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Purpose: It is important to fully automate the evaluation of gadoxetate disodium–enhanced arterial phase images because the efficient quantification of transient severe motion artifacts can be used in a variety of applications. Our study proposes a fully automatic evaluation method of motion artifacts during the arterial phase of gadoxetate disodium–enhanced MR imaging. Methods: The proposed method was based on the construction of quality‐aware features to represent the motion artifact using MR image statistics and multidirectional filtered coefficients. Using the quality‐aware features, the method calculated quantitative quality scores of gadoxetate disodium–enhanced images fully automatically. The performance of our proposed method, as well as two other methods, was acquired by correlating scores against subjective scores from radiologists based on the 5‐point scale and binary evaluation. The subjective scores evaluated by two radiologists were severity scores of motion artifacts in the evaluation set on a scale of 1 (no motion artifacts) to 5 (severe motion artifacts). Results: Pearson's linear correlation coefficient (PLCC) and Spearman's rank–ordered correlation coefficient (SROCC) values of our proposed method against the subjective scores were 0.9036 and 0.9057, respectively, whereas the PLCC values of two other methods were 0.6525 and 0.8243, and the SROCC values were 0.6070 and 0.8348. Also, in terms of binary quantification of transient severe respiratory motion, the proposed method achieved 0.9310 sensitivity, 0.9048 specificity, and 0.9200 accuracy, whereas the other two methods achieved 0.7586, 0.8996 sensitivities, 0.8098, 0.8905 specificities, and 0.9200, 0.9048 accuracies Conclusions: This study demonstrated the high performance of the proposed automatic quantification method in evaluating transient severe motion artifacts in arterial phase images. [ABSTRACT FROM AUTHOR]

Herein, we assessed whether hepatobiliary phase (HBP) signal intensity (SI) can be used to differentiate HCC and non-HCC malignancies within LR-M observations. 106 LR-M patients based on LI-RADS v2018 who underwent gadoxetate-disodium magnetic resonance imaging and surgery from January 2009 to December 2018 were included. SI of LR-M observation on HBP was analyzed by two radiologists and categorized into dark, low and iso-to-high groups. Tumor was classified as dark when more than 50% of tumor showed hypointensity compared to spleen, as low when more than 50% of tumor showed hyperintensity compared to spleen but hypointensity compared to liver parenchyma, and as iso-to-high if there was even a focal iso-intensity or hyperintensity compared to liver parenchyma. Analysis of clinicopathological factors and association between imaging and histology was performed. Out of 106 LR-M, 42 (40%) were showed dark, 61 (58%) showed low, and 3 (3%) showed iso-to-high SI in HBP. Three iso-to-high SI LR-M were HCCs (P = 0.060) and their major histologic differentiation was Edmondson grade 1 (P = 0.001). 43 out of 61 (71%) low SI LR-M were iCCA or cHCC-CCA (P = 0.002). Inter-reader agreement of HBP SI classification was excellent, with a kappa coefficient of 0.872. LR-M with iso-to-high SI in HBP is prone to being HCC while LR-M with low SI in HBP is prone to being tumor with fibrous stroma such as iCCA and cHCC-CCA. Classification of LR-M based on HBP SI may be a helpful method of differentiating HCC from non-HCC malignancies. [ABSTRACT FROM AUTHOR]

The Liver Imaging Reporting and Data System (LI-RADS) is widely adopted for the noninvasive diagnosis of hepatocellular carcinoma (HCC). Herein, possible strategies to improve the diagnostic performance of LR-5 without reducing specificity for HCC were investigated. This retrospective study included 792 patients who underwent gadoxetate disodium-enhanced magnetic resonance imaging. Hepatic observations were categorized according to LI-RADS v2018 and categories were readjusted by upgrading LR4 to LR5 using ancillary features, arterial phase hyperenhancement (APHE) interpreted with subtraction images, indication of no washout when APHE was absent, extension of washout to the transitional phase, and subthreshold growth as a major feature. Based on LI-RADS v2018, LR-5 showed a sensitivity of 71.9% and a specificity of 97.9% for the diagnosis of HCC. Category-readjusted LR-5 after upgrading LR-4 to LR-5 using ancillary features favoring HCC in particular, subthreshold growth as a major feature, extending washout to transitional phase and APHE interpreted using subtraction images showed significantly increased sensitivity (P<0.001) without decreased specificity (Ps>0.05). The sensitivity of LR-5 can be improved without loss of specificity via category readjustment using AFs favoring HCC in particular, subthreshold growth as a major feature, extending washout to transitional phase and APHE interpreted with subtraction images. [ABSTRACT FROM AUTHOR]

