Inversion time optimization in postmortem 1.5 tesla FLAIR brain imaging: a pilot study

Postmortem magnetic resonance imaging (PMMR) has gained importance during the last decade in forensic pathology. While many clinical radiology sequences are applicable for the evaluation of the brain, the 3D FLAIR sequence shows different contrast in postmortem cases compared to living patients. Two factors-the temperature and the interval between official declaration of the death and PMMR (DC-PMMR interval) are suspected to influence the optimal inversion time (TI) needed to achieve living patient-like image contrast. This study aimed to investigate if our empirical approach had the same results as previous study.

3D FLAIR sequences with varying TI values (from 1660 ms to 900 ms, every 110 ms) were acquired. Two radiologists independently assessed the images, selecting the TI that produced the most patient-like contrast. Rectal temperature and the DC-PMMR interval were recorded, and Pearson correlation tests were conducted to evaluate interrelations between TI, temperature, and DC-PMMR interval. Interobserver reliability was assessed using PABAK.

Overall, 23 cases were analyzed. Rectal temperature ranged from 5.7 °C to 29.0 °C, and the DC-PMMR interval from 13.05 to 768 h. A moderate interobserver reliability (PABAK = 0.56) was observed. Significant correlations were observed between TI and both temperature (r = 0.70, p = 0.0014) and DC-PMMR interval (r = - 0.68, p < 0.0003).

Our empirical approach trends the results of previous studies: Postmortem 3D FLAIR contrast is significantly affected by the temperature and the DC-PMMR interval, suggesting that TI should be adapted accordingly.