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Objective The purpose of this study was to compare the effects of high-concentration contrast material and low-voltage CT simulated by virtual monochromatic (VM) imaging on contrast enhancement at multiphasic CT of the upper abdomen. Methods This study included 72 patients who underwent CT during early arterial (EAP), late arterial and portal venous phases after 300-mgI/ml (Group A; 34 patients) or 350-mg/ml (Group B; 38 patients) contrast-material injection at the same volumetric rate (0.067 mL/sec/kg). VM images were generated at 50 and 65 keV. Contrast-to-noise ratios (CNRs) of aorta, portal vein, and liver parenchyma were calculated and statistically compared. Results Mean CNRs for 50-keV VM images were significantly higher than 65-keV VM images of each organ at any phases (p Conclusions Low-voltage CT simulated by VM image improved contrast enhancement through any phases, while high-concentration contrast material increased only arterial contrast in EAP more effectively.

OBJECTIVE The aim of this study was to evaluate the image quality of low-dose computed tomographic (CT) urography using adaptive iterative dose reduction 3-dimensional (AIDR 3D) compared with routine-dose CT using filtered back projection (FBP). METHODS Thirty patients underwent low- and routine-dose CT scans in the nephrographic and excretory phases of CT urography. Low-dose CT was reconstructed with AIDR 3D, and routine-dose CT was reconstructed with FBP. In quantitative analyses, image noises were measured on the renal cortex, aorta, retroperitoneal fat, and psoas muscle in both CT scans and compared. Qualitative analyses of the urinary system were performed in both CT scans and compared. These results were compared on the basis of the body mass index (BMI) of the patients. The CT dose index (CTDIvol) was measured, and the dose reduction was calculated. RESULTS In quantitative analyses, image noises in all organs on low-dose CT were less than those on routine-dose CT in both phases independently of the patient's BMI. There were no statistical differences between low- and routine-dose CT for diagnostic acceptability on all urinary systems in both phases independently of the patient's BMI. The average CTDIvol on routine-dose CT was 14.5 mGy in the nephrographic phase and 9.2 mGy in the excretory phase. The average CTDIvol on low-dose CT was 4.2 mGy in the nephrographic phase and 2.7 mGy in the excretory phase. CONCLUSIONS Low-dose CT urography using AIDR 3D can offer diagnostic acceptability comparable with routine-dose CT urography with FBP with approximately 70% dose reduction.

Objective To prospectively compare the detection of bladder cancer between low-dose scans with adaptive iterative dose reduction three dimensional projection (AIDR 3D) and routine-dose scans with filtered back projection (FBP) on the excretory phase (EP) in CT urography. Methods 42 patients were included. Routine- and low-dose EP were performed in each patient. Routine-dose images were reconstructed with FBP, and low-dose images were reconstructed with AIDR 3D. Two radiologists scored confidence levels for the presence or absence of bladder cancer using a 5-point scale. The CT dose index of each EP was measured, and the dose reduction was calculated. Results Sensitivity, specificity and accuracy were 86.4%, 95.0% and 90.5% on routine-dose scans and were 86.4%, 90.0% and 88.1% on low-dose scans, respectively. There was no significant difference (p; not significant, 1.00 and 1.00, respectively). The average CT dose index was 8.07 and 2.63 mGy on routine- and low-dose scans, and the ratio of dose reduction was 67.6%. Conclusion The detection of bladder cancer on low-dose scans with AIDR 3D is almost equal to that on routine-dose scans with FBP on the EP, with nearly 70% dose reduction. Advances in knowledge Using AIDR 3D, the radiation dose may be reduced on the EP in CT urography for the detection of bladder cancer.

PURPOSE We retrospectively compared the efficacy of 3-dimensional (3D) gradient-echo magnetic resonance T(1)-weighted sequence using the iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) technique with the efficacy of conventional 3D gradient-echo sequences for diagnosing ovarian masses at 3T. MATERIALS AND METHODS In images of 32 women (mean age, 45.3 years) with ovarian masses who underwent T(1)-weighted imaging with both IDEAL and conventional techniques, we quantitatively analyzed signal-to-noise ratio (SNR) and contrast between gluteal muscle and T(1)-weighted high-signal materials within lesions and assessed image quality. Two radiologists independently evaluated fat detection. RESULTS Mean SNR of subcutaneous fat did not differ significantly between IDEAL and conventional techniques for both fat-suppressed (P=.32) and non-fat-suppressed (P=.85) images. Mean absolute contrast between gluteal muscle and T(1)-weighted high signal materials within teratomas (n=15) was significantly higher with IDEAL on fat-suppressed images (P=.002) and lower with IDEAL on non-fat-suppressed images (P=.010). Fat suppression was significantly superior with IDEAL (P

