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Purpose: Hepatobiliary-phase (HBP) MRI with gadoxetic acid facilitates the differentiation between lesions with and without functional hepatocytes. Thus, high-quality HBP images are required for the detection and evaluation of hepatic lesions. However, the long scan time may increase artifacts due to intestinal peristalsis, resulting in the loss of diagnostic information. Pseudo-random acquisition order disperses artifacts into the background. The aim of this study was to investigate the clinical applicability of pseudo-random trajectory scanning for the suppression of motion artifacts on T1-weighted images including HBP. Methods: Our investigation included computer simulation, phantom experiments, and a clinical study. For computer simulation and phantom experiments a region of interest (ROI) was placed on the area with motion artifact and the standard deviation inside the ROI was measured as image noise. For clinical study we subjected 62 patients to gadoxetic acid-enhanced hepatobiliary-phase imaging with a circular- and a pseudo-random trajectory (c-HBP and p-HBP); two radiologists graded the motion artifacts, sharpness of the liver edge, visibility of intrahepatic vessels, and overall image quality using a five-point scale where 1 = unacceptable and 5 = excellent. Differences in the qualitative scores were determined using the two-sided Wilcoxon signed-rank test. Results: The image noise was higher on the circular image compared with pseudo-random image (101.0 vs 60.9 on computer simulation image, 91.2 vs 67.7 on axial, 95.5 vs 86.9 on reformatted sagittal image for phantom experiments). For clinical study the score for motion artifacts was significantly higher with p-HBP than c-HBP imaging (left lobe: mean 3.4 vs 3.2, P < 0.01; right lobe: mean 3.6 vs 3.4, P < 0.01) as was the qualitative score for the overall image quality (mean 3.6 vs 3.3, P < 0.01). Conclusion: At gadoxetic acid-enhanced hepatobiliary-phase imaging, p-HBP scanning suppressed motion artifacts and yielded better image quality than c-HBP scanning.

Upper urinary tract urothelial carcinoma is staged using the TNM classification of malignant tumors. Preoperative TNM is important for treatment planning. Computed tomography urography is now widely used for clinical survey of upper urinary tract carcinoma because of its diagnostic accuracy. Computed tomography urography is recommended as the first-line imaging procedure in several guidelines. Several reports stated that computed tomography urography is also useful for staging. However, no educational and practical reviews detailing the T staging of upper urinary tract urothelial carcinomas using imaging are available. We discuss the scanning protocol, T staging using computed tomography urography, limitations, magnetic resonance imaging, computed tomography comparison and pitfalls in imaging of upper urinary tract urothelial carcinoma. A recent study reported the high diagnostic accuracy of computed tomography urography with respect to T3 or higher stage tumors. To date, images that show a Tis-T2 stage have not been reported, but various studies are ongoing. Although magnetic resonance imaging has lower spatial resolution than computed tomography urography, magnetic resonance imaging can be carried out without radiation exposure or contrast agents. Magnetic resonance imaging also offers the unique ability of diffusion-weighted imaging without contrast agent use. Some researchers reported that diffusion-weighted imaging is useful not only for detecting lesions, but for predicting the T stage and tumor grade. We recommend the appropriate use of computed tomography and magnetic resonance while considering the limitations of each modality and the pitfalls in upper urinary tract urothelial carcinoma imaging.

The purpose of this study was to compare the image quality of coronary computed tomography angiography (CTA) subjected to deep learning–based image restoration (DLR) method with images subjected to hybrid iterative reconstruction (IR). We enrolled 30 patients (22 men, 8 women) who underwent coronary CTA on a 320-slice CT scanner. The images were reconstructed with hybrid IR and with DLR. The image noise in the ascending aorta, left atrium, and septal wall of the ventricle was measured on all images and the contrast-to-noise ratio (CNR) in the proximal coronary arteries was calculated. We also generated CT attenuation profiles across the proximal coronary arteries and measured the width of the edge rise distance (ERD) and the edge rise slope (ERS). Two observers visually evaluated the overall image quality using a 4-point scale (1 = poor, 4 = excellent). On DLR images, the mean image noise was lower than that on hybrid IR images (18.5 ± 2.8 HU vs. 23.0 ± 4.6 HU, p

The objective of this study is to investigate the influence of damping from the PTO device on the cumulative output of the oscillating water column wave energy converter under real sea conditions which encompasses wide range of wave period and height. In this presentation, a time domain dynamic simulation model of OWC motion is developed and validated with water tank test results. Then the model is used to calculate a wide range of wave period and height. Finally, annual cumulative air power output of OWC is calculated with different damping values. In the water tank experiment, a cylindrical oscillating water column with a diameter of 0.3 m and submerged depth of 0.2 m is tested. PTO damping was emulated by using several orifice plates. Since the orifice pressure is proportional to square of flow-rate of the orifice, In the simulation, a model was constructed to solve the dynamic equation of motion assuming water column as a rigid equivalent floating body. Validation showed the model captures the influence of PTO damping as observed in the water tank testing. Using simulation, output air power from real scale OWC was evaluated under wide range of inlet wave period and height. With the output power database from dynamic simulation and frequency of wave height and period at specific sites in Japan (Fukui and Kamaishi), annual cumulative output power is calculated. From the results, it was confirmed that a higher output can be obtained with higher energy in high waves by adopting a damping characteristic that increases the efficiency under a wide wave condition rather than a nozzle characteristic that achieves maximum efficiency in the resonance period. Furthermore, it became clear that the damping that increases the maximum efficiency does not necessarily increase the accumulated energy. When considering operation in real sea condition in the future, it is not always effective to select PTO damping that maximizes the output at specific wave height or period. And it is important to adopt a method that can estimate wide range of wave condition and evaluate the cumulative output power.

OBJECTIVES This study aimed to compare the accuracy of assessing the arterial hypervascularity of hepatocellular carcinoma (HCC) on dynamic computed tomography (CT) scans and gadoxetic acid (EOB)-enhanced magnetic resonance imaging (MRI) scans performed with radial sampling. METHODS We studied the images of 40 patients with hypervascular HCC. A radiologist recorded the standard deviation of the attenuation (or the signal intensity [SI]) in subcutaneous fat tissue as the image noise (N) and calculated the contrast-to-noise ratio (CNR) as follows: (CNR) = (n-ROIT - n-ROIL)/N, where n-ROIT is the mean attenuation (or SI) of the tumor divided by the mean attenuation (or SI) of the aorta and n-ROIL is the mean attenuation (or SI) of the liver parenchyma divided by the mean attenuation (or SI) of the aorta. RESULTS The CNR was significantly higher on EOB-enhanced MRI than on dynamic CT scans. CONCLUSIONS For the assessment of HCC vascularity, EOB-enhanced MRI scans acquired with radial sampling were more accurate than dynamic CT images.

Tubulocystic renal cell carcinoma (TC-RCC) has been classified as an independent subtype according to the 2016 World Health Organization (WHO) classification. It is a rare subtype that predominantly affects men. Although few in number, radiological imaging reports have suggested that TC-RCC is characterized by multilocular cystic lesions, which are categorized as the Bosniak classification II-IV, with signature pathological characteristics comprising numerous small cysts or a tubular structure. The Bosniak classification system facilitates patient management; however, the differentiation of cystic tumors exhibiting similar imaging findings remains impossible; in fact, the differentiation of multilocular cystic RCC, adult cystic nephroma, and mixed epithelial and stromal tumor remains challenging. This review aims to discuss TC-RCC with a focus on implications of radiological findings in the differential diagnosis of TC-RCC.

Objective To compare the utility of high-precision computed diffusion-weighted imaging (hc-DWI) and conventional computed DWI (cc-DWI) for the diagnosis of hepatocellular carcinoma (HCC) at 3 T. Methods We subjected 75 HCC patients to DWI (b-value 150 and 600 s/mm2). To generate hc-DWI we applied non-rigid image registration to avoid the mis-registration of images obtained with different b-values. We defined c-DWI with a b-value of 1500 s/mm2 using DWI with b-value 150 and 600 s/mm2 as cc-DWI, and c-DWI with b-value 1500 s/mm2 using registered DWI with b-value 150 and 600 s/mm2 as hc-DWI. A radiologist recorded the contrast ratio (CR) between HCC and the surrounding hepatic parenchyma. Results The CR for HCC was significantly higher on hc- than cc-DWIs (median 2.0 vs. 1.8, P < 0.01). Conclusion The CR of HCC can be improved with image registration, indicating that hc-DWI is more useful than cc-DWI for the diagnosis of HCC.

