A hybrid (iron-fat-water) phantom for liver iron overload quantification in the presence of contaminating fat using magnetic resonance imaging

Objective Assessment of iron content in the liver is crucial for diagnosis/treatment of iron-overload diseases. Nonetheless, T-2*-based methods become challenging when fat and iron are simultaneously present. This study proposes a phantom design concomitantly containing various concentrations of iron and fat suitable for devising accurate simultaneous T-2* and fat quantification technique. Materials and methods A 46-vial iron-fat-water phantom with various iron concentrations covering clinically relevant T-2* relaxation time values, from healthy to severely overloaded liver and wide fat percentages ranges from 0 to 100% was prepared. The phantom was constructed using insoluble iron (II, III) oxide powder containing microscale particles. T-2*-weighted imaging using multi-gradient-echo (mGRE) sequence, and chemical shift imaging spin-echo (CSI-SE) Magnetic Resonance Spectroscopy (MRS) data were considered for the analysis. T-2* relaxation times and fat fractions were extracted from the MR signals to explore the effects of fat and iron overload. Results Size distribution of iron oxide particles for Magnetite fits with a lognormal function with a mean size of about 1.17 mu m. Comparison of FF color maps, estimated from bi- and mono-exponential model indicated that single-T-2* fitting model resulted in lower NRMSD. Therefore, T-2* values from the mono-exponential signal equation were used and expressed the relationship between relaxation time value across all iron (Fe) and fat concentration as Fe=-28.02+302.84T2*-0.045FF with R-squared = 0.89. Discussion The proposed phantom design with microsphere iron particles closely simulated the single-T-2* behavior of fatty iron-overloaded liver in vivo.