Effects of Diet on Near-Infrared Autofluorescence in Preclinical Imaging

Fluorescence imaging is an increasingly popular modality being used intraoperatively to assist surgeons in delineating tumors accurately. Most current systems operate in the first near-infrared (NIR-I) range, which is limited by shallow tissue penetration, reduced spatial resolution, and high autofluorescence. The second near-infrared (NIR-II) window provides enhanced performance yet is constrained in the clinical setting due to the lack of high-performance imaging systems and the absence of FDA-approved NIR-II imaging dyes. This study examines autofluorescence in the NIR-I and NIR-II windows and attempts to simulate NIR-II levels of contrast in NIR-I images by removing fluorophores present in the standard mice chow diet. One group of mice on the standard diet and another group on a chlorophyll-free diet were imaged over a period of fourteen days to examine how autofluorescent metabolites were affected. Dyes were also injected to assess how autofluorescence impacts the contrast to noise ratio of near-infrared dyes. The autofluorescence in the NIR-I window followed a decay trend, with most of the observable changes being present within the first day. The contrast to noise ratio increased with the introduction of diet chow from 1.53 to 2.73 in NIR-I and from 5.08 to 6.02 in NIR-II. The chlorophyll-free diet decreased autofluorescence in the abdomen for NIR-I images but fell short of the quality achieved using the NIR-II range.