Masayuki Kanematsu

Contrast Enhancement in Cardiovascular MDCT: Effect of Body Weight, Height, Body Surface Area, Body Mass Index, and Obesity

OBJECTIVE The purpose of our study was to evaluate the effect of body weight, height, body surface area (BSA), body mass index (BMI), and obesity on aortic contrast enhancement in cardiac MDCT. MATERIALS AND METHODS Seventy-three consecutive patients underwent cardiac CT angiography on a 64-MDCT scanner. Seventy-five mL of contrast medium (350 mg I/mL) was injected at 4.5 mL/s, followed by a 40-mL saline flush at 4.5 mL/s. The scanning delay of CT was determined with a bolus tracking technique. Aortic attenuation was measured over the aortic-root lumen. BMI and BSA were calculated from the patients body weight and height. The patients were divided into low-(BMI < 30) and high-(> or = 30) BMI groups. Associations of aortic attenuation with body weight, height, BMI, and BSA were evaluated with regression analysis and the Students t test. RESULTS Strong inverse correlations were seen between aortic attenuation and body weight (r = -0.73), height (r = -0.47), BMI (r = -0.63), and BSA (r = -0.74) (p < 0.001 for all). The regression formula of aortic attenuation versus body weight suggests that 1.0 mL/kg of contrast medium would yield a mean aortic attenuation of 355 H. The mean aortic attenuation was significantly higher in the low-BMI (352.6 +/- 59.1 H) than in the high-BMI (286.2 +/- 55.5 H) group. The regression formula for aortic attenuation on body weight was aortic attenuation = 586-3.1 body weight (p < 0.001) for the low-BMI group and aortic attenuation = 485-1.9 body weight (p < 0.001) for the high-BMI group, suggesting that the amount of contrast medium required with increased body weight is less in the high-BMI group. This group difference was less pronounced for the regression of aortic attenuation on BSA. CONCLUSION 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.

Staging Hepatic Fibrosis: Comparison of Gadoxetate Disodium- enhanced and Diffusion-weighted MR Imaging: Preliminary Observations

PURPOSE To evaluate the utility of hepatocyte-phase gadoxetate disodium-enhanced magnetic resonance (MR) imaging in staging hepatic fibrosis and to compare it with diffusion-weighted imaging. MATERIALS AND METHODS This retrospective study had institutional review board approval, and the requirement for informed consent was waived. Gadoxetate disodium-enhanced and diffusion-weighted MR images obtained in 114 consecutive patients (70 men, 44 women; age range, 37-91 years) were evaluated. Liver-to-muscle signal intensity (SI) ratio on hepatocyte-phase images (SI(post)), contrast enhancement index calculated as SI(post) /SI(pre), where SI(pre) is liver-to-muscle SI ratio on nonenhanced images, and apparent diffusion coefficient (ADC) of the liver were measured. Necroinflammatory activity grades and hepatic fibrosis stages were histopathologically determined in 99 patients. Multiple regressions of SI(post), contrast enhancement index, ADC, serum albumin concentration, serum total bilirubin level, prothrombin time, and Child-Pugh score were examined to determine correlation with hepatic necroinflammatory activity grades and fibrosis stages. RESULTS Among the MR, hematologic, and clinical parameters, contrast enhancement index was most strongly correlated with fibrosis stage (r = -0.79, P < .001). Multiple regression analysis showed that the contrast enhancement index, ADC, and prothrombin time were significantly correlated (r(2) = 0.66, P < .05) with fibrosis stage and that the contrast enhancement index and serum total bilirubin level were weakly correlated (r(2) = 0.24, P < .05) with the necroinflammatory activity grade. CONCLUSION Gadoxetate disodium-enhanced MR imaging is more reliable for staging hepatic fibrosis than are diffusion-weighted MR imaging, hematologic, and clinical parameters.

Hepatocellular carcinoma of diffuse type: MR imaging findings and clinical manifestations

To assess MR imaging findings and clinical manifestations of diffuse‐type hepatocellular carcinoma (HCC).

Diffusion-weighted imaging of the liver: Optimizing b value for the detection and characterization of benign and malignant hepatic lesions

To determine the optimal b values required for diffusion‐weighted (DW) imaging of the liver in the detection and characterization of benign and malignant hepatic lesions.

Preoperative T Staging of Urinary Bladder Cancer: Does Diffusion-Weighted MRI Have Supplementary Value?

