Changes in magnetic resonance imaging relaxation time on postmortem magnetic resonance imaging of formalin-fixed human normal heart tissue

Background Postmortem magnetic resonance imaging (MRI) has been used to investigate the cause of death, but due to time constraints, it is not widely applied to the heart. Therefore, MRI analysis of the heart after formalin fixation was previously performed. However, the changes in MRI signal values based on the fixation time of formalin were not investigated. The objective was to investigate changes over time in the T1- and T2-values of MRI signals in normal areas of hearts removed during autopsy, hearts subsequently fixed in formalin, and heart specimens sliced for the preparation of pathological specimens. Methods The study subjects were 21 autopsy cases in our hospital between May 26, 2019 and February 16, 2020 whose hearts were removed and scanned by MRI. The male:female ratio was 14:7, and their ages at death ranged from 9 to 92 years (mean age 65.0 ± 19.7 years). Postmortem (PM)-MRI was conducted with a 0.3-Tesla (0.3-T) scanner containing a permanent magnet. A 4-channel QD head coil was used as the receiver coil. Scans were performed immediately after removal, post-formalin fixation, and after slicing; 7 cases were scanned at all three time points. Results The T1- and T2-values were calculated from the MRI signals of each sample organ at each scanning stage. Specimens were sliced from removed organs after formalin fixation, and the changes in T1- and T2-values over time were graphed to obtain an approximate curve. The median T1-values at each measurement time point tended to decrease from immediately after removal. The T2-values showed the same tendency to decrease, but this tendency was more pronounced for the T1-values. Conclusion MRI signal changes in images of heart specimens were investigated. Formalin fixation shortened both T1- and T2-values over time, and approximation formulae were derived to show these decreases over time. The shortening of T1- and T2-values can be understood as commensurate with the reduction in the water content (water molecules) of the formalin-fixed heart.

Gunshot wounds to the head: a comparison of postmortem magnetic resonance imaging, computed tomography, and autopsy

Background Postmortem imaging has become a powerful diagnostic tool in forensics. Postmortem computed tomography (PMCT) is often used currently to complement and sometimes even replace an autopsy. Purpose To compare PMCT, postmortem magnetic resonance imaging (PMMRI), and autopsy findings for gunshot wounds to the head. Material and Methods Cross-sectional study. We performed a retrospective analysis of 24 cases with gunshot wounds to the head that underwent both PMCT and PMMRI between 2011 and 2018 at the Institute of Forensic Medicine, University of Zurich (Switzerland). Results Our study confirms that PMCT and, to a slightly lesser degree, PMMRI provide additional information that is valuable when combined with autopsy findings. Air embolism was solely detected in PMCT (67% vs. 0% at autopsy). A retained bullet or projectile and bone fragments were diagnosed more frequently with PMCT (42%, 67%, and 92%) than at autopsy (33%, 42%, and 46%). Soft tissue lesions were more often detected with PMMRI than with PMCT. With regard to autopsy, subdural hemorrhage and ventricular hemorrhage were slightly more frequently diagnosed with PMMRI (63% and 75% vs. 38% and 58% at autopsy). Intracerebral hemorrhage was by far most often diagnosed with PMMRI (92%) compared with both PMCT (38%) and autopsy (14%). Conclusion All three modalities should ideally be considered in cases of craniocerebral gunshot wounds. However, it might be conceivable that depending on the forensic query, PMCT and PMMRI may be an adequate replacement for an autopsy.

Clinical Application of Postmortem Magnetic Resonance Imaging in Neonates

<b><i>Background:</i></b> Recent reports advocate the use of MRI either as a substitute for postmortem examinations or for a more targeted autopsy. <b><i>Methods:</i></b> A full-body postmortem MRI (pMRI) of infants was performed as early as possible after death, and findings were compared to clinical premortem diagnoses. <b><i>Results:</i></b> Thirty-one infants were scanned during the study period. Median gestation at birth was 34 weeks (ranges: 24–43). In 3 (10%) cases, no new findings were detected. In 2 (6%), new minor findings not related to the cause of death were detected, and in 17 (55%), new minor findings related to the cause of death were detected. New major findings related to the cause of death were detected in 4 (13%) cases, and new major findings not related to the cause of death were detected in 5 (16%) cases. In 3 (10%), findings thought to alter the perceived cause of death were detected. Overall, in 23 (74%) cases, pMRI findings reinforced the clinical premortem diagnoses. <b><i>Conclusions:</i></b> pMRI is a culturally accepted alternative when autopsy is not performed and can either reinforce, refute, or add to premortem clinical diagnoses.