Rapid Look-Up Table Method for Noise-Corrected Curve Fitting in the R2*Mapping of Iron Loaded Liver

PurposeFitting the measured decay signal to the first moment in the presence of noncentral chi noise ((MNCM)-N-1) can correctly address the effect of noise on the effective transverse relaxation rate (R2*) relaxometry of iron loaded liver. However, this method requires intensive computation, which restricts its application to R2* mapping. This work aims to develop a rapid implementation of the (MNCM)-N-1 method for R2* mapping. MethodsThe computation of the confluent hypergeometric function in the (MNCM)-N-1 model was approximated using cubic spline interpolation with breakpoints and coefficients precalculated and stored in a look-up table ((MNCM)-N-1-LUT). The performance of the proposed (MNCM)-N-1-LUT method was evaluated through simulation and based on in vivo liver R2* relaxometry data. ResultsIn both simulation and in vivo studies, the maximum absolute difference between R2* maps generated by the (MNCM)-N-1 and (MNCM)-N-1-LUT methods was nearly 10(-3) s(-1) or less, and the (MNCM)-N-1-LUT method obtained a R2* map in approximately 1 s and achieved an acceleration of approximately five orders of magnitude. ConclusionThe proposed (MNCM)-N-1-LUT method can significantly increase the speed of the liver R2* mapping using the (MNCM)-N-1 model. This development is important in promoting application of this R2* mapping technique for tissue iron quantification. Magn Reson Med 73:865-871, 2015. (c) 2014 Wiley Periodicals, Inc.