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PURPOSE To evaluate the image quality of ultra-high-resolution CT (U-HRCT) in the comparison among four different reconstruction methods, focusing on the gastric wall structure, and to compare the conspicuity of a three-layered structure of the gastric wall between conventional HRCT (C-HRCT) and U-HRCT. METHOD Our retrospective study included 48 patients who underwent contrast-enhanced U-HRCT. Quantitative analyses were performed to compare image noise of U-HRCT between deep-learning reconstruction (DLR) and other three methods (filtered back projection: FBP, hybrid iterative reconstruction: Hybrid-IR, and Model-based iterative reconstruction: MBIR). The mean overall image quality scores were also compared between the DLR and other three methods. In addition, the mean conspicuity scores for the three-layered structure of the gastric wall at five regions were compared between C-HRCT and U-HRCT. RESULTS The mean noise of U-HRCT with DLR was significantly lower than that with the other three methods (P

Purpose To examine the frequency and patterns of renal parenchymal retention of iodinated contrast agent during follow-up computed tomography (CT) performed one day after undergoing contrast-enhanced CT and to evaluate the association with the renal function before and after contrast-enhanced CT. Materials and Methods This retrospective study included 55 patients who underwent follow-up CT the day after contrast-enhanced CT had been performed. Two radiologists categorized the retention patterns on a scale of 0–6 (0: no retention, 1: diffuse parenchymal, 2: diffuse cortical, 3: subcapsular tiny nodular, 4: cortical wedge-shaped, 5: medullary focal, 6: renal pelvic). In addition, we collected the patients’ clinical data, including the development of contrast-induced nephropathy (CIN). Results A total of 37 patients (67 %) showed retention of contrast agent in the kidney (retention group), while 18 did not (non-retention group). A diffuse parenchymal pattern and renal pelvis pattern were the most common. High levels of creatinine (Cre) and blood urea nitrogen (BUN) before contrast-enhanced CT were significantly associated with the retention in the kidney (p = 0.018, 0.006, respectively). The frequency of the development of CIN was significantly higher (p = 0.021) in the retention group (10/37) than in the non-retention group (0/18). A diffuse parenchymal pattern and diffuse cortical pattern were significantly more common in patients with CIN than in those without CIN (p = 0.003, p = 0.045, respectively). Conclusion Renal parenchymal retention of iodinated contrast agent the day after contrast-enhanced CT was a frequently recognized finding and was associated with renal dysfunction. This finding, especially diffuse parenchymal and cortical patterns, may be a potential biomarker of CIN development.

Purpose To investigate the clinical value of measuring the ECV fraction of the pancreas by DECT in association with an impaired glucose tolerance (IGT) estimated by the hemoglobin A1C (HbA1C) value in patients with or without cirrhosis. Materials and Methods This retrospective study included patients who underwent contrast-enhanced dynamic CT with dual-energy mode between March 2018 and February 2019. The ECV fraction of the pancreas was calculated from iodine map images created from equilibrium-phase contrast-enhanced DECT images. The cross-sectional areas of the pancreas were also measured. Results In total, 51 patients were analyzed (median age, 69 years old; 22 women). The ECV fraction of the pancreas showed a significant negative correlation with the HbA1c value in the cirrhotic group (ρ=-0.346, p = 0.048), while there was no significant correlation in the non-cirrhotic group (ρ=-0.086, p = 0.734). In the elevated HbA1C group, the ECV fraction of the pancreas in the cirrhotic patients (median, 0.247; interquartile range [IQR], 0.098) was significantly lower than that in the non-cirrhotic patients (0.332, IQR 0.113) (p = 0.024). In the elevated HbA1C group, the cross-sectional area of the pancreas was significantly larger in the cirrhotic patients than that in the non-cirrhotic patients (median [IQR]; 2945 [904] vs. 1885 [909] mm2, p = 0.019). Conclusion A reduction in the ECV fraction of the pancreas measured by DECT as well as the enlargement of the pancreatic parenchyma was observed in cirrhotic patients with IGT. These findings suggest that the measurement of the pancreatic ECV fraction by DECT may help clarify the pathophysiology of IGT in patients with cirrhosis.

