Purpose: Dynamic MR cholangiography was conducted on patients with cholelithiasis or choledocholithiasis who had consumed a fatty test meal (Molyork) and the cystic contractility and dynamics of biliary stasis was evaluated.
Subjects and Method: The subjects were 25 with intracystic cholelithiasis, 10 with choledocholithiasis and 10 normal controls. For an imaging sequence, the rapid acquisition with relaxation enhancement (RARE) method was employed and imaging was conducted for 40 min (every 30 s following Molyork administration) without breath-holding. The gallbladder contraction ratio was computed and the contractile ratio for the common bile duct was calculated. To determine the bile flow to the duodenum, the high-intensity signal, indicating the flow from the lower common bile duct, and perfusion of the duodenum were observed in dynamic mode on the monitor with the naked eye and interpreted as positive bile flow. The frequency of this flow was visually monitored.
Results: The gallbladder contractile ratio was significantly reduced in patients with cholelithiasis or choledocholithiasis compared with the controls. In a comparison with the normal controls, no sequential changes were noted in the mean contractile ratio of the common bile duct of the patients with cholelithiasis or choledocholithiasis. The mean frequency of bile flow observed for each 40 min period was 13±2.4, 6±2.2, and 4±1.3 times for the controls, those with intracystic cholelithiasis, and those with choledocholithiasis, respectively. Compared with the controls, the latter two patient groups showed evident reductions in the frequency of bile flow to the duodenum (p<0.001).
Conclusion: Dynamic MRC combined with Molyork loading makes it possible to compute cystic contractile ratios and perform a dynamic examination of bile flow under non-invasive, near-physiological conditions.

View full abstract

Rationale and Objectives: To assess the efficacy of MRM in providing preoperative locoregional information on patients with breast cancer.
Methods: MRI was performed on 62 female breast cancer patients. A 1.5T MR-system was used to acquire fat-suppressed T₁WI, T₂WI and dynamic-contrast-enhanced images with an SPGR pulse sequence. The extent of the cancer measured with MRM was confirmed histologically in all patients.
Results: The size obtained from MRM correlated well with the size obtained histologically, including intraductal spread of cancer (R: 0.853). As for shape, the round/oval type evident from MRM correlated more accurately (R: 0.934) than the ill-defined type associated with a linear and/or clumped enhanced area (R: 0.744). The difference between the size obtained from MRM and the size obtained histologically, including IDS, was less than 15 mm in the majority of patients (93.5%).
Conclusions: MRM accurately reveals the extent of cancer, including IDS, and is effective at providing preoperative locoregional information for breast-conserving therapy for breast cancer.

View full abstract

The purpose of this study was to determine whether a distinction could be made between benign and malignant urinary obstructions in moderately T₂-weighted images obtained with the single-shot fast spin-echo technique. Forty-four lesions in 39 patients with urinary obstruction were evaluated with the single-shot fast spin-echo (SSFSE) technique with an effective TE of 90-100 ms and without fat saturation. Benign and malignant lesions were compared for the presence of ureteral wall thickening and a signal intensity relative to the proximal ureteral wall.
Statistically significant differences were found between benign and malignant lesions in both morphologic change (P<0.0001) and signal intensity of the lesions at the obstruction position (P<0.0001). The combination of wall thickening and increased signal intensity as a predictor of malignant disease yielded a sensitivity of 88% and a specificity of 100%. Neither increased signal intensity nor wall thickening as a predictor of benign disease yielded a sensitivity of 89% and a specificity of 88%. The moderately T₂-weighted SSFSE technique without fat saturation can accurately distinguish between benign and malignant urinary obstructions.