Metal implants not only deteriorate image quality, but also increase radiation exposure. The purpose of this study was to evaluate the effect of metal hip prosthesis on absorbed radiation dose and assess the efficacy of organ dose modulation (ODM) and metal artifact reduction (MAR) protocols on dose reduction. An anthropomorphic phantom was scanned with and without bilateral metal hip prostheses, and surface and deep level radiation doses were measured at the abdomen and pelvis. Finally, the absorbed radiation doses at pelvic and abdominal cavities in the reference, ODM, and two MAR scans (Gemstone spectral imaging, GE) were compared. The Mann Whitney-U test and Kruskal-Wallis test were performed to compare the volume CT dose index (CTDIvol) and mean absorbed radiation doses. Unilateral and bilateral metal hip prostheses increased CTDIVOL by 14.4% and 30.5%, respectively. MAR protocols decreased absorbed radiation doses in the pelvis. MAR showed the most significant dose reduction in the deep pelvic cavity followed by ODM. However, MAR protocols increased absorbed radiation doses in the upper abdomen. ODM significantly reduced absorbed radiation in the pelvis and abdomen. In conclusion, metal hip implants increased radiation doses in abdominopelvic CT scans. MAR and ODM techniques reduced absorbed radiation dose in abdominopelvic CT scans with metal hip prostheses. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the impact of mesorectal fat area (MFA) on oncologic outcomes in patients with mid-to-lower rectal cancer who received curative-intent surgery.Methods: Patients with mid-to-lower rectal cancer who underwent preoperative abdominopelvic computed tomography (CT) and curative-intent surgery in 2011 were divided into two groups by tumour recurrence (group A) or no recurrence (group B) during a 5-year follow-up. Visceral fat area (VFA) and MFA were measured on preoperative CT and cutoff values were calculated using the Youden index. Univariate and multivariate regression analyses including BMI, VFA, and MFA were performed to investigate meaningful prognostic biomarkers. The Kaplan-Meier method with log-rank testing was used to validate prognostic biomarkers.Results: Group A contained 42 patients and group B had 155 patients. Cutoff values were 25 kg/m2 for BMI, 130 cm2 for VFA, and 10 cm2 for MFA using the Youden index. On multivariate Cox regression analysis, MFA (odds ratio [OR] = 0.426, p = 0.010), TNM stage (p = 0.027), and perioperative complication grade (p = 0.028) were significantly different between groups. BMI and VFA did not show significant differences. By the Kaplan-Meier method with log-rank testing, disease-free survival (DFS) was significantly longer in patients with MFA ≥10 cm2 compared to patients with MFA <10 cm2 (p = 0.021), with no significant difference in overall survival (OS).Conclusions: MFA was an independent biomarker for predicting DFS in patients who underwent curative-intent surgery for mid-to-lower rectal cancer.Key Points: • Mesorectal fat area is associated with the prognosis of rectal cancer patients. • Mesorectal fat area can be calculated easily in pre-operative CT scan. • Predicting prognosis of the cancer patient before operation is important. [ABSTRACT FROM AUTHOR]

Background: The arms-down position increases computed tomography (CT) radiation dose. Iterative reconstruction (IR) could enhance image quality without increasing radiation dose in patients with arms-down position. Aim: To investigate the feasibility of reduced-dose CT with IR for patients with inappropriate arm positioning Methods: Twenty patients who underwent two-phase abdominopelvic CT including standard-dose and reduced-dose CT (performed with 80% of the radiation dose of the standard protocol) with their arms positioned in the abdominal area were included in this study. Reduced-dose CT images were reconstructed using filtered back projection (FBP), hybrid IR, and iterative model reconstruction (IMR). These images were compared with standard-dose CT images reconstructed with FBP. Objective image noise in the liver and subcutaneous fat was measured by standard deviation for the quantitative analysis. Then, two radiologists qualitatively assessed beam hardening artifacts, artificial texture, noise, sharpness, and overall image quality in consensus. Results: Reduced-dose CT with all IR levels had lower objective image noise compared to standard-dose CT with FBP reconstruction (P < 0.05). Quantitatively measured beam hardening artifacts were similar in reduced-dose CT with iDose levels 5–6 and fewer with IMR compared to standard-dose CT. In the qualitative analysis, beam hardening artifacts and noise decreased as the IR levels increased. However, artificial texture was significantly aggravated with iDose 5–6 and IMR, and overall image quality significantly worsened with IMR. Conclusions: IR algorithms can reduce beam hardening artifacts in a reduced-dose CT setting in patients with arms-down position, and an intermediate level of hybrid IR allows radiologists to obtain the best image quality. Because the retrospective and single-center nature of our study limited the number of patients, multicenter prospective clinical studies are required to validate our results. [ABSTRACT FROM AUTHOR]

