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.

Multidetector CT findings suggesting a perforation site in the gastrointestinal tract: analysis in surgically confirmed 155 patients.

PURPOSE: The aim of this study was to investigate how accurately we could diagnose the level of gastrointestinal (GI) tract perforation using multidetector computed tomography (MDCT). MATERIALS AND METHODS: We reviewed 155 patients with surgically confirmed GI tract perforation. MDCT scans were obtained with eight-detector CT; 5 mm thick axial images and 2.5 mm thick coronal multiplanar reconstruction (MPR) images were generated for all patients. Contrast enhancement was performed in 44 of the 155 patients. Two board-certified radiologists reviewed the images for direct findings (free air, ruptured GI tract wall) and indirect findings (inflammatory changes, fluid collection, focal thickening of the GI tract wall) and attempted to identify the perforation site in each patient. RESULTS: Free air was seen in more than 95% of the patients with perforation at sites other than the appendix; free air was seen in 44% of patients with appendicitis. On contrast-enhanced CT performed in 44 patients, rupture of the wall of the GI tract was directly visualized in 14 (32%) on axial images only and in 23 (52%) on axial or MPR images, respectively. The perforation site was correctly diagnosed in 90% of the patients when the radiologists referred to both direct and indirect findings. CONCLUSION: MDCT was valuable for identifying the presence and level of GI tract perforation.

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.

Diffusion-weighted imaging of radiation-induced brain injury for differentiation from tumor recurrence.

BACKGROUND AND PURPOSE: Differentiation between tumor recurrence and treatment-related brain injury is often difficult with conventional MRI. We hypothesized that the diffusion-weighted imaging (DWI) could help differentiate these 2 conditions, because water diffusion may be greater for necrotic tissues in the treatment-related brain injury than for tumor tissues in recurrence. Our aim was to analyze whether DWI findings of recurrent tumor are distinct from those of radiation necrosis. METHODS: Seventeen patients were examined prospectively. Two readers assessed the images by consensus for homogeneity and signal intensity of the lesions. Five regions of interest were drawn within the lesions on trace DWI images and apparent diffusion coefficient (ADC) maps. The minimal, maximal, and mean values of each lesion were compared between the 2 groups. Findings in 12 of 17 patients were verified histologically by surgery or biopsy; the diagnoses in the remaining 5 patients were made on the basis of follow-up MRI findings and clinical follow-up. RESULTS: There were a total of 20 lesions; 12 lesions were due to radiation necrosis and 8 lesions to tumor recurrence. In the radiation necrosis group, 8 lesions had marked hypointensity. In the recurrence group, however, no marked hypointensity was seen. The maximal ADC values within each lesion were significantly smaller for the recurrence group than for the necrosis group (P = .039). CONCLUSION: Radiation necrosis usually showed heterogeneity on DWI images and often included spotty, marked hypointensity. Significant difference was found in the maximal ADC values between radiation necrosis and tumor recurrence. DWI was useful in differentiating recurrent neoplasm from radiation necrosis.