Effects of Gradient Nonlinearity, Its Correction Methods & Distortion on Diffusion Weighted Imaging

Ek T. Tan¹, Luca Marinelli¹, Zachary W. Slavens², Christopher J. Hardy¹, Kevin F. King²

The apparent diffusion coefficient (ADC) obtained with diffusion weighted imaging (DWI) is a promising non-contrast cancer imaging bio-marker. Gradient nonlinearity (GN) results in spatially-varying ADC, an effect that is confounded by distortion related to the DWI acquisition. Evaluations were performed in two whole-body MRI systems at 1.5T in various anatomical regions. GN correction (GNC) used up to 13 orders of spherical harmonics, and was used with and without the full b-matrix in the diffusion-tensor computation. GNC resulted in a significant reduction in ADC error in both systems. Distortion effects resulted in a significant ADC difference between both systems.