Objectives: To compare the ability of diffusion-weighted imaging (DWI) parameters acquired from three different models for the diagnosis of hepatic fibrosis (HF).Methods: Ninety-five patients underwent DWI using nine b values at 3 T magnetic resonance. The hepatic apparent diffusion coefficient (ADC) from a mono-exponential model, the true diffusion coefficient (D t ), pseudo-diffusion coefficient (D p ) and perfusion fraction (f) from a biexponential model, and the distributed diffusion coefficient (DDC) and intravoxel heterogeneity index (α) from a stretched exponential model were compared with the pathological HF stage. For the stretched exponential model, parameters were also obtained using a dataset of six b values (DDC#, α#). The diagnostic performances of the parameters for HF staging were evaluated with Obuchowski measures and receiver operating characteristics (ROC) analysis. The measurement variability of DWI parameters was evaluated using the coefficient of variation (CoV).Results: Diagnostic accuracy for HF staging was highest for DDC# (Obuchowski measures, 0.770 ± 0.03), and it was significantly higher than that of ADC (0.597 ± 0.05, p < 0.001), D t (0.575 ± 0.05, p < 0.001) and f (0.669 ± 0.04, p = 0.035). The parameters from stretched exponential DWI and D p showed higher areas under the ROC curve (AUCs) for determining significant fibrosis (≥F2) and cirrhosis (F = 4) than other parameters. However, D p showed significantly higher measurement variability (CoV, 74.6%) than DDC# (16.1%, p < 0.001) and α# (15.1%, p < 0.001).Conclusions: Stretched exponential DWI is a promising method for HF staging with good diagnostic performance and fewer b-value acquisitions, allowing shorter acquisition time.Key Points: • Stretched exponential DWI provides a precise and accurate model for HF staging. • Stretched exponential DWI parameters are more reliable than D p from bi-exponential DWI model • Acquisition of six b values is sufficient to obtain accurate DDC and α. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the optimal magnetic resonance (MR) imaging protocol in pregnant women suspected of having acute appendicitis.Materials and Methods: One hundred and forty-six pregnant women with suspected appendicitis were included. MR images were reviewed by two radiologists in three separate sessions. In session 1, only axial single-shot turbo spin echo (SSH-TSE) T2-weighted images (WI) were included with other routine sequences. In sessions 2 and 3, coronal and sagittal T2WI were sequentially added. The visibility of the appendix and diagnostic confidence of appendicitis were evaluated in each session using a 5-point grading scale. If diseases other than appendicitis were suspected, specific diagnosis with a 5-point confidence scale was recorded. Diagnostic performance for appendicitis and other diseases were evaluated.Results: Twenty-five patients (17.1%) were diagnosed with appendicitis. Among the patients with normal appendix, 28 were diagnosed with other disease. Diagnostic performance including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve values for diagnosing appendicitis and other diseases showed no significant difference among sets for both reviewers (p>0.05).Conclusion: Diagnostic performance of MR in pregnant patients with suspected appendicitis can be preserved with omission of sagittal or both coronal and sagittal SSH-T2WI.Key Points: • Diagnostic performance of appendicitis is preserved with omission of sagittal/coronal T2WIs. • Diagnosis of other disease may be sufficient with axial T2WIs only. • Careful serial omission of sagittal and coronal T2WIs can be considered. [ABSTRACT FROM AUTHOR]

Objective: To investigate the feasibility of dual-energy CT for contrast media (CM) reduction in the diagnosis of hypervascular and hypovascular focal liver lesions (FLL). Subjects and Methods: The Institutional Animal Care and Use Committee approved this study. VX2 tumors were implanted in two different segments of the liver in 13 rabbits. After 2 weeks, two phase contrast enhanced CT scans including the arterial phase (AP) and portal-venous phase (PVP) were performed three times with 24-hour intervals with three different concentrations of iodine, 300 (I300), 150 (I150) and 75 mg I/mL (I75). The mean HU and standard deviation (SD) were measured in the liver, the hypervascular portion of the VX2 tumor which represented hypervascular tumors, and the central necrotic area of the VX2 tumor which represented hypovascular tumors in 140kVp images with I300 as a reference standard and in monoenergetic images (between 40keV and 140keV) with I150 and I75. The contrast-to-noise ratio (CNR) for FLLs and the ratio of the CNRs (CNRratio) between monoenergetic image sets with I150 and I75, and the reference standard were calculated. Results: For hypervascular lesions, the CNRratio was not statistically different from 1.0 between 40keV and 70keV images with I150, whereas the CNRratio was significantly lower than 1.0 in all keV images with I75. For hypovascular lesions, the CNRratio was similar to or higher than 1.0 between 40keV and 80keV with I150 and between 40keV and 70keV with I75. Conclusions: With dual-energy CT, the total amount of CM might be halved in the diagnosis of hypervascular FLLs and reduced to one-fourth in the diagnosis of hypovascular FLLs, while still preserving CNRs. [ABSTRACT FROM AUTHOR]

Objective: To assess the added value of arterial enhancement fraction (AEF) color maps for the differentiation of small metastases from hepatic benign lesions. Subjects and Methods: We retrospectively analyzed 46 patients with colorectal cancer who underwent multiphasic liver CT imaging and had low-attenuating liver lesions smaller than 3 cm (123 total lesions; metastasis: benign = 32:91). AEF color maps of the liver were created from multiphasic liver CT images using dedicated software. Two radiologists independently reviewed multiphasic CT image sets alone and in combination with image sets with AEF color maps using a five-point scale. The additional diagnostic value of the color maps was assessed by means of receiver-operating characteristic (ROC) analysis. Results: The area under the ROC curve (Az) increased when multiphasic CT images were combined with AEF color map analysis as compared with evaluation based only on multiphasic CT images (from 0.698 to 0.897 for reader 1, and from 0.825 to 0.945 for reader 2; P < 0.001 and 0.002, respectively). The increase Az was especially significant for lesions less than 1 cm (from 0.702 to 0.888 for reader 1, and from 0.768 to 0.958 for reader 2; P = 0.001 and P = 0.001, respectively). The mean AEF of tumor-adjacent parenchyma (35.07 ± 27.2) was significantly higher than that of tumor-free liver parenchyma (27.3 ± 20.6) (P = 0.04). Conclusions: AEF color mapping can improve the diagnostic performance for small hepatic metastases from colorectal cancer and may allow for the elimination of additional examinations. [ABSTRACT FROM AUTHOR]

