Detection, characterization, staging, and treatment monitoring are major roles of diagnostic imaging of liver cancers. Developments in multidetector-row computed tomography (MDCT) technology have increased the spatial and temporal resolution of CT to allow more precise evaluation of the hemodynamics of liver tumors and improve the diagnostic accuracy of dynamic MDCT. The high spatial and temporal resolutions of dynamic MDCT enable us to reconstruct 3-dimensional (3D) images that are very useful for pretreatment evaluation. Dynamic MR imaging with fast 3D T₁-weighted gradient echo imaging sequence using nonspecific contrast medium can be highly sensitive for detecting hypervascular HCC. However, the use of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA), a contrast medium specific to hepatic tissue, offers greater diagnostic ability and, so, has become essential to liver imaging. MR imaging with Gd-EOB-DTPA may replace CT during hepatic arteriography and CT during arterioportography.

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Sarcoidosis is a multisystem disorder of unknown etiology that involves multiple organs. Computed tomography is the first-line imaging modality for diagnosing sarcoidosis because of its capacity to detect hilar lymphadenopathy and pulmonary lesions. Magnetic resonance (MR) imaging provides good soft tissue contrast that is useful for detecting sarcoidosis in some body parts, including skeletal muscle. Signal intensity on pre- and postcontrast T₁- and T₂-weighted imaging may reflect disease activity and the pathological appearance of sarcoidosis. In this review, we demonstrate these conventional MR imaging findings of hepatosplenic and muscular sarcoidosis and describe the usefulness of diffusion-weighted imaging for detecting sarcoidosis.

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Purpose: We assessed what MR imaging parameters affected ringing artifacts during the arterial phase of gadoxetic acid-enhanced dynamic magnetic resonance (MR) imaging.
Materials and Methods: We tested various parameters, including imaging matrices, choice of either sequential or elliptical centric phase-encoding scheme, scanning time, and contrast injection rate using new simulation software on a personal computer and visually evaluated clinical MR images retrospectively using a 4-point scale to assess ringing artifacts.
Results: The simulation study revealed that square matrices, short scanning time, slow injection rate, and sequential view ordering effectively reduced ringing artifacts, findings confirmed in clinical practice using gadoxetic acid-enhanced MR imaging. Significantly fewer artifacts resulted using a slow injection rate (P<0.05) and using square matrices in the arterial (P<0.05), portal (P<0.01), and hepatocytic (P<0.05) phases.
Conclusion: Choice of square matrix, slower injection rate, shorter scanning time, and sequential view ordering could reduce ringing artifacts.

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Purpose: We investigated the characteristics and capability of interstitial MR lymphography in mice using gadofluorine 8, gadofluorine M, and gadofluorine P.
Methods: We injected healthy mice with 0.5 μmol of Gd gadofluorine 8, gadofluorine M, or gadofluorine P subcutaneously into the right rear footpad and assessed the time courses of contrast enhancement in the lymph nodes. Six mice were studied for each contrast agent. We also used gadofluorine M to assess the lymphatic pathway from the right and left rear feet or tail.
Results: Contrast enhancement was demonstrated for the right popliteal, sacral, and iliac lymph nodes in all mice 5 minutes after injection of each of the 3 agents and decreased gradually. Enhancement in the lymph nodes was still detectable 30 minutes after injection of gadofluorine 8 or gadofluorine M. Enhancement became obscure sooner after gadofluorine P injection and was mildly stronger with the other 2 contrast agents. Clear differences were found in the hepatobiliary and urinary kinetics of the 3 agents. Gadofluorine M injected into various sites delineated the lymphatic pathway from the site of injection.
Conclusion: Interstitial MR lymphography using gadofluorine 8, gadofluorine M, and gadofluorine P offered clear visualization of the lymphatic pathway in healthy mice during a sufficient imaging time window, and allowed repeated assessment of the pathway and clarification of the lymphatic system.

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Imaging of cerebral oxygen metabolism is useful for selecting and monitoring therapy, matching patients with interventions, and optimizing outcomes while reducing the incidence of hemorrhagic changes. We aimed to measure oxygen metabolism using magnetic resonance (MR) imaging. Because the magnetic susceptibility of hemoglobin varies with its redox status, the regional oxygen saturation should be measurable by MR imaging. We derived equations based on the blood oxygenation level-dependent (BOLD) theory and evaluated their validity in patients with chronic cerebral ischemia. From changes in BOLD signal, cerebral blood flow (CBF), and cerebral blood volume (CBV) after loading of acetazolamide or breath-holding, we calculated the cerebral metabolic rate of oxygen (CMRO₂) pixel by pixel and compared the results to those of positron emission tomography (PET) examination. The correlation coefficient between the 2 modalities was between 0.70 and 0.75 in 4 patients, suggesting the applicability of BOLD-contrast MR imaging, but ranged from 0.39 to 0.47 in assessment of oxygen extraction fraction (OEF). BOLD contrast MR imaging tended to overestimate the region of decreased OEF. Some technical challenges remain for improving the sensitivity of delta BOLD, selective measurement of venous blood volume, and shortening of examination time.

