Vitreous body MRI relaxometry as a potential biomarker of the postmortem interval

Accurate estimation of the postmortem interval (PMI) is fundamental in forensic investigations. A routine approach is the biochemical analysis of vitreous humour. However, challenges include invasive sample collection and the potential for multiple sources of error in the analytical workflow, which may affect the precision of PMI estimation. Magnetic resonance imaging (MRI) relaxation parameters may provide non-invasive indicators of cumulative postmortem alterations within the vitreous humour. This study therefore aimed to evaluate associations between PMI and MRI relaxometry in the vitreous humour. Postmortem head MRI at 3T was performed in 17 forensic cases (age at death = 56.1 ± 14.8 years; 4 females, 13 males; PMI = 40.9 ± 22.8 hours [12 h, 82 h]). Forehead temperature was continuously measured during scanning. The vitreous body was manually segmented to enable quantification of the relaxation parameters T 1 , T 2 , and T 2 *. Linear regression analysis was conducted to assess association with PMI. Forehead temperature was included as a statistical covariate. The model including T 2 * showed the strongest association with PMI (R 2 = 0.56, p < 0.01), with both temperature (p < 0.01) and T 2 * (p = 0.02) independently contributing to the prediction. The association between T 2 * and PMI was negative. Models including T 1 or T 2 demonstrated weaker associations and no significant independent effects of the relaxation parameters or temperature. The observed associations in this exploratory study suggest that vitreous T 2 * may be a potential marker for PMI estimation, although larger datasets are required for model calibration and validation.