Abstract: Surgical resection is the primary method of treatment for sarcomas. The standard clinical approach relies on pre-operative imaging, intraoperative palpation and visual inspection, and additional intraoperative frozen sections of biopsies in areas of concern. These methods are subjective, unreliable, and do not provide real-time feedback to the operating surgeon. This leads to microscopically and macroscopically positive margin resections which correlate with the development of local recurrence and of metastases, increasing patient morbidity and mortality. On the other hand, excessive removal of tissue could lead to unnecessary morbidity and loss of normal function. There is a vital need for intra-operative techniques that can provide accurate and immediate feedback regarding the presence of residual cancer in the surgical bed, ensuring complete tumor removal while minimizing loss of healthy tissue, subsequently reducing recurrence rates, and improving the quality of life of patients. Fluorescence imaging using exogenous contrast agents is being evaluated for enhancing tumor visualization during surgeries. However, a major drawback is the presence of non-specific fluorescence in normal tissue, which reduces accuracy. Traditional fluorescence imaging detects total light intensity, which is a relative parameter that strongly depends on probe uptake in tissue, tumor size, tissue attenuation and system-specific measurement parameters, making comparisons across different measurements and imaging systems difficult. Fluorescence lifetime (FLT) imaging is an alternative approach where the decay rate of photons emitted by the fluorophore is measured. FLT is not affected by changes in brightness of the light source, dye uptake, and tissue attenuation. FLT imaging of endogenous chromophores in the visible spectrum has been evaluated for tumor imaging. However, the clinical utility of endogenous FLT imaging has been limited due to poor contrast between tumor and normal tissue. We have shown that FLT imaging in combination with exogeneous near infrared agents, including the FDA approved Indocyanine green (ICG), significantly improves the detection sensitivity and accuracy of tumor vs. normal classification in multiple cancer types, including different histologic subtypes of sarcomas. FLT can differentiate between cancer cells and non-specific fluorescence background even at a microscopic level. Building on these exciting results, we propose to develop and validate a wide-field FLT imaging system for open surgery of sarcomas and other cancers. We will develop a portable wide-field time domain fluorescence imaging system and incorporate algorithms for real-time FLT imaging of the surgical bed. We will then perform a preclinical validation, followed by a clinical study to optimize the system for intraoperative imaging of sarcomas, and validate the accuracy of FLT imaging by comparing with gold standard pathology. This proposal brings together a team with extensive experience in fluorescence imaging, sarcoma surgeries and pathology to develop the first intraoperative imaging system capable of wide-field NIR FLT imaging for cancer surgery.

There is an urgent need for imaging methods that can allow surgeons to distinguish cancer from heathy tissue during surgery of bone and soft tissue sarcomas, to ensure that the tumor is fully removed and to preserve healthy tissue and function. We will test an optical imaging system that captures differences between the decay time of light emitted from tumors and normal tissue in patients who are injected with fluorescent dyes and undergoing surgery of bone and soft tissue sarcomas.