Premium
Correction of systematic errors in quantitative proton density mapping
Author(s) -
Volz Steffen,
Nöth Ulrike,
Deichmann Ralf
Publication year - 2012
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.23206
Subject(s) - weighting , sensitivity (control systems) , proton , reciprocity (cultural anthropology) , systematic error , electromagnetic coil , nuclear magnetic resonance , amplitude , computational physics , mathematics , physics , algorithm , statistics , optics , acoustics , nuclear physics , quantum mechanics , electronic engineering , psychology , social psychology , engineering
Interest in techniques yielding quantitative information about brain tissue proton densities is increasing. In general, all parameters influencing the signal amplitude are mapped in several acquisitions and then eliminated from the image data to obtain pure proton density weighting. Particularly, the measurement of the receiver coil sensitivity profile is problematic. Several methods published so far are based on the reciprocity theorem, assuming that receive and transmit sensitivities are identical. Goals of this study were (1) to determine quantitative proton density maps using an optimized variable flip angle method for T 1 mapping at 3 T, (2) to investigate if systematic errors can arise from insufficient spoiling of transverse magnetization, and (3) to compare two methods for mapping the receiver coil sensitivity, based on either the reciprocity theorem or bias field correction. Results show that insufficient spoiling yields systematic errors in absolute proton density of about 3–4 pu. A correction algorithm is proposed. It is shown that receiver coil sensitivity mapping based on the reciprocity theorem yields erroneous proton density values, whereas reliable data are obtained with bias field correction. Absolute proton density values in different brain areas, evaluated on six healthy subjects, are in excellent agreement with recent literature results. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.