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Spectral fitting using basis set modified by measured B 0 field distribution
Author(s) -
Li Ningzhi,
An Li,
Shen Jun
Publication year - 2015
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3430
Subject(s) - voxel , basis (linear algebra) , basis function , monte carlo method , kurtosis , nuclear magnetic resonance , imaging phantom , physics , algorithm , mathematics , computer science , artificial intelligence , optics , mathematical analysis , statistics , geometry
This study sought to demonstrate and evaluate a novel spectral fitting method to improve quantification accuracy in the presence of large magnetic field distortion, especially with high fields. MRS experiments were performed using a point‐resolved spectroscopy (PRESS)‐type sequence at 7 T. A double‐echo gradient echo (GRE) sequence was used to acquire B 0 maps following MRS experiments. The basis set was modified based on the measured B 0 distribution within the MRS voxel. Quantification results were obtained after fitting the measured MRS data using the modified basis set. The proposed method was validated using numerical Monte Carlo simulations, phantom measurements, and comparison of occipital lobe MRS measurements under homogeneous and inhomogeneous magnetic field conditions. In vivo results acquired from voxels placed in thalamus and prefrontal cortex regions close to the frontal sinus agreed well with published values. Instead of noise‐amplifying complex division, the proposed method treats field variations as part of the signal model, thereby avoiding inherent statistical bias associated with regularization. Simulations and experiments showed that the proposed approach reliably quantified results in the presence of relatively large magnetic field distortion. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.