Biomedical subjects

Y Dodo

Publications and source records attributed to Y Dodo.

60 records · Page 4Linked to original sources

PubMedDate not supplied

Struma ovarii: MR findings.

PURPOSE: The purpose of this study was to determine the MR appearance of struma ovarii correlating with the pathological features. METHOD: MR findings of two patients with struma ovarii were retrospectively reviewed and compared with the pathological findings. RESULTS: Both tumors were complex masses composed of multiple cysts and solid components. The size and signal intensity of multiple cysts varied within the tumor. Hyperintense cystic areas on T1-weighted images were thought to correspond pathologically to hemorrhagic cysts and follicles containing viscous proteinaceous colloid. Solid components had as high a signal intensity as did uterine endometrium on T2-weighted images and as intermediate a signal intensity as did uterine muscle layer on T1-weighted images. After intravenous administration of gadolinium-DTPA, the solid components showed marked contrast enhancement. There was also ascitic fluid associated with adhesion and peritoneal thickening. CONCLUSION: The characteristic MR appearance of struma ovarii is thought to be a mixed mass composed of T2-hyperintense solid components with intense contrast enhancement and multiple T1-hyperintense cystic areas suggestive of hemorrhagic degeneration and viscous proteinaceous colloid.

Adult↗

PubMedDate not supplied

Diagnostic pitfalls of MR cholangiopancreatography in the evaluation of the biliary tract and gallbladder.

Magnetic resonance (MR) cholangiopancreatography is a noninvasive imaging technique that has proved accurate in the diagnosis of biliary obstruction. However, various diagnostic pitfalls have been reported with MR cholangiopancreatography that were not encountered previously at conventional biliary imaging. These pitfalls may simulate or mask various pathologic conditions of the extrahepatic bile duct or main pancreatic duct and may be caused by a variety of factors. Because of its postprocessing nature, maximum-intensity-projection reconstruction may mask a small gallstone if the stone is surrounded by hyperintense bile and may cause false ductal disconnection or duplication when a breath hold is not performed perfectly. Extraductal factors (e.g., metallic surgical clips, intravascular metallic coils, gas in the stomach or duodenum) can cause signal loss in the adjacent part of the extrahepatic bile duct, which may in turn lead to a false-positive diagnosis of ductal narrowing or obstruction. Normal vascular structures including the right hepatic and gastroduodenal arteries can cause pseudo-obstruction of the extrahepatic bile duct by pulsatile compression. Intraductal factors (e.g., gas, hemorrhage, debris, iodinated contrast material) reduce the signal intensity of the bile, which may result in pseudo-obstruction, false filling defects, or a nonvisualized gallbladder or bile duct. Knowledge of the existence and high prevalence of these diagnostic pitfalls should help prevent misinterpretation of MR cholangiopancreatograms.

Artifacts↗

PubMedDate not supplied

Contrast-enhanced three-dimensional MR portography.

Three-dimensional (3D) magnetic resonance (MR) portography with contrast material enhancement is a fast means of evaluating the portal venous system that has some advantages over currently used modalities, such as digital subtraction angiography, helical computed tomography, ultrasonography, and nonenhanced MR angiography with time-of-flight and phase-contrast techniques. With contrast-enhanced 3D MR portography, a first-pass study of the mesenteric vasculature is performed after rapid bolus injection of gadopentetate dimeglumine; a 3D fast field echo sequence is used, which can demonstrate the intrahepatic and extrahepatic portal venous system clearly. Repeated sequences after administration of gadopentetate dimeglumine allow separate demonstration of the splanchnic arteries and portomesenteric veins. The images are reconstructed by means of maximum-intensity projection postprocessing, and a subtraction technique can be used to eliminate arterial enhancement and demonstrate portosystemic shunts. The coronal source images simultaneously demonstrate parenchymal lesions of the liver, pancreas, biliary tract, and spleen. This technique is clinically indicated in portosystemic shunt, portal vein thrombosis, hepatocellular carcinoma, pancreatobiliary tumor, hepatic vein obstruction, differentiation of splanchnic arterial from portal venous disease, and gastrointestinal hemorrhage. Its limitations include allergic reactions to contrast media, inappropriate positioning of the 3D acquisition slab, respiratory motion artifacts, and pseudodissection.

