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Summary: Signal-to-NoiseMeasurements in Magnitude Images from
NMR Phased Arrays
Chris D. Constantinides, Ergin Atalar, Elliot R. McVeigh
A method is proposedto estimate signal-to-noise ratio (SNR)
values in phasedarray magnitudeimages,based on a region-
of-interest (ROI) analysis. It is shown that the SNR can be
found by correcting the measured signal intensity for the
noisebiaseffects and by evaluatingthe noisevariance as the
mean square value of all the pixel intensities in a chosen
background ROI, divided by twice the number of receivers
used.EstimatedSNR values are shownto vary spatiallywithin
a boundof 20% with respectto the true SNR valuesas a result
of noise correlations between receivers.
Key words: phased array coils; noise correlations; signal-to-
noise.
INTRODUCTION
Magnetic resonance images traditionally have been pre-
sented as the magnitude value of a complex data array.
These images have been used in practical imaging sys-
tems for clinical interpretation because they are not sus-
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