To achieve a consistent contrast enhancement in cardiac CT angiography (CTA), contrast-medium dose should be adjusted with the body weight or the BSA (which accounts for both the body weight and height factors) to provide adjustment of iodine dose over a wide range of body sizes.

Gadoxetate disodium-enhanced MR imaging is more reliable for staging hepatic fibrosis than are diffusion-weighted MR imaging, hematologic, and clinical parameters.

Advances in image quality over the past few years, mainly due to refinements in hardware and coil systems, have made diffusion-weighted ( DW diffusion weighted ) magnetic resonance (MR) imaging a promising technique for the detection and characterization of pancreatic conditions. DW diffusion weighted MR imaging can be routinely implemented in clinical protocols, as it can be performed relatively quickly, does not require administration of gadolinium-based contrast agents, and enables qualitative and quantitative assessment of tissue diffusivity (diffusion coefficients). In this review, acquisition parameters, postprocessing, and quantification methods applied to pancreatic DW diffusion weighted MR imaging will be discussed. The current common clinical uses of DW diffusion weighted MR imaging (ie, pancreatic lesion detection and characterization) and the less-common applications of DW diffusion weighted MR imaging used for the diagnosis of pancreatic parenchymal diseases will be reviewed. Also, the limitations of the technique, mainly image quality and reproducibility of diffusion parameters, as well as future directions for pancreatic DW diffusion weighted MR imaging will be discussed. The utility of apparent diffusion coefficient ( ADC apparent diffusion coefficient ) measurement for the characterization of pancreatic lesions is now well accepted but there are a number of limitations. Future well-designed, multicenter studies are needed to better determine the most appropriate use of ADC apparent diffusion coefficient in the area of pancreatic disease.

MRI allows the identification of a wide spectrum of appearances of untreated liver metastases. The extent and pattern of enhancement of various histologic types of tumor are depicted on MRI.

Purpose: To assess MR imaging findings and clinical manifestations of diffuse-type hepatocellular carcinoma (HCC). Materials and Methods:We retrospectively reviewed our experience with diffuse HCC from November 1994 to October 2001. MR imaging findings and clinical features were assessed.Results: Twenty-two consecutive patients with diffuse-type HCC (19 men and three women, age range 16 -80 years [mean, 52 years]) were identified in a review of liver MR studies. This represented 13% of all patients with HCC imaged during this time period. Diffuse HCC showed a permeative, infiltrative pattern with ill-defined borders and no evidence of convex margination in all cases. At least 50% of the liver volume was involved with tumor. Diffuse-type HCC showed hypointensity in 15 patients, mixed intensity in three, and isointensity in four on T1-weighted images; heterogeneous hyperintensity in 16 patients; and homogeneous hyperintensity in six on T2-weighted MR images. Diffuse-type HCC showed patchy enhancement in 12 patients, miliary enhancement in nine, and minimal enhancement in one on postcontrast early-phase images, and showed heterogeneous washout in all patients on postcontrast late-phase images. Proximal portal venous tumor thrombosis was seen in all patients. Serum ␣-fetoprotein (AFP) value was elevated (Ͼ10 ng/mL) in 14 of 18 patients, and 13 showed a value greater than 500 ng/mL. The four patients who did not have elevated AFP had tumors which were indistinguishable from those in patients with elevated AFP; they also did not have a distinctive clinical history.Conclusion: Diffuse-type HCC was typically seen as an extensive, heterogeneous permeative hepatic tumor, with portal venous tumor thrombosis on MR images in all cases. Early enhancement, observed as patchy in 12 and miliary in nine of 22 patients, was a distinctive imaging feature. Elevated serum AFP value was a common finding; however, 22% had normal values.

