Field and TE independent liver iron concentration estimation using signal intensity ratios

Motivation: Estimation of liver iron concentration by R2* relaxation (LICR2*) is a powerful and widely used technique, however, it may fail from signal loss at high liver iron concentration. Goal(s): To estimate LIC from a single-TE liver-muscle signal intensity ratio (LICSIR) and validate at 1.5 and 3.0 Tesla. Approach: Using LICR2* estimates collected at 1.5T as a reference, we compared LICSIR estimates in 15 subjects who had undergone MRI examination at both 1.5T and 3.0T. Results: We were able to derive field-independent scaling constants that allow LICSIR estimation at 1.5 and 3.0T, more than doubling the effective dynamic range of LICR2* estimation. Impact: This generalized framework for LICSIR estimation allows reasonable LIC values to be reported (and trended) in patients for whom traditional relaxometry has failed. It also allows approximate LIC calculation from commonly used single and dual echo gradient echo acquisitions.