PREMORTEM AND POSTMORTEM DIFFUSION-COEFFICIENTS IN RAT NEURAL AND MUSCLE TISSUES

Pulsed gradient diffusion‐weighted spin‐echo images (7 to 11 gradient strengths) were obtained in a coronal slice through the midbrain for five normal adult white rats before and after sacrifice in a 2‐T CSI system with air temperature control. The pulse sequence was cardiac gated and respiratory synchronized in order to minimize motion artifacts (Tr > 2 s, Te ‐ 30 ms). Diffusion coefficients reflecting several tissue compartments (D*) in brain and muscle were calculated and referenced to simultaneously imaged tubes of water. In the living animals, brain cortical matter had a value of D* = (0.82 ± 0.02) × 103 mm2/s, deeper brain regions had a value of D* = (0.73 ± 0.02) × 10‐3 mm2/s, and the muscle had a value of D* = (1.4 ± 0.1) × 103 mm2/s. Postmortem the values in brain dropped by approximately 30%, while remaining constant in muscle. Signal intensity in the spin‐echo images for muscle tissue rose by 50% over a 1‐ to 2‐h interval after sacrifice while that of brain tissue remained relatively stable. © 1991 Academic Press, Inc. Copyright © 1991 Wiley‐Liss, Inc., A Wiley Company