To compare a three-dimensional (3D) T2-weighted turbo spin-echo (TSE) magnetic resonance (MR) sequence (VISTA; Philips Medical Systems, Best, the Netherlands) with a two-dimensional (2D) T2-weighted TSE sequence in terms of image quality, signal intensity (SI) difference ratios, conspicuity, and staging of uterine tumors.This retrospective study was approved by the institutional review board, and informed consent was waived. Sixty-one women (mean age, 53.0 years ± 13.7 [standard deviation]; range, 30-87 years) with cervical carcinoma (n = 28), endometrial carcinoma (n = 21), or leiomyoma (n = 30) of the uterus were included. Patients underwent T2-weighted MR imaging at 3 T with both 1-mm-thick 3D and 5-mm-thick 2D T2-weighted TSE sequences. Three-dimensional T2-weighted TSE images were reconstructed at 5-mm thickness with the aid of a workstation. Quantitative analyses of signal-to-noise ratio (SNR) and SI difference ratios between tumors and other tissues and qualitative analyses of image quality and tissue conspicuity were performed. Two radiologists independently assessed local-regional staging for carcinomas. Quantitative values, qualitative scores, and tumor staging were analyzed by using the paired t test, Wilcoxon signed rank test, and McNemar test, respectively.Mean myometrial SNR was higher on 3D than 2D images (14.3 vs 9.8; P.0001). Mean SI difference ratios between cervical (0.45 vs 0.34; P.0001) or endometrial (0.46 vs 0.40; P = .044) carcinomas and gluteal muscle were higher on 3D images, but those between leiomyoma and myometrium (0.33 vs 0.43; P.0001) were lower than those on 2D images. Image quality (P = .0004) and carcinoma conspicuity (P.0005) were superior with the 3D T2-weighted TSE sequence. Although multiplanar reconstruction of 3D T2-weighted TSE images was useful for staging in one case, there were no significant differences between 3D and 2D T2-weighted TSE imaging in accuracy of staging for the two readers for cervical or endometrial carcinoma.The 3D T2-weighted TSE sequence showed certain advantages over the 2D T2-weighted TSE sequence, and it has the potential to improve the performance of MR imaging for the evaluation of uterine carcinoma.

Objective: To compare the diagnostic performance of magnetic resonance (MR) imaging and multidetector row computed tomography (MDCT) for an anomalous pancreaticobiliary ductal junction (PBJ). Methods: This study included 26 patients who underwent MR imaging, MDCT, and endoscopic retrograde cholangiopancreatography. Seventeen of the patients were diagnosed by endoscopic retrograde cholangiopancreatography as having an anomalous PBJ. Three radiologists independently reviewed MR images alone, contrast-enhanced CT images alone, and MR images and CT images combined. Receiver operating characteristic curve analysis was used to compare diagnostic capabilities. Results: The mean area under the receiver operating characteristic curve (Az [95% confidence interval]) was 0.75 (0.73-0.77) for MR imaging alone, 0.79 (0.70-0.89) for CT alone, and 0.84 (0.82-0.86) for the 2 modalities combined. Only between the combination and MR imaging alone was there significant difference in Az value (P < 0.05). Conclusions: The diagnostic performance of MR imaging and MDCT was equivalent for an anomalous PBJ. The addition of MDCT to MR imaging improved the diagnostic performance.

Background and Purpose Preoperative T staging demands high accuracy, because it greatly influences subsequent therapies in advanced gastric cancer. Patients and Methods 616 patients with gastric cancer underwent multi-detector row computed tomography (MDCT) before operation. The results were compared with operative and pathologic findings. Especially, we evaluated the correlations among the diagnostic accuracy of T staging and various clinicopathologic parameters by focusing on 276 patients who had detectable lesions by MDCT. Results The overall diagnostic accuracy of preoperative T staging by MDCT was 90.9% (560/616). For each pathologic T stage, the accuracy was 95% for pT1, 76% for pT2-3, 92% for pT4a, and 75% for pT4b, respectively. Among the 276 patients, 239 (87%) were correctly staged by MDCT whereas 29 (11%) and 8 (3%) were over- or under-staged, respectively. Antral tumors ( P = .045), and Borrmann type 1 tumors ( P = .0001) were incorrectly T staged by MDCT, whereas differentiated type tumors tended to be over-staged. All patients with positive cytology ( n = 12 cases) and peritoneal metastasis ( n = 7 cases) diagnosed at laparotomy had been diagnosed as T4a or deeper by MDCT. The 5-year overall survival rates classified by preoperative T staging by MDCT (T1/T2-3/T4a/T4b) were 100%, 89%, 59%, and 31%, respectively, whereas those for each pT stage were 100%, 84%, 59%, and 19%. Conclusion Preoperative T staging of gastric cancer by MDCT is highly accurate and could contribute to treatment strategies, particularly in advanced disease.

