Calculating T2 in images from a phased array receiver.
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.
Hardy
Peter A
PA
Center for Biomedical Engineering, University of Kentucky, Lexington, Kentucky 40536-0098, USA. PeterHardy@mri.uky.edu
Andersen
Anders H
AH
D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers