Portable Spectroscopic Probe for Real-time Quantification of fat droplets in liver, under Ambient Light: Proof of Concept, Development, and Early Commercialization

Abstract

Hepatic steatosis (HS) is the abnormal accumulation of lipids (fat) in liver cells, negatively impacting post-transplant outcomes. Accurate measurements of HS severity and the size of fat droplets in liver cells are critical for choosing suitable grafts. Traditional assessment methods are limited, but non-invasive spectroscopic techniques, such as Raman and reflectance spectroscopy show potential in improving donor liver selection and reducing the unnecessary disposal of viable livers, which can be as high as 11.9% of donations, according to research in this dissertation. This dissertation focuses on the development and testing of a portable spectroscopic system - compatible with ambient light conditions - for assessing overall HS and capable of distinguishing microsteatosis (accumulation of small fat droplets) from macrosteatosis (accumulation of large fat droplets). The system comprises a 1064 nm laser, handheld probe, optical filters, photodiodes, and a lock-in amplifier, enabling real-time evaluation of liver fat content under both normal and strong ambient lighting conditions. In pre-clinical trials using duck liver phantoms, the optical system's signal intensity was linearly correlated with MRI-calibrated fat content, demonstrating its accuracy in liver fat quantification and compatibility under ambient light conditions. Subsequent clinical studies on snap-frozen human liver specimens revealed promising correlations between measurements obtained from the Raman spectroscopy and conventional assessment methods. By integrating data from the Raman and reflectance channels, we developed a predictive model that accurately quantifies HS with potential for distinguishing microsteatosis and macrosteatosis in human livers. Further investigation into the combined use of Raman and reflectance spectroscopy through Monte Carlo simulations and experiments with oil-in-water phantoms illustrated that Raman scattering could distinguish different fat contents independently, while reflectance was affected by both fat content and droplet size - exhibiting a high sensitivity to the size of the fat droplets. Additionally, this dissertation addresses the early-stage commercialization strategies for this spectroscopic system, highlighting its potential application in clinical settings. This step is crucial for transitioning the technology from research to practical use, offering a new tool for enhancing liver transplant outcomes by improving the accuracy of liver graft assessment.