Background and Purpose: We compared 3-dimensional time-of-flight magnetic resonance angiography (3D TOF MRA) using a 3-tesla (T) MR unit with 64-channel multi-detector row computed tomographic angiography (64-MDCTA) for detection and characterization of angiographically proven unruptured intracranial aneurysms.
Methods: Thirty-eight patients with 47 aneurysms and 8 patients without aneurysms underwent 3T, 3D TOF MRA; 64-MDCTA; and intra-arterial angiography. As a first study, 3 radiologists blinded to pertinent clinical information independently reviewed MRA and CTA images. We evaluated diagnostic accuracy using an alternative free-response receiver operating characteristic (AFROC) analysis and evaluated the sensitivity and specificity of each technique. Next, 2 radiologists used volume-rendering images generated from MRA or CTA data to evaluate the morphology of the 47 aneurysms detected, and MRA and CTA results were compared. Three-dimensional digital angiography (DA) images were used as the standard of reference.
Results: On the AFROC analysis, the value of the mean area under the AFROC curve (A₁) was 0.91 for both modalities. Mean sensitivity of 89% and specificity of 76% for MRA were not significantly different from sensitivity of 87% and specificity of 79% for CTA. Therefore, when used to evaluate aneurysmal morphology, both modalities appear satisfactory for determining these vascular anomalies.
Conclusion: Three-tesla, 3D TOF MRA and 64-MDCTA are excellent modalities with high diagnostic accuracy for evaluating unruptured intracranial aneurysms and no significant difference between them in diagnostic performance.

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We established a simple method for measuring and quantifying uptake dynamics of hyperpolarized (HP) ¹²⁹Xe in mouse brain, which includes application of a saturation recovery pulse sequence under controlled flow of HP ¹²⁹Xe. The technique allows pursuit of the time-dependent change in ¹²⁹Xe nuclear magnetic resonance signal in the uptake process without effect from radiofrequency destruction of the polarization and the dynamics in mouse lung. The uptake behavior is well described by a simple model that depends only on a decay rate constant comprising cerebral blood flow and the longitudinal relaxation rate of HP ¹²⁹Xe in the brain tissue. The improved analysis enabled precise determination of the decay rate constant as 0.107±0.013 s^-1 (±standard deviation, n=5), leading to estimation of longitudinal relaxation time, T_1i, as 15.3±3.5 s.

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Purpose: Although previous studies have revealed the mechanisms of changes in diffusivity (apparent diffusion coefficient [ADC]) in acute brain infarction, changes in diffusion anisotropy (fractional anisotropy [FA]) in white matter have not been examined. We hypothesized that membrane permeability as well as axonal swelling play important roles, and we therefore constructed a simulation model using random walk simulation to replicate the diffusion of water molecules.
Materials and Methods: We implemented a numerical diffusion simulation model of normal and infarcted human brains using C++ language. We constructed this 2-pool model using simple tubes aligned in a single direction. Random walk simulation diffused water. Axon diameters and membrane permeability were then altered in step-wise fashion. To estimate the effects of axonal swelling, axon diameters were changed from 6 to 10 μm. Membrane permeability was altered from 0% to 40%. Finally, both elements were combined to explain increasing FA in the hyperacute stage of white matter infarction.
Results: The simulation demonstrated that simple water shift into the intracellular space reduces ADC and increases FA, but not to the extent expected from actual human cases (ADC approximately 50%; FA approximately +20%). Similarly, membrane permeability alone was insufficient to explain this phenomenon. However, a combination of both factors successfully replicated changes in diffusivity indices.
Conclusion: Both axonal swelling and reduced membrane permeability appear important in explaining changes in ADC and FA based on eigenvalues in hyperacute-stage white matter infarction.

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Purpose: We evaluated the magnetic resonance (MR) features of breast lesions showing circumscribed mass on mammography to understand the characteristics that differentiate malignancy and benignancy.
Materials and Methods: Our institutional review board approved the study, and informed consent was waived. Using logistic regression analysis, we examined morphologic and kinetic MR imaging data of 90 breast lesions (43 malignant, 47 benign) that showed circumscribed mass on mammography.
Results: Features identified as having high odds for malignancy included: rim enhancement (odds ratio, 70.894; 95% confidence interval (CI), 7.525-667.938); heterogeneous enhancement (odds ratio, 10.839; 95% CI, 1.032-113.856); and washout dynamic pattern (odds ratio, 46.262; 95% CI, 3.716-575.901). Combinations of washout dynamic pattern and either rim or heterogeneous enhancement reflected excessively high prediction probability for malignancy (>0.95), whereas combinations lacking washout dynamic pattern and with either homogeneous enhancement or dark internal septation revealed excessively low prediction probability for malignancy (<0.05).
Conclusion: Breast cancers with circumscribed mass on mammography could be differentiated from benign masses using internal enhancement and the kinetic pattern of contrast-enhanced breast MR imaging.

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Recent technical advances have enabled the visualization of neuromelanin in the substantia nigra pars compacta (SNc) and locus ceruleus (LC) by 3-tesla (T) magnetic resonance imaging in vivo. In the present study, we successfully detected neuromelanin in the SNc and LC of 6 healthy volunteers at 1.5T using a 3D gradient echo sequence with off-resonance magnetization transfer contrast.

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We report a case of a fetal omphalocele in which the internal structure of the hernia sac was imaged in detail by magnetic resonance (MR) imaging. The hernia sac consisted of amnion, Wharton jelly, and externally, peritoneum. The umbilical vascular channels (2 arteries, one vein) were surrounded by Wharton jelly. Use of MR imaging facilitates a more accurate evaluation of fetal omphalocele with regard to hernial sac, intestinal structure, and differential diagnosis.

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