Health effects of ionising radiation from diagnostic CT.
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DNA↗
Biomedical subjects
Richard C Semelka
Publications and source records attributed to Richard C Semelka.
Hepatocellular carcinoma missed on gadolinium enhanced MR imaging, discovered in liver explants: retrospective evaluation.
The main purpose of this study was to determine if hepatocellular carcinomas (HCCs) missed on prospective magnetic resonance (MR) study could be identified on retrospective MR analysis, and to determine the cause for misdiagnosis. Among 555 patients who underwent liver transplantation between 1993 and 2004, 279 were imaged with MR imaging and four of these revealed HCCs in explanted livers that were not reported on prospective MR reading. The main cause of missed lesions were suboptimal image quality due to inability of patients to suspend respiration; other causes were HCC misinterpreted as high-grade dysplastic nodule and isoenhancement of HCC on early phase images.
Adult↗
Accurate quantification of visceral adipose tissue (VAT) using water-saturation MRI and computer segmentation: preliminary results.
PURPOSE: To describe and evaluate the accuracy of water-saturation MRI and a computer segmentation program for quantification of visceral adipose tissue (VAT). MATERIALS AND METHODS: MRI was performed on five patients with whole-volume coverage of the abdomen using two different sequences: 1) a T1-weighted spoiled gradient-echo breath-hold sequence (non-water-saturation) and 2) a T1-weighted spoiled gradient-echo water-saturation breath-hold sequence (water-saturation). The computer segmentation program analyzed the data and calculated VAT volumes (cm3) from both sequences. The data from one patient were additionally processed with the use of a manual technique. The intrastudy reproducibility of the proposed method using the water-saturation MRI sequence and the computer segmentation technique was tested by repeated measures of the automated system analysis (x 10) on MRI data from a single subject to calculate variability. RESULTS: VAT volumes measured by the water-saturation MRI sequences were consistently greater than those measured by the non-water-saturation sequences. Comparison of VAT volumes derived from the water-saturation images and measured by the computer segmentation technique vs. the manual technique showed good correlation (K = 0.8), with a significant time-saving benefit associated with the automated method (5 minutes vs. 1 hour). There was poor correlation between VAT volume measurement calculated by the manual technique and the computer segmentation technique using non-water-saturation images. The reproducibility of the computer segmentation technique using data derived from water-saturation images was high, with a low variability (+/- 5%). CONCLUSION: The results obtained demonstrate that the proposed method may be able to provide accurate quantification of VAT in a highly reproducible and efficient manner.
Body Water↗
Adult celiac disease: what is the role of MRI?
PURPOSE: To evaluate the ability of MRI to identify intra- and extraintestinal findings of celiac disease in an adult population. MATERIALS AND METHODS: Forty-one subjects (18 men and 23 women; mean age = 41.3 years; 31 with biopsy-proven celiac disease, and 10 healthy volunteers) underwent MRI of the small bowel. MR studies were performed on a 1.5-T magnet using T2-weighted half-Fourier single-shot turbo spin-echo (HASTE) and true fast imaging in steady-state precession (True-FISP) sequences. The MR features and sensitivity, and the specificity and accuracy of some of these features are described. RESULTS: In the 31 celiac patients, MRI showed bowel dilatation in 61.3% (N = 19), increased number of ileal folds in 48.4% (N = 15), reversed fold pattern abnormality in 38.7% (N = 12), increased wall thickness in 16.1% (N = 5), duodenal stenosis in 6.5% (N = 2), intussusception in 12.9% (N = 4), mesenteric lymphadenopathy in 41.9% (N = 13), mesenteric vascular changes in 22.6% (N = 7), ascites in 6.5% (N = 2), and no abnormalities in 12.9% (N = 4). The volunteers had unremarkable exams. The overall specificity and accuracy were 100%, and sensitivity was 79% and 75% for increased number of ileal folders and reversed fold pattern abnormality, respectively. CONCLUSION: MRI is able to demonstrate intra- and extraintestinal features that may lead to the diagnosis of celiac disease in adults.
Adult↗
Emerging techniques: whole-body screening and staging with MRI.