Contrast Media↗

PubMedDate not supplied

Dynamic subtraction contrast-enhanced MR angiography: technique, clinical applications, and pitfalls.

Rapid advances in techniques of contrast material-enhanced magnetic resonance (MR) angiography have enabled evaluation of the entire aorta and the main arteries. Dynamic subtraction MR angiography consists of first-pass imaging of long segments of arteries by using a three-dimensional fast field echo sequence with multiple rapid bolus injections of a small dose of gadopentetate dimeglumine. Subtraction enables clear demonstration of the enhanced vascular lumen by eliminating background signal. Improved temporal resolution and repeated sequences after gadopentetate dimeglumine administration allow demonstration of arteries and veins separately. Double subtraction postprocessing can be used to eliminate arterial enhancement in demonstration of the portal and systemic veins. Additional postprocessing can be used to demonstrate arteries in a single image in patients with aortic dissection or a prolonged circulation time. To optimize the examination, the pulse sequence, injection dose, injection rate, timing of the start of data acquisition, imaging time, breath holding, section thickness, and coil selection should be considered. This technique is flexible enough to be applied in a variety of clinical settings, including atherosclerotic occlusive disease, aneurysm of aortoiliac arteries, bypass graft, Takayasu arteritis, aortic dissection, antiphospholipid antibody syndrome, renal artery disease, pelvic vascular disease, and the portomesenteric venous system.

Contrast Media↗

PubMedDate not supplied

Comprehensive MR imaging of acute gynecologic diseases.

Rapid advances in techniques of magnetic resonance (MR) imaging have enabled diagnosis of acute gynecologic conditions, which are characterized by sudden onset of lower abdominal pain, fever, genital bleeding, intraperitoneal bleeding, or symptoms of shock. The chemical-selective fat-suppression technique not only helps establish the characteristics of lesions that contain fat components but also increases the conspicuity of inflammatory lesions. When a T2-weighted image is obtained with a very long effective echo time (>250 msec), even a small amount of ascites can be easily identified and the contrast between urine and complex fluid becomes more conspicuous. T2*-weighted images are useful for identification of hemorrhagic lesions by demonstrating deoxyhemoglobin and hemosiderin. Contrast material-enhanced dynamic subtraction MR imaging performed with a three-dimensional fast field-echo sequence and a rapid bolus injection of gadopentetate dimeglumine allows evaluation of lesion vascularity and the anatomic relationship between pelvic vessels and a lesion and allows identification of the bleeding point by demonstrating extravasation of contrast material. To optimize the MR imaging examination, attention should be given to the parameters of each pulse sequence and proper combination of the sequences.

Diagnosis, Differential↗

PubMedDate not supplied

Studies in radiosensitizing effects of misonidazole and SR-2508 on C3H/He mouse mammary tumors.

The radiosensitizing efficacy of SR-2508, a new 2-nitroimidazole, which is less neurotoxic than misonidazole (MISO) was studied using transplantable mammary carcinoma of C3H/He mice. Tumor responses to treatments were evaluated by growth-delay time assay. In single irradiations, the enhancement ratios of 0.5 mmole/kg of MISO and 1.5 mmole/kg of SR-2508, which were equitoxic to C3H/He mice, were 1.42 and 1.84 respectively. In fractionated irradiations with three fractions over two days or five fractions over four days, the enhancement ratios of 1.5 mmole/kg of SR-2508 were 1.40 and 1.34 respectively. On the other hand the enhancement ratios of MISO at the above mentioned dose in respective fractionated irradiations were 1.15 or 1.11. SR-2508 is considered promising as a hypoxic cell radiosensitizer for clinical use.

Animals↗