A comprehensive numerical analysis of background phase correction with V-SHARP

作者：Ozbay Pinar Senay; Deistung Andreas; Feng Xiang; Nanz Daniel; Reichenbach Juergen Rainer; Schweser Ferdinand

来源：NMR in Biomedicine, 2017, 30(4): e3550.

DOI：10.1002/nbm.3550

• background field removal
• phase
• quantitative susceptibility mapping (QSM)
• sophisticated harmonic artifact reduction for phase data (SHARP)

Sophisticated harmonic artifact reduction for phase data (SHARP) is a method to remove background field contributions in MRI phase images, which is an essential processing step for quantitative susceptibility mapping (QSM). To perform SHARP, a spherical kernel radius and a regularization parameter need to be defined. In this study, we carried out an extensive analysis of the effect of these two parameters on the corrected phase images and on the reconstructed susceptibility maps. As a result of the dependence of the parameters on acquisition and processing characteristics, we propose a new SHARP scheme with generalized parameters. The new SHARP scheme uses a high-pass filtering approach to define the regularization parameter. We employed the variable-kernel SHARP (VSHARP) approach, using different maximum radii (R-m) between 1 and 15mm and varying regularization parameters (f) in a numerical brain model. The local root-mean-square error (RMSE) between the ground-truth, background-corrected field map and the results from SHARP decreased towards the center of the brain. RMSE of susceptibility maps calculated with a spatial domain algorithm was smallest for R-m between 6 and 10mm and f between 0 and 0.01mm(-1), and for maps calculated with a Fourier domain algorithm for R-m between 10 and 15mm and f between 0 and 0.0091mm(-1). We demonstrated and confirmed the new parameter scheme in vivo. The novel regularization scheme allows the use of the same regularization parameter irrespective of other imaging parameters, such as image resolution.

• 出版日期2017-4