T1 and T2 signal appearance of different age stages of intracranial hemorrhage in post-mortem MRI.

Background
In forensic post-mortem medicine, intracranial hemorrhage is a relatively common and usually relevant finding. In recent years, the feasibility of post-mortem MRI (PMMR) for visualization of relevant intracranial findings, such as hemorrhage, has been demonstrated. The aim of this study was to investigate the PMMR T1 and T2 signal behavior of intracranial hemorrhages of different ages and the influence of post-mortem interval and degree of putrefaction on PMMR signal.Methods
N = 200 forensic cases with natural and traumatic intracranial hemorrhages were examined in T1 and T2 weighted PMMR of the head. Hemorrhage age was determined based on police and/or medical case information and categorized into different age stages (hyperacute: < 12 hours; acute: 12-48 hours; early subacute: 2-7 days; late subacute: 7 days-1 month; chronic: > 1 month). T1w and T2w signal behavior was recorded and correlated according to the assessed individual age stages. Multinomial logistic regression was used to analyze whether signal behavior was influenced by the postmortem interval or the degree of putrefaction as assed by the radiological alteration index (RAI).Results
In all age groups, predominant signal intensities were observed on both the T1 and T2 weighted images across all different hemorrhage types. The predominant PMMR signals corresponded to the known signal patterns of living patients in clinical MRI. However, deviations from the predominant signal intensity were observed in all age groups. The T1 and T2 signal characteristics of intracranial hemorrhage were not significantly influenced in cases with high RAI respectively advanced putrefaction.