Purpose/Aim of the study. To assess the feasibility of krypton-enhanced ventilation CT using dual energy (DE) technique for various krypton concentrations and to determine the appropriate krypton concentration for DE ventilation CT through an animal study. Materials and Methods. Baseline DECT was first performed on seven New Zealand white rabbits. The animals were then ventilated using 20%, 30%, 40%, 50%, 60%, to 70% krypton concentration, and DECT was performed for each concentration. Krypton extraction was performed through a workstation, and results were displayed on a color map. Overlay Hounsfield unit (HU) values were obtained by two observers in consensus readings. A linear mixed model was used to correlate overlay HU values and krypton concentrations. Visual assessments of the homogeneity of krypton maps were also performed. Results. Mean overlay HU values according to krypton concentration were as follows; 20% krypton, 1.68 ± 5.15; 30% krypton, 3.73 ± 5.93; 40% krypton, 6.92 ± 5.51; 50% krypton, 10.88 ± 5.17; 60% krypton, 14.54 ± 4.23; and 70% krypton, 18.79 ± 3.63. We observed a significant correlation between overlay HU values on krypton maps and krypton concentrations ( P < .001). For the krypton color maps, all observers determined universal enhancement on the 70% krypton map for all animals. Conclusion. It is feasible to evaluate lung ventilation function using DECT with a krypton concentration of at least 70%. [ABSTRACT FROM AUTHOR]

This study was carried out to demonstrate whether the radiation dose for patients in arms-down position can be reduced without affecting the diagnosis on abdominal computed tomography (CT). The patients were divided into two groups: group A, which included patients with arms-down position using dose modulation on, and group B, which included patients with arms-down position using dose modulation turned off. Quantitative evaluation was compared using Hounsfield units, standard deviation, and signal-to-noise ratio of the four regions. The qualitative evaluation was assessed for overall image quality, subjective image noise, and beam hardening artifacts. Dose evaluation for CT dose index (CTDI) and dose length product (DLP) was compared by comparing the CT images with dose modulation turned on and off. In the quantitative and qualitative evaluation, there was no statistically significant difference between groups A and B (p > 0.05). In the dose evaluation, the CT images with dose modulation turned off had significantly lower CTDI and DLP than the CT images with dose modulation turned on (p < 0.05). Our results suggest that, for the GE Revolution EVO CT scanner, turning off dose modulation and increasing the tube voltage can reduce the radiation dose for patients with the arms-down position without affecting the diagnosis. This study did not consider the change of tube potential according to the use of dose modulation, and we plan to conduct additional research in the future. [ABSTRACT FROM AUTHOR]

As a result of recent developments in imaging modalities and wide spread routine medical checkups and screening, more incidental liver lesions are found frequently on US these days. When incidental liver lesions are found on US, physicians have to make a decision whether to just follow up or to undergo additional imaging studies for lesion characterization. In order to choose the next appropriate imaging modality, the diagnostic accuracy of each imaging study needs to be considered. Therefore, we tried to compare the accuracy of contrast-enhanced multidetector CT (MDCT) and Gd-EOB-DTPA-enhanced MRI for characterization of incidental liver masses. We included 127 incidentally found focal liver lesions (94 benign and 33 malignant) from 80 patients (M∶F = 45∶35) without primary extrahepatic malignancy or chronic liver disease. Two radiologists independently reviewed Gd-EOB-DTPA-enhanced MRI and MDCT. The proportion of confident interpretations for differentiation of benign and malignant lesions and for the specific diagnosis of diseases were compared. The proportion of confident interpretations for the differentiation of benign and malignant lesions was significantly higher with EOB-MRI(94.5%–97.6%) than with MDCT (74.0%–92.9%). In terms of specific diagnosis, sensitivity and accuracy were significantly higher with EOB-MRI than with MDCT for the diagnosis of focal nodular hyperplasia (FNH) and focal eosinophilic infiltration. The diagnoses of the remaining diseases were comparable between EOB-MRI and MDCT. Hence, our results suggested that Gd-EOB-MRI may provide a higher proportion of confident interpretations than MDCT, especially for the diagnosis of incidentally found FNH and focal eosinophilic infiltration. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To define diagnostic criteria for differentiating malignant ampullary carcinoma from benign ampullary obstruction on MR imaging. Materials and methods: Nineteen patients with ampullary carcinoma and 22 patients with benign ampullary obstruction were enrolled. At the first session, two radiologists independently evaluated specific imaging findings, and then reached consensus decisions. At the second session, another two radiologists, who were informed about useful differentiation criteria based on the results from the first session, reviewed images and determined the causes of ampullary obstruction. Sensitivity and specificity were calculated for each interpretation session, and the Cohen κ statistic was used to evaluate interobserver agreement. Results: Findings of the presence of an ampullary mass (P <0.001), papillary bulging (P <0.001), irregular (P =0.021) and asymmetric (P <0.001) common bile duct (CBD) narrowing, and proportional biliary dilatation (P <0.001) were more commonly seen in patients with an ampullary carcinoma. The sensitivity and specificity of the first session were 84.2% and 86.4% after consensus. The sensitivity increased to 100% for both the readers at the second session, while the specificity decreased to 63.6% and 59.1%, respectively. Conclusions: Identification of an ampullary mass, papillary bulging, irregular and asymmetric narrowing of the CBD, or proportional biliary dilatation may improve the diagnosis of ampullary carcinoma in patients with ampullary obstruction. [Copyright &y& Elsevier]

