Purpose: Differences in acute adverse reactions to different gadolinium (Gd)-based contrast agents have not been thoroughly evaluated. We investigated the relationships among the incidence and severity of acute adverse reactions, backgrounds of patients, and 4 types of different Gd-based contrast agents (gadopentetate dimeglumine, gadoteridol, gadoterate meglumine, and gadoxetate disodium).
Materials and Methods: We retrospectively reviewed the radiological records of 10,595 consecutive patients (4,343 female; 6,252 male; mean age, 63.8 ± 14.0 years) who underwent contrast-enhanced magnetic resonance imaging between August 2006 and March 2011. Adverse reactions were classified as mild, moderate, and severe according to the definition of the American College of Radiology. The incidence of adverse reactions were compared on the basis of clinical characteristics and type, dose, and delivery methods of contrast agents by univariate and multivariate logistic regression analyses.
Results: The incidence of overall reactions was 0.45% (48/10,595); 45 reactions were mild and three were moderate. No severe reactions were observed. Although the incidence of adverse reactions did not differ significantly between male and female patients, younger individuals were at higher risk for acute adverse reactions. The contrast injection rate and contrast dose were not significantly related to the incidence of adverse reactions. The incidence of adverse reactions was significantly higher for gadoxetate disodium (0.82%) than gadopentetate dimeglumine (0.43%).
Conclusion: The incidence of acute adverse reactions elicited by Gd-based contrast agents injection was only 0.45%. Younger age was a risk factor for acute reactions. All 4 agents were found to be safe, although gadoxetate disodium showed a relatively higher incidence of adverse reactions.

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Purpose: Heavily T₂-weighted, 3-dimensional, fluid-attenuated inversion recovery (hT₂W-3D-FLAIR) imaging has been reported to detect low concentrations of gadolinium-based contrast media (GBCM) in the anterior eye segment (AES), subarachnoid space (SAS), and labyrinthine perilymph as well as in the cerebrospinal fluid (CSF) of the internal auditory canal (IAC) 4 hours after intravenous administration of a single dose (IV-SD-GBCM) in patients with inner ear disorders. To elucidate the time course of contrast enhancement in healthy volunteers, we obtained hT₂W-3D-FLAIR serially after IV-SD-GBCM.
Materials and Methods: We obtained hT₂W-3D-FLAIR before and 0.5, 1.5, 3, 4.5 and 6 hours after IV-SD-GBCM in 6 healthy volunteers and measured signal intensity of the AES, SAS surrounding the optic nerve (SAS-ON), SAS in Meckel's cave (SAS-MC), pontine parenchyma, CSF in the IAC (CSF-IAC), CSF in the ambient cistern (CSF-AC), CSF in the lateral ventricles (CSF-LV), perilymph (PL), and endolymph (EL) in the labyrinth. We then compared averaged values among all time points using analysis of variance (ANOVA).
Results: After IV-SD-GBCM, we observed no change in signal intensity in the pontine parenchyma, CSF-LV, or EL and significant enhancement in all other structures. Maximum enhancement was most frequent at 4.5 hours after IV-SD-GBCM in the SAS-ON and PL, at 1.5 hours in the AES and SAS-MC, and at 3 hours in the CSF-IAC and CSF-AC.
Conclusions: Contrast enhancement can be detected by hT₂W-3D-FLAIR in the AES, SAS-ON, SAS-MC, PL, CSF-IAC, and CSF-AC in healthy volunteers after IV-SD-GBCM. Timing of maximum enhancement differed among locations. These data might serve as basic knowledge for future clinical research.