View full abstract

Since the first successful demonstration of primary visual cortex “activation” by Sokoloff in 1961, activation studies based on regional blood flow alteration became one of the gold standards for neuroscientific investigation. The rapid advancement of non-invasive imaging techniques provided an appropriate stage for the human application of this original method. Following the tremendous success of positron emission tomography (PET) utilizing O¹⁵ labeled H₂O (H₂O¹⁵-PET), the magnetic resonance imaging (MRI) version, which is now referred to as functional MRI (fMRI), was introduced. fMRI is the method created based on the empirical observation that MRI exhibits spontaneous signal alteration associated with blood flow changes. It is now believed that the principle of fMRI is identical to H₂O¹⁵-PET, namely, that it is blood flow based in accordance with the well-known Munro-Kellie doctrine which predicts a decline in cerebral venous blood volume secondary to an increase in cerebral arterial blood volume. The method is inherently qualitative and does not provide quantitative information regarding flow alteration. With the growing use of fMRI, however, exponentially increasing well founded criticism questioning the validity of fMRI data has been raised. The majority of validation issues arise during the process of obtaining raw images, which eventually provides raw numerical data for post-processing statistical analysis. This article provides a distillation of the essential knowledge necessary for the non-MR physicist fMRI investigator.

View full abstract

Functional magnetic resonance imaging (fMRI) has been a useful tool for the noninvasive mapping of brain function associated with various motor and cognitive tasks. Because fMRI is based on the blood oxygenation level dependent (BOLD) effect, it does not directly record neural activity. With the fMRI technique, distinguishing BOLD signals created by cortical projection neurons from those created by intracortical neurons appears to be difficult. Two major experimental designs are used in fMRI studies: block designs and event-related designs. Block-designed fMRI presupposes the steady state of regional cerebral blood flow and has been applied to examinations of brain activation caused by tasks requiring sustained or repetitive movements. By contrast, the more recently developed event-related fMRI with time resolution of a few seconds allows the mapping of brain activation associated with a single movement according to the transient aspects of the hemodynamic response. Increasing evidence suggests that multiple motor areas are engaged in a networked manner to execute various motor acts. In order to understand functional brain maps, it is important that one understands sequential and parallel organizations of anatomical connections between multiple motor areas. In fMRI studies of complex motor tasks, elementary parameters such as movement length, force, velocity, acceleration and frequency should be controlled, because inconsistency in those parameters may alter the extent and intensity of motor cortical activation, confounding interpretation of the findings obtained. In addition to initiation of movements, termination of movements plays an important role in the successful achievement of complex movements. Brain areas exclusively related to the termination of movements have been, for the first time, uncovered with an event-related fMRI technique. We propose the application of fMRI to the elucidation of the pathophysiology of movement disorders, particularly dystonia, which exhibits involuntary co-contraction of agonist and antagonist muscles and manifests abnormal posture or slow repetition of movements.

View full abstract

Purpose: To evaluate the efficacy of a fully automatic, single-voxel, proton MR spectroscopy algorithm on a 3.0T MR system.
Methods: The PROBE/SVQ algorithm (GE Medical Systems) was evaluated on a General Electric (GE) Signa LX-3T system. Ten normal volunteers (female, 21.1±2.0 years old) participated in the study. Nine representative regions of interest were examined, namely, right and left frontal white matter; right and left parietal white matter; right and left basal ganglia; right and left dentate nucleus; and pons.
Results: The mean coefficients of variation in all regions for the N-acetyl-aspartate to creatine ratio (NAA/Cr), choline to creatine ratio (Cho/Cr), and choline to N-acetyl-aspartate ratio (Cho/NAA) were 10.2±2.4%, 11.4±3.2% and 12.6±1.4%, respectively.
Conclusion: A fully automated spectroscopic examination under clinical setting utilizing the PROBE/SVQ algorithm appears to be a reliable method, extending the window of routine clinical assessment of brain metabolism.

View full abstract

The authors reported a case of fundal-type adenomyomatosis in which mural stratification corresponding to histopathological findings was clearly demonstrated with MR imaging. Single-shot fast spin echo images for MR cholangiopancreatography clearly visualized Rokitansky-Aschoff sinuses (RAS), which are a diagnostic clue for this disease. However, mural stratification comprising RAS with muscular proliferation, massive fibrosis and subserosal fat deposition was more precisely demonstrated in T₂-weighted images obtained with fast spin echo.

View full abstract