Objectives: To compare the diagnostic performance of the stretched exponential model to those of other DWI models and transient elastography (TE) and to evaluate the influence of confounding factors on the staging of liver fibrosis. Methods: This retrospective study included 78 consecutive patients who underwent both DWI and TE. The distributed diffusion coefficient (DDC) and intravoxel heterogeneity index (α) from the stretched exponential model, apparent diffusion coefficient (ADC), perfusion fraction (f), pseudodiffusion coefficient (Dp), true diffusion coefficient (Dt), and TE were obtained. Associations between imaging parameters and pathological fibrosis, inflammation, and steatosis were evaluated using Spearman's correlation and multiple regression analysis. Diagnostic accuracy of parameters for fibrosis staging was assessed via the Obuchowski measures. Results: DDC was the only parameter to differ between F0–1 and F2–3 (p < 0.001) and between F2–3 and F4 (p = 0.013). DDC showed significant correlation with fibrosis (p < 0.001) and inflammation (p = 0.001), but not with steatosis (p = 0.619), and was independently associated with only fibrosis in multiple regression analysis (β = − 0.114, p < 0.001). ADC, Dp, and Dt showed a significant correlation with steatosis (ps ≤ 0.038). DDC showed the highest diagnostic performance for liver fibrosis (0.717; 95% confidence interval, 0.653–0.765) followed by TE (0.681, 0.623–0.733) without a significant difference between DDC and TE (p > 0.999). Conclusions: DDC from the stretched exponential model is the most accurate DWI parameter with no confounding effect from steatosis and with overall similar diagnostic performance to TE. Key Points: • The distributed diffusion coefficient (DDC) from the stretched exponential model is the most accurate DWI parameter for staging liver fibrosis. • DDC and transient elastography have similar good diagnostic performance for evaluating liver fibrosis. • The stretched exponential DWI model has no confounding effect by steatosis, unlike other DWI models. [ABSTRACT FROM AUTHOR]

Background: An aberrant left hepatic artery is frequently encountered during upper gastrointestinal surgery, and researchers have yet to propose optimal strategies with which to address this arterial variation. The objective of this study was to determine whether the areas perfused by an aberrant left hepatic artery can be visualized in real-time using near-infrared fluorescence imaging with indocyanine green. Methods: Patients with gastric adenocarcinoma who underwent minimally invasive radical gastrectomy from May 2018 to August 2019 were enrolled and retrospectively analyzed at a single-center. Patients with an aberrant left hepatic artery and normal preoperative liver function were examined. After the clamping of an aberrant left hepatic artery, indocyanine green was administered via a peripheral intravenous route during surgery. Fluorescence at the liver was visualized under near-infrared fluorescence imaging. Results: In 31 patients with aberrant left hepatic arteries, near-infrared fluorescence imaging was used without adverse events associated with indocyanine green. Six (19%) patients were reported to have an aberrant left hepatic artery upon preoperative CT imaging, while all other instances were detected during surgery. Fluorescence excitation on the liver was, on average, visible after 43 s (range, 25–65). Fluorescence across the entire surface of the liver was noted in 20 (65%) patients in whom the aberrant left hepatic artery could be ligated. Aberrant left hepatic arteries were safely preserved in 10 (32%) patients who showed areas of no or partial fluorescence excitation. Guided by near-infrared fluorescence imaging, ligation of aberrant left hepatic arteries elicited no significant changes in postoperative liver function. Conclusion: Near-infrared fluorescence imaging facilitates the identification of aberrant left hepatic arterial territories, guiding decisions on the preservation or ligation of this arterial variation. [ABSTRACT FROM AUTHOR]

This retrospective study investigated whether repetitive exposure to intravenous iodinated contrast media (ICM) affects long-term renal function in patients who undergo curative surgery for early gastric cancer (EGC) collected from the Korean Health Insurance and Review Assessment (HIRA) database. Patients diagnosed with gastric cancer between January 2010 and December 2013 underwent regular computed tomography (CT) scans to monitor for extragastric recurrence. Patients who already had chronic kidney disease (CKD) before cancer diagnosis or had undergone chemotherapy or repeated surgery were excluded. A nested case–control study design was chosen to analyze the effect of repetitive ICM exposure to long-term renal function by comparing patients who developed CKD 2 years after cancer diagnosis and patients who did not. Among 59,971 patients collected according to inclusion and exclusion criteria, 1021 were diagnosed with CKD 2 years after cancer diagnosis. Using 1:5 matching after adjusting for age, sex and date of cancer diagnosis, 5097 control patients were matched to 1021 CKD patients. Conditional logistic regression showed that the number of CTs taken using ICM slightly increased the odds of CKD (odds ratio, 1.080; 95% confidence interval (CI): 1.059, 1.100; P < 0.0001). Thus, the administration of ICM might contribute to chronic renal function impairment. [ABSTRACT FROM AUTHOR]

