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Biomedical subjects

D G Mitchell

Publications and source records attributed to D G Mitchell.

At least 37 records · Page 2Linked to original sources
PubMed2000

Efficacy and safety of mangafodipir trisodium (MnDPDP) injection for hepatic MRI in adults: results of the U.S. Multicenter phase III clinical trials. Efficacy of early imaging.

The efficacy of contrast-enhanced magnetic resonance imaging (MRI) for detecting and characterizing, or excluding, hepatic masses was assessed in 404 patients, following the intravenous administration of mangafodipir trisodium (MnDPDP) injection, a hepatic MRI contrast agent. An initial contrast-enhanced computed tomography (CT) examination was followed by unenhanced MRI, injection of MnDPDP (5 micromol/kg IV), and enhanced MRI at 15 minutes post injection. Agreement of the radiologic diagnoses with the patients' final diagnoses was higher for enhanced MRI and for the combined unenhanced and enhanced MRI evaluations than for unenhanced MRI alone or enhanced CT using the clinical diagnosis as the gold standard. Mangafodipir-enhanced MRI uniquely provided additional diagnostic information in 48% of the patients, and patient management was consequently altered in 6% of the patients. MnDPDP-enhanced MRI was comparable or superior to unenhanced MRI and enhanced CT for the detection, classification, and diagnosis of focal liver lesions in patients with known or suspected focal liver disease.

Adult↗
PubMed2000

Biliary dilatation: differentiation of benign from malignant causes--value of adding conventional MR imaging to MR cholangiopancreatography.

PURPOSE: To determine the value of conventional T1 - and T2-weighted images and gadolinium-enhanced dynamic magnetic resonance (MR) images as a supplement to MR cholangiopancreatographic (MRCP) images in differentiation of benign from malignant causes of biliary dilatation. MATERIALS AND METHODS: MR studies in 62 patients with biliary dilatation with proved causes included conventional T1- and less heavily T2-weighted images, as well as gadolinium-enhanced dynamic images and heavily T2-weighted MRCP images. Two radiologists reviewed MRCP images alone, MRCP images with nonenhanced T1 - and T2-weighted MR images, and MRCP images with nonenhanced and gadolinium-enhanced dynamic images. RESULTS: For differentiation of benign from malignant causes of biliary dilatation, the area under the receiver operating characteristic curve (A(z)) was significantly (P < .05) larger for MRCP images interpreted with T1 - and T2-weighted images (0.9547 for reader 1, 0.8404 for reader 2) than for MRCP images alone (0.8144 for reader 1, 0.8122 for reader 2). The addition of gadolinium-enhanced dynamic MR images to MRCP images with nonenhanced T1- and T2-weighted images did not significantly increase accuracy (A(z) = 0.9554 for reader 1 and 0.8650 for reader 2), but the level of confidence was increased in 17%-24% of cases. CONCLUSION: Use of nonenhanced T1- and less heavily T2-weighted images with MRCP images significantly improved the diagnostic accuracy of MR examinations of pancreaticobiliary disease.

Adolescent↗
PubMed2000

Portal vein and its tributaries: evaluation with thin-section three-dimensional contrast-enhanced dynamic fat-suppressed MR imaging.

PURPOSE: To evaluate the visibility of the main portal vein (MPV) and its tributaries in healthy subjects at thin-section three-dimensional (3D) contrast material-enhanced dynamic fat-suppressed magnetic resonance (MR) imaging and to determine whether this technique provides useful information in the evaluation of patients with cirrhosis. MATERIALS AND METHODS: Seventy-two patients (37 control subjects, 35 patients with cirrhosis) underwent imaging with a high-performance-gradient (25 mT/m) system. RESULTS: In the 37 subjects in the control group, the MPV was visualized in 37; splenic vein (SV), in 37; superior mesenteric vein (SMV), in 37; inferior mesenteric vein (IMV), in 35; posterior superior pancreaticoduodenal vein (PSPDV), in 35; gastrocolic trunk (GT), in 34; right gastroepiploic vein (RGEV), in 31; right colic vein, in 30; anterior superior pancreaticoduodenal vein, in 22; middle colic vein (MCV), in 29; and first jejunal vein (FJV), in 36. Satisfactory visualization (mean ratings of 2 or higher) was achieved in the MPV, SV, SMV, IMV, PSPDV, GT, RGEV, and FJV in the control group. Mean diameters of the SV, SMV, MCV, and FJV were significantly larger in the cirrhosis group than in the control group (P <.001, P <.001, P =.048, and P =.002, respectively). CONCLUSION: Thin-section 3D contrast-enhanced dynamic fat-suppressed MR imaging can facilitate precise visualization of the MPV and its tributaries. Dilatation of the tributaries may be a nonspecific secondary finding that is suggestive of cirrhosis.

