[en] The purpose of this study was to evaluate the effect of the concentration of contrast material to obtain good quality arterial phase images with a multi-detector CT. We divided 77 patients into the following 2 groups: the moderate concentration group (300 mgI/mL, maximum dose 150 mL, 37 cases), and the high concentration group (370 mgI/mL, maximum dose 100 mL, 40 cases). The contrast material dose was adjusted by the patient's body weight (600 mgI/kg) and administration was followed by saline flush. The injection duration was fixed (30 seconds). A monitoring scan was used with the trigger threshold set at 200 HU. Quantitative evaluation of the aorta, liver parenchyma and tumor-liver contrast between moderate and high concentration contrast material was performed. We qualitatively evaluated the conspicuity of the hepatic artery, portal vein, hepatic vein and tumor. There was no significant difference in the time to reach the trigger threshold and the beginning of the arterial phase scan. Quantitative and qualitative evaluation of the aorta, hepatic parenchyma and tumor-liver contrast also revealed no significant difference. Interobserver agreement was good for the qualitative evaluation of the conspicuity of the hepatic artery, portal vein and hepatic vein. Similar arterial phase images could be obtained by both moderate and high concentration of contrast material. (author)

[en] We evaluated whether a perfusion study with Resovist is useful to assess blood flow in tumors in patients with hypervascular hepatocellular carcinoma (HCC). The subjects were 28 patients; the lesions consisted of 68 hypervascular HCC, 14 post-treatment nodules, and 7 hepatocellular hypovascular nodules. After rapid intravenous injection of Resovist, 7-phase imaging was performed using the single-shot echo-planar method. Diagnostic accuracy and tumor vascularity were evaluated by 3 radiologists using the alternative free response receiver operating characteristic method. Sensitivity, Az values, and positive predictive values were calculated. To assess interobserver variability, we evaluated the kappa static to measure the degree of agreement. The 3 observers indicated no significant difference in Az value related to the presence or absence of a perfusion study, and only one remarked a significant difference in sensitivity. However, kappa values were better in the presence than in the absence of a perfusion study. Blood flow assessment was poor in less than 1 cm. The 3 observers showed a positive predictive value of 90% or more. A perfusion study may facilitate the diagnosis of hypervascular HCC, improving the diagnostic accuracy. (author)

[en] The purpose of this study was to evaluate the utility of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) for the quantitative evaluation of hepatocellular carcinoma (HCC) and dysplastic nodules in the hepatobiliary phase. The subjects comprised 12 patients with 27 lesions (22 HCCs and 5 dysplastic nodules). Chemical-shift-selective fat-suppressed T₁-weighted sequences were obtained before and 10, 20, and 40 min after the injection of Gd-EOB-DTPA. Quantitative analyses were performed with the enhancement ratio of the lesion and the contrast-to-noise (C/N) ratio. The enhancement ratios of the HCCs were 44.0±36.5, 44.7±46.8, and 47.7±52.8 (%) at 10, 20, and 40 min, respectively, after the injection of Gd-EOB-DTPA. The enhancement ratios of the dysplastic nodules were 36.2±34.3, 44.3±37.3, and 40.1±46.8 (%). The C/N ratios of the HCCs were 0.2±6.6 for the precontrast image, and -9.2±12.6, -9.9±14.8, and -12.7±15.7 at 10, 20, and 40 min, respectively, after the injection of Gd-EOB-DTPA. The C/N ratios of the dysplastic nodules were 1.4±8.0, -13.7±11.1, -13.3±7.6, and -13.1±10.4. No significant differences were found between the HCCs and the dysplastic nodules in the enhancement ratio and the C/N ratio. Only two HCCs showed a positive C/N ratio value, and these HCCs were pathologically confirmed to be a well differentiated and a moderately differentiated carcinoma, respectively. HCCs and some of the dysplastic nodules showed hypointensity in the hepatobiliary phase in Gd-EOB-DTPA-enhanced MRI. No specific enhancement was observed, regardless of tumor differentiation. (author)

[en] We evaluated the quality of dynamic magnetic resonance (MR) imaging of the temporomandibular joint (TMJ) in 20 normal volunteers with 40 TMJs. To confirm TMJ, we obtained static proton density weighted images (PDWI) before performing dynamic MR imaging with true-fast imaging in a steady-state precession (true-FISP) sequence. Four sequences of the first 10 volunteers were examined to determine the optimal sequence. The 4 sequences included the integrated parallel acquisition technique (iPAT) and/or fat saturation technique. The optimal sequence was then determined and performed in all 20 volunteers. The quality of imaging was evaluated, especially with respect to the conspicuity of the articular disk, mandibular condyle, articular eminence and lateral pterygoid muscle. One of 3 confidence levels was assigned for this evaluation. Neither iPAT nor fat saturation obtained the best quality imaging. Detection rates in the 20 volunteers were 83% for the articular disk, 95% for the mandibular condyle, 96% for the articular eminence and 7.5% for the lateral pterygoid muscle. We recommend dynamic MR imaging of the TMJ with the true-first imaging with steady-state precession (FISP) sequence using neither iPAT nor fat saturation. Nevertheless, dynamic MR imaging was inferior to static imaging in detecting the articular disk and still requires improvement. (author)

[en] We evaluated the optimal timing for breath-hold MR imaging with bolus-injectable superparamagnetic iron oxide (SPIO) for detecting hepatocellular carcinoma (HCC). Twenty patients with 62 HCCs (52 hypervascular, 10 non-hypervascular) underwent MR imaging that included unenhanced and SPIO-enhanced T₁-weighted gradient echo (GRE) and T₂-weighted fast spin echo (FSE) sequences, perfusion study, and SPIO-enhanced T₂*-weighted GRE sequences. We obtained SPIO-enhanced T₂*-weighted sequences 10 and 30 min after injecting SPIO and made 2 image sets, comprising 10- or 30-min delayed T₂*-weighted images. Three observers performed alternative free response receiver operating characteristic (AFROC) analysis, and quantitative evaluation was performed. Only Observers 2 and 3 recognized a significant difference in the area under the AFROC curve (Az) value in the 10-min delayed images; no significant difference was observed in the 30-min delayed images. There was no significant difference in the sensitivity of individual observers between 10- and 30-min delayed images. The contrast-to-noise (C/N) ratio of the 30-min delayed images was significantly higher than that of the 10-min delayed images. The C/N ratio of hypervascular HCCs in the 30-min delayed images was significantly higher than in the 10-min delayed images, but that of non-hypervascular HCCs showed no significant difference. In most cases, 10-min delayed SPIO-enhanced T₂*-weighted images are sufficient to detect HCCs. (author)