Objective: To compare the stretched exponential model of diffusion-weighted imaging (DWI) with monoexponential and biexponential models in terms of the ability to characterize focal liver lesions (FLLs).Methods: This retrospective study included 180 patients with FLLs who underwent magnetic resonance imaging including DWI with nine b values at 3.0 T. The distributed diffusion coefficient (DDC) and intravoxel diffusion heterogeneity index (α) from a stretched exponential model; true diffusion coefficient (Dt), pseudo-diffusion coefficient (Dp), and perfusion fraction (f) from a biexponential model; and apparent diffusion coefficient (ADC) were calculated for each lesion. Diagnostic performances of the parameters were assessed through receiver operating characteristic (ROC) analysis. For 20 patients with treated hepatic metastases, the correlation between the DWI parameters and the percentage of tumor necrosis on pathology was evaluated using the Spearman correlation coefficient.Results: DDC had the highest area under the ROC curve (AUC, 0.905) for differentiating malignant from benign lesions, followed by Dt (0.903) and ADC (0.866), without significant differences among them (DDC vs. Dt, p = 0.946; DDC vs. ADC, p = 0.157). For distinguishing hypovascular from hypervascular lesions, and hepatocellular carcinoma from metastasis, f  had a significantly higher AUC than the other DWI parameters (p < 0.05). The α had the strongest correlation with the degree of tumor necrosis (ρ = 0.655, p = 0.002).Conclusion: The DDC from stretched exponential model of DWI demonstrated excellent diagnostic performance for differentiating malignant from benign FLLs. The α is promising for evaluating the degree of necrosis in treated metastases.Key Points: • The stretched exponential DWI model is valuable for characterizing focal liver lesions. • The DDC from stretched exponential model shows excellent performance for differentiating malignant from benign focal liver lesions. • The α from stretched exponential model is promising for evaluating the degree of necrosis in hepatic metastases after chemotherapy. [ABSTRACT FROM AUTHOR]

Background & Aims: Fatty change is commonly observed in hepatocellular carcinoma (HCC); however, the characteristics of steatotic and steatohepatitic HCCs are not well understood. Methods: This retrospective study included patients with HCCs who underwent resection between January 2014 and December 2019 to evaluate clinicopathological and magnetic resonance imaging features. Tumours were categorized as magnetic resonance imaging‐steatotic, pathology‐steatotic and steatohepatitic HCCs and were defined as HCCs with ≥50% steatosis on in‐and‐oppose phase images, ≥34% tumour cells with lipid droplets and ≥50% tumour areas with steatohepatitic features on light microscopy respectively. Results: Of 465 HCCs, 38 (8%), 23 (5%) and 15 (3%) were diagnosed as magnetic resonance imaging‐steatotic, pathology‐steatotic and steatohepatitic HCCs respectively. These HCC variants were less likely to be associated with hepatitis B virus infections than with type 2 diabetes mellitus, metabolic syndrome, non‐tumour liver steatosis and steatohepatitis. Moreover, microvascular invasion was less likely to be associated with them than either tumour size or differentiation. Type 2 diabetes and non‐tumour steatosis were independent risk factors for magnetic resonance imaging‐steatotic HCCs. Pathology‐steatotic HCCs and steatohepatitic HCCs were significantly associated with magnetic resonance imaging‐steatotic HCCs. A targetoid appearance in the transitional or hepatobiliary phase was also more prevalent in steatohepatitic‐HCCs than in non–steatohepatitic‐HCCs. When magnetic resonance imaging‐steatotic HCCs were combined with one or more ancillary features, the sensitivity and specificity were 60% and 97% respectively. Conclusion: Underlying fatty liver disease and metabolic syndrome are strongly associated with both steatotic and steatohepatitic HCCs. Clinicoradiological characteristics help identify steatohepatitic HCC with high specificity. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis. [ABSTRACT FROM AUTHOR]

Purpose This study aims to propose a physics-based method of reducing beam-hardening artifacts induced by high-attenuation materials such as metal stents or other metallic implants. Methods The proposed approach consists of deriving a sinogram inconsistency formula representing the energy dependence of the attenuation coefficient of high-attenuation materials. This inconsistency formula more accurately represents the inconsistencies of the sinogram than that of a previously reported formula (called the MAC- BC method). This is achieved by considering the properties of the high-attenuation materials, which include the materials' shapes and locations and their effects on the incident X-ray spectrum, including their attenuation coefficients. Results Numerical simulation and phantom experiment demonstrate that the modeling error of MAC- BC method are nearly completely removed by means of the proposed method. Conclusion The proposed method reduces beam-hardening artifacts arising from high-attenuation materials by relaxing the assumptions of the MAC- BC method. In doing so, it outperforms the original MAC- BC method. Further research is required to address other potential sources of metal artifacts, such as photon starvation, scattering, and noise. [ABSTRACT FROM AUTHOR]