Strategies for screening or tumor staging include various modalities such as plain radiography, computed tomography (CT), MRI, and ultrasound. Technical innovations have created the feasibility to use MRI to image the entire body in a relatively short time-period. Whole-body MRI may play a potentially important role in evaluating for cancer or vascular disease. This article describes the rationale for using MRI to display the entire body, the techniques employed in whole-body MRI, possibilities and limitations, and summarizes first clinical results for screening and staging purposes.
Female↗
Accuracy of magnetic resonance imaging for preoperative detection of portal vein thrombosis in liver transplant candidates.
The detection of main portal vein thrombosis (PVT) on preoperative imaging of liver transplant candidates has important technical implications for the transplantation procedure. Data are scarce regarding the accuracy of magnetic resonance imaging (MRI) at detecting PVT. The aim of our study was to compare preoperative findings of the portal vein on MRI to operative findings at liver transplantation. Abdominal MRI and clinical records of 172 consecutive patients who received liver transplants between January 1999 and September 2004 were reviewed. Two radiologists independently evaluated the last abdominal magnetic resonance examinations obtained before liver transplantation, blinded to the original reading, operative findings, and clinical data. Findings on MRI were compared with intraoperative findings at transplantation. Main PVT was detected in 12 patients, in whom 8 were found to have thrombus at surgery, with 6 requiring a jump graft or thrombectomy. Sensitivity and specificity of MRI for detecting main PVT were 100% and 98%, respectively. The cause of discordance between findings on MRI and at transplantation in 2 cases was a diminutive caliber of the main portal vein that was interpreted as recanalized chronic thrombosis on MRI. In conclusion, in our study group MRI detected PVT in all liver transplant recipients requiring jump grafts at transplantation. The major reason for a false-positive MRI was a diminutive but patent portal vein.
Adult↗
Magnetic resonance imaging of the liver: how I do it.
The present paper provides a brief overview of the rationale behind magnetic resonance imaging (MRI) techniques, a description of the most common sequences used, and a general approach to performing liver MRI.
Humans↗
The risk of hepatocellular carcinoma in cirrhotic patients with small liver nodules on MRI.
BACKGROUND AND AIM: The presence of hepatocellular carcinoma (HCC) has important implications for patients with cirrhosis. Studies have not compared the risk of cancer in cirrhotic patients with small liver nodules to cirrhotic patients without nodules. Our aim was to determine the risk of HCC in cirrhotic patients with small liver nodules on MRI compared to those without nodules. METHODS: We conducted a prospective study to determine the rate of HCC in cirrhotic patients with and without liver nodules. Cases were patients with liver nodule(s) less than 2 cm on MRI and controls were cirrhotic patients without nodules. Kaplan-Meier estimates and multivariate analysis were performed to estimate the risk of HCC in the two groups. RESULTS: A total of 310 liver transplant candidates with a mean follow-up of 663 days were included in the study and 133 underwent liver transplant during follow-up. The 1-yr incidence of HCC in the liver nodule group and control group was 11% and 0.5%, respectively, p < 0.001. The adjusted risk for HCC in the liver nodule group was 25 times higher compared to the control group, HR = 25.1 [95% CI 8.0, 78.9]. In 133 candidates who underwent transplant with and without liver nodules the rate of HCC was 11 (50%) and 4 (3.6%), respectively, p < 0.001. CONCLUSION: The incidence of HCC in patients with small liver nodules is significantly higher compared to patients with cirrhosis without liver nodules. The presence of small liver nodules warrants increased imaging surveillance for HCC.
Adult↗
Focal liver lesions evaluated by MR imaging.
Magnetic resonance signal intensity of focal liver lesions is the result of their histological and cytological features. Therefore, analysis of lesion signal intensity and enhancement patterns obtained with magnetic resonance imaging is essential for the differential diagnosis of focal liver lesions. In this article, we review the magnetic resonance imaging features of the most common focal liver lesions.
Humans↗
Hepatocellular adenomas in men: MRI findings in four patients.
