Takashi Yoshiura MD, PhD, Presenter: Nothing to Disclose

Akio Hiwatashi MD, Abstract Co-Author: Nothing to Disclose

Koji Yamashita MD, Abstract Co-Author: Nothing to Disclose

Satoshi O Suzuki MD, PhD, Abstract Co-Author: Nothing to Disclose

Hironori Kamano MD, Abstract Co-Author: Nothing to Disclose

Hiroshi Honda MD, Abstract Co-Author: Nothing to Disclose

Intracortical myelinated fibers in the medial temporal lobe (MTL) such as the perforant pathway are among the key structures of the hippocampal function, and are known to play a crucial role in Alzheimer’s disease. Our purpose was to test the clinical feasibility of assessment of intracortical myelinated fibers in MTL using high-resolution diffusion-tensor imaging (HR-DTI).

15 healthy subjects (mean age 31 years) were studied using a 3T imager. Coronal HR-DTIs of the left MTL were obtained using the small FOV technique at an in-plane resolution of 1.0x1.0 mm2: b factor=700s/mm2, slice thickness=3mm, number of slices=15, number of averaging=16 (b=700)/8 (b=0), imaging time=11min 54s. Mean values of mean diffusivity (MD) and fractional anisotropy (FA) were measured in manually drawn ROIs by 2 independent raters within the following 4 cortical regions: entorhinal cortex (ERC), subiculum (SUB), cornu ammonis 1 (CA1), and CA4/dentate gyrus (CA4/DG). The inter-rater agreement of the measurements was assessed using intraclass correlation coefficient (ICC). MD and FA values within the 4 regions were statistically compared using ANOVA and post-hoc Tukey HSD test at a significance level of P < .05. The DTI results were compared with histological findings of a human specimen prepared with myelin sheath staining.

The inter-rater agreement was excellent for both MD (ICC=0.805) and FA (0.958). The two raters agreed in the following statistical results. Comparison of MD showed that MD in SUB was significantly lower than that in the other 3 regions, while MD in CA4/DG was significantly higher than that in the other 3 regions. Comparison of FA showed that FA in SUB was significantly higher than that in the other 3 regions. In addition, FA in ERC was significantly higher FA than that in CA1 and CA4/DG, respectively. Histological examination revealed that SUB and, to a lesser degree, ERC were characterized by denser intracortical myelinated fibers than CA1 and CA4/DG, corresponding to the lower MD and higher FA in these regions.

Our results suggested that HR-DTI can be used to assess intracortical myelinated fibers with clinically relevant imaging time and good inter-rater agreement.

Quantitative evaluation of intracortical myelinated fibers by high-resolution DTI may be useful to detect early microstructural changes in neurological diseases such as Alzheimer disease.

Yoshiura, T, Hiwatashi, A, Yamashita, K, Suzuki, S, Kamano, H, Honda, H, High-Resolution Diffusion-tensor Imaging: In Vivo Assessment of Intracortical Myelinated Fibers in the Medial Temporal Lobe.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11011084.html