The signal intensity of diffusion-weighted imaging (DWI) is sensitive to the intra- and extracellular diffusion coefficient of water and cell membrane permeability. We applied a method we proposed in previous papers to estimate noninvasively the membrane permeability and intracellular diffusion coefficient of normal human brain (gray matter) in 3 normal volunteers. We theoretically compared predicted signals and experiment results using a 1.5-tesla magnetic resonance (MR) imaging system. We acquired images using an echo planar imaging (EPI) sequence, applying motion-probing gradient (MPG) pulses in 3 directions. We periodically performed numerical simulations for various combinations of membrane permeability and intracellular diffusion coefficients using the finite-difference method. By minimizing the difference between signals obtained experimentally and those from numerical simulation, we could estimate membrane permeability (76±9 mm²/s μm) and intracellular diffusion coefficient (1.0±0.0 mm²/s) for the human brain. The estimated membrane permeability was the criterion value for diagnosing disease in gray matter.

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Purpose: Our goal was to visualize diffusion tensor tractography (DTT) of the corticospinal tract (CST) with areas of activation on functional magnetic resonance imaging (fMRI) to acquire useful, highly accurate preoperative information. We investigated the usefulness of the technique and our method of precisely evaluating the depicted DTT in patients with brain disease.
Materials and methods: Nineteen subjects underwent 3-dimensional T₁-weighted imaging for anatomical reference; gradient-echo, echo-planar imaging (EPI) for fMRI; and single-shot, diffusion-weighted EPI for DTT. The target point for DTT was placed within activated areas in the primary motor area on fMRI, and the seed point was placed in the cerebral peduncle. DTT was depicted with the seed and target points. We examined the precision of DTT using this method by assessing the anteroposterior relationship of depicted DTTs of the upper and lower extremities in the posterior limb of the internal capsule.
Results: DTT was depicted in 18 of 19 cases of the upper extremity and in 12 of 19 cases of the lower extremity. In the evaluation of precision, DTT reflected the posterior limb of the internal capsule in all cases. In terms of the anteroposterior relationship of DTTs, nine of 12 cases showed that fibers in the upper extremities passed in front of fibers in the lower extremities.
Conclusion: This technique allows depiction of DTT associated with a local brain function in the CST in patients with brain disease and may be useful for operative planning. Our method of evaluating precision is also likely to prove useful.

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Purpose: We prospectively compared the quality of images obtained by navigator setting on the left and right diaphragm on whole-heart coronary magnetic resonance angiography (WHCMRA).
Methods: In 10 healthy volunteers, we performed free-breathing, 3-dimensional segmented true fast imaging with steady-state precession (trueFISP) WHCMRA by setting the navigator on the left and right diaphragm in random order. For the left diaphragm, we set the navigator outside the scope of the heart to avoid the influence on coronary arteries. We compared image acquisition time and visible length of coronary arteries using paired t-test and subjective image quality on a 4-point scale (1, poor; 4, excellent) using Wilcoxon signed-rank test.
Results: Mean overall subjective image quality was significantly better in the left diaphragm than the right (3.3±0.7 versus 2.9±0.9, P=0.02). Mean overall visible length of the coronary arteries was significantly better in the left diaphragm than the right (115.4±31.1 vs. 112.6±29.9 mm, P=0.02). Mean acquisition time between the left and right diaphragm was not significantly different (15.6±5.0 versus 16.0±5.7 min, P=0.79).
Conclusion: In this small group of healthy volunteers, navigator setting for WHCMRA was superior on the left diaphragm than the right; however, feasibility of the technique requires additional consideration in a larger group of actual patients.

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Spot the Differences is a simple and popular game in which an observer compares a pair of similar pictures to detect the differences between them. Functional activation of the brain while playing this game has not been investigated. We used functional magnetic resonance imaging to investigate the main cortical regions involved in playing this game and compared the sites of cortical activation between a session of playing the game and a session of viewing 2 identical pictures. The right posterior parietal cortex showed more activation during game playing, and cortical activation volume correlated with game-playing accuracy. This cortical region may play an important role in awareness of differences between 2 similar pictures.

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Background: Imaging diagnosis of Alzheimer disease (AD), the leading cause of dementia, requires evaluation of the extent of hippocampal atrophy. Coronal magnetic resonance (MR) images of patients with AD often demonstrate outward rotation of the hippocampus that is altered from a long horizontal elliptical to a long vertical elliptical shape. Such rotation may be related to the disease process of AD.
Purpose and Methods: To determine whether hippocampal rotation is associated with AD, we investigated MR images from 11 patients with AD and 11 normal controls, measuring the hippocampal angle (HA) and the volume of the left hippocampus on coronal T₁-weighted MR images.
The HA is the angle between a horizontal line orthogonal to the falx cerebri and the uncal sulcus line between the deepest point of the uncal sulcus and the point nearest to the side of the ambient cistern in the uncal gyrus facing the uncal sulcus. The HA is measured on the most rostral slice in which the uncal sulcus can be identified and increases with hippocampal rotation.
Results: We found correlation between the HA and standardized hippocampal volume in the AD group, but not in controls.
Conclusion: Hippocampal rotation is a new marker associated with the pathology of AD.

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We repeatedly measured the trabecular bone (TB) microstructure of the distal radius in 5 healthy volunteers using a compact magnetic resonance (MR) imaging system to evaluate the reproducibility of the TB structural parameters. The compact system was specially developed with a 1.0-tesla permanent magnet for the distal radius in a previous study. We measured the distal radius using a 3-dimensional (3D), driven-equilibrium, spin-echo sequence (repetition time/echo time=80 ms/10 ms, number of excitations=1, field of view=76.8 mm×57.6 mm×16.0 mm, acquisition time=17 min, matrix size=512×384×32, voxel size=150 μm×150 μm×500 μm) and analyzed the acquired image datasets using the virtual bone biopsy system developed by the University of Pennsylvania. Root mean squares of the coefficients of variance expressed as percentages ranged from 2.9% to 14% for the TB structural parameters. Therefore, we concluded that this compact MR imaging system could be used to assess TB microstructure of the distal radius and provide results consistent with those using a whole-body MR imaging system and showing the promise of this system for evaluating bone quality in clinical settings.

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We admitted an 11-year-old girl with enlarged endolymphatic duct and sac syndrome to our hospital with severe nausea and vertigo. Three-dimensional constructive interference in steady state (3D-CISS) and fluid-attenuated inversion recovery (3D-FLAIR) images revealed a reflux of proteinous or hemorrhagic fluid into enlarged endolymphatic space in the labyrinth. This is the first imaging report to show endolymphatic hydrops visualized by noncontrast-enhanced MR imaging in a living human patient.

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