Purpose: In patients with perimedullary arteriovenous fistula (AVF) with subarachnoid hemorrhage (SAH), knowledge of lesion location is necessary to select the appropriate approach for catheter spinal angiography. We evaluated the utility of 3-dimensional (3D) fast imaging with steady-state precession (FISP) sequence for detecting type 1 perimedullary AVF with SAH.
Materials and Methods: We evaluated 4 patients (2 men, 2 women, aged 53 to 68 years, mean age, 59.25 years) with type 1 perimedullary AVF who presented with SAH and underwent conventional spin-echo MR and contrast-enhanced 3D FISP imaging. Two neuroradiologists assessed detection of vascular lesions and delineation of their relationships to the adjacent vessels. Catheter angiography was used as the reference standard and compared with the MR findings.
Results: Perimedullary AVF was located at the medullocervical junction in 2 patients, cervical spine in one, and thoracic spine in one. For all patients, use of contrast-enhanced 3D FISP in addition to conventional MR imaging improved lesion detection and delineation of the relationship between the lesion and surrounding vessels.
Conclusion: Contrast-enhanced 3D FISP imaging was useful for detecting and delineating type 1 perimedullary AVF with SAH.

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Pulmonary study using hyperpolarized (HP) ¹²⁹Xe gas as an imaging medium must focus on dissolved-phase signals to make the most of the characteristic affinity of xenon for biological tissues, including blood. However, the spectral pattern of these signals differs between mice and other animals, including rats, canines, and humans. Dissolved-phase study has been reported only scarcely in mice, so spectral assignment has been an important subject for HP ¹²⁹Xe magnetic resonance (MR) spectroscopy (MRS) and MR imaging for its wider application. We performed MRS, including magnetization transfer experiments, and MR imaging studies to confirm the origin of dissolved-phase signals of mice ex vivo and in vivo and obtained evidence to assign dissolved-phase signals at 192 ppm for epicardial fat, 196 ppm for lung parenchyma, and 200 ppm for blood. These results were the first to show the possibility of fast exchange of xenon between plasma and red blood cells.

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Purpose: Manganese-enhanced magnetic resonance imaging (MEMRI), used to trace neuronal connections and visualize brain activity, has recently been suggested useful for tumor detection, but the mechanism of tumor enhancement by manganese (Mn) is poorly understood. Our recent report of preferential enhancement of human mesothelioma cells with higher levels of manganese-superoxide dismutase (Mn-SOD) expression may suggest a correlation between Mn-SOD expression and enhancement. We investigate this possibility further using engineered human ovarian cancer cells overexpressing Mn-SOD.
Methods: We subcutaneously implanted SK-OV-3 human ovarian cancer cells stably overexpressing Mn-SOD (SK-Mn-SOD) into athymic nude mice and SK-OV-3 cells with plasmid DNAs carrying neomycin-resistant genes (SK-neo) into the same mice for controls. We conducted MEMRI in the tumor-bearing mice and compared enhancement between the 2 tumors.
Results: Subcutaneous SK-Mn-SOD tumors were preferentially enhanced in MEMRI compared to SK-neo tumors. After Mn enhancement, the T₁-relaxation rate (R₁=1/T₁) increased significantly for SK-Mn-SOD but not SK-neo tumors.
Conclusion: In some tumors, high expression of Mn-SOD may be a biological factor responsible for enhanced signal in MEMRI.

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We measured the homogeneity and stability of the magnetic field of a high field (about 1.04 tesla) yokeless permanent magnet with 40-mm gap for high resolution nuclear magnetic resonance (NMR) imaging. Homogeneity was evaluated using a 3-dimensional (3D) lattice phantom and 3D spin-echo imaging sequences. In the central sphere (20-mm diameter), peak-to-peak magnetic field inhomogeneity was about 60 ppm, and the root-mean-square was 8 ppm. We measured room temperature, magnet temperature, and NMR frequency of the magnet simultaneously every minute for about 68 hours with and without the thermal insulator of the magnet. A simple mathematical model described the magnet's thermal property. Based on magnet performance, we performed high resolution (up to [20 µm]²) imaging with internal NMR lock sequences of several biological samples. Our results demonstrated the usefulness of the high field small yokeless permanent magnet for high resolution NMR imaging.

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Purpose: We assessed intrarenal oxygenation in gentamicin-induced nephrotoxicity (GIN) and the protective effect of hydrogen-rich water (HW) against GIN using blood oxygenation level-dependent magnetic resonance (MR) imaging.
Materials and Methods: We acquired T₂*-weighted images (T₂*WI) of 21 rats on Days 0, 2, 4, and 7 using a 1.5-tesla MR imaging system. The rats were divided into 3 groups of seven each: control rats had free access to standard water and no gentamicin (GM) injection; rats designated the GM group had free access to standard water and were injected with GM (80 mg/kg/day) subcutaneously for 7 days; and the third group, designated the GM+HW group, had free access to HW and were injected with GM. R₂* (=1/T₂*) was estimated from T₂*WI.
Results: R₂* values in the cortex were significantly decreased on Days 2, 4, and 7 compared with those on Day 0 in the GM group but not significantly changed in the control and GM+HW groups. R₂* values in the medulla did not change significantly in any group.
Conclusions: Our findings suggested reduced oxygen utility, mainly in the cortex, in gentamicin-induced nephrotoxicity and an ameliorative effect of hydrogen-rich water against GIN.

