Biomedical subjects

Donald G Mitchell

Publications and source records attributed to Donald G Mitchell.

28 records · Page 2Linked to original sources

PubMed2002

MR imaging of hepatocellular carcinoma.

In this article, MR imaging features of hepatocellular carcinoma (HCC) are described. To better understand the MR imaging features of HCC, recent progress regarding its etiology, treatment, carcinogenesis, histology, and gross pathology will be described. Currently, T2-weighted fast spin-echo with fat saturation, and multiphasic dynamic gadolinium-enhanced two-dimensional and three-dimensional T1-weighted gradient echo imaging provides excellent results for detection and characterization of HCC.

Carcinoma, Hepatocellular↗

PubMed2002

Cirrhosis: MR imaging features.

The intent of this article is to provide a comprehensive review of MR imaging findings of cirrhosis and discusses clinical implications. Areas of focus include: (1) Morphologic changes of the liver in advanced cirrhosis and in early cirrhosis, (2) the frequency and imaging spectrum of intra- and extrahepatic changes in cirrhosis such as regenerative nodules, nodular liver surface, hepatic iron deposition, fibrosis, dilation of right inferior phrenic artery, gastrointestinal wall thickening, and portal hypertension, (3) serial MR findings of clinically progressive cirrhosis, (4) newly described MR sign of cirrhosis (an expanded gallbladder fossa sign), and (5) complications after liver transplantation. Understanding these MR features related to cirrhosis is helpful in clinical MR practice.

Humans↗

PubMed2002

Normal adrenal gland: in vivo observations, and high-resolution in vitro chemical shift MR imaging-histologic correlation.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether adrenal cortical lipid affects signal intensity on magnetic resonance (MR) images and to evaluate contrast between cortex and medulla. MATERIALS AND METHODS: From their clinical database, the authors selected 37 MR imaging studies of patients with adrenal adenomas. Two independent readers compared in-phase and fat-suppressed T1-weighted images, looking for visible lipid-induced signal intensity loss in the adrenal gland. Six adrenal gland specimens obtained after radical nephrectomy were also studied with high-resolution MR imaging, including in-phase, opposed-phase, and fat-suppressed T1-weighted images, and T2-weighted images. Adjacent histologic sections were stained with oil red O for neutral fats and with hematoxylin-eosin, and they were also viewed with polarization light microscopy. The relative amount of lipid was graded as mild, moderate, or intense, and the appearance of the cortex and medulla was compared with that on the MR images. RESULTS: On the 37 clinical MR studies, there was no visible signal intensity loss within the limbs of the ipsilateral adrenal glands. T2-weighted images of the adrenal specimens showed a thin high-intensity band, corresponding to the appearance of medulla on histologic slices. This could not be seen on any of the T1-weighted images. Region-of-interest measurements were nearly identical for in-phase and opposed-phase images. Histologic analysis showed abundant cortical lipid. CONCLUSION: Adrenal corticomedullary contrast can be depicted on high-resolution T2-weighted images but not on any T1-weighted images. There is abundant cortical lipid in adrenal specimens, but comparison of in-phase with opposed-phase MR images does not depict it.

Adrenal Cortex Neoplasms↗

PubMed2002

Hepatic tumor detection: MR imaging and conventional US versus pulse-inversion harmonic US of NC100100 during its reticuloendothelial system-specific phase.

PURPOSE: To compare conventional ultrasonography (US) and magnetic resonance (MR) imaging with contrast agent-enhanced US for detection of VX-2 liver tumors in rabbits. MATERIALS AND METHODS: Conventional gray-scale liver US was performed in 65 rabbits, 38 of which had VX-2 hepatic tumor implants. Twenty minutes after contrast agent injection, gray-scale pulse-inversion harmonic US images of the liver-specific phase were obtained. Following sacrifice of the animals, T1- and T2-weighted MR imaging was performed at 4-mm intervals. Pathologic analysis was performed as the reference standard. The capability of each imaging modality to correctly depict tumor presence or absence and the number of tumors was compared. RESULTS: Conventional US correctly depicted the presence or absence of tumors in 54 rabbits, for an accuracy of 83%, sensitivity of 71%, and specificity of 100%. With contrast-enhanced US, accuracy increased to 92% (60 correct cases); sensitivity, to 87%; and specificity, to 100%. MR imaging facilitated 56 correct diagnoses, for an accuracy of 86%, sensitivity of 82%, and specificity of 93%. There was a marginally significant difference between US with and US without contrast agent (P =.07) but not between MR imaging and contrast-enhanced US (P > or = .34). When the numbers of correctly detected tumors were compared, contrast-enhanced US performed significantly better than MR imaging (P =.02) and conventional US (P =.04). CONCLUSION: There was no significant difference between contrast-enhanced US and MR imaging in the detection of hepatic tumors, whereas contrast-enhanced US had the highest accuracy (92%) of the three modalities studied.

Animals↗

PubMed2002

Pancreatic cysts: depiction on single-shot fast spin-echo MR images.

