title: Calculating T2 in images from a phased array receiver.
abstract: 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.
authors.affiliation: Center for Biomedical Engineering, University of Kentucky, Lexington, Kentucky 40536-0098, USA. PeterHardy@mri.uky.edu
authors.forename: Peter A
authors.initials: PA
authors.lastname: Hardy
authors.forename: Anders H
authors.initials: AH
authors.lastname: Andersen
mesh_terms: 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