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Purpose: A drawback of time-resolved 3-dimensional phase contrast magnetic resonance (4D Flow MR) imaging is its lengthy scan time for clinical application in the brain. We assessed the feasibility for flow measurement and visualization of 4D Flow MR imaging using Cartesian y-z radial sampling and that using k-t sensitivity encoding (k-t SENSE) by comparison with the standard scan using SENSE.
Materials and Methods: Sixteen volunteers underwent 3 types of 4D Flow MR imaging of the brain using a 3.0-tesla scanner. As the standard scan, 4D Flow MR imaging with SENSE was performed first and then followed by 2 types of acceleration scan—with Cartesian y-z radial sampling and with k-t SENSE. We measured peak systolic velocity (PSV) and blood flow volume (BFV) in 9 arteries, and the percentage of particles arriving from the emitter plane at the target plane in 3 arteries, visually graded image quality in 9 arteries, and compared these quantitative and visual data between the standard scan and each acceleration scan.
Results: 4D Flow MR imaging examinations were completed in all but one volunteer, who did not undergo the last examination because of headache. Each acceleration scan reduced scan time by 50% compared with the standard scan. The k-t SENSE imaging underestimated PSV and BFV (P < 0.05). There were significant correlations for PSV and BFV between the standard scan and each acceleration scan (P < 0.01). The percentage of particles reaching the target plane did not differ between the standard scan and each acceleration scan. For visual assessment, y-z radial sampling deteriorated the image quality of the 3 arteries.
Conclusion: Cartesian y-z radial sampling is feasible for measuring flow, and k-t SENSE offers sufficient flow visualization; both allow acquisition of 4D Flow MR imaging with shorter scan time.

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Purpose: We propose an absolute quantitation method for metabolites with strongly coupled spin systems using localized 2-dimensional (2D) constant-time correlation spectroscopy (CT-COSY). We also develop two methods for improving the quality of in vivo CT-COSY spectra.
Methods: We substituted an image selected in vivo spectroscopy (ISIS) pulse for a 180° slice pulse in the CT-COSY module to decrease the slice displacement error caused by the chemical shift difference. We measured the slice displacement error due to the differences in the carrier frequency of slice pulse in a phantom experiment to demonstrate this feature. We also developed an asymmetric sampling scheme along the t₁ direction to resolve diagonal peaks even in the magnitude mode of 2D spectra. We collected CT-COSY signals of a human brain for a 14% asymmetric sampling scheme. After reconstruction, we obtained a 2D CT-COSY spectrum in magnitude mode and compared a peak of glutamate (Glu) C4H on that spectrum to a peak displayed in absorption mode. In our proposed absolute quantitation method, we developed T₂ correction, curve-fitting for computing peak volume and calibration by an internal water reference. We used the method to measure the Glu concentration in 10-mM glutamate phantom experiments. We also attempted to measure concentrations of Glu, γ-aminobutyric acid (GABA) and glutamine (Gln) in a human brain.
Results: Slice displacement error was decreased by a factor of 2.5 using the proposed sequence. Spectra with narrow linewidths could be obtained using the asymmetric sampling scheme in the magnitude mode. Measured Glu concentration in the solution phantom was 9.4 mM. Concentrations of Glu (9.5 mM), GABA (0.61 mM) and Gln (3.6 mM) in a human brain measured by our method agreed well with previously reported values.
Conclusion: Concentrations of metabolites with strongly coupled spin systems can be measured using our proposed absolute quantitation method on 2D CT-COSY spectra.

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Purpose: We compared the suppression of lingering fat signals in chemical shift selective (CHESS) images by pads filled with flour and pads filled with rice in a phantom and human subjects.
Materials and Methods: First, we prepared a phantom by creating an empty space in a mass of lard and filling the space with air, rice, or flour. Then, we obtained MR images of the phantoms in the center of the magnetic field and at a position 8 cm to the left (off-center) to compare lingering fat signals. MR images of the knee were obtained in 10 healthy volunteers using CHESS after placing a polyurethane sponge pillow, rice pad, or flour pad in the popliteal space under the flexed knee. We visually assessed the number of areas with lingering fat signals and the statistical differences among the groups were assessed using Tukey's test.
Results: Similarly to rice, flour clearly decreased lingering fat signals in the phantom study. A similar effect was obtained in the off-center images. In the volunteer study, the mean number of areas with lingering fat signals was 2.5 with a sponge pillow, 0.5 with the rice pad, and 0.3 with the flour pad. Those numbers were significantly different using flour pad and rice pad compared with sponge pillow (P < 0.001). No significant differences were seen between flour pads and rice pads (P = 0.662).
Conclusion: Flour pads can suppress lingering fat signals in CHESS images.

