify SLNs with weak tracer uptake (< 5% of primary injection). This new imaging system could be a valuable new tool allowing surgeons to more quickly identify more SLNs.