Clinical Implementation of a Focused MRI Protocol for Hepatic Fat and Iron Quantification

Abstract

OBJECTIVE. The purpose of this article is to describe our institutional experience with the clinical implementation of a novel focused rapid chemical shift-encoded MRI protocol specifically intended to detect and quantify hepatic steatosis and iron overload, highlighting usage statistics and issues related to cost. CONCLUSION. Focused MRI examinations for specific clinical indications, such as this protocol for detection and quantification of hepatic steatosis and iron overload, are feasible in a busy clinical practice and add value for patients and referring providers.

Keywords: MRI; R2*; chemical shift–encoded MRI; focused protocol; hepatic steatosis; iron overload; limited examination; liver; proton density fat fraction; rapid examination.

Fig. 1–

10-year-old boy with elevated aminotransferase level. Rapid fat and iron chemical shift–encoded MRI protocol shows severe hepatic steatosis. Proton density fat fraction (PDFF) map (middle) shows that patient has elevated PDFF of 45% (normal, < 5%) measured in posterior right hepatic lobe. R2* map (right) shows that R2* is normal at 35 s⁻¹ (normal, < 60 s⁻¹ at 1.5 T). Axial T2-weighted single-shot fast spin-echo MR image (left) is shown for reference. Interpretation of images is simple and straightforward, requiring only placement of ROIs (circles) over liver and reporting corresponding value.

Fig. 2–

49-year-old man with hereditary hemochromatosis. Rapid fat and iron chemical shift–encoded MRI protocol shows mild hepatic iron overload. R2* map (right) shows elevated R2* of 134 s⁻¹ (normal, < 120 s⁻¹ at 3 T) as measured in posterior right hepatic lobe. Proton density fat fraction (PDFF) map (middle) shows that PDFF is normal at 4% (normal, < 5%). Axial T2-weighted single-shot fast spin-echo MR image (left) is shown for reference. Note cirrhotic configuration of liver and T2 hypointensity of liver parenchyma due to increased iron, as well as lower R2* signal in spleen (S, right), indicative of normal iron content, which is typical pattern of iron overload in patients with hemochromatosis. Circles denote ROIs.

Fig. 3–

9-year-old girl with suspected hepatic steatosis. Rapid fat and iron chemical shift-encoded MRI protocol shows interval improvement in liver proton density fat fraction (PDFF) at follow-up. PDFF maps from initial examination (left) and follow-up examination performed 189 days later (right) show interval decrease in liver PDFF from 25% to 10% (normal liver PDFF, < 5%), thus showing substantial interval improvement in hepatic steatosis. Circles denote ROIs.