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Measurement of signal‐to‐noise ratios in MR images: Influence of multichannel coils, parallel imaging, and reconstruction filters
Author(s) -
Dietrich Olaf,
Raya José G.,
Reeder Scott B.,
Reiser Maximilian F.,
Schoenberg Stefan O.
Publication year - 2007
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.20969
Subject(s) - imaging phantom , noise (video) , signal to noise ratio (imaging) , standard deviation , pixel , signal (programming language) , iterative reconstruction , electromagnetic coil , image noise , computer science , mathematics , physics , artificial intelligence , optics , image (mathematics) , statistics , quantum mechanics , programming language
Purpose To evaluate the validity of different approaches to determine the signal‐to‐noise ratio (SNR) in MRI experiments with multi‐element surface coils, parallel imaging, and different reconstruction filters. Materials and Methods Four different approaches of SNR calculation were compared in phantom measurements and in vivo based on: 1) the pixel‐by‐pixel standard deviation (SD) in multiple repeated acquisitions; 2) the signal statistics in a difference image; and 3) and 4) the statistics in two separate regions of a single image employing either the mean value or the SD of background noise. Different receiver coil systems (with one and eight channels), acquisitions with and without parallel imaging, and five different reconstruction filters were compared. Results Averaged over all phantom measurements, the deviations from the reference value provided by the multiple‐acquisitions method are 2.7% (SD 1.6%) for the difference method, 37.7% (25.9%) for the evaluation of the mean value of background noise, and 34.0% (38.1%) for the evaluation of the SD of background noise. Conclusion The conventionally determined SNR based on separate signal and noise regions in a single image will in general not agree with the true SNR measured in images after the application of certain reconstruction filters, multichannel reconstruction, or parallel imaging. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.