WE-C-217BCD-01: Development of an Integrated Multimodal Imaging System (IMIS) for Surgical Guidance.

PURPOSE To develop an intraoperative multimodal imaging system (IMIS) for surgical guidance, combining gamma ray scintigraphy with a video camera system for simultaneous real-time visible and near infrared fluorescence (NIRf) imaging. METHODS The gamma camera component has been tested in a pilot human study for intraoperative SLN biopsy in melanoma patients. To characterize the optical components, the spatial resolution of the visible light video camera, the depth-dependent visualization by the NIRf system of targets containing indocyanine green (ICG) and the excitation radiation rejection of the NIRf system were evaluated in bench-top tests. Spatial resolution was quantified using a USAF test pattern and NIRf performance was evaluated using phantoms containing fluorescent targets in mixtures of fat-emulsion (Intralipid) and india ink to simulate optical transport in human tissue. The visible/NIRf system was also used to image a live anaesthetized mouse model of breast cancer. RESULTS Intraoperatively the SiPM gamma camera detected 100% of positive lymph nodes. The visible light camera system contrast transfer function is >10% up to 3.2 1p/mm. The NIRf image SNR when imaging a 9.9 mm diameter lesion containing a 20 μM ICG concentration is > 2 for lesion depths up to 8 mm. The current combination of excitation and emission filters results in nearly complete rejection of backscattered light, resulting in a leakage count rate less than 1% of the system dark count rate. CONCLUSIONS The optical component of the IMIS system demonstrates high spatial resolution, excellent rejection of background excitation radiation, and good target SNR for realistic tracer concentration and target depth. It is capable of accurately coregistered video rate visible/NIRf imaging.