Adipose Tissue↗
PubMed2000

Preoperative evaluation of living renal donors: comparison of CT angiography and MR angiography.

PURPOSE: To compare computed tomographic (CT) angiography and magnetic resonance (MR) angiography for preoperative evaluation of living renal donors. MATERIALS AND METHODS: Thirty-five living renal donors underwent preoperative contrast material-enhanced CT angiography and gadolinium-enhanced MR angiography. Each study was interpreted by two independent radiologists blinded to all other studies and to interpretations provided by other reviewers. Eighteen kidneys had surgical correlation. RESULTS: CT demonstrated 33 supernumerary arteries in 19 patients, bilateral solitary arteries in 16 patients, and 18 proximal arterial branches in 16 patients. MR demonstrated 26 supernumerary arteries in 15 patients, bilateral solitary renal arteries in 20 patients, and 21 proximal arterial branches in 16 patients. Interobserver agreements for MR (kappa = 0. 74) and CT (kappa = 0.73) were similar to the agreement between MR and CT (kappa = 0.74). Among the kidneys chosen for nephrectomy, one small accessory artery and one proximal arterial branch were missed with CT and MR. Two of the accessory arteries suggested at CT were not found at nephrectomy. By averaging data for both modalities, supernumerary arteries were present in 49% of kidney donors and were bilateral in approximately 17%. Proximal arterial branches were present in 46% of kidney donors. CONCLUSION: Preoperative CT and MR angiography of the renal arteries in renal donors demonstrate substantial agreement. Interobserver disagreement in the interpretation of CT and MR angiograms is related to 1-2-mm-diameter vessels.

Adult↗
PubMed2000

Arterial pseudostenosis on first-pass gadolinium-enhanced three-dimensional MR angiography: new observation of a potential pitfall.

OBJECTIVE: The purpose of this study was to determine the frequency of apparent stenosis of normal aortic branches in patients on first-pass gadolinium-enhanced three-dimensional (3D) MR angiography and to reproduce the same phenomenon in a pulsatile flow phantom model. CONCLUSION: Apparent stenosis of normal vessels on gadolinium-enhanced 3D MR angiography seen on the first-pass acquisition was observed in only a small proportion (approximately 2%) of our patients. The pseudostenosis was reproducible in the phantom model using rapid injection. A stenosis on first-pass images should be interpreted with caution. Confirmation of the findings on other sequences, such as the second-pass gadolinium-enhanced 3D MR angiography or 3D phase-contrast MR angiography, prevented overdiagnosis of significant stenoses.

Aortic Valve Stenosis↗
PubMed1999

Mangafodipir trisodium: effects on T2- and T1-weighted MR cholangiography.

The purpose of this study was to determine the effects of mangafodipir trisodium on heavily T2-weighted magnetic resonance cholangiography (MRC) images and on functional T1-weighted MRC. Pre- and post-mangafodipir trisodium heavily T2-weighted MRC and fat-suppressed T1-weighted three-dimensional (3D) gradient-echo MRC images were obtained in a patient with a prior cholecystectomy and a long cystic duct remnant that had apparent biliary stasis. Multiplanar reconstructed images were created. The precontrast T2-weighted MRC showed a long cystic duct remnant and a normal common bile duct (CBD). The postcontrast T2-weighted MRC showed loss of CBD signal, but persistent signal in the cystic duct remnant due to biliary stasis. Post-mangafodipir T1-weighted 3D gradient-echo images showed the main right and left hepatic ducts, but the cystic duct was not depicted. Conventional T2-weighted MRC sequences should not be obtained after administering mangafodipir trisodium because this contrast agent decreases the T2 and therefore the signal intensity of bile within normally functioning bile ducts. Functional MRC images can be acquired by using a post-mangafodipir T1-weighted technique.