The purpose of this study was to compare the results of a histogram-based analysis of static and dynamic lung perfused blood volume (LPBV) images.Sixty-five patients (mean age: 61.3 years, 36 male) underwent dynamic and static LPBV for evaluation of pulmonary vascular diseases (n = 11), lung carcinoma (n = 27) or pulmonary thromboembolism (PTE: n = 27). Seven sets of dynamic sequential scans were performed at the pulmonary trunk using dual-energy technique before the static LPBV scan. The image of lung parenchyma that showed the greatest mean attenuation in dynamic series was defined as the peak dynamic LPBV image. The differences and correlations in the mean attenuation, image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), histogram skewness and histogram kurtosis were evaluated according to the type of disease in static and dynamic LPBV images.Static LPBV images showed significantly larger mean attenuation (Rt:24.2, Lt: 24.2), SNR (Rt:2.31, Lt:2.30), and CNR (Rt:2.40, Lt:2.39), and smaller kurtosis values (Rt:1.06, Lt:0.61) values in comparison to dynamic LPBV images (p 0.001); however, with the exception of kurtosis of the left lung (r = 0.17), these values were well-corrected with that of the dynamic LPBV images in these values (r = 0.4-0.77, p ≤ 0.001) without kurtosis of left lung (r = 0.17) in all patients. The histogram kurtosis of static LPBV image showed a good correlation with that of dynamic LPBV (r = 0.41-0.77, p 0.05), especially in patients with PTE.In patients with PTE, the static LPBV image valueswere well correlated with the peak dynamic LPBV images which demonstrated pulmonary artery-dominant flow.

Objective To compare three different injection methods for optimizing hepatic arterial phase of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) enhanced MR imaging. Methods Arterial phase images were obtained after the injection of contrast agent at a rate of 3 mL/s with diluted Gd-EOB-DTPA (dilution method) in 27 patients, 3 mL/s with undiluted Gd-EOB-DTPA (3 mL method) in 26 patients and 1 mL/s with undiluted Gd-EOB-DTPA (1 mL method) in 28 patients. In the quantitative evaluation, signal-to-phantom ratios (SPR) of the liver parenchyma, pancreas, renal cortex, portal vein and aorta were evaluated. In the qualitative evaluation, the seven items for image quality of hepatic arterial phase were assessed, and the total score of all items in each subject was calculated. Results The score of enhancement of abdominal aorta and total score of seven items in 1 mL method were significantly higher than those in 3 mL method. The SPR of the liver parenchyma in 3 mL method was significantly higher than that in 1 mL method, suggesting substantial hepatic inflow from portal venous return. Conclusion For the optimal arterial phase imaging, injection rate of 1 mL/s with undiluted Gd-EOB-DTPA is convenient and preferable, compared with other two methods, based on our qualitative analysis.

To clarify whether the uptake of SPIO increases or decreases in areas of fatty change compared with surrounding areas of nonfatty change at SPIO-enhanced MR imaging.Approval for this retrospective study was obtained from our institutional review board. This study included 14 patients with nondiffuse fatty infiltration of the liver who underwent SPIO-enhanced MR imaging. Additionally, 30 patients without nondiffuse fatty infiltration of the liver were also evaluated.Among 14 patients, areas of fatty change showed relatively high signal intensity in 7 patents, indicating decreased uptake of SPIO in areas of fatty change. In these 7 patients, 4 had mild cirrhosis and 3 did not have cirrhosis. The mean percentage of signal intensity loss (42%) of fatty areas was significantly lower (p0.007) than that of adjacent areas of nonfatty change (52%). In the remaining 7 of 14 patients, areas of fatty change showed relatively low signal intensity, indicating increased uptake of SPIO in areas of fatty change. Among these 7 patients, 6 had advanced cirrhosis. The mean percentage of signal intensity loss (47%) of fatty areas was significantly higher (p0.008) than that of adjacent areas of nonfatty change (31%).The uptake of SPIO generally decreased in areas of fatty change compared with normal liver parenchyma at SPIO-enhanced MR imaging. However, in patients with advanced cirrhosis, areas of fatty change shows relatively low signal intensity because the uptake of SPIO in surrounding areas of nonfatty change severely decreased probably due to liver fibrosis.

