Purpose: We measured T 1 and T 2 values of cerebral postmortem magnetic resonance (PMMR) imaging and compared the data of cadavers with that of living human subjects.Materials and Methods: We performed PMMR imaging of the brains of 30 adults (22 men, 8 women; mean age, 58.2 years) whose deaths were for reasons other than brain injury or disease at a mean of 29.4 hours after death. Before imaging, the bodies were kept in cold storage at 4°C (mean rectal temperature, 15.6°C). We measured T 1 and T 2 values in the brain bilaterally at 5 sites (bilateral caudate nucleus, putamen, thalamus and gray matter and white matter of the frontal lobe) and compared the data of PMMR imaging with that from MR imaging of the corresponding sites in 24 healthy volunteers (9 men, 15 women; mean age, 51.8 years). We also investigated the influence of body temperature on T 1 and T 2 values.Results: Compared with MR imaging findings in the living subjects, PMMR imaging showed significantly shorter T 1 values in the caudate nucleus, putamen, thalamus and gray matter and white matter of the frontal lobe and significantly longer T 2 values in the gray matter and white matter of the frontal lobe; T 2 values in the caudate nucleus, putamen, and thalamus showed no such differences. T 1 values correlated significantly with body temperature in all 5 brain sites measured, but T 2 values did not.Conclusion: Compared with findings of cerebral MR imaging in living adult subjects, those of PMMR imaging tended to demonstrate shorter T 1 values and longer T 2 values. We attribute this to increased water content of tissue, reduced pH, and reduced body temperature after death.

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Purpose: Signal intensity (SI) and image contrast on postmortem magnetic resonance (MR) imaging are different from those of imaging of living bodies. We sought to suppress the SI of cerebrospinal fluid (CSF) sufficiently for fluid-attenuated inversion recovery (FLAIR) sequence in postmortem MR (PMMR) imaging by optimizing inversion time (TI).Materials and Methods: We subject 28 deceased patients to PMMR imaging 3 to 113 hours after confirmation of death (mean, 27.4 hrs.). PMMR imaging was performed at 1.5 tesla, and T 1 values of CSF were measured with maps of relaxation time. Rectal temperatures (RT) measured immediately after PMMR imaging ranged from 6 to 32°C (mean, 15.4°C). We analyzed the relationship between T 1 and RT statistically using Pearson's correlation coefficient. We obtained FLAIR images from one cadaver using both a TI routinely used for living bodies and an optimized TI calculated from the RT.Results: T 1 values of CSF ranged from 2159 to 4063 ms (mean 2962.4), and there was a significantly positive correlation between T 1 and RT (r = 0.96, P < 0.0001). The regression expression for the relationship was T 1 = 74.4 * RT + 1813 for a magnetic field strength of 1.5T. The SI of CSF was effectively suppressed with the optimized TI (0.693 * T 1 ), namely, TI = 0.693 * (77.4 * RT + 1813).Conclusion: Use of the TI calculated from the linear regression of the T 1 and RT optimizes the FLAIR sequence of PMMR imaging.

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