Adult↗
PubMed1999

MR imaging of the liver: techniques and clinical applications.

With a recent advance of fast MR imaging techniques including fast gradient-echo (GRE), fast spin-echo (FSE), single shot FSE (SSFSE) and echo-planar imaging (EPI), and availability of a phased-array torso coil, there can be many possible pulse sequences for liver MR imaging. In clinical practice, optimization of pulse sequences is important for improving diagnostic performance of liver diseases. In this article, we review the current status of liver MR imaging, focusing on the description of standard pulse sequences, and the utility of fast scanning technique and contrast-enhancement studies.

Carcinoma, Hepatocellular↗
PubMed1999

US, CT, and MR evaluation of accessory renal arteries and proximal renal arterial branches.

RATIONALE AND OBJECTIVES: The purpose of this study was to compare color Doppler ultrasound (US), computed tomographic (CT) angiography, and magnetic resonance (MR) angiography for the evaluation of accessory renal arteries and proximal branches of the main renal artery. MATERIALS AND METHODS: Fifty-six subjects who had undergone conventional arteriography of the renal arteries participated in a prospective comparison of Doppler US (45 patients), CT angiography (52 patients), and nonenhanced MR angiography (28 patients). Conventional arteriography depicted 28 accessory renal arteries and 21 proximal branches of the main renal artery within 2 cm of the aorta. RESULTS: US depicted five of 24 accessory renal arteries seen at arteriography but no proximal arterial branches. CT angiography depicted 24 of 26 accessory renal arteries and 13 of 17 proximal arterial branches, as well as 15 additional accessory renal arteries not seen at conventional arteriography. MR demonstrated 11 of 15 accessory arteries, as well as four additional accessory arteries not seen at conventional arteriography. MR did not depict any of nine proximal arterial branches seen at conventional arteriography. CONCLUSION: When compared with US or nonenhanced MR angiography, CT is the preferred method for evaluation of accessory renal arteries and proximal branches of the renal artery.

Adult↗
PubMed1999

Mirizzi syndrome: evaluation by MRI imaging.

We report three cases of Mirizzi syndrome diagnosed by MR imaging. MR cholangiography revealed dilation of the intrahepatic bile ducts, narrowing of the common hepatic duct, the level of obstruction, and the location of gallstone in the cystic duct. MR showed thickening of the gallbladder wall and the pattern of wall enhancement. MR evaluation with MR cholangiography sequences proved to be useful in these patients with Mirizzi syndrome.

Adult↗
PubMed1999

Expanded gallbladder fossa: simple MR imaging sign of cirrhosis.

PURPOSE: To determine the frequency on magnetic resonance (MR) images of a widened pericholecystic space, which the authors call the expanded gallbladder fossa sign, and to assess the sensitivity and specificity of this sign for cirrhosis. MATERIALS AND METHODS: Three-hundred thirteen patients who underwent MR imaging were included in this study, including 190 with pathologically proved cirrhosis (cirrhosis patients) and 123 without history of chronic liver diseases (control subjects). MR images were qualitatively evaluated by three independent observers for the presence of the expanded gallbladder fossa sign. This sign was considered present if there was enlargement of the pericholecystic space (i.e., gallbladder fossa) and the space was bounded laterally by the edge of the right hepatic lobe and medially by the edge of the left lateral segment, in conjunction with nonvisualization of the left medial segment. RESULTS: The expanded gallbladder fossa sign was seen in 129 cirrhosis patients and in three control subjects (P < .001). The sensitivity, specificity, accuracy, and positive predictive value of this sign for the MR diagnosis of cirrhosis were 68%, 98%, 80%, and 98%, respectively. CONCLUSION: The expanded gallbladder fossa sign on MR images is a frequently present, specific indicator of cirrhosis. This sign can be used as a simple and highly specific sign of cirrhosis, if present, despite the overall sensitivity of 68%.

