Zhongwei Zhang MD, Presenter: Nothing to Disclose

Jens H Jensen PhD, Abstract Co-Author: Nothing to Disclose

Hina Jaggi, Abstract Co-Author: Nothing to Disclose

Yulin Ge MD, Abstract Co-Author: Nothing to Disclose

Robert I. Grossman MD, Abstract Co-Author: Nothing to Disclose

Water in biological tissue often shows non-Gaussian diffusion behavior due to the structural complexity of the tissue. In this study, we used diffusional kurtosis imaging (DKI), a method based on non-Gaussian model, to characterize water diffusion behavior in multiple sclerosis (MS) lesions and brain tissues.

18 relapsing-remtting (RR) MS patients and 20 normal controls were enrolled in this study. DKI data, which also provide the conventional diffusion tensor, were acquired at 3T using a dual-spin-echo echo planar imaging (EPI) diffusion sequence with TR/TE=3700/90 msec, 30 gradient encoding directions with 3 b values (0, 1000, 2000 s/mm2) for each direction. DKI data were processed offline with the following voxel-by-voxel parametric maps derived: axial diffusivity (Dax), radial diffusivity (Drad), mean diffusivity (MD), fractional anisotropy (FA), axial kurtosis (Kax), radial kurtosis (Krad) and mean kurtosis (MK). The gray matter (GM), white matter (WM) and cerebrospinal fluid (CSF) were segmented using FAST algorithm implemented in FSL for global histogram analysis

Relative to contralateral normal tissues, MS lesions (n=25) showed increased diffusivity (i.e. Dax, Drad, MD), decreased FA, and decreased kurtosis (i.e. Kax, Krad, and MK). Kax, an index of kurtosis along the axons in WM, was significantly decreased in T1-hypointense lesions (mean±SD: 0.63 ± 0.10) compared to T1-isointense lesions (0.74±0.14, P < .05), indicating the different degree of axonal injury. Compared to nonenhancing lesions, kurtosis measures showed lower Kax, Krad and MK values in enhancing lesions than in non-ehancing lesions. There was significantly decreased Kax (P<0.05) in global GM and increased Krad (P<0.001) in global WM.

Our preliminary results suggest that kurtosis imaging (particularly Kax) may have potential in identifying the degrees of axonal injury in MS lesions. DKI is also sensitive in detecting global pathological changes of GM and WM in MS.

The MS patients demonstrate kurtosis metrics changes. This may prove useful in detecting pathology, predicting clinical course, and monitoring disease progression and therapeutic effect in MS.

Zhang, Z, Jensen, J, Jaggi, H, Ge, Y, Grossman, R, Diffusional Kurtosis Imaging in Multiple Sclerosis.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11013893.html