Towards intra-operative PET for head and neck cancer: lymph node localization using high-energy probes

We present a novel approach for intra-operative localization of lymph nodes and metastases in the head and neck region using the radio-tracer [18F]FDG. By combining an optical tracking system with a high-energy gamma probe to detect 511keV annihilation gammas, we enable intra-operative PET to visualize activity distributions. Detection of these gammas is modeled ad-hoc analytically, taking into account several factors affecting the detection process. This allows us to iteratively reconstruct the radio-tracer distribution within a localized volume of interest. As a feasibility study we analyze clinical data of 7 patients with tumors in the head and neck region, and derive a realistic neck phantom configuration with [18F]FDG-filled lesions mimicking tumors and lymph nodes. We demonstrate the capabilities and limitations of our approach using that neck phantom. We also outline possible improvements to make our method clinically viable towards less invasive surgeries.