Hepatic hemosiderosis in non‐human primates: Quantification of liver iron using different field strengths

Using a non‐human primate model of idiopathic hemochro‐matosis, hemosiderin‐induced T 2 shortening of the liver was assessed at nine different field strengths over a range of 0.05 to 1.5 Tesla. The 1/ T 2 values increased linearly with field strength, with all specimens having approximately the same zero‐field intercept. The slope of the field increase, termed “field‐dependent T 2 proton relaxation enhancement (PRE)”, appeared to be proportional to the chemically determined tissue iron content, viz. 10.8 s −1 T −1 (mg Fe/g wet tissue) −1 . The correlation between iron content and field‐dependent T 2 PRE ( r = 0.94) was better than the correlation between iron content and 1/ T 2 values obtained at single field strengths. For livers containing ± 2 mg Fe/g wet weight, biexponential T 2 relaxation behavior emerged at higher field strengths, with the short T 2 component (intracellular water) exhibiting a linear dependence of 1/ T 2 on field, while T 2 of the long component (extracellular/sinusoidal water) was nearly field‐independent. After maceration of the specimens, all T 2 relaxation curves became monoexponential, including those for high iron content at high field strengths. The present data suggest that the use of double‐field MR imaging to assess the field‐dependent T 2 PRE has potential for specific quantification of (liver) tissue iron stores.