Nonlinear least squares fitting for variable flip angle T1 estimation

Abstract

The niiT1vfa program enables a fast nonlinear least squares fit for T1 estimation using a robust and efficient version of the Levenberg-Marquardt minimization algorithm provided by a derivative solver in the Gnu Scientific Library (GSL, http://www.gnu.org/software/gsl/). Input data are variable flip angle (VFA) '.nii' data and (optionally) a processed actual flip angle imaging (AFI) 'nii' data set containing the flip angle (FA) distribution resulting from the prescribed AFI flip angle. FA maps provide a voxel wise FA correction for the VFA FA prescription during fitting. Output data are a T1 estimate (T1_VFA.nii), a M0* = Mo.exp(-TE/T2*) estimate (M0_VFA.nii), and (optionally) the number of iterations (NIT_VFA.nii). The 'nii' data are in the NIfTI-1 format, http://nifti.nimh.nih.gov/ ImageJ is a suitable viewer, http://imagej.nih.gov/ij/ The niiT1vfa program was used to calculate the T1 maps from the VFA data and FA maps of four consecutively scanned mice that are publically available courtesy of the Bodleian Digital Library Systems and Services of the University of Oxford at http://dx.doi.org/10.5287/bodleian:a4awG5r7R. See Content.txt for further details