Despite significant progress in medical imaging technologies, there currently exist no tools capable of objectively helping healthcare professionals during liver transplantation surgeries. Instead, surgeons still rely on their own senses (vision and touch, primarily) to determine whether a transplant is healthy either before, during or after the procedure. In turn, surgery remains subjective and dependent on the experience of the surgeon, resulting in unacceptable failure, recurrence and morbidity rates, as well as in significant quality of care disparities across hospitals. As of January 1st, 2018, 1437 patients are on the wait list for liver transplantation, a number that is continuously increasing, with only 574 patients a decade ago. Every year, 10 to 12% of these patients will not survive the wait-time for getting a transplant. By large, these numbers are the result of the lack of objective decision criteria to determine whether a donor liver is healthy enough to be transplanted. In addition, following liver surgery, 7 to 10% of the patients will suffer liver function deficiencies. While the reasons behind these deficiencies are well known (combination of defects in micro-circulation, venous congestion, arterial thrombosis, asynchronies in hepatocyte regeneration leading to physiological disorganization), no tool currently exists to detect these deficiencies early during surgery and intervene in a timely manner. In turn, these deficiencies lead to costly emergency re-operations, and a survival rate decrease as important as 15%. Because these failures and complications can be mainly related to the lack of information regarding the liver, they could be avoided if tools were available to assist surgeons in visualizing the viability of the liver tissue both before and after transplantation allowing to select viable donors, as well as proper & timely intervention. Instead, surgeons subjectively rely on their own visual senses to assess the quality of the procedure, leading to an unacceptable morbidity and mortality rates. The hypothesis underlying our study is that Near-Infrared (NIR) light travels relatively deeply into tissues and is capable of providing critical information during surgery. In particular, oxy- and deoxy-hemoglobin, water and lipids can provide functional information, while scattering can provide micro-structural information. We recently developed a novel method called Single Snapshot of Optical Properties (SSOP) that relies on the analysis of the tissue response in the Spatial Frequency Domain to extract its optical properties (absorption and scattering). Because SSOP works entirely in the frequency domain, it is today the first and only method amenable to provide video-rate quantitative images during surgery. In this project we propose to develop innovative solutions to allow quantitative multispectral optical imaging in real-time during liver transplant surgery. To solve this challenging problem we have assembled a multidisciplinary team of scientists, engineers and surgeons. Pr Vibert from the Paul Brousse Hospital (HPB) in Paris is an expert in liver transplantation procedures. Dr. Diana from the University Hospital Institute (IHU) in Strasbourg is an expert experimental surgeon specialized in innovative surgical guidance techniques. Finally, the coordinator has invented SSOP, and our group and others at the ICube laboratory have a proven expertise in advanced photonics methods and the design of surgical guidance systems.