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T 2 and T 2 * quantification using optimal B 1 image reconstruction for multicoil arrays
Author(s) -
Graves Martin J.,
Emmens Daniel,
Lejay Hubert,
Hariharan Hari,
Polzin Jason,
Lomas David J.
Publication year - 2008
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21420
Subject(s) - rss , noise (video) , signal to noise ratio (imaging) , nuclear magnetic resonance , signal (programming language) , calibration , iterative reconstruction , computer science , nuclear medicine , biomedical engineering , physics , mathematics , algorithm , artificial intelligence , image (mathematics) , optics , medicine , statistics , programming language , operating system
Purpose To investigate the accuracy of low signal‐to‐noise ratio (SNR) T 2 and T 2 *measurements using array coils and optimal B 1 image reconstruction (OBR) compared to the standard root sum of squares (RSS) reconstruction. Materials and Methods Calibrated gels were used for the in vitro study of T 2 . T 2 and T 2 *measurements were obtained from a volunteer's knee and liver, respectively. T 2 and T 2 *measurements were performed using multiecho spin echo and multiecho gradient echo sequences, respectively. SNR was deliberately kept low. The same raw data were used for both reconstructions. For the in vivo studies the effect of signal averaging was also investigated. Results The optimal reconstructions demonstrated a lower mean background noise level than RSS. In vitro, the T 2 measurements made with OBR images agreed better with a reference high SNR measurement than measurements made from RSS images; the RSS image results overestimated the T 2. In vivo, increasing the signal averages decreased the difference between the measurements obtained using the OBR and RSS methods, with RSS resulting in longer relaxation times. Conclusion This work demonstrates improvements to the accuracy of T 2 and T 2 *measurements obtained when OBR is used compared to RSS, particularly in the case of low SNR. J. Magn. Reson. Imaging 2008;28:278–281. © 2008 Wiley‐Liss, Inc.