PURPOSE: To demonstrate both MRI and histopathological findings of hepatocellular adenomas (HCAs) in men. MATERIALS AND METHODS: HCAs in four men are reported. All patients underwent MR studies at 1.5T including serial gadolinium-enhanced gradient echo imaging. RESULTS: Three men had solitary non-hemorrhagic adenomas that exhibited a uniform capillary blush with no central scar, and uniform fading of the tumor to near isointensity with the liver parenchyma by one minute. One of the subjects had uniform fat content as shown by uniform low signal on out-of-phase images. One patient had a solitary hemorrhagic adenoma that measured 17 cm in diameter and was heterogeneous on all sequences. Two of the four patients had a history of anabolic steroid use, and in the other two patients no underlying explanation for the tumor was found. CONCLUSIONS: Although three of the four patients had tumors that exhibited uniform homogeneous tumor blush and rapid fading of enhancement, because HCAs are rare in men and resemble hepatocellular carcinoma (HCC) in appearance, our findings suggest that histological confirmation of HCAs may not be avoidable in men.
Adenoma, Liver Cell↗
Imaging and localization of islet-cell tumours of the pancreas on CT and MRI.
Islet-cell tumours are neuroendocrine tumours that arise from the endocrine pancreas. They may be associated with a variety of syndromes and are subclassified into functioning and non-functioning tumours. They range from benign to malignant. They demonstrate characteristic features when imaged with both computed tomography (CT) and magnetic resonance imaging (MRI). Sensitivity and specificity, as well as detection of extrapancreatic extension, are generally superior with MRI. However, CT is currently still more readily available to patients. Multiphase, post-contrast series are commended for the evaluation of islet-cell tumours with either modality.
Adenoma, Islet Cell↗
MRI findings of gastric metastases from breast carcinoma.
We describe the MR appearance of breast cancer metastases to the stomach. The stomach wall was diffusely thickened with loss of the regular fold pattern best shown on the single shot T2-weighted images and enhanced with moderate mural enhancement on early and late post gadolinium images. The combination of gastric wall thickening and abnormal enhancement should suggest the diagnosis of diffuse mural metastases in a woman with a history of breast cancer.
Adenocarcinoma↗
MRI findings of primary small-cell carcinoma of kidney.
We report the MRI findings of primary small-cell carcinoma of the kidney (PSCCK) in a 59-year-old female. This tumor appeared as a 16-cm mass that arose from the right kidney. This lesion had diminished signal on T1-weighted images and heterogeneous mixed signal on T2-weighted images. The tumor primarily involved the renal medulla with persistent thin renal cortex. Despite the tumors' large size, no substantial central necrosis was present. The predominant medullary location and the lack of central necrosis in this large tumor were features unusual for renal cell carcinoma and should raise the suspicion of another malignancy, the differential diagnosis of which should contain extrapulmonary small-cell carcinoma of the kidney.
Carcinoma, Small Cell↗
Hepatic nodules in liver transplantation candidates: MR imaging and underlying hepatic disease.
OBJECTIVE: To assess by MR imaging the frequency of hepatic nodules in patients waiting on the liver transplant list and to determine whether certain underlying hepatic diseases were more often associated with the development of such hepatic nodules. MATERIAL AND METHODS: We reviewed the MR and clinical records in all patients seen by the liver transplant service at our center since its inception in January 1998 until September 2002. A total of 371 patients (207 men and 164 women, age range 18-68 years, mean 45 years) were included in the study. The presence of hepatic nodules, size, number and underlying hepatic diseases were determined in all patients. Magnetic resonance imaging was performed on a 1.5-T MR imager using T1-weighted, T2-weighted and multi-phase gadolinium-enhanced sequences. Odds ratio (OR) and 95% confidence intervals (CIs) were computed to evaluate the association between the underlying hepatic disease and the development of hepatic nodule. RESULTS: Among 371 liver transplantation candidates, the most common underlying hepatic disease was hepatitis C virus (HCV) infection, either alone (n=93; 25%) or associated with other hepatic diseases (n=40; 10.8%). Of all patients, 33 (8.9%) had regenerative nodules (RNs), 40 (10.7%) dysplastic nodules (DNs) and 57 (15.3%) hepatocellular carcinomas (HCCs). Hepatocellular carcinoma was observed in 35.3% of patients with HCV infection and alcohol abuse combined, 24.5% with cryptogenic cirrhosis, 25% with hemochromatosis and 19% with alcohol abuse. Patients who had either DNs or HCC were 2.5 times more likely to have either alcohol abuse or HCV, alone or combined, as the substrate of their liver disease (OR 2.54, 95% CI 1.56-4.13). Our data suggest a supra-additive interaction between HCV infection and ethanol in their association with MR imaging detected lesions. CONCLUSION: Patients with cryptogenic cirrhosis, alcohol abuse, HCV infection (alone or combined) and hemochromatosis had the greatest likelihood of having HCC, with the combination of HCV infection and alcohol abuse having the highest of all.
