Time related changes of T1, T2, and T2(*)(2) of human blood in vitro.

In view of a potential future use for dating hemorrhage in forensic medicine the correlation of MR relaxation parameters with time was evaluated in blood samples. A systematic relationship could be valuable for using MRI for estimating the age of hemorrhage and soft tissue hematomas particularly in clinical forensic medicine. Relaxation times T1, T2, and T2(*) of venous blood samples from 6 volunteers were measured using 3T MRI regularly up to 30 days. The time progression of the relaxation parameters was systematically analyzed and examined for possible interrelations. T2 initially decreased to a minimum, and then increased again (range 24-97ms), while T1 started with a plateau phase followed by an almost linear decrease (range 333-2153ms). T2(*) remained relatively constant during the entire investigation period. The higher the initial T2 was, the lower was its minimum, and the greater was the decrease of the associated T1. The inter- and intra-individual variability was relatively large, one reason being very likely the metabolic differences in the blood samples. The observed characteristic changes in blood samples over time measured by quantitative MR techniques add objective information in view of an estimation of the age of hemorrhage. However, in vivo studies will be needed to verify the data with respect to influencing metabolic factors.