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Purpose: We retrospectively compared the efficacy of 3-dimensional (3D) gradient-echo magnetic resonance T₁-weighted sequence using the iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) technique with the efficacy of conventional 3D gradient-echo sequences for diagnosing ovarian masses at 3T.
Materials and Methods: In images of 32 women (mean age, 45.3 years) with ovarian masses who underwent T₁-weighted imaging with both IDEAL and conventional techniques, we quantitatively analyzed signal-to-noise ratio (SNR) and contrast between gluteal muscle and T₁-weighted high-signal materials within lesions and assessed image quality. Two radiologists independently evaluated fat detection.
Results: Mean SNR of subcutaneous fat did not differ significantly between IDEAL and conventional techniques for both fat-suppressed (P=.32) and non-fat-suppressed (P=.85) images. Mean absolute contrast between gluteal muscle and T₁-weighted high signal materials within teratomas (n=15) was significantly higher with IDEAL on fat-suppressed images (P=.002) and lower with IDEAL on non-fat-suppressed images (P=.010). Fat suppression was significantly superior with IDEAL (P<.0001). Readers' assessments of fat detection did not differ between IDEAL and conventional sequences.
Conclusion: The quality of T₁-weighted fat-suppressed images of ovarian masses was better with 3D gradient-echo IDEAL than conventional 3D gradient-echo sequences.

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When radiofrequency (RF) transmission field represents B₁⁺, the reception field represents B₁⁻*. The distribution of those maps demonstrates asymmetric features at high field magnetic resonance (MR) imaging. Both maps are in mirror symmetry to one another. Almost symmetric distribution of the B₁ field was expected on the laboratory frame in a symmetric sample loaded inside the RF coil designed to achieve a homogeneous B₁ field. Then, a simple change was made in the coordinate transformation equation of RF fields between the rotating and laboratory frames in both linear and quadrature modes to investigate the source of this feature of asymmetry. The magnitude of rotating frame components, B₁⁺ and B₁⁻, consists of the magnitude and the phase difference of the laboratory frame components. The rotating frame components differ in the sign of the sinusoidal phase difference. B₁⁺ is equal to B₁⁻ at lower field because phase changes that depend on position can be ignored. At higher fields, the magnitude component has a symmetric profile, and distribution in the phase component is antisymmetric. Thus, the distributions of B₁⁺ and B₁⁻ maps demonstrate mirror symmetry. Maps of magnitude and phase components were examined in the laboratory frame. Their maps were computed from B₁⁺ and B₁⁻ maps of the human brain and of a spherical saline phantom measured at 4.7T. It was concluded from these analytical and experimental results that the asymmetric and mirror symmetric distributions in B₁⁺ and B₁⁻ are derived from the phase difference in the laboratory frame.

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Walker-Warburg syndrome (WWS) is a rare autosomal recessive disorder characterized by a triad of congenital muscular dystrophy, brain anomalies, and ocular abnormalities. The brain anomalies mainly include type II lissencephaly (cobblestone cortex), pontine and cerebellar hypogenesis, cerebral or cerebellar hypomyelination, cerebellar polymicrogyria with or without cysts, and variable callosal hypogenesis. Constructive interference in steady state (CISS) sequence, a heavily T₂-weighted sequence, is ideal for demonstrating the presence of cerebellar cysts on magnetic resonance (MR) imaging. We report the complete imaging spectrum in a patient with WWS and emphasize the utility of CISS sequence in the imaging of cerebellar cysts.

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Idiopathic hypertrophic pachymeningitis (IHP) is a chronic inflammatory disease of unknown cause. We report a case of IHP with bilateral distended subarachnoid space (SAS) of the optic nerves and unilateral visual disturbance. We observed marked amelioration of magnetic resonance (MR) imaging findings after initiation of treatment with prednisolone. This radiological finding implicates optic nerve sheath involvement that affects cerebrospinal fluid (CSF) dynamics around the optic nerve.

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To visualize endolymph as bright signal after intravenous injection of single-dose gadodiamide, we shortened the inversion time of heavily T₂-weighted 3-dimensional (3D) fluid-attenuated inversion recovery (FLAIR) to 2050 ms. In 14 patients with suspected Ménière's disease, we observed high signal of vestibular endolymph in all ears, including 6 ears without vestibular endolymphatic hydrops. We observed high signal of cochlear endolymph in 17 ears with cochlear endolymphatic hydrops but not 11 ears without cochlear endolymphatic hydrops.

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