Proton magnetic resonance spectroscopy (MRS) allows the noninvasive exploration of tissue metabolism in vivo, providing neurophysiological and neurochemical information. N-acetylaspartate (NAA) is generally considered to be a marker of neurons and axons, and many neurodegenerative disorders, including demyelinating disorders, exhibit a decrease in total NAA (tNAA). MRS in human hypomyelination disorders, such as Pelizaeus-Merzbacher disease (PMD), is characterized by normal to elevated tNAA, elevated myo-inositol and creatine (Cr), and normal to decreased choline (Cho).
MRS in the thalamus of a hypomyelinating mouse model, a myelin synthesis-deficient (msd) mouse, a model of connatal PMD with mutation of the Plp1 gene, revealed increased tNAA and Cr and decreased Cho. That of a shiverer mouse with an autosomal recessive mutation of the Mbp gene showed decreased Cho with normal tNAA and Cr. Accordingly, the reduction of Cho on MRS might be a common marker for hypomyelinating disorders. tNAA concentrations range from normal to increased, probably depending upon the underlying pathology of oligodendrocytes. tNAA may be increased in hypomyelination with a reduced number of mature oligodendrocytes, such as PMD.

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In clinical MR neuroimaging, 3D fluid-attenuated inversion recovery (3D-FLAIR) with a variable-flip-angle turbo spin echo sequence is becoming popular. There are more than 100 reports regarding 3D-FLAIR in the PubMed database. In this article, the technical and clinical features of 3D-FLAIR for neuroimaging are reviewed and summarized. 3D-FLAIR allows thinner slices with multi-planar reformation capability, a higher flow sensitivity, high sensitivity to subtle T₁ changes in fluid, images without cerebrospinal fluid (CSF) inflow artifacts, and a 3D dataset compatible with computer-aided analysis. In addition, 3D-FLAIR can be obtained within a clinically reasonable scan time. It is important for radiologists to be familiar with the features of 3D-FLAIR and to provide useful information for patients.

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Purpose: The aim of the study was to assess the presence and spectrum of cardiac abnormalities identified by cardiac magnetic resonance (CMR) in women with hypereosinophilic syndrome (HES) of undefined etiology, who present with normal electrocardiography (ECG) and transthoracic echocardiography (TTE) and no history of heart disease.Methods: Ten women (mean age, 48 ± 14 years) with HES of undefined etiology, normal ECG and TTE, and no history of heart disease underwent CMR.Results: CMR showed cardiac abnormalities in 6 subjects. Five patients had nonischemic late gadolinium enhancement (LGE) lesions within the left ventricular (LV) myocardium, and 3 patients demonstrated CMR evidence of myocardial inflammation. The LV ejection fraction was 68.5 ± 5.7%, and the end-diastolic volume index was 62.7 ± 14.7 mL/m². The maximum measured blood eosinophil count correlated with LVLGE volume (r = 0.80, P = 0.006) and was 11374 ± 6242 cells/µL and 4114 ± 2972 cells/µL (P = 0.047) in patients with and without LGE lesions, respectively. The actual blood eosinophil count in subjects with and without CMR evidence of myocarditis was 1058 ± 520 cells/µL and 354 ± 377 cells/µL (P = 0.04), respectively.Conclusions: Despite normal ECG, TTE, and absence of history of heart disease, women with HES of unknown etiology frequently demonstrate cardiac abnormalities on CMR, the presence and extent of which are related to blood eosinophil count.

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Purpose: We analyzed the anatomical structure of the temporomandibular joint (TMJ) and molecular weight dependency of synovial membrane permeability in mice using 7-tesla magnetic resonance (MR) imaging.
Methods: We obtained 3-dimensional (3D) T₁-weighted gradient echo (3D-T₁W) and 3D T₂-weighted rapid acquisition with relaxation enhancement (3D-T₂W RARE) MR images of the TMJ of male C57BL6 mice with voxel resolution of 65 µm. Two-dimensional (2D) T₁w images were measured every 45 s before and after bolus intravenous (IV) injection of contrast reagents: gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA; 0.5 kDa); oligomer-based contrast agent (CH3-DTPA-Gd; 2.1 kDa); gadolinium-labeled polylysine (Gd-polylysine; 10 kDa); and gadolinium-labeled albumin (Gd-albumin; 74 kDa).
Results: T₁W images depicted the temporal bone and mandibular condyle as regions with lower signal intensity and the disc as a region of intermediate intensity. In the Gd-DTPA-enhanced T₁W and T₂W images, the articular disc could be identified as a region with lower signal intensity than that of the upper and lower joint cavities. After IV injection of Gd-DTPA or CH3-DTPA-Gd, the signal intensity of the joint cavities increased within 10 min, but this increase was not shown with Gd-polylysine and Gd-albumin.
Conclusion: The structural findings obtained by MR imaging agreed with those obtained by hematoxylin-eosin staining under light microscopy. Contrast-enhanced MR imaging suggested that smaller (<2.1 kDa) but not larger (>10 kDa) molecules can permeate the synovial membrane. Our results suggest the utility of MR imaging for analyzing the structure of the TMJ as well as permeability of the synovial membrane.