Objectives: We aimed to investigate the optimal radiologic method to determine Milan criteria (MC) for the prediction of recurrence in patients who underwent locoregional treatment (LRT) for hepatocellular carcinoma (HCC) and subsequent liver transplantation (LT). Methods: This retrospective study included 121 HCC patients who underwent LRT and had both liver dynamic CT and MRI. They were classified with MC using four cross combinations of two imaging modalities (CT and MRI) and two diagnostic criteria (modified Response Evaluation Criteria in Solid Tumors [mRECIST] and Liver Imaging Reporting and Data System treatment response algorithm [LI-RADS TRA]). Competing risk regression was performed to analyze the time to recurrence after LT. The predictive abilities of the four methods for recurrence were evaluated using the time-dependent area under the curve (AUC). Results: Competing risk regression analyses found that beyond MC determined by MRI with mRECIST was independently associated with recurrence (hazard ratio, 6.926; p = 0.001). With mRECIST, MRI showed significantly higher AUCs than CT at 3 years and 5 years after LT (0.597 vs. 0.756, p = 0.012 at 3 years; and 0.588 vs. 0.733, p = 0.024 at 5 years). Using the pathologic reference standard, MRI with LI-RADS TRA showed higher sensitivity (61.5%) than CT with LI-RADS TRA (30.8%, p < 0.001) or MRI with mRECIST (38.5%, p < 0.001). Conclusions: MRI with mRECIST was the optimal radiologic method to determine MC for the prediction of post-LT recurrence in HCC patients with prior LRT. Key Points: • MRI with modified RECIST (mRECIST) is the optimal preoperative method to determine Milan criteria for the prediction of post-transplant HCC recurrence in patients with prior locoregional treatment. • With mRECIST, MRI was better than CT for the prediction of post-transplant recurrence. [ABSTRACT FROM AUTHOR]

Objectives: We performed a meta-analysis to determine the probability of hepatocellular carcinoma (HCC) and non-HCC malignancies in Liver Imaging Reporting and Data System (LI-RADS) category M (LR-M) observations and the frequency of defined LR-M imaging features on MRI using LI-RADS v2018. Methods: We searched the MEDLINE and EMBASE databases to identify studies published from 1 January 2018 to 16 March 2021 reporting the probability of category LR-M in HCC and non-HCC malignancies on MRI. The pooled percentages of HCC and non-HCC malignancies in the LR-M observations were evaluated. Meta-regression analysis was performed to identify factors for study heterogeneity. The frequencies of defined LR-M imaging features were also calculated. Risk of bias and concerns regarding applicability were evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Results: We identified 18 studies reporting the diagnostic performance of the LR-M category (3,812 observations in 3,615 patients), with nine studies reporting the frequencies of LR-M imaging features. The pooled percentages of HCC and non-HCC malignancies in the LR-M observations were 29% (95% confidence interval [CI], 21–38%) and 67% (95%CI, 57–77%), respectively. The study type and inclusion of benign lesions were significant factors for study heterogeneity. Of the 10 LR-M imaging features, rim arterial phase hyperenhancement (APHE) showed the highest frequency in non-HCC malignancies (68%; 95%CI, 61–75%). Conclusions: The LR-M category was commonly used to characterize non-HCC malignancies, but also included 29% of HCC. The frequencies of the different LR-M imaging features were variable, with rim APHE showing the highest frequency in non-HCC malignancies. Key Points: • In the LR-M category using LI-RADS v2018 for MRI, the pooled percentage of malignancies in general was 96%, with 29% HCC and 67% non-HCC malignancies, while the remaining 4% was benign entity. • The study type and inclusion of benign lesions were significant factors contributing to substantial heterogeneity among included studies. • The frequencies of the different LR-M imaging features were variable, with rim APHE showing the highest frequency in non-HCC malignancies. [ABSTRACT FROM AUTHOR]

In this open‐label, single‐dose, parallel‐group study, we compared the pharmacokinetic profile and safety of lobeglitazone, a thiazolidinedione acting as an agonist for peroxisome proliferator‐activated receptors, in patients with hepatic impairment (HI) and healthy matched controls for age, sex, and body weight. After a single oral dose of lobeglitazone (0.5 mg), the lobeglitazone (parent drug) and M7 (major metabolite) plasma concentrations and pharmacokinetic parameters were analyzed and compared between the HI patient groups and healthy matched control groups. The geometric mean ratio (GMR; 90% confidence interval [CI]) for maximum concentration (Cmax) and area under the plasma concentration–time curve from time 0 extrapolated to infinity (AUCinf) of lobeglitazone was 1.06 (0.90‐1.24) and 1.07 (0.82‐1.40), respectively, for mild HI vs control A. The GMR (90%CI) of Cmax and AUCinf was 0.70 (0.56‐0.88) and 1.00 (0.72‐1.37), respectively, for moderate HI vs control B. For M7, the GMR (90%CI) of Cmax and AUCinf was 1.09 (0.75‐1.57) and 1.18 (0.71‐1.97), respectively, for mild HI vs control A and 1.50 (0.95‐2.38) and 1.79 (1.06‐3.04), respectively, for moderate HI vs control B. Notable adverse events or tolerability issues were not observed. Lobeglitazone may be safely used in patients with mild or moderate HI without dose adjustment. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The aim of this study was to determine the registration error of an ultrasound (US) fusion imaging system during an ex vivo study and its clinical value for percutaneous radiofrequency ablation (pRFA) during an in vivo study. Materials and methods: An ex vivo study was performed using 4 bovine livers and 66 sonographically invisible lead pellets. Real-time CT-US fusion imaging was applied to assist the targeting of pellets with needles in each liver; the 4 sessions were performed by either an experienced radiologist (R1, 3 sessions) or an inexperienced resident (R2, 1 session). The distance between the pellet target and needle was measured. An in vivo study was retrospectively performed with 51 nodules (42 HCCs and 9 metastases; mean diameter, 16mm) of 37 patients. Fusion imaging was used to create a sufficient safety margin (>5mm) during pRFA in 24 nodules (group 1), accurately target 21 nodules obscured in the US images (group 2) and precisely identify 6 nodules surrounded by similar looking nodules (group 3). Image fusion was achieved using MR and CT images in 16 and 21 patients, respectively. The reablation rate, 1-year local recurrence rate and complications were assessed. Results: In the ex vivo study, the mean target–needle distances were 2.7mm±1.9mm (R1) and 3.1±3.3mm (R2) (p >0.05). In the in vivo study, the reablation rates in groups 1–3 were 13%, 19% and 0%, respectively. At 1year, the local recurrence rate was 11.8% (6/51). In our assessment of complications, one bile duct injury was observed. Conclusion: US fusion imaging system has an acceptable registration error and can be an efficacious tool for overcoming the major limitations of US-guided pRFA. [Copyright &y& Elsevier]