OBJECTIVE The objective of our study was to evaluate whether diffusion-weighted MRI has supplementary value in the preoperative T staging of urinary bladder cancer. MATERIALS AND METHODS Nineteen consecutive patients (18 men and one woman; age range, 55-83 years; mean, 71 years) known to have or suspected of having urinary bladder cancer underwent MRI at our institution. Urinary bladder cancer was pathologically proven in 18 patients. The pathologic stages were T1 in 14 patients, T2 in two, T3 in one, and T4 in one. Three separate MR image sets were retrospectively reviewed by two independent radiologists: unenhanced T1-weighted images (TR/TE, 607/10) and T2-weighted images (TR(eff)/TE(eff), 4,415/100); unenhanced T1-weighted, T2-weighted, and gadolinium-enhanced images (TR/TE, 10/4.2); and unenhanced T1-weighted, T2-weighted, and diffusion-weighted images (TR(eff)/TE(eff), 2,191/69; b factor, 1,000 s/mm(2)). The radiologists, who were blinded to the pathology findings, assigned T stages and confidence levels for tumors of stage T2 or greater. We used pathologic stages documented in the official pathologic reports as the standard of reference. Observer performance was tested using Spearmans rank correlation, the McNemar test, and receiver operating characteristic (ROC) curve analysis. RESULTS The correlation between the radiologic and pathologic stages was greater with the diffusion sequence (rho = 0.66) than with the unenhanced (0.62) or gadolinium-enhanced (0.62) sequence (p = 0.34). The sensitivity, specificity, accuracy, and area under the ROC curve for tumors of stage T2 or greater were 80%, 79%, 79%, and 0.71 for the unenhanced sequence; 80%, 79%, 79%, and 0.77 for the gadolinium sequence; and 40%, 93%, 79%, and 0.56 for the diffusion-weighted sequence, respectively (p > 0.05). CONCLUSION Our results suggest that diffusion-weighted MRI might have high specificity for the detection of invasive urinary bladder tumors. Patients with suspected urinary bladder carcinomas may well be evaluated by MRI including diffusion-weighted imaging for better preoperative T staging.

High-Intensity Signal on Time-of-Flight Magnetic Resonance Angiography Indicates Carotid Plaques at High Risk for Cerebral Embolism During Stenting

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%±9.8%) than in HIS-negative plaques (8.6%±9.4%; P<0.001). 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%; P=0.002). Periprocedural ischemic symptoms were more frequently observed in HIS-positive plaques (7/38; 18.4%) than in HIS-negative plaques (1/74; 1.4%; P=0.003). 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.

Diagnostic Accuracy of Imaging for Liver Cirrhosis Compared to Histologically Proven Liver Cirrhosis

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 techniques play an important role in the diagnosis of cirrhosis, especially in the evaluation of P-LC.

Head and neck squamous cell carcinoma: usefulness of diffusion-weighted MR imaging in the prediction of a neoadjuvant therapeutic effect.

The purpose of our study was to evaluate the usefulness of diffusion-weighted imaging in predicting the responses to neoadjuvant therapy for head and neck squamous cell carcinomas. Diffusion-weighted, T2-weighted, and gadolinium-enhanced T1-weighted images were obtained from 28 patients with untreated head and neck squamous cell carcinomas with histological proof. A blinded radiologist evaluated the quantitative and qualitative signal intensities and apparent diffusion coefficients (ADCs) in the lesions on each sequence. All patients were treated by neoadjuvant therapies, and the post-therapeutic tumor regression rate was determined. Both the quantitative and qualitative signal intensities on diffusion-weighted images showed positive correlations (r = 0.367 and 0.412, p < .05), and the ADCs showed a weak, inversed correlation (r = −0.384, p < .05) with the tumor regression rates. Diffusion-weighted imaging including an assessment by ADCs may be able to predict tumor response to neoadjuvant therapy for head and neck squamous cell carcinomas.

Evaluating local hepatocellular carcinoma recurrence post-transcatheter arterial chemoembolization: Is diffusion-weighted MRI reliable as an indicator?

To evaluate the detectability of local hepatocellular carcinoma (HCC) recurrence after transcatheter arterial chemoembolization (TACE) by diffusion‐weighted MR imaging in correlation with those of gadolinium‐enhanced MR imaging.

Preoperative detection of prostate cancer: A comparison with 11C‐choline PET, 18F‐fluorodeoxyglucose PET and MR imaging

To compare 11C‐choline positron emission tomography (C‐PET), 18F‐fluorodeoxyglucose PET (FDG‐PET), and MR imaging in the preoperative detection of prostate cancer.