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Purpose: We compared the image quality of free-breathing diffusion-weighted imaging (FB-DWI) to that of respiratory-triggered DWI (RT-DWI) after proper optimization.
Materials and Methods: Three healthy subjects were scanned to optimize magnetic resonance (MR) parameters of FB-DWI to improve image quality, including spatial resolution, image noise, and chemical shift artifacts. After this optimization, we scanned 32 patients with liver disease to assess the clinical feasibility of the optimized FB-DWI. Of the 32 patients, 14 had a total of 28 hepatocellular carcinomas (HCCs), four had a total of 15 metastatic liver tumors, and the other 14 had no tumor. Qualitatively, we compared the image quality scores of FB-DWI with those of RT-DWI with the Wilcoxon signed-rank test. Quantitatively, we compared the signal-to-noise ratios (SNRs) of the liver parenchyma, lesion-to-nonlesion contrast-to-noise ratios (CNRs) and apparent diffusion coefficient (ADC) values of the liver parenchyma and liver tumor by the paired t-test.
Results: The average scores of image quality for sharpness of liver contour, image noise, and chemical shift artifacts were significantly higher for FB-DWI than RT-DWI (P < 0.05). SNRs, CNRs, and ADC values of the liver parenchyma and tumors did not differ significantly between the 2 DWI methods.
Conclusion: Compared with RT-DWI, the optimized FB-DWI provided better spatial resolution, fewer artifacts, and comparable SNRs, lesion-to-nonlesion CNRs, and ADC values.

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We experienced a rare case of gallbladder metastasis from renal cell carcinoma (RCC). Ultrasound, computed tomographic, and magnetic resonance findings showed a hypervascular polypoid mass and correlated well with histopathologic findings. The mass showed high intensity on diffusion-weighted images, and the apparent diffusion coefficient was relatively low. These imaging findings are considered characteristic and may assist preoperative diagnosis in patients with history of RCC.

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We performed 3-dimensional cine phase-contrast magnetic resonance-based computational fluid dynamics for a basilar artery that developed a sidewall aneurysm over a 25-month period. There was an area with high gradient oscillatory number in the location of the future aneurysm ostium and an area with high wall shear stress (WSS) and high spatial WSS gradient at the distal edge of the future aneurysm. These could be biomarkers for development of intracranial aneurysms.

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Readout-segmented echo planar imaging (rs-EPI) is a form of multi-shot EPI. rs-EPI is affected less by susceptibility artifacts than single-shot EPI (ss-EPI), which is widely used for diffusion-weighted imaging, so rs-EPI is expected to produce less image distortion. In this study, we compared rs-EPI and conventional ss-EPI of the temporal bone region, which contains abundant amounts of air and frequently exhibits changes in magnetic susceptibility. In addition, we used a phantom to determine the optimum rs-EPI acquisition conditions for clinical use and investigated the clinical utility of rs-EPI in 20 patients (8 men, 12 women, mean age, 54.3 ± 16.7-years-old) with cholesteatoma (mean apparent diffusion coefficient on ss-EPI, 0.88 × 10⁻³ ± 0.18 mm²/s). The images of the temporal bone region produced using rs-EPI exhibited less distortion than those obtained with ss-EPI (P < 0.05).

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We acquired magnetic resonance (MR) microscopic images of chemically fixed human embryos of Carnegie stages 16 to 22 with a large image matrix (256 × 256 × 512) using an MR microscope that we developed with a 9.4-tesla vertical wide-bore superconducting magnet and a dual-channel receiver system to extend the dynamic range of the MR signal. The images showed clear anatomical structures at spatial resolutions of (40 µm)³ to (60 µm)³. We concluded that the experimental technique we developed will aid construction of the next anatomical database of the collection of chemically fixed human embryos.

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Clearing methods that render the brain optically transparent allow high-resolution three-dimensional (3D) imaging of neural networks. We used diffusion tensor imaging (DTI) and two-photon imaging of cleared brains to analyze white matter in BTBR mice. We confirmed corpus callosum agenesis and identified an abnormal commissure close to the third ventricle. DTI and cleared-brain two-photon imaging revealed that these commissural fibers constituted a frontal clustering of the ventral hippocampal commissure and provided a detailed assessment of white matter structure in mice.

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