Glycyrrhizin (GL) is a direct inhibitor of HMGB1 which acts as an alarmin when excreted into the extracellular space. High-dose radiation in radiotherapy induces collateral damage to the normal tissue, which can be mitigated by GL inhibiting HMGB1. The purpose of this study was to assess changes in HMGB1 and pro-inflammatory cytokines and to evaluate the protective effect of GL after low-dose radiation exposure. BALB/c mice were irradiated with 0.1 Gy (n = 10) and 1 Gy (n = 10) with GL being administered to half of the mice (n = 5, respectively) before irradiation. Blood and spleen samples were harvested and assessed for oxidative stress, HMGB1, pro-inflammatory cytokines, and cell viability. HMGB1 and pro-inflammatory cytokines increased and cell viability decreased after irradiation in a dose-dependent manner. Oxidative stress also increased after irradiation, but did not differ between 0.1 Gy and 1 Gy. With the pretreatment of GL, oxidative stress, HMGB1, and all of the pro-inflammatory cytokines decreased while cell viability was preserved. Our findings indicate that even low-dose radiation can induce sterile inflammation by increasing serum HMGB1 and pro-inflammatory cytokines and that GL can ameliorate the sterile inflammatory process by inhibiting HMGB1 to preserve cell viability. [ABSTRACT FROM AUTHOR]

Post contrast-acute kidney injury (PC-AKI) is defined as the deterioration of renal function after administration of iodinated contrast media. HMGB1 is known to play an important role in the development of acute kidney injury. The purpose of this study was to investigate the association between HMGB1 and PC-AKI and the protective effect of glycyrrhizin, a direct inhibitor of HMGB1, in rats. Rats were divided into three groups: control, PC-AKI and PC-AKI with glycyrrhizin. Oxidative stress was measured with MDA levels and H2DCFDA fluorescence intensity. The mRNA expressions of pro-inflammatory cytokines (IL-1α, IL-1β, IL-6 and TNF-α) and kidney injury markers (KIM-1, NGAL and IL-18) were assessed using RT-PCR and ELISA in kidney tissue. In addition, the serum and intracellular protein levels of HMGB1were analyzed with the enzyme-linked immunosorbent assay (ELISA) and western blotting. Histologic changes were assessed with H&E staining using the transmission electron microscope (TEM). Moreover, serum creatinine (SCr), blood urea nitrogen (BUN) and lactate dehydrogenase (LDH) levels were assessed. Oxidative stress, pro-inflammatory cytokines, kidney injury markers and LDH were significantly higher in PC-AKI compared to the controls, but were lower in PC-AKI with glycyrrhizin. Intracellular and serum HMGB1 levels significantly increased after contrast media exposure, whereas they markedly decreased after glycyrrhizin pretreatment. SCr and BUN also decreased in PC-AKI with glycyrrhizin compared to PC-AKI. In PC-AKI, we could frequently observe tubular dilatation with H&E staining and cytoplasmic vacuoles on TEM, whereas these findings were attenuated in PC-AKI with glycyrrhizin. Our findings indicate that HMGB1 plays an important role in the development of PC-AKI and that glycyrrhizin has a protective effect against renal injury and dysfunction by inhibiting HMGB1 and reducing oxidative stress. [ABSTRACT FROM AUTHOR]

Objectives: This study aimed to assess the detection of hepatocellular carcinoma (HCC) utilizing subtraction AP (arterial phase) imaging only for T1 hyperintense observations compared with the detection of HCC on subtraction AP imaging that included T1 hyper-, iso-, and hypointense lesions on gadoxetate disodium–enhanced MRI. Materials and methods: This retrospective study included 234 patients (311 observations including 239 HCCs) at high risk for HCC who underwent gadoxetate disodium–enhanced MRI with subtraction AP imaging between 2015 and 2017. Arterial phase hyperenhancement (APHE) was divided into two subtypes: conventional APHE, where subtraction AP imaging is used to detect APHE only for T1 hyperintense observations; and modified APHE, where subtraction AP imaging is applied to T1 hyper-, iso-, and hypointense lesions. Two readers independently reviewed all observations and the per-observation diagnostic performances were compared using McNemar's test. Results: Modified nonrim APHE showed significantly higher sensitivity than conventional nonrim APHE (90.0% vs 82.8%; p < 0.001) for diagnosing HCC, without a significant difference in specificity (66.7% vs 68.1%; p > 0.999). The LR-5 category with modified nonrim APHE provided better sensitivity than the LR-5 with conventional nonrim APHE (70.3% vs 63.2%; p < 0.001), without a significant decrease in specificity (94.4% vs 95.8%; p > 0.999). Conclusion: Extended application of subtraction AP imaging for T1 hypo- or isