title: The bias/variance trade-off when estimating the MR signal magnitude from the complex average of repeated measurements.
abstract: The signal-dependent bias of MR images has been considered a hindrance to visual interpretation almost since the beginning of clinical MRI. Over time, a variety of procedures have been suggested to produce less-biased images from the complex average of repeated measurements. In this work, we re-evaluate these approaches using first a survey of previous estimators in the MRI literature, then a survey of the methods statisticians employ for our specific problem. Our conclusions are substantially different from much of the previous work: first, removing bias completely is impossible if we demand the estimator have bounded variance; second, reducing bias may not be beneficial to image quality.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA. tisdall@nmr.mgh.harvard.edu
authors.forename: M Dylan
authors.initials: MD
authors.lastname: Tisdall
authors.forename: Richard A
authors.initials: RA
authors.lastname: Lockhart
authors.forename: M Stella
authors.initials: MS
authors.lastname: Atkins
mesh_terms: D001499:Bayes Theorem; D015982:Bias; D003201:Computers; D016013:Likelihood Functions; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008433:Mathematics; D059629:Signal-To-Noise Ratio