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We examined the temperature dependence of relaxation times in proton components of fatty acids in various samples in vitro at 11 tesla as a standard calibration data for quantitative temperature imaging of fat. The spin-lattice relaxation time, T₁, of both the methylene (CH₂) chain and terminal methyl (CH₃) was linearly related to temperature (r>0.98, P<0.001) in samples of animal fat. The temperature coefficients for the 2 primary proton components differed significantly; in 5 bovine fat samples, the coefficient at 30℃ was 1.79±0.07 (%/℃) for methylene and 2.98±0.38 (%/℃) for methyl. Numerical simulations based on such a difference demonstrated the possibility of considerable error from inconsistent ratios in fatty acid components when calibrating and estimating temperature. The error reached 3.3℃ per 15℃ in temperature elevation when we used a pure CH₂ signal for calibration and observed the signal with 18% of CH₃ to estimate temperature. These findings suggested that separating the fatty acid components would significantly improve accuracy in quantitative thermometry for fat. Use of the T₁ of CH₂ seems promising in terms of reliability and reproducibility in measuring temperature of fat.

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Purpose: Susceptibility-weighted (SW) imaging is a magnetic resonance (MR) imaging technique reported effective in visualizing multiple sclerosis (MS) plaques, but its capacity to distinguish active plaques remains unclear. We evaluated active plaque detection by SW compared with contrast-enhanced MR imaging.
Methods: We prospectively examined 11 patients using a 3-tesla scanner. Two neuroradiologists independently evaluated signal changes of plaques and accompanying low signal rims in 74 plaques on various SW images (magnitude, phase, and minimum intensity projection [minIP]), and on contrast-enhanced T₁-weighted images (T₁WI). We correlated signal alterations on various SW images and contrast enhancement on T₁WI using Fisher's exact test and calculated sensitivity and specificity for predicting gadolinium enhancement.
Results: Only changes in plaque signal on SW magnitude images correlated significantly with contrast enhancement of the plaques (P=0.008), and high signal intensity had 0.556 sensitivity and 0.787 specificity for predicting contrast-enhanced plaques. Furthermore, plaques with rims of low signal showed sensitivity of 0.296 and specificity of 0.957.
Conclusions: Susceptibility-weighted magnitude, but not phase or minIP, images can predict MS plaques with contrast enhancement with high specificity.

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Purpose: Fluid-attenuated inversion recovery (FLAIR) has been reported more sensitive than T₁-weighted images in detecting low concentration gadolinium-based contrast media (GBCM) in fluid, and heavily T₂-weighted (hT₂W) 3-dimensional (3D) FLAIR has recently been reported even more sensitive than conventional 3D FLAIR. We investigated whether high signal of the anterior eye segment (AES) and subarachnoid space (SAS) in various locations as well as cerebrospinal fluid (CSF) in cisterns and ventricles can be detected on hT₂W 3D FLAIR images obtained 4 hours after intravenous administration of GBCM in subjects without eye and SAS diseases.
Methods: Ten patients suspected of having Ménière's disease underwent hT₂W 3D FLAIR 4 hours after intravenous administration of single-dose GBCM to evaluate endolymphatic hydrops. We evaluated signal intensity of AES, SAS surrounding the optic nerve, SAS in Meckel's cave, CSF in the internal auditory canal, CSF in the prepontine cistern, CSF in the lateral and fourth ventricles, and lymph fluid in the cochlea by comparison with non-contrast images obtained in a separate group of 5 patients. The signal intensity of each structure was normalized by that of the pontine parenchyma.
Results: We observed no signal difference in images of the pontine parenchyma obtained before and after enhancement. Significant signal difference was seen in all structures except the lateral and fourth ventricles.
Conclusion: Four hours after intravenous injection, GBCM can be detected by hT₂W 3D FLAIR in various fluid-containing spaces, such as the AES and various SAS and CSF spaces.

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A 52-year-old woman with abdominal distension underwent computed tomography (CT) that demonstrated extensive paraaortic lymphadenopathy and a right renal mass. Compared to the renal cortex, the lesions exhibited low signal intensity on T₁- and T₂-weighted images and high intensity on diffusion-weighted magnetic resonance (MR) images. We suspected malignant lymphoma and performed excisional biopsy, which revealed metastatic papillary renal cell carcinoma. Retrospectively, significantly reduced signal on in-phase chemical shift MR images compared to out-of-phase images suggested the presence of intratumoral hemosiderin, a characteristic finding of this entity.

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Ovarian carcinoid tumor is a rare neoplasm that may appear as a solid mass or often combined with teratomas or mucinous tumors. We report 2 cases associated with mucinous cystadenomas and describe their magnetic resonance imaging characteristics. On T₂-weighted images, the tumors appeared as multilocular cystic masses with hypointense solid components as a result of abundant fibrous stroma induced by serotonin. Demonstration of prominent hypervascularity of the tumors following contrast administration on dynamic study may be the clue to differential diagnosis.

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