PURPOSE: To evaluate single-shot fast spin-echo (SE) magnetic resonance (MR) imaging for depiction of pancreatic cysts in a large number of patients and to analyze cyst prevalence with respect to patient age and sex and other clinical information. MATERIALS AND METHODS: Single-shot fast SE images of the pancreas were obtained in 1,444 patients. The images were reviewed for presence of pancreatic cysts, which were classified as simple and nonsimple types, and cyst diameters were measured. kappa statistic, Fisher exact, McNemar Q, and Pearson product moment correlation tests were performed. RESULTS: Two hundred eighty-three (19.6%) patients had at least one pancreatic cyst. The prevalence of pancreatic cysts increased with age (r = 0.96). The percentages of male and female patients with pancreatic cysts (20.4% vs 18.8%) were not significantly different. Two hundred seventy-one (18.8%) patients had simple cysts, and 147 (10.2%) had nonsimple cysts. Of 283 patients with pancreatic cysts, 158 (55.8%) had only one pancreatic cyst. The number of patients with multiple cysts increased with age after 70 years. Four hundred fifteen (83.8%) cysts were 10 mm in diameter or smaller; 56 (11.3%), 11-20 mm in diameter; and 24 (4.9%), 21 mm in diameter or larger. Sixteen (5.7%) patients with pancreatic cysts had malignant pancreatic tumors, and 75 (26.5%) patients had pancreatitis. CONCLUSION: The prevalence of pancreatic cysts at single-shot fast SE MR imaging-especially cysts with a diameter smaller than 10 mm-is similar to that of pancreatic cysts at autopsy and higher than that of pancreatic cysts at transabdominal ultrasonography. Prevalence is especially high in patients with pancreatitis.

Adolescent↗

PubMed2002

Cirrhosis: modified caudate-right lobe ratio.

PURPOSE: To determine whether a modified caudate-right lobe ratio (C/RL) with use of the right portal vein to set the lateral boundary (C/RL-r) is more accurate for diagnosing cirrhosis and evaluating its clinical severity than is the previously described C/RL with use of the main portal vein to set the lateral boundary (C/RL-m). MATERIALS AND METHODS: Two hundred thirty-six patients (121 with pathologically proved cirrhosis and 115 without history of chronic hepatic diseases) underwent magnetic resonance (MR) imaging. Two independent observers measured C/RL-r and compared it with C/RL-m. Results were compared by using receiver operating characteristic (ROC) curves and accuracy measures at various thresholds. RESULTS: The area below the ROC curve was greater for C/RL-r (0.797) than for C/RL-m (0.731; P =.040). By using a C/RL-r greater than 0.90, the sensitivity, specificity, and accuracy for the MR imaging diagnosis of cirrhosis were 71.7%, 77.4%, and 74.2%, respectively. The highest accuracy of the C/RL-m was 65.7%, when the C/RL-m was greater than 0.55. Interobserver agreement was statistically confirmed for both measurements by using kappa analysis. Significant differences were found among the three Child-Pugh classes by using C/RL-r (P =.0105) but not by using C/RL-m. CONCLUSION: C/RL-r is more accurate for diagnosing cirrhosis and evaluating its clinical severity than is C/RL-m.

Adult↗

PubMed2002

Small (<20 mm) enhancing hepatic nodules seen on arterial phase MR imaging of the cirrhotic liver: clinical implications.

OBJECTIVE: To determine the significance in patients with cirrhosis of small (<20 mm) hepatic nodules that show no hyperintensity on T2-weighted MR images but that enhance during arterial phase MR imaging, we reviewed the cases of patients with such nodules. MATERIALS AND METHODS: Our review of radiology reports yielded 68 nodules in 40 patients with cirrhosis that showed no hyperintensity on T2-weighted MR images but had rapid enhancement during arterial phase MR imaging after administration of a gadolinium contrast agent. Thirty-four patients (60 nodules) had multiple follow-up MR imaging examinations (range of length of follow-up, 1-72 months; average length of follow-up, 15 months 2 weeks). The final diagnosis of the nodule was determined by pathology reports or after at least 2 years of follow-up to ensure nodule stability and, therefore, benignity. Two radiologists independently reviewed MR images of the nodules, noting the size, signal intensity on T1- or T2-weighted images, and homogeneity of contrast enhancement. RESULTS: Nine (13%) of the 68 nodules were hepatocellular carcinomas (HCCs). The size of nodules on the first MR examination was between 4 and 20 mm (mean size, 9.5 mm). No significant correlation between the diagnosis of HCC and nodule signal intensity (p = 0.48) or contrast enhancement homogeneity (p = 0.56) on first MR examination was found. Positive predictive value (PPV) and negative predictive value (NPV) for diagnosing HCC on the basis of nodule growth were 100% and 98%, respectively. For diagnosing HCC on the basis of a change in nodule signal intensity, the PPV was 60% and the NPV was 91%. For diagnosing HCC on the basis of a change of enhancement homogeneity, the PPV was 63%, and the NPV was 94%. CONCLUSION: A finding of growth in small, early-enhancing nodules in patients with cirrhosis is highly predictive of HCC. When small nodules are observed on a single examination, close follow-up of the patient appears appropriate.

Adult↗

PubMed2002

Body MR imaging and CT volume: variations and trends based on an analysis of medicare and fee-for-service health insurance databases.

