Human cerebral cortices: signal variation on diffusion-weighted MR imaging.

INTRODUCTION: We have often encountered high signal intensity (SI) of the cingulate gyrus and insula during diffusion-weighted magnetic resonance imaging (DW-MRI) on neurologically healthy adults. To date, cortical signal heterogeneity on DW images has not been investigated systematically. The purpose of our study was to determine whether there is regional signal variation in the brain cortices of neurologically healthy adults on DW-MR images. METHODS: The SI of the cerebral cortices on DW-MR images at 1.5 T was evaluated in 50 neurologically healthy subjects (34 men, 16 women; age range 33-84 years; mean age 57.6 years). The cortical SI in the cingulate gyrus, insula, and temporal, occipital, and parietal lobes was graded relative to the SI of the frontal lobe. Contrast-to-noise ratios (CNRs) on DW-MR images were compared for each cortical area. Diffusion changes were analyzed by visually assessment of the differences in appearance among the cortices on apparent diffusion coefficient (ADC) maps. RESULTS: Increased SI was frequently seen in the cingulate gyrus and insula regardless of patient age. There were no significant gender- or laterality-related differences. The CNR was significantly higher in the cingulate gyrus and insula than in the other cortices (p< .01) , and significant differences existed among the cortical regions (p< .001). There were no apparent ADC differences among the cortices on ADC maps. CONCLUSION: Regional signal variation of the brain cortices was observed on DW-MR images of healthy subjects, and the cingulate gyrus and insula frequently manifested high SI. These findings may help in the recognition of cortical signal abnormalities as visualized on DW-MR images.

Signal intensity of the normal pontine tegmentum on T2-weighted MR imaging.

On T2-weighted MR images, the pontine tegmentum frequently shows a signal of high intensity in neurologically healthy individuals. We examined whether the signal intensity of the pontine tegmentum normally differs from that of the pontine base. We evaluated the signal intensity of the pontine tegmentum and pontine base on T2-weighted images from 38 neurologically healthy subjects. The subjects included 29 adults (16 males and 13 females, age range 23-48 years, mean age 39.5 years) and 9 children (4 boys and 5 girls (age range 4-9 years mean age 6.5 years). We compared the contrast-to-noise ratio (CNR) between the tegmentum and the base in the upper pons, midpons and lower pons, and evaluated the signal intensity ratio of the tegmentum to the base. The CNR was significantly higher for the tegmentum than the base at each level of the pons (P<0.0001), and the signal intensity ratio of the tegmentum to the base in the upper pons was significantly higher in children than in adults (P<0.005). On T2-weighted images, a high signal intensity of the pontine tegmentum is frequently seen in neurologically healthy subjects. This finding should not be considered abnormal, particularly in children.

Mechanism of pancreatitis caused by ERCP.

BACKGROUND: Acute pancreatitis can develop after either ERCP or endoscopic sphincterotomy (ES). The pathogenesis of this complication remains poorly understood. METHODS: The frequency and severity of acute pancreatitis were retrospectively evaluated after 17,602 ERCP procedures and 3003 ES procedures. Pancreatitis was diagnosed and evaluated according to the scoring system of Ranson and criteria developed in Japan. RESULTS: Pancreatitis developed after 15 (0.09%) of 17,602 ERCP procedures and 13 (0.43%) of 3003 ES procedures (p = 0.0001, chi-square). The severity of pancreatitis (Ranson score) was less than 3 in 10 cases of ERCP-induced pancreatitis and from 3 to 5 in 5 cases. One (7%) of the 15 patients with ERCP-related pancreatitis died. All 13 patients with ES-induced pancreatitis had a Ranson score of less than 3; none died (p = 0.04, Fisher exact test). The ERCP pancreatitis score (Japanese criteria) beyond 48 hours after the onset of pancreatitis increased in 5 (33%) of the 15 patients with ERCP-induced pancreatitis; the score did not increase in any of the 13 patients with ES-induced pancreatitis (p = 0.04, Fisher exact test). CONCLUSIONS: Although the frequency of ES-induced pancreatitis is significantly higher than that of post-ERCP pancreatitis, the frequency of severe pancreatitis within 48 hours and worsening of pancreatitis after 48 hours is significantly lower with ES-induced pancreatitis. Our hypothesis is that the lowering of pancreatic intraductal pressure after ES mitigates the severity of postprocedure pancreatitis.