Background and Purpose-A major disadvantage of carotid artery stenting (CAS) compared to carotid endarterectomy is the increased risk of cerebral embolism. Thus, establishing a simple method to discriminate fragile plaques on preoperative routine examination is important. The present study examined whether high-intensity signal (HIS) in the plaque on time-of-flight (TOF) MRA, performed for screening, can discriminate plaque at high risk for cerebral embolism during CAS. Methods-In the 30 patients treated using carotid endarterectomy, relationships between pathological findings of the plaques and TOF-MRA findings were analyzed. In the 112 patients treated using CAS, postoperative ipsilateral ischemic lesions on diffusion-weighted imaging and periprocedural ischemic symptoms were analyzed. Results-The percentage area of intraplaque hemorrhage stained by glycophorin A was significantly larger in HIS-positive plaques (51.8%Ϯ9.8%) than in HIS-negative plaques (8.6%Ϯ9.4%; PϽ0.001). Postoperative ischemic lesions on diffusion-weighted imaging were more frequent in the HIS-positive plaques (25/38; 65.8%) than in the HIS-negative plaques (26/74; 35.1%; Pϭ0.002). Periprocedural ischemic symptoms were more frequently observed in HIS-positive plaques (7/38; 18.4%) than in HIS-negative plaques (1/74; 1.4%; Pϭ0.003). Multivariate logistic regression analysis identified HIS on TOF-MRA as an independent predictor of periprocedural ischemic symptoms (odds ratio, 15.08; 95% confidence interval, 1.76 -129.0). Conclusions-HIS in the plaque on TOF-MRA performed for screening could discriminate plaques at high risk for cerebral embolism during CAS. (Stroke. 2011;42:3132-3137.)Key Words: carotid endarterectomy Ⅲ carotid stenosis Ⅲ risk factors Ⅲ stenting A lthough carotid endarterectomy (CEA) is the established treatment for stroke prevention, carotid artery stenting (CAS) recently has emerged as a less invasive alternative to CEA. Two randomized controlled trials have shown that CAS and CEA offer similar efficacy, 1,2 whereas another 3 randomized studies have reported that CEA is superior to CAS. [3][4][5] Indications for CAS thus remain controversial. One of the major disadvantages of CAS is a high incidence of cerebral embolism. Recent reports described that there was an association between specific plaque components evaluated by preoperative examinations and an increased number of emboli after CAS, 6,7 and that multispectral MRI could identify plaque constituents, such as the necrotic core and intraplaque hemorrhage, with high sensitivity and specificity. 8,9 However, this examination requiring high-resolution MRI is not always available before revascularization procedures. Establishing a simple method to discriminate plaques at high risk for cerebral embolism during CAS on preoperative routine examination is important. We focused on high-intensity signal (HIS) in the plaque on time-of-flight (TOF) MRA performed for screening. The aims of this study were to validate HIS in the plaque on TOF-MRA with histology in CEA patients and t...

Objective: To evaluate the diagnostic accuracy of liver cirrhosis by imaging modalities, including CT, MRI and US, compared to results obtained from histopathological diagnoses of resected specimens. Materials and Methods: CT, MRI and US examinations of 142 patients with chronic liver disease who underwent surgery for complicated hepatocellular carcinoma (<3 cm in diameter) in 10 institutions were blindly reviewed in a multicenter study by three radiologists experienced in CT, MRI and US. The images were evaluated for five imaging parameters (irregular or nodular liver surface, blunt liver edge, liver parenchymal abnormalities, liver morphological changes and manifestations of portal hypertension) using a severity scale. The diagnostic imaging impression score was also calculated. Patients were histologically classified into chronic hepatitis (CH; n = 54), liver cirrhosis (LC; n = 71) and pre-cirrhosis (P-LC; n = 17) by three pathologists, independently, who reviewed the resected liver specimens. The results of the three imaging methods were compared to those from histological diagnoses, and a multivariate analysis (stepwise forward logistic regression analysis) was performed to identify independent predictive signs of cirrhosis. The diagnostic efficacies for LC and early cirrhosis were also compared among CT, MRI and US using a receiver-operating characteristic (ROC) curve analysis. Results: The differences in the five imaging parameters evaluated by CT, MRI and US between LC and CH were statistically significant (p < 0.001) except for the manifestations of portal hypertension on US. Irregular or nodular surface, blunt edge or morphological changes in the liver were selected as the best predictive signs for cirrhosis on US whereas liver parenchymal abnormalities, manifestations of portal hypertension and morphological changes in the liver were the best predictive signs on MRI and CT by multivariate analysis. The predictive diagnostic accuracy, sensitivity and specificity in discriminating LC from CH based on the best predictive signs were 71.9, 77.1 and 67.6% by CT; 67.9, 67.5 and 68.3% by MRI, and 66.0, 38.4 (lower than CT and MRI, p =0.001) and 88.8% (higher than CT and MRI, p =0.001)by US. According to the imaging impression scoring system, diagnostic accuracy, sensitivity and specificity were 67.0, 84.3 and 52.9% by CT; 70.3, 86.7 and 53.9% by MRI, and 64.0, 52.4 (lower than CT and MRI, p =0.0001) and 73.5% (higher than CT and MRI, p < 0.003) by US. ROC analysis showed that MRI and CT were slightly superior to US in the diagnosis of LC but no statistically significant difference was found between them. For the pathological diagnosis of P-LC, cirrhosis was diagnosed in 59.5, 46.7 and 41.7% of the P-LC cases by US, CT and MRI, respectively, with no significant difference among these methods. Conclusion: US, CT and MRI had different independent predictive signs for the diagnosis of LC. MRI and CT were slightly superior to US in predicting cirrhosis, especially regarding sensitivity. Noninvasive imaging techniqu...

The pancreas-to-muscle SI ratio on T1-weighted MR images of the pancreas may be a potential biomarker for assessment of pancreatic fibrosis and prediction of postoperative pancreatic fistula.