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Purpose: We undertook this study to evaluate the need for diffusion-weighted (DW) magnetic resonance (MR) imaging in detecting hemorrhagic infarction following ovarian torsion.
Methods: The study included 14 consecutive patients aged 12 to 74 years (average age, 36 years) with surgical confirmation of ovarian torsion who underwent 1.5-tesla MR imaging. Pathologically, hemorrhagic infarction was found in 7 patients. We retrospectively reviewed signal intensity on T₁-, T₂-, and diffusion-weighted images and apparent diffusion coefficients (ADCs) in swollen ovarian stroma.
Results: Fallopian tube thickening was seen in all patients. In patients with ovarian cystic lesion, maximum cyst wall thickness was significantly higher in patients with hemorrhagic infarction (mean, 13.5 ± 4.1 mm) than those without (mean, 5.0 ± 1.0 mm) (P < .05). Signal intensity did not differ significantly on T₁-weighted, T₂-weighted, and DW images between patients with and without hemorrhagic infarction. ADCs were significantly lower in patients with hemorrhagic infarction (1.20 ± 0.50 [× 10⁻³ mm²/s]) than those without (2.04 ± 0.26 [× 10⁻³ mm²/s]) (P < .01). With an ADC threshold of 1.80 [× 10⁻³ mm²/s], sensitivity for hemorrhagic infarction was 0.88 (7 of 8), and specificity was 1.00 (6 of 6).
Conclusion: ADC measurements were useful for detecting hemorrhagic infarction in patients with ovarian torsion.

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Purpose: We compared the performances of a Bayesian estimation method and oscillation index singular value decomposition (oSVD) deconvolution for predicting final infarction using data previously obtained from 10 cynomolgus monkeys with permanent unilateral middle cerebral artery (MCA) occlusion.
Methods: We conducted baseline perfusion-weighted imaging 3 hours after MCA occlusion and generated time to peak, first moment of transit, cerebral blood flow, cerebral blood volume, and mean transit time maps using Bayesian and oSVD methods. Final infarct volume was determined by follow-up diffusion-weighted imaging (DWI) scanned 47 hours after MCA occlusion and from histological specimens. We used a region growing technique with various thresholds to determine perfusion abnormality volume. The best threshold was defined when the mean perfusion volume matched the mean final infarct volume, and Pearson's correlation coefficients (r) and intraclass correlations (ICC) were calculated between perfusion abnormality and final infarct volume at that threshold. These coefficients were compared between Bayesian and oSVD using Wilcoxon's signed rank test. P-value < 0.05 was considered a statistically significant difference.
Results: The Pearson's correlation coefficients were larger but not significantly different for the Bayesian technique than oSVD in 4 of 5 perfusion maps when final infarct was determined by specimen volume (P = 0.104). When final infarct volume was defined by DWI volume, all perfusion maps had a significantly higher correlation coefficient by Bayesian technique than oSVD (P = 0.043). For ICC, all perfusion maps had higher value in Bayesian than oSVD calculation, and significant differences were observed both on specimen- and DWI-defined volumes (P = 0.043 for both).
Conclusion: The Bayesian method is more reliable than oSVD deconvolution in estimating final infarct volume.

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We report here a rare case of focal multiple venous malformations (VMs) in the white matter, via a draining vein arising from each VM, connecting with an ipsilateral cerebral surface venous varix. The male teen was asymptomatic neurologically. A diagnostic process using of MRI/MRDSA in this extremely rare entity is important as the more incidental discovery is expected with increasing opportunities of performing brain CT/MRI for various indications.

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Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the brain caused by the JC virus in immunocompromised patients. We report characteristic features of proton MR spectroscopy, 3-dimensional pseudo-continuous arterial spin labeling imaging, and diffusion tensor imaging in a 53-year-old patient with PML. The utility of multi-modal magnetic resonance techniques for longitudinal monitoring was indicated by their reevaluation over time and consideration of their relation to prognosis.

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We demonstrated a new scheme for performing the T₁-enhanced whole-brain black-blood imaging pulse sequence using motion-sensitized driven-equilibrium prepared 3-dimensional (3D) turbo spin echo (MSDE-TSE) with anti-driven-equilibrium post pulse. The use of an anti-driven-equilibrium pulse considerably improved the T₁ contrast of MSDE-TSE black-blood images. This sequence can be used for whole-brain 3D volumetric T₁-weighted black-blood imaging and may improve the accuracy of anatomical localization for certain brain lesions.

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