In vitro proton T 1 and T 2 studies on rat liver: Analysis of multiexponential relaxation processes

At 37°C and 20 MHz, the T 1 and T 2 proton relaxation processes in intact rat liver tissue are multiexponential functions which in the majority of cases were decomposed into a major (α* ≈ 90%, T   1 *= 374 ms, T   2 *= 58 ms) and a minor (α** ≈ 10%, T   1 **= 130 ms, T   2 **= 181 ms) component. Both, T 1 and T 2 , are temperature‐dependent with a temperature shift of Δ T 1 = 1.5 ms/°C and Δ T 2 = 0.5 ms/°C, respectively. Storage of liver tissue at 4°C and 37°C led to remarkable changes of the T 1 and T 2 values. For T 2 these changes occurred after a shorter storage time than for T 1 , but they are more pronounced for T 1 , To avoid such influences the relaxation measurements were performed within one hour after excision of the tissue. Even at 4°C, long‐term storage (>3h) must be avoided. A method for the quantitative determination of the fat content in liver based on multiexponential analysis of the T 1 relaxation process was evaluated employing mixtures of triolein with liver homogenate. Triolein is a two‐component system with T   1 *= 144 ms (α* = 62%) and T   1 **= 355 ms (α** = 38%). Finally, liver‐specific protocol conditions were defined for in vitro relaxation studies. © 1986 Academic Press, Inc.