Non-invasive estimation of absorbed ionizing radiation dose in mice using Near-Infrared Spectroscopy (NIRS) and aquaphotomics

Accurate measurement of ionizing radiation exposure, whether therapeutic or accidental, is of utmost importance in various scenarios. This paper presents a study that addresses this critical need by utilizing near-infrared (NIR) spectroscopy and aquaphotomics to estimate radiation dose exposure in mouse models subjected to X-ray irradiation. The analysis of NIR spectra acquired from the mouse abdomen enabled non-invasive estimation of radiation doses ranging from 0.5 to 6.5 Gy, immediately following the irradiation exposure. The findings were consistent with the impact of total body irradiation in mice, as evidenced by measures such as animal survival rate, alterations in body weight observed over a 30-day post-exposure period, and changes in hematocrit levels. The spectroscopic measurements were based on detecting changes in the molecular structure of body water after radiation exposure, utilizing the water spectral pattern as a multidimensional biomarker. While further validation in nonhuman primates is necessary, the findings demonstrate a simple, non-destructive, and rapid method that holds promise for the estimation of radiation exposure across a range of doses, applicable to both clinical applications and catastrophic radiation events. These advancements in radiation dose quantification have significant implications for the timely and precise assessment of radiation exposure in humans.

Methods
Near infrared spectra acquisition was performed during a period of 30 days, at specific time points: prior to ionizing irradiation (after one week of acclimatization to laboratory conditions), immediately post-irradiation (0 h), and at 6, 12, 24, 48, and 72 hours, followed by subsequent measurements every 5 days until 30 days post-irradiation. At each measurement time, the spectra were collected from mouse abdomen using a portable, hand-held microNIR spectrometer (Viavi Solutions, Santa Rosa, CA, USA) in the spectral range 908 – 1670 nm, with approximately 7 nm resolution step. Five consecutive spectra were acquired for each mouse, at each time when the measurements were performed. 

The spectral data were analyzed using multivariate analysis methods and preprocessed using extended multiplicative scatter correction.