awsLocalSigma {aws} R Documentation

3D variance estimation

Description

Functions for 3D variance estimation. awsLocalSigma implements the local adaptive variance estimation procedure introduced in Tabelow, Voss and Polzehl (2015). awslinsd uses a parametric model for varianc/mesn dependence. Functions AFLocalSigma and estGlobalSigma implement various proposals for local and global variance estimates from Aja-Fernandez (2009, 2013) and a global variant of the approach from Tabelow, Voss and Polzehl (2015).

Usage

awsLocalSigma(y, steps, mask, ncoils, vext = c(1, 1), lambda = 5,
minni = 2, hsig = 5, sigma = NULL, family = c("NCchi", "Gauss"),
verbose = FALSE, trace = FALSE, u = NULL)
awslinsd(y, hmax = NULL, hpre = NULL, h0 = NULL, mask = NULL,
ladjust = 1, wghts = NULL, varprop = 0.1, A0, A1)
AFLocalSigma(y, ncoils, level = NULL, mask = NULL, h = 2, hadj = 1,
vext = c(1, 1))
estGlobalSigma(y, mask = NULL, ncoils = 1, steps = 16, vext = c(1, 1),
lambda = 20, hinit = 2, hadj = 1, q = 0.25, level = NULL,
sequence = FALSE, method = c("awsVar", "awsMAD", "AFmodevn",
"AFmodem1chi", "AFbkm2chi", "AFbkm1chi"))
estimateSigmaCompl(magnitude, phase, mask, kstar = 20, kmin = 8, hsig = 5,
lambda = 12, verbose = TRUE)

Value

all functions return lists with variance estimates in component sigma

Author(s)

J\"org Polzehl polzehl@wias-berlin.de

References

K. Tabelow, H.U. Voss, J. Polzehl, Local estimation of the noise level in MRI using structural adaptation, Medical Image Analysis, 20 (2015), 76–86. DOI:10.1016/j.media.2014.10.008.

S. Aja-Fernandez, V. Brion, A. Tristan-Vega, Effective noise estimation and filtering from correlated multiple-coil MR data. Magn Reson Imaging, 31 (2013), 272-285. DOI:10.1016/j.mri.2012.07.006

S. Aja-Fernandez, A. Tristan-Vega, C. Alberola-Lopez, Noise estimation in single- and multiple-coil magnetic resonance data based on statistical models. Magn Reson Imaging, 27 (2009), 1397-1409. DOI:10.1016/j.mri.2009.05.025.

[Package aws version 2.5-5 Index]