OBJECTIVE: We examined Medicare and fee-for-service data sets to understand better the utilization of MR imaging for imaging the pelvis, abdomen, and chest relative to its use in imaging for other body parts and to the utilization of CT. MATERIALS AND METHODS: CT and MR imaging procedure volumes for pelvis, abdomen, chest, and total were extracted from the 1993, 1996, and 1999 Health Care Financing Administration Physician/Supplier Procedure Summary Master Files, based on CPT-4 codes. We also analyzed a fee-for-service health insurance database for January 1998 through July 1999 from a single northeastern state, which included provider location (rural, suburban, or urban) and type (teaching or nonteaching site). RESULTS: The greatest 3-year Medicare increase was for abdominal MR imaging, from 1996 to 1999 (101% increase). However, pelvic, abdominal, and chest MR imaging together remained less than 5% of total MR imaging. Abdominal MR imaging increased more than did total MR imaging in all 10 Health Care Financing Administration regions. In the fee-for-service database, the relative procedure volume of abdominal MR imaging varied approximately fivefold from rural to urban provider locations, and approximately double from nonteaching to teaching hospitals. CONCLUSION: Although far more abdominal CT than abdominal MR imaging is performed, the rate of abdominal MR imaging utilization has increased more rapidly since 1993. The relative procedure volume of abdominal MR imaging varied more than fivefold from rural to urban provider locations and double from nonteaching to teaching hospitals.

Abdomen↗

PubMed2002

Chronic hepatitis C activity: correlation with lymphadenopathy on MR imaging.

OBJECTIVE: To study the MR appearance of lymph nodes in relation to activity of chronic active hepatitis C, we correlated the findings on MR imaging with a histologic grading of the activity level. MATERIALS AND METHODS: Fifty patients with chronic active hepatitis C, who had MR imaging examinations and a related histology report from a liver biopsy obtained within 1 month of the MR imaging were chosen from our radiology database and studied retrospectively. All patients were examined over a 4-year period at a single institution to detect cirrhosis or hepatocellular carcinoma. We divided the 50 patients into the mild, moderate, or severe activity groups, according to their histology reports. Two radiologists, unaware of the histologic classifications, individually reviewed the MR images to observe the perihepatic locations, number, size (defined as the sum of the length-by-width products of the largest three nodes), and intensity of the lymph nodes relative to the spleen. The clinical records of the patients were reviewed to check the results of their liver function tests. The lymph node findings on MR imaging were compared with the histologically confirmed activity level of chronic hepatitis C. RESULTS: Forty-four (88.0%) of 50 patients had perihepatic lymph nodes larger than 5 mm on MR images, including 64.2% (9/14) of the patients with mild activity, 96.3% (26/27) of the patients with moderate activity, and 100% (9/9) of the patients with severe activity (p = 0.0034). The average number +/- the standard deviation (SD) of perihepatic lymph nodes was 2.5 +/- 1.8 in patients with mild activity, 5.6 +/- 2.2 in patients with moderate activity, and 8.3 +/- 3.5 in patients with severe activity (p = 0.0001). The average size (+/- SD) of the lymph nodes was 151.0 +/- 104.9 mm(2) in the mild activity group, 366.8 +/- 143.0 mm(2) in the moderate activity group, and 488.2 +/- 244.8 mm(2) in the severe activity group (p = 0.0001). On fat-saturated fast spin-echo T2-weighted MR images, the average number (+/- SD) of hyperintense nodes was 0.17 +/- 0.25 in the mild activity group, 1.7 +/- 0.80 in the moderate activity group, and 2.4 +/- 0.60 nodes in the severe activity group (p = 0.0001). No relationship between histologic activity and results from liver function tests was found. CONCLUSION: MR imaging depicts perihepatic lymph nodes in most patients with chronic hepatitis C. Lymph node number, size, and hyperintensity were related to the activity of chronic hepatitis C, but the results of liver function tests were not.

Adult↗

PubMedDate not supplied

Hepatic iron deposition on magnetic resonance imaging: correlation with inflammatory activity.

PURPOSES: To define the relation between pathologic inflammatory activity and magnetic resonance imaging (MRI) grades of iron deposition in patients with liver cirrhosis. PATIENTS AND METHODS: In 53 patients with biopsy-proven liver cirrhosis, T2*-weighted gradient echo MRI (echo time > or =6 milliseconds) was reviewed. Grading of parenchymal iron deposition and siderotic nodules in the liver and liver-to-skeletal muscle signal intensity ratios were compared with pathologically defined inflammatory activity. RESULTS: The MRI grade of hepatic siderotic nodules correlated significantly with the grade of periportal inflammation (r = 0.301, P < 0.05) but not with the grade of piecemeal necrosis. The grade of parenchymal iron deposition was not correlated with the grade of periportal inflammation or piecemeal necrosis. There was a nonsignificant trend toward correlation between the histologic grade of hepatic iron content and the grades of periportal inflammation and piecemeal necrosis. CONCLUSION: MRI grading of siderotic nodules correlates with inflammatory activity in cirrhotic patients.

Adult↗