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Calculating T 2 in images from a phased array receiver
Author(s) -
Hardy Peter A.,
Andersen Anders H.
Publication year - 2009
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.21904
Subject(s) - phased array , distortion (music) , noise (video) , signal (programming language) , signal to noise ratio (imaging) , electromagnetic coil , mathematics , lookup table , least squares function approximation , square root , algorithm , physics , image (mathematics) , optics , statistics , acoustics , computer science , artificial intelligence , telecommunications , geometry , amplifier , bandwidth (computing) , quantum mechanics , antenna (radio) , programming language , estimator
Images reconstructed from multielement, phased array coils and presented as the square root of the sum of the squares of the signals received by the individual elements have a distribution of signal and noise that distorts the relationship between the image intensity and the underlying signal. The distortion is accentuated for long echo times for which the signal‐to‐noise ratio (SNR) may be low. When measuring T 2 or T 2 *this signal distortion leads to biased estimates of these parameters. We demonstrate this effect and its dependence on the image SNR and the number of elements in a phased array coil. We evaluated the effects of four techniques for calculating T 2 from data acquired in phased array coils (log transform, least squares, lookup table correction, and maximum likelihood [ML] estimation). The ML estimation gave the most accurate T 2 in the presence of this bias. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.