Description:
<jats:sec><jats:title>Purpose</jats:title><jats:p>To improve distortion correction for isotropic high‐resolution whole‐brain 3D diffusion MRI when in a time‐saving acquisition scenario.</jats:p></jats:sec><jats:sec><jats:title>Theory and methods</jats:title><jats:p>Data were acquired using simultaneous multi‐slab (SMSlab) acquisitions, with a b = 0 image pair encoded by reversed polarity gradients (RPG) for phase encoding (PE) and diffusion weighted images encoded by a single PE direction. Eddy current‐induced distortions were corrected first. During the following susceptibility distortion correction, image deformation was first corrected by the field map estimated from the b = 0 image pair. Intensity variation was subsequently corrected by Jacobian modulation. Two Jacobian modulation methods were compared. They calculated the Jacobian modulation map from the field map, or from the deformation corrected b = 0 image pair, termed as <jats:italic>J<jats:sub>Field</jats:sub></jats:italic> and <jats:italic>J<jats:sub>RPG</jats:sub></jats:italic>, respectively. A modified version of the <jats:italic>J<jats:sub>RPG</jats:sub></jats:italic> method, with proper smoothing, was further proposed for improved correction performance, termed as <jats:italic>J<jats:sub>RPG‐smooth</jats:sub></jats:italic>.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Compared to <jats:italic>J<jats:sub>Field</jats:sub></jats:italic> modulation, less remaining distortions are observed when using the <jats:italic>J<jats:sub>RPG</jats:sub></jats:italic> and <jats:italic>J<jats:sub>RPG‐smooth</jats:sub></jats:italic> methods, especially in areas with large B0 field inhomogeneity. The original <jats:italic>J<jats:sub>RPG</jats:sub></jats:italic> method causes signal‐to‐noise ratio (SNR) deficiency problem, which manifests as degraded SNR of the diffusion weighted images, while the <jats:italic>J<jats:sub>RPG‐smooth</jats:sub></jats:italic> method maintains the original image SNR. Less estimation errors of diffusion metrics are observed when using the <jats:italic>J<jats:sub>RPG‐smooth</jats:sub></jats:italic> method.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>This study improves the distortion correction for isotropic high‐resolution whole‐brain 3D diffusion MRI by optimizing Jacobian modulation. The optimized method outperforms the conventional <jats:italic>J<jats:sub>Field</jats:sub></jats:italic> method regarding intensity variation correction and accuracy of diffusion metrics estimation, and outperforms the original <jats:italic>J<jats:sub>RPG</jats:sub></jats:italic> method regarding SNR performance.</jats:p></jats:sec>