PurposeTo investigate the utility of computed 3T diffusion-weighted imaging (c-DWI) for the diagnosis of non-complicated hepatic cysts with a focus on the T2 shine-through effect.Materials and methodsIn 50 patients with non-complicated hepatic cysts we acquired one set of DWIs (b-value 0 and 1000 s/mm2) at 1.5T, and two sets at 3T (b-value 0 and 1000 s/mm2, TE 70 ms; b-value 0 and 600 s/mm2, TE 60 ms). We defined the original DWIs acquired with b = 1000 s/mm2 at 1.5T and 3T as “o-1.5T-1000” and “o-3T-1000”. c-DWIs were calculated with 3T DWI at b-values of 0 and 600 s/mm2. c-DWI with b = 1000 and 1500 s/mm2 were defined as “c-1000” and “c-1500”. Radiologists evaluated the signal intensity (SI) of the cysts using a 3-point score where 1 = not visible, 2 = discernible, and 3 = clearly visible. They calculated the contrast ratio (CR) between the cysts and the surrounding liver parenchyma on each DWIs and recorded the apparent diffusion coefficient (ADC) with a b-value = 0 and 1000 s/mm2 on 1.5T- and 3T DWIs.ResultsCompared with o-1.5T-1000 DWI, the visual scores of all but the c-1500 DWIs were higher (p = 0.07 for c-1500- and p < 0.01 for the other DWIs). The CR at b = 1000 s/mm2 was higher on o-3T-1000- than on o-1.5T-1000- (p < 0.01) but not higher than on c-1500 DWIs (p = 0.96). The CR at b = 0 s/mm2 on 3T images with TE 70 ms was higher than on 1.5T images (p < 0.01). The ADC value was higher for 3T- than 1.5T images (p < 0.01).ConclusionsNon-complicated hepatic cysts showed higher SI on o-3T-1000- than o-1.5T-1000 DWIs due to the T2-shine through effect. This high SI was suppressed on c-1500 DWIs.
Primary anorectal malignant melanoma is a fairly uncommon but highly malignant disease. This disease is sometimes mistaken for such benign conditions as either a hemorrhoid or rectal polyp. We herein describe a case of early primary malignant melanoma of the anal canal. In this case, magnetic resonance (MR) imaging was found to be useful for diagnosing the melanotic melanoma. We especially emphasize the usefulness of a fat-saturation MR image in distinguishing melanotic melanoma from other rectal tumors.
Purpose: Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) is a recently developed liver-speciˆc contrast agent for magnetic resonance (MR) imaging that is excreted equally via the kidneys and the biliary system. To our knowledge, its eŠects on T 2 -weighted MR cholangiopancreatography (MRCP) images have not been explored. Acquisition of the hepatobiliary phase is recommended 20 min after administration of Gd-EOB-DTPA. Examination time cannot be extended if the contrast does not take eŠect on T 2 -weighted MRCP within 20 min after administration.We attempted to assess the change in signal of T 2 -weighted MRCP by excretion of Gd-EOB-DTPA.Methods: Between March and July 2008, 40 patients (15 women, 25 men; mean age 70.8 years) were examined with abdominal MR imaging. T 2 -weighted MRCP was performed before and 10 and 20 min after administration of Gd-EOB-DTPA. We analyzed signal intensity of the bile duct, gallbladder, cystic duct, and pancreatic duct on MRCP for changes in intensity.Results: T 2 -weighted MRCP 20 min after contrast administration showed loss of signal of the bile duct (intrahepatic bile duct in all cases, upper extrahepatic duct in 36 [90z], middle extrahepatic duct in 33 [85z], and lower extrahepatic duct in 26 [67z]), the gallbladder in 23 cases (72z), and the cystic duct in 25 (64z). This signal change increased with time. We observed no change in signal of the pancreatic duct.Conclusion: T 2 -weighted MRCP sequences should not be obtained after administration of Gd-EOB-DTPA because this contrast agent decreases signal intensity of the biliary structure on these images.
Primary anorectal malignant melanoma is a fairly uncommon but highly malignant disease. This disease is sometimes mistaken for such benign conditions as either a hemorrhoid or rectal polyp. We herein describe a case of early primary malignant melanoma of the anal canal. In this case, magnetic resonance (MR) imaging was found to be useful for diagnosing the melanotic melanoma. We especially emphasize the usefulness of a fat-saturation MR image in distinguishing melanotic melanoma from other rectal tumors.
Clearance of substances over a wide range of molecular weights was higher with the TS-UL than with the APS-S, and differences in the design of the dialysate compartment may have been involved in this feature.
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