Dual-Source Contrast-Enhanced Multiphasic CT of the Liver Using Low Voltage (70 kVp): Feasibility of a Reduced Radiation Dose and a 50% of Contrast Dose.

This study investigated the feasibility of both a reduced radiation dose and a 50% of contrast dose in multiphasic CT of the liver with a 70 kVp protocol compared with a standard-tube-voltage protocol derived from dual-energy (DE) CT (blended DE protocol) with a full-dose contrast-agents in the same patient group. This study included 46 patients who underwent multiphasic contrast-enhanced dynamic CT of the liver with both a 70 kVp and a blended DE protocols. For quantitative analysis, median CT values for the liver, aorta, and portal vein, as well as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), were measured and calculated. In addition, as a qualitative analysis, the contrast effect and overall image quality of the abdominal organs were evaluated on a five-point scale. CNR and SNR of the hepatic parenchyma were not significantly different between the 70kV protocol and the Blended DE protocol in all phases. The 70 kVp protocol showed significantly better image quality compared with the blended DE protocol in the arterial phase (p = 0.035) and the equilibrium layer phase (p = 0.016). A 70 kVp CT protocol in combination with a reduced radiation dose and half-dose iodine load is feasible for multiphasic dynamic CT of the liver by maintaining the contrast enhancement effects and image quality in comparison with the blended DE CT protocol.

Portal vein embolization via the ipsilateral percutaneous transhepatic approach versus laparotomic transileocecal approach: complications, profile and changes in future liver remnant volume.

OBJECTIVE: Major liver resection is an effective treatment option for patients with liver malignancy. The future liver remnant (FLR) volume and complications after portal vein embolization (PVE) were compared between the ipsilateral right portal vein (PTPE) and transileocolic (TIPE) approaches. METHODS: A total of 42 patients (TIPE, n = 22; PTPE, n = 20) underwent right lobectomy after PVE. CT and hepatobiliary scintigraphy were repeated before and after PVE. The blood examination findings and the FLR values (FLRCT: calculated from CT, %FLRCT: FLRCT ratio, %FLRSPECT: FLR ratio using single photon emission CT, FLRCT/BS: FLRCT to body surface ratio) were compared between two approach sites. The complications and mortality were also analyzed after PVE and major right hepatectomy. RESULTS: There were no significant differences in the patient characteristics, blood examination findings or FLR values between two groups. Adequate liver regeneration was observed without significant differences between PTPE and TIPE (increased ratio of FLRCT: 8.7% vs 19.2%, p = 0.15 [25-75 percentile: 17.1-60.4], %FLRCT: 11.2% vs 8.3%, p = 0.25 [6.3-13.3], %FLRSPECT: 15.4% vs 19.2%, p = 0.09 [16.0-22.4], FLRCT/BS: 33.6% vs 47.1%, p = 0.19 [17.2-60.4], respectively), but TIPE required a significantly longer procedure time than PTPE [181.4 min vs 108.7 min, p < 0.01 (103.3-193.5)]. However, one patient was converted to TIPE due to bleeding during PTPE. After right lobectomy, portal vein stenosis or thrombosis was noted in three patients [two with TIPE (9.1%) and one with PTPE (5%)] and three TIPE patients died within 90 days (13.6%) after right hepatectomy. CONCLUSION: FLR volume significantly increased after PVE, regardless of the approach sites; however, PTPE is a useful technique with a shorter procedure time.

Assessment of gastric wall structure using ultra-high-resolution computed tomography.

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 < 0.001). The mean overall image quality scores with DLR images were significantly higher than those with the other three methods (P < 0.001). Regarding the comparison between C-HRCT and U-HRCT, the mean conspicuity scores for the three-layered structure of the gastric wall on U-HRCT were significantly better than those on C-HRCT in the fornix (5 [5-5] vs. 3.5 [3-4], P < 0.001), body (4 [3.25-5] vs. 4 [3-4], P = 0.039), angle (5 [4-5] vs. 3 [2-4], P < 0.001), and antral posterior (4 [3.25-5] vs. 2 [2-4], P < 0.001), except for antral anterior (4 [3-5] vs. 3 [3-4], P = 0.230) CONCLUSION: U-HRCT using DLR improved the image noise and overall image quality of the gastric wall as well as the conspicuity of the three-layered structure, suggesting its utility for the evaluation of the anatomical details of the gastric wall structure.

Reduced Field-of-View Diffusion-Weighted Magnetic Resonance Imaging of the Pancreas With Tilted Excitation Plane: A Preliminary Study.