Adolescent↗
Liver masses.
In summary, MR imaging is superior to other imaging modalities, including CT, for the work-up of liver masses. The current challenge is whether the superior performance of MR imaging translates into a beneficial effect on patient management, disease outcome, and health care costs. New MR sequences, phased-array surface coils, and tissue-specific MR contrast agents suggest that MR imaging may exceed further the diagnostic ability of CT.
Contrast Media↗
Future horizons in MR imaging.
In this article, we defined the major areas of active research in clinical MR imaging. Further increases in the number of parallel coils within an imaging array and in advances in parallel imaging pulse sequences and postprocessing will lead to further reductions in imaging time analogous to the impact of multidetector CT on helical CT. The synergism between parallel and high-field imaging will aid the development of high-field imaging. The combined dynamic and hepatic parenchymal enhancement of new contrast agents that have or may soon receive FDA approval will enable improved detection and characterization of liver lesions. The lymphotropic SPIO agents will remain an active area of clinical research to further assess their role in oncologic staging. Molecular imaging contrast research using magnetic particles and MR microscopy will continue to flourish. Screening examinations by MR imaging will re-main an area of research for the short- and intermediate term, with the final outcome dependent more on socioeconomic costs than the underlying capability of achieving high-quality screening studies.
Contrast Media↗
MR imaging of the pancreas.
MR imaging is a valuable tool in the assessment of the full spectrum of pancreatic diseases. MR imaging techniques are sensitive for the evaluation of pancreatic disorders in the following settings: (1) TI-weighted fat-suppressed and dynamic gadolinium-enhanced SGE imaging for the detection of chronic pancreatitis, ductal adeno-carcinoma, and islet-cell tumors; (2) T2-weighted fat-suppressed imaging and T2-weighted breath-hold imaging for the detection of islet-cell tumors;and (3) precontrast breath-hold SGE imaging for the detection of acute pancreatitis. Relatively specific morphologic and signal intensity features permit characterization of acute pancreatitis,chronic pancreatitis, ductal adenocarcinoma, insulinoma, gastrinoma, glucagonoma, microcystic cystadenoma, macrocystic cystadenoma, and solid and papillary epithelial neoplasm. MR imaging is effective as a problem-solving modality because it distinguishes chronic pancreatitis from normal pancreas and chronic pancreatitis with focal enlargement from pancreatic cancer in the majority of cases.MR imaging studies should be considered in the following settings: (1) in patients with elevated serum creatinine, allergy to iodine contrast, or other contraindications for iodine contrast administration; (2) in patients with prior CT imaging who have focal enlargement of the pancreas with no definable mass; (3) in patients in whom clinical history is worrisome for malignancy and in whom findings on CT imaging are equivocal or difficult to interpret; and (4) in situations requiring distinction between chronic pancreatitis with focal enlargement and pancreatic cancer. Patients with biochemical evidence of islet-cell tumors should be examined by MR imaging as the first-line imaging modality because of the high sensitivity of MR imaging for detecting the presence of islet-cell tumors and determining the presence of metastatic disease.
Contrast Media↗
Contrast agents for MR imaging of the liver.
Imaging of the liver is performed most often to detect and characterize focal liver lesions. MR imaging has been the method of choice to assess focal liver lesions accurately. Nonspecific intravenous contrast agents have been used for routine abdominal MR imaging protocols including liver imaging. Over the last 10 to 15 years new contrast agents have been developed that combine the excellent contrast resolution of MR imaging with improved tissue specificity. This article reviews various contrast agents that are in clinical use for liver MR imaging and discusses their potential clinical role.
Contrast Media↗