This study aims to compare the image quality of coronary artery stent scans on computed tomography images reconstructed with forward projected model-based iterative reconstruction solution (FIRST) and adaptive iterative dose reduction 3D (AIDR 3D).Coronary computed tomography angiography scans of 23 patients with 32 coronary stents were used. The images were reconstructed with AIDR 3D and FIRST. We generated computed tomography attenuation profiles across the stents and measured the width of the edge rise distance and the edge rise slope (ERS). We also calculated the stent lumen attenuation increase ratio (SAIR) and measured visible stent lumen diameters. Two radiologists visually evaluated the image quality of the stents using a 4-point scale (1 = poor, 4 = excellent).There was no significant difference in the edge rise distance between the two reconstruction methods (P = 0.36). The ERS on FIRST images was greater than the ERS on AIDR 3D images (325.2 HU/mm vs 224.4 HU/mm; P 0.01). The rate of the visible stent lumen diameter compared to the true diameter on FIRST images was higher than that on AIDR 3D images (51.4% vs 47.3%, P 0.01). The SAIR on FIRST images was lower than the SAIR on AIDR 3D images (0.19 vs 0.30, P 0.01). The mean image quality scores for AIDR 3D and FIRST images were 3.18 and 3.63, respectively; the difference was also significant (P 0.01).The image quality of coronary artery stent scans is better on FIRST than on AIDR 3D images.

Papillary renal cell carcinoma (P-RCC) typically exhibits a homogeneous, solid hypovascular mass; P-RCC with a cystic appearance is atypical. Tubulocystic RCC (TC-RCC), a newly proposed entity for renal tumors in the 2016 WHO classification, and cystic papillary RCC, may yield similar imaging findings. Therefore, we investigated the incidence of papillary RCC with cystic changes and compared its CT and pathologic features to differentiate between two entities.We retrospectively evaluated 26 consecutive patients diagnosed with P-RCC. Two radiologists consensually identified dominant masses indicative of cystic changes on CT scans and recorded their Bosniak classification. In addition, two pathologists inspected the whole area of tumors macroscopically, labeled them as solid- or cystic change-dominant tumors, determined the pathogenesis of the cystic components (necrosis or hemorrhage), and recorded their inherent cystic characteristics (with/without TC-RCC components). We defined masses with cystic changes involving more than 50% of the entire tumor as cystic change-dominant tumors.Of the 26 tumors, 7 (27%) were diagnosed cystic change-dominant based on imaging and pathologic findings, of these, 2 were classified as Bosniak type III and 5 as Bosniak type IV. The pathologists confirmed that two type IV tumors demonstrated extensive necrosis and one type IV tumor revealed extensive hemorrhage. Four P-RCCs (type III and IV, 2 each) were of a mixed type harboring both solid and cystic components. Only one tumor exhibited a multilocular cystic appearance. All 7 cystic change-dominant P-RCCs were pathologically diagnosed as a pure P-RCC without TC-RCC components.While P-RCCs may contain cystic features, the multilocular type of cystic P-RCC is rare.

SummaryObjective This study examined the association between sudden natural death and abdominal fat using postmortem computed tomography (CT) scans. Subjects and methods Postmortem CT images at the umbilical level of 241 subjects were used to measure abdominal areas of subcutaneous- and visceral fat, the rate of visceral fat and the waist circumference. Of the study subjects, 174 died of sudden natural death (130 men and 44 women), and 67 died of different causes (46 men and 21 women). All were between 40 and 75 years of age. Logistic regression analysis was performed to identify independent abdominal parameters associated with sudden natural death. Results By univariate analysis, the areas of subcutaneous and visceral fat were significantly larger in sudden natural death than who died of different causes (subcutaneous fat, odds ratio [OR] = 1.004, 95% confidence interval [CI] = 1.000–1.007, p = 0.03; visceral fat, OR = 1.008, 95% CI = 1.003–1.013, p

Oscillating water column (OWC) wave energy converters are adopted in many marine applications such as buoys. This research investigates how inclination-induced changes in motion affect the oscillation characteristics of an OWC. As the collector of the OWC wave energy converter is inclined, the direction of motion of the water column is also inclined because it is constrained by collector walls. To investigate this idea, we developed a mechanical 1-degree-of-freedom oscillator model of an inclined OWC. The usefulness of the mechanical model was confirmed in a water tank test with OWCs inclined at 90° (vertical), 45°, and 18.4°. We then investigated the effect of inclination on the resonance period and the optimum power take-off damping of the OWC. The resonance period was mainly prolonged by the reduced restoring force as the motion direction changed. The optimum power take-off damping of an inclined OWC equaled the radiation damping, as observed in vertical OWCs. Finally, we varied the air chamber volume and observed much smaller effects than when varying the inclination. We conclude that changing the direction of motion affects the oscillation characteristics of OWCs mostly because of the reduction of gravity restoring force.