Biomedical subjects

Haruyasu Yamada

Publications and source records attributed to Haruyasu Yamada.

21 records · Page 2Linked to original sources

PubMedDate not supplied

Normal aging in the central nervous system: quantitative MR diffusion-tensor analysis.

The purpose of this study is to elucidate changes in mean diffusivity (ADC) and fractional anisotropy (FA) using MR diffusion tensor imaging (DTI) in the central nervous system during normal aging. We studied 50 normal volunteers (30 men, 20 women; mean age 44.8 +/- 14.0; age range, 21-69 years) without disorders affecting the central nervous system. The frontal, parietal white matter, lentiform nucleus, posterior limb of internal capsule, thalamus, genu and splenium of the corpus callosum were selected for investigation. There was no significant difference in ADC or FA between male and female or between the right and left hemisphere. A significant ADC increase with advancing age was observed in frontal white matter (P = 0.010) and lentiform nucleus (P = 0.022). A significant FA decline was found only in the genu of the corpus callosum (P < 0.001) with advancing age. Quantitative diffusion tensor analysis correlate with normal aging and may help in assessing normal age-related changes and serve as a standard for comparison with neurodegenerative disorders.

Adult↗

PubMedDate not supplied

Topography of the human corpus callosum using diffusion tensor tractography.

OBJECTIVE: To evaluate the crossing fiber trajectory through the corpus callosum using distortion-corrected diffusion tensor tractography in the human brain. METHODS: After correcting distortion associated with large-diffusion gradients, T2-weighted echo planar images (EPIs) acquired from 10 right-handed healthy men were coregistered into T2-weighted fast spin echo images using linear through sixth-order nonlinear, 3-dimensional, polynomial warping functions. The optimal transformation parameters were also applied to the distortion-corrected diffusion-weighted EPIs. Diffusion tensor tractography through the corpus callosum was reconstructed, employing the "1 or 2 regions of interest" method. RESULTS: Compared with the lines through the genu, those through the rostrum ran more inferiorly and seemed to enter the orbital gyrus. Those lines entering posterior temporal white matter (tapetum) crossed through the ventral portion of the splenium and were clearly distinguished from lines that reached parieto-occipital white matter (forceps major). CONCLUSION: Diffusion tensor tractography is a feasible noninvasive tool to evaluate commissural fiber trajectory.

Adult↗

PubMedDate not supplied

Periodically rotated overlapping parallel lines with enhanced reconstruction-based diffusion tensor imaging. Comparison with echo planar imaging-based diffusion tensor imaging.

OBJECTIVE: To evaluate diffusion tensor imaging (DTI) based on periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) compared with DTI based on single-shot echo planar imaging (EPI). METHODS: Diffusion tensor data were acquired with PROPELLER (PROPELLER-DTI, 3 NEX), EPI (EPI-DTI2, 16 NEX) with the same acquisition time (11.4 minutes) and with EPI (EPI-DTI1, number of excitations = 4) with a shorter acquisition time (2.8 minutes). Regions of interest were set in the genu and splenium of the corpus callosum, as determined on T2-weighted fast spin echo images and fractional anisotropy (FA) maps, separately. Two neuroradiologists visually evaluated image distortion and quality in the supra- and infratentorial structures. RESULTS: In the genu, standard deviation determined by respective FA maps was decreased in order of PROPELLER-DTI, EPI-DTI1, and EPI-DTI2. Both EPI-DTI sequences were quantitatively superior in the splenium, but PROPELLER-DTI was less distorted. CONCLUSION: Periodically rotated overlapping parallel lines with enhanced reconstruction-DTI could become a complementary tool when qualitatively evaluating seriously distorted structures.

Adult↗