To investigate the mechanism of enhancement of hepatocellular carcinoma (HCC) on gadoxetic acid-enhanced hepatobiliary phase magnetic resonance (MR) images and to characterize HCC thus enhanced.This retrospective study was approved by the institutional review board, and patient informed consent for research use of the resected specimen was obtained. MR images in 25 patients (20 men, five women; mean age, 68 years; range, 49-82 years) with 27 resected hypervascular HCCs (one well, 13 moderately, 13 poorly differentiated) that demonstrated hepatocyte-selective enhancement on gadoxetic acid-enhanced MR images, were quantitatively studied, and findings were correlated with results of immunohistochemical staining for a sinusoidal transporter, organic anion transporting polypeptide (OATP) 1B1 (OATP1B1) and/or OATP1B3 (OATP1B1 and/or -1B3), and a canalicular transporter, multidrug resistance-associated protein 2 (MRP2), and also with bile accumulation in tumors. Statistical analysis was performed with the Student t test and Scheffé post hoc test.Combined with positive OATP1B1 and/or -1B3 expression (O+), two patterns of MRP2 expression contributed to high enhancement: decreased expression (M-, n = 3) and increased expression at the luminal membrane of pseudoglands (M+[P], n = 3). Nodules without OATP1B1 and/or -1B3 expression (O-, n = 13) and nodules with O+ associated with increased MRP2 expression only at the canaliculi (M+[C], n = 8) induced significantly lower enhancement than those with the two expression patterns described before (O+/M- group vs O- group, P = .002; O+/M- group vs O+/M+[C] group, P = .047; O+/M+[P] group vs O- group, P.001; O+/M+[P] group vs O+/M+[C] group, P.001). Nodules with bile pigment (n = 12) showed significantly higher enhancement (P = .004); all five nodules (one well differentiated HCC, four moderately differentiated HCCs), which were enhanced more than adjacent liver parenchyma, contained bile pigment.High hepatocyte-selective enhancement is induced by expression patterns of transporters, which may result in accumulation of gadoxetic acid in cytoplasm of tumor cells or in lumina of pseudoglands. An HCC with gadoxetic acid enhancement is characterized by bile accumulation in tumors.

Purpose The purpose of this study was to investigate correlations between the aorto-popliteal bolus transit speed and aortic and popliteal bolus transit time in order to evaluate the possibility for prediction of bolus transit speed by single test injection technique. Materials and methods Approval was obtained from our institutional review board for this study, which included 42 patients, from all of whom written informed consent was obtained. Low-dose serial CT scanning after injection of 12 ml contrast material (300 mg/ml) at a rate of 3 ml/s followed by saline flush was performed twice, first at the level of the upper abdomen and second at the level of the knee joint. The times needed to reach peak enhancement of the upper abdominal aorta (T-aorta) and bilateral popliteal arteries (T-popliteal) were obtained, and aorto-popliteal bolus transit speeds between the abdominal aorta and popliteal arteries were calculated. ABI was recorded for the bilateral feet. The Pearson's product–moment correlation coefficient was used to investigate the correlation between the bolus transit speed and T-aorta, T-popliteal, ABI, and patient age. Result The respective correlation coefficients for bolus transit speed on the one hand and T-aorta, T-popliteal, ABI, patient age on the other were −0.50, −0.84, 0.36, and −0.52. Conclusion The time to peak enhancement for popliteal arteries showed the strongest correlation with aorto-popliteal bolus transit speeds, and was considered to be the most accurate predictor for aorto-popliteal bolus transit speeds.

Motion artifact is problematic in the diagnosis of Creutzfeldt-Jakob disease (CJD) because of dementia. The purpose was to compare the occurrence of this artifact between a diffusion-weighted (DW) magnetic resonance (MR) imaging sequence and conventional sequences. Ten MR examinations comprising T2-weighted, T1-weighted, DW, and fluid-attenuated inversion recovery imaging in seven CJD patients were retrospectively evaluated. The occurrence of motion artifacts on each sequence were assessed, and the examination was classified into four groups as follows: group A, motion artifact not revealed on DW imaging but revealed on one or more other sequences; group B, revealed on DW imaging and one or more other sequences; group C, not revealed on any sequences; and group D, revealed on DW imaging but not on any other sequences. The 10 MR examinations were classified as eight group A (80%), one B (10%), one C (10%), and zero D (0%). Motion artifacts are likely to occur in any conventional imaging sequences in CJD, but the fast-imaging ability of DW imaging can reduce this artifact. The combination of an absence of motion artifact on DW imaging and the presence on conventional sequences may be one of the frequent findings of CJD.