The purpose of this study was to assess differences in enhancement effects of liver parenchyma between normal and cirrhotic livers on contrast-enhanced MR imaging (CE-MRI) obtained with Gd-EOB-DTPA.A total of 99 patients with cirrhotic liver (n=58; Child-Pugh class A, n=30; B, n=22; C, n=6) and normal liver (n=41) underwent Gd-EOB-DTPA-enhanced MR imaging. CE images were obtained before contrast injection, in the arterial phase (AP) at 25s or modified scan delay, in the portal phase (PP) at 70s, in the equilibrium phase (EP) at 3 min, and in the hepatobiliary phase (HP) at 3 times (10, 15 and 20 min). Signal intensity of the liver in all phases was defined using region-of-interest measurements for relative enhancement (RE) calculation.In normal-liver and Child-Pugh class A and B patients, mean RE of liver parenchyma increased significantly (P0.03-0.001) with time until 20-min HP. Conversely, mean RE for Child-Pugh class C patients did not show any increasing tendency after PP. Mean RE of liver parenchyma at EP and HP (10-, 15- and 20-min) was highest in normal liver, followed by Child-Pugh class A, B and C cirrhosis (P0.02-0.001).Hepatic parenchymal enhancement on CE-MR images obtained using Gd-EOB-DTPA is affected by the severity of cirrhosis.

The purpose of this study was to assess the difference in the activity of biliary and renal excretion between normal and cirrhotic livers on contrast-enhanced MR imaging obtained with gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA).A total of 78 patients with cirrhotic liver (n=44) and with normal liver (n=34) underwent multi-phase Gd-EOB-DTPA enhanced MR imaging (arterial, portal, equilibrium, and three hepatobiliary phases (10, 15 and 20 min HP), respectively), and these contrast-enhanced images were qualitatively and quantitatively evaluated for the differences of the biliary and renal excretion between normal and cirrhotic livers.The timing of biliary excretion of contrast agents in the cirrhotic liver was significantly slower than that in the normal liver (P0.001). The degree of contrast enhancement in the common bile duct in the normal liver was significantly better than that in the cirrhotic liver (P=0.003). Contrast agents were demonstrated in the duodenum at 20 min HP in 8/44 (18%) cirrhotic liver while they were seen in 15/34 (44%) normal liver (P=0.013). The enhancement effects of renal medulla and portal vein at 20 min HP in the cirrhotic liver were significantly higher than those of normal liver (P=0.043 and P0.001, respectively).Biliary excretion of Gd-EOB-DPTA was impaired in cirrhotic livers in comparison with normal livers while renal excretion of Gd-EOB-DPTA was increased.

A great variety of MR pulse sequences for hepatocellular carcinomas (HCCs) are now available. In this article, we reviewed the current MR imaging techniques that are routinely used for hepatic imaging, and described the optimization of these sequences as well as the utility and characteristics of each sequence for the accurate diagnosis of HCCs. Then, we reviewed various MR imaging findings of advanced and early HCCs with emphasis on signal intensity and hemodynamic patterns. Finally, we described the value of multi-arterial-phase contrast-enhanced dynamic MR imaging of the whole liver with excellent temporal resolution for evaluating transitional hemodynamics of hepatic lesions during the six arterial phases.

This article presents current MR imaging techniques for the pancreas, and review a spectrum of MR imaging features of various pancreatic diseases. These include: 1) congenital anomalies such as anomalous union of pancreatobiliary ducts, divisum, and annular pancreas, 2) inflammatory diseases, including acute or chronic pancreatitis with complications, groove pancreatitis, and autoimmune pancreatitis, tumor-forming pancreatitis, 3) pancreatic neoplasms, including adenocarcinoma, islet cell tumors, and cystic neoplasms (microcystic adenoma, mucinous cystic neoplasms, and intraductal mucin-producing pancreatic tumor). Particular attention is paid to technical advances in MR imaging of the pancreas such as fat-suppression, MR pancreatography (single- or multi-slice HASTE), and thin-section 3D multiphasic contrast-enhanced dynamic sequences. Imaging characteristics that may lead to a specific diagnosis or narrow the differential diagnosis are also discussed.

With a recent advance of fast MR imaging techniques including fast gradient-echo (GRE), fast spin-echo (FSE), single shot FSE (SSFSE) and echo-planar imaging (EPI), and availability of a phased-array torso coil, there can be many possible pulse sequences for liver MR imaging. In clinical practice, optimization of pulse sequences is important for improving diagnostic performance of liver diseases. In this article, we review the current status of liver MR imaging, focusing on the description of standard pulse sequences, and the utility of fast scanning technique and contrast-enhancement studies.