Adult↗
PubMed1999

Diagnosis and staging of ovarian cancer: comparative values of Doppler and conventional US, CT, and MR imaging correlated with surgery and histopathologic analysis--report of the Radiology Diagnostic Oncology Group.

PURPOSE: To determine the optimal imaging modality for diagnosis and staging of ovarian cancer. MATERIALS AND METHODS: Two hundred eighty women suspected to have ovarian cancer were enrolled in a prospective study before surgery. Doppler ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging were used to evaluate the mass; conventional US, CT, and MR imaging were used to stage spread. RESULTS: All three modalities had high accuracy (0.91) for the overall diagnosis of malignancy. In the ovaries, the accuracy of MR imaging (0.91) was higher than that of CT and significantly higher than that of Doppler US (0.78). In the extraovarian pelvis and in the abdomen, conventional US, CT, and MR imaging had similar accuracies (0.87-0.95). In differentiation of disease confined to the pelvis from abdominal spread, the specificity of conventional US (96%) was higher than that of CT and significantly higher than that of MR imaging (88%), whereas the sensitivities of MR imaging (98%) and CT (92%) were significantly higher than that of conventional US (75%). CONCLUSION: MR imaging is superior to Doppler US and CT in diagnosis of malignant ovarian masses. There is little variation among conventional US, CT, and MR imaging as regards staging.

Adult↗
PubMed1999

Hepatocellular carcinoma: association with increased iron deposition in the cirrhotic liver at MR imaging.

PURPOSE: To determine whether the frequency of hepatocellular carcinoma (HCC) in patients with cirrhosis is affected by hepatic iron deposition as detected with magnetic resonance (MR) imaging. MATERIALS AND METHODS: In a retrospective search of MR imaging and histopathology records, 196 patients with histopathologically proved cirrhosis and with (n = 80) or without (n = 116) HCC who underwent T2-weighted conventional or fast spin-echo and gradient-echo (GRE) (echo time > or = 6.0 msec) imaging were identified. MR images were qualitatively and quantitatively evaluated for diffuse hepatic iron deposition and siderotic regenerative nodules to assess their correlation with the presence of HCC. RESULTS: Hepatic parenchymal iron deposition was seen in 79 (40%) patients, and iron deposition in regenerative nodules was seen in 71 (36%) at MR imaging. The mean signal intensity ratio of GRE images in patients with hepatic iron deposition was significantly lower than that in patients without it (P < .001). The frequency of HCC in patients with iron deposition in regenerative nodules (52% [37 of 71 patients]) was significantly higher (P = .015) than that in patients without iron in regenerative nodules (34% [43 of 125 patients]). CONCLUSION: The occurrence of HCC may be associated causally with iron deposition in regenerative nodules in patients with cirrhosis. MR imaging can enable detection of iron deposition in regenerative nodules as a possible risk factor for the development of HCC.

Adult↗
PubMed1999

Primary sclerosing cholangitis: MR imaging features.