BACKGROUND: Reduced field-of-view diffusion-weighted imaging (rDWI) with tilted two-dimensional radiofrequency (RF) excitation planes has not yet been applied to the imaging of the pancreas although the utility of this technique which allows the acquisition of high-quality images without aliasing artifacts in the phase-encoding direction has been evaluated for brain and spinal cord imaging. PURPOSE: To evaluate the visual image quality of the pancreas by tilting the excitation plane (tilted rDWI) in comparison to conventional DWI (cDWI) and rDWI without using the tilted excitation plane. STUDY TYPE: Retrospective. POPULATION: Thirty-two patients evaluated for suspected pancreatobiliary diseases. FIELD STRENGTH/SEQUENCE: Echo-planar imaging DWI (cDWI, rDWI, and tilted rDWI) acquired at 3 T. ASSESSMENT: Images from each DWI sequence were analyzed by five radiologists to compare image quality (conspicuity of pancreatic edges, interslice signal homogeneity, overall image quality, and conspicuity of focal pancreatic lesions) and artifacts (presence of blurring or ghosting artifacts, susceptibility artifacts, and aliasing artifact). STATISTICAL TESTS: Shapiro-Wilk test was performed to assess whether data were normally distributed. Friedman test followed by Bonferroni-adjusted Wilcoxon signed-rank test for post hoc analysis was performed to compare image quality and artifact scores. RESULTS: The mean scores for conspicuity of pancreatic edges (3.36 vs. 2.37), interslice signal homogeneity (3.14 vs. 2.81), presence of ghosting artifacts (3.32 vs. 2.66), susceptibility artifacts (3.06 vs. 2.30), and aliasing artifacts (3.90 vs. 2.34), and overall image quality (3.49 vs. 2.36) were significantly higher in the tilted rDWI than in the rDWI (P < 0.017 for all parameters). The conspicuity score for focal pancreatic lesions tended to be higher in tilted rDWI than in rDWI (2.44 vs. 2.00, P = 0.07). DATA CONCLUSION: Tilted rDWI had better image quality and reduced artifacts relative to cDWI and rDWI techniques in the pancreas. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY: Stage 2.

Transient respiratory motion artifacts in multiple arterial phases on abdominal dynamic magnetic resonance imaging: a comparison using gadoxetate disodium and gadobutrol.

PURPOSE: To compare the occurrence of transient respiratory motion artifacts (TRMAs) in multiple arterial phases on abdominal magnetic resonance (MR) images between those obtained using gadobutrol and gadoxetate disodium. MATERIALS AND METHODS: Two hundred and fourteen abdominal MR examinations (101 with gadoxetate disodium, 113 with gadobutrol) were evaluated. Dynamic three-dimensional contrast-enhanced T1-weighted imaging (CAIPIRINHA-Dixon-TWIST-VIBE) including single-breath-hold six arterial phase acquisitions was performed on a 3.0-T MRI scanner. The TRMAs frequency and the mean TRMA scores were compared between patients assessed with gadoxetate disodium and those assessed with gadobutrol. In addition, the timing of TRMAs appearing for the first time was also recorded and compared between the two groups. RESULTS: The mean TRMA scores in all arterial phases using gadoxetate disodium were significantly worse than in those using gadobutrol (1.49 ± 0.78 vs. 1.18 ± 0.53, P < .001). Regarding the timing of the occurrence of TRMAs, the severe TRMAs frequency after the third arterial phase was significantly higher in patients using gadoxetate disodium (10/101, 10%) than in those using gadobutrol (0/113, 0%) (P < .001). CONCLUSION: In multiple-arterial-phase dynamic MRI, the TRMAs frequency when using gadoxetate disodium increased compared with gadobutrol, due to intolerable respiratory suspension after the third arterial phase.

Image quality in dual-source multiphasic dynamic computed tomography of the abdomen: evaluating the effects of a low tube voltage (70 kVp) in combination with contrast dose reduction.

