Innovative determination of time since injury in mice intracerebral hematomas through ATR-FTIR spectroscopy

Determining the time since injury plays an important role in forensic science, providing valuable scientific evidence. Traumatic intracerebral hemorrhage (TICH), comprising 13-48 % of lesions resulting from traumatic brain injury (TBI), arises when blood vessels break and leak into the brain. The development and resorption of a hematoma are intricately linked to the timing of the injury, with its slow absorption mirroring spontaneous remission. This attribute renders it appropriate for modeling the duration since damage. This work built a mouse model of intracerebral hemorrhage with damage durations spanning from 0 to 7 days. Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy, in conjunction with chemometrics, was employed to evaluate survival time. The volume and color of the hematoma undergo progressive alterations over time. Preliminary Principal Component Analysis (PCA) revealed diversity across hematoma samples obtained at various post-injury time points. Subsequently, spectral data were utilized to develop a robust Partial Least Squares (PLS) regression model for prediction. The root mean square error of cross-validation (RMSECV) and the root mean square error of prediction (RMSEP) values generated by PLS were 0.69 d (R² = 0.93) and 0.79 d (R² = 0.92), respectively. Variable Importance in Projection (VIP) scores demonstrated that spectral areas associated with lipids, carbohydrates, and proteins had regular fluctuations. The most prominent features were identified at 2920 cm^-1 (lipid CH stretching vibration), 2850 cm^-1 (lipid CH stretching vibration), and 1057 cm^-1 (carbohydrate CO stretching vibration), which are crucial for assessing the time elapsed since injury. Our initial findings indicate that the integration of rapid and non-invasive ATR-FTIR spectroscopy with chemometrics holds potential as an effective method for calculating survival time in forensic contexts.