OBJECTIVE: The purpose of this study was to evaluate the spectrum of MR imaging features of primary sclerosing cholangitis. MATERIALS AND METHODS: A retrospective review was performed of MR imaging findings including MR cholangiography and multiphasic contrast-enhanced dynamic sequences in 22 patients with primary sclerosing cholangitis. MR imaging analysis included abnormalities of intra- and extrahepatic bile ducts, abnormalities of liver parenchyma, changes in liver morphology, and lymphadenopathy. RESULTS: Abnormal findings of bile ducts were seen in all 22 patients; the most common finding was intrahepatic bile duct dilatation (77%), followed by intrahepatic bile duct stenosis (64%), extrahepatic bile duct wall enhancement (67%), extrahepatic bile duct wall thickening (50%), extrahepatic bile duct stenosis (50%), and intrahepatic bile duct beading (36%). Increased enhancement of the liver parenchyma on dynamic arterial-phase images, predominantly in the peripheral areas of the liver, was identified in 56% of patients. Other findings included periportal lymphadenopathy (77%), periportal high signal intensity on T2-weighted images (68%), hypertrophy of the caudate lobe (68%), and abnormal hyperintensity of the liver parenchyma on T1-weighted images (23%). CONCLUSION: On MR imaging, primary sclerosing cholangitis showed several characteristic features, including bile duct abnormalities and increased enhancement of the liver parenchyma. MR cholangiography and contrast-enhanced dynamic MR techniques are useful for revealing intra- and extrahepatic signs of primary sclerosing cholangitis.

Adult↗
PubMed1999

Viral-induced cirrhosis: grading of severity using MR imaging.

OBJECTIVE: The purpose of this study was to determine whether MR imaging can be used to grade the severity of cirrhosis. MATERIALS AND METHODS: The MR examinations of 46 patients with cirrhosis were retrospectively reviewed independently by two radiologists and correlated with clinical severity assessed by Child-Pugh classification. MR imaging analysis by reviewers who were unaware of clinical status included comparison of volume indexes (computed as the product of three axis measurements) of the spleen and each segment of the liver, and changes in hepatic contour, iron or fat deposition, and presence of varices and collaterals. RESULTS: Volume index of the spleen and the presence of ascites and varices were significantly and positively correlated (p = .008, .002, .0001, respectively) with the clinical severity of cirrhosis (Child-Pugh classifications), and volume indexes of the posterior, medial, and lateral segments of the liver were significantly and inversely correlated (p = .001, .049, .041, respectively). On an MR scoring system based on four items (volume index of the spleen; volume index of posterior + medial + lateral segments; presence of ascites; and presence of varices and collaterals), averaged total MR scores were 2.5 +/- 0.3, 4.9 +/- 0.6, and 7.9 +/- 0.8 for Child-Pugh grades A, B, and C, respectively (p < .0001). The accuracy of MR scoring in distinguishing between clinical Child-Pugh grade A cirrhosis and further grades was 89%, the sensitivity was 93%, and the specificity was 82%. CONCLUSION: An MR scoring system can be used to grade the severity of cirrhosis.

Contrast Media↗
PubMed1999

Pancreatic changes in primary sclerosing cholangitis: evaluation with MR imaging.

OBJECTIVE: The purpose of this study was to determine the frequency and the spectrum of MR imaging findings of pancreatic abnormalities in patients with primary sclerosing cholangitis. MATERIALS AND METHODS: MR images in 24 patients with primary sclerosing cholangitis were retrospectively reviewed for evidence of pancreatic abnormalities, including abnormalities of signal intensity; changes in size and morphology; abnormalities of pancreatic ducts; presence of focal lesions, pseudocysts, and peripancreatic edema or fluid; and contrast-enhancement pattern if dynamic studies were available. RESULTS: Eleven patients with pancreatic abnormalities on MR images (case patients) and 13 patients with normal MR findings of the pancreas (cohort patients) were identified. The most common finding in case patients was increased signal intensity of the pancreas on T2-weighted images (73%), followed by decreased signal intensity on T1-weighted images (55%) and decreased enhancement on arterial-phase contrast-enhanced images (50%). Other findings included marked enlargement of the pancreas (27%), narrowing of pancreatic ducts (27%), and peripancreatic edema or fluid (27%). The mean value of the anteroposterior diameter of the pancreatic head in the case patients was significantly greater than that in the cohort patients (p = .039). The mean signal-intensity ratio on the T2-weighted images was significantly higher in the case patients than in the cohort patients (p = .007). CONCLUSION: Increased signal on T2-weighted images, decreased signal on T1-weighted images, enlargement of the pancreas, and decreased contrast-enhancement were MR findings of pancreatic disease associated with primary sclerosing cholangitis.

Adult↗