BACKGROUND AND PURPOSE Along with cortical abnormalities, white matter microstructural changes such as axonal loss and myelin breakdown are implicated in the pathogenesis of Alzheimer disease. Recently, a white matter model was introduced that relates non-Gaussian diffusional kurtosis imaging metrics to characteristics of white matter tract integrity, including the axonal water fraction, the intra-axonal diffusivity, and the extra-axonal axial and radial diffusivities. MATERIALS AND METHODS This study reports these white matter tract integrity metrics in subjects with amnestic mild cognitive impairment (n = 12), Alzheimer disease (n = 14), and age-matched healthy controls (n = 15) in an effort to investigate their sensitivity, diagnostic accuracy, and associations with white matter changes through the course of Alzheimer disease. RESULTS With tract-based spatial statistics and region-of-interest analyses, increased diffusivity in the extra-axonal space (extra-axonal axial and radial diffusivities) in several white matter tracts sensitively and accurately discriminated healthy controls from those with amnestic mild cognitive impairment (area under the receiver operating characteristic curve = 0.82–0.95), while widespread decreased axonal water fraction discriminated amnestic mild cognitive impairment from Alzheimer disease (area under the receiver operating characteristic curve = 0.84). Additionally, these white matter tract integrity metrics in the body of the corpus callosum were strongly correlated with processing speed in amnestic mild cognitive impairment (r= |0.80–0.82|, P< .001). CONCLUSIONS These findings have implications for the course and spatial progression of white matter degeneration in Alzheimer disease, suggest the mechanisms by which these changes occur, and demonstrate the viability of these white matter tract integrity metrics as potential neuroimaging biomarkers of the earliest stages of Alzheimer disease and disease progression.

Careful review of MR imaging in patients with refractory temporal lobe epilepsy by a board-certified neuroradiologist with special attention paid to a high-resolution T2 sequence can increase the detection of subtle temporal encephaloceles, and certain clinical and neurophysiologic findings should raise the suspicion for their presence.

BACKGROUND AND PURPOSE:Gadobenate dimeglumine (MultiHance) has higher r1 relaxivity than gadoterate meglumine (Dotarem) which may permit the use of lower doses for MR imaging applications. Our aim was to compare 0.1-and 0.05-mmol/kg body weight gadobenate with 0.1-mmol/kg body weight gadoterate for MR imaging assessment of brain tumors.

Background and Purpose To evaluate whether diffusional kurtosis imaging (DKI) can detect corticospinal tract (CST) microstructural changes in the acute phase for patients with first-ever ischemic stroke and motor impairment, and to assess the correlations between DKI-derived diffusion metrics for the CST and motor impairment 3 months post-stroke. Materials and Methods We evaluated seventeen stroke patients who underwent a brain MRI including DKI within four days after the onset of symptoms. Neurological evaluation included the Fugl-Meyer Motor Upper Extremity scale (FM-UE) in the acute phase and 3 months post-stroke. For the CST in the lesioned and contralateral hemispheres, we estimated with DKI both pure diffusion metrics, such as the mean diffusivity and mean kurtosis, as well as model-dependent quantities, such as the axonal water fraction. We evaluated the correlations between CST diffusion metrics and FM-UE at 3 months. Results Among all the diffusion metrics, the largest percent signal changes of the lesioned hemisphere CST were observed using axial kurtosis, with an average 12% increase compared to the contralateral CST. The strongest associations between 3-month FM-UE and diffusion metrics were found for the lesioned / contralateral hemisphere CST mean kurtosis (rho = − 0.85) and axial kurtosis (rho = − 0.78) ratios. Conclusion This study was designed to be one of hypothesis generation. Diffusion metrics related to the kurtosis were found to be more sensitive than conventional diffusivity metrics to early post-stroke CST microstructural changes and may have potential value in the prediction of motor impairment at 3 months.

Improved image quality and vascular contrast enhancement of spinal MRA at 1.5T is achieved with high T1 relaxivity gadolinium contrast agents compared with conventional agents at equivalent doses.