PURPOSE: To compare the image quality of multiphasic (arterial, portal, and equilibrium phases) dynamic computed tomography (CT) of the abdomen obtained by a low tube voltage (70kVp) in combination with a half-dose iodine load using low-concentration contrast agent in high tube output dual-source CT with a standard tube voltage (120kVp) and full-dose iodine load using the same group of adult patients. METHODS: Fifty-five patients who underwent both low-tube-voltage (70kVp) abdominal CT with a half-dose iodine load and standard-tube-voltage (120kVp) CT with a full-dose iodine load were analyzed. The mean CT values and signal-to-noise ratio (SNR) of the liver, aorta and portal veins were quantitatively assessed. In addition, the contrast enhancement of the abdominal organs and overall image quality were qualitatively evaluated. RESULTS: The mean CT values and SNR of the liver parenchyma were significantly higher in 70-kVp protocol than in 120-kVp protocol in all 3 phases (p = 0.018 ~ < 0.001). Regarding the qualitative analysis, the overall image quality in the 70-kVp protocol was significantly better than in the 120-kVp protocol in all 3 phases (p < 0.001). In addition, the contrast enhancement scores of the liver parenchyma and hepatic vein in the equilibrium phase were also significantly higher in the 70-kVp protocol than in the 120-kVp protocol (p < 0.001). CONCLUSION: A low tube voltage (70kVp) in combination with a half-dose iodine load using a low-concentration contrast agent and an iterative reconstruction algorithm in high tube output dual-source CT may improve the contrast enhancement and image quality in multiphasic dynamic CT of the abdomen in patients under 71 kg of body weight.

Incidentally detected pancreatic adenocarcinomas on computed tomography obtained during the follow-up for other diseases.

PURPOSE: To determine imaging findings of pancreatic adenocarcinomas incidentally detected on contrast-enhanced multiphasic dynamic computed tomography (CT) obtained during the follow-up for other diseases. METHODS: From January 2007 to December 2018, 14 patients with pancreatic adenocarcinomas incidentally detected on CT obtained during the follow-up for other diseases (incidental group) and 105 patients with pancreatic adenocarcinomas symptomatically detected on ultrasound or CT (non-incidental group) were included. Imaging characteristics of the tumor were compared between the two groups. Additionally, imaging findings prior to the detection of a tumor on previous CT images in the incidental group were also assessed. RESULTS: In cancers of the pancreas body/tail, there was a significantly smaller tumor size (median, 17 mm vs. 42 mm, p < 0.001), a significantly lower incidence of loss of fatty marbling (p = 0.025), vascular involvement (p < 0.001), lymph node metastasis (p = 0.046) and distant metastasis (p = 0.017), and a significantly higher incidence of preserved lobulation (p < 0.001) in the incidental group than in the non-incidental group. Regarding the cancers of the pancreas head, there were no significant differences in the radiological findings between the two groups. On previous CT images, small pancreatic nodules, secondary signs, and loss of fatty marbling tended to be the preceding findings of incidental pancreatic adenocarcinomas. CONCLUSION: Incidentally detected pancreatic adenocarcinomas in the pancreas body/tail were characterized by an earlier tumor stage than in cases of symptomatically detected pancreatic adenocarcinoma. Several CT findings prior to the detection of a tumor may be useful for the early detection of pancreatic adenocarcinoma during the follow-up for other diseases.

Liver imaging reporting and data system (LI-RADS) v2018: comparison between computed tomography and gadoxetic acid-enhanced magnetic resonance imaging.

PURPOSE: To determine the consistency of major hepatocellular carcinoma (HCC) features between CT and MRI based on Liver Imaging Reporting and Data System (LI-RADS) v2018 and to investigate the additional value on gadoxetic acid-enhanced MRI. MATERIALS AND METHODS: Patients who underwent dynamic CT and gadoxetic acid-enhanced MRI within 1 month were investigated. Two radiologists evaluated the presence of major HCC features and categorized observations using LI-RADS v2018 algorithm. In addition, each observation was recorded as hyper-, iso-, or hypo-intensity on hepatobiliary-phase (HBP) images. RESULTS: Sixty-one patients with 110 observations were identified. Among 88 observations classified as LR-3, 4 or 5, arterial phase hyper-enhancement and washout appearance showed higher frequencies on CT than on MRI (75.0% vs. 58.0%, P < 0.001, and 60.2% vs. 44.3%, P = 0.014, respectively). Of the 59 LR-3 observations categorized on MRI, 70.0% of observations with hypo-intensity on HBP images were HCCs, whereas 89.5% of observations with iso- or hyper-intensity on HBP images were non-HCCs (P < 0.001) CONCLUSION: The frequencies of arterial phase hyper-enhancement and washout appearances were higher on CT than on gadoxetic acid-enhanced MRI. For LR-3 observations, adding the hepatobiliary-phase hypo-intensity to major features improved the diagnostic performance of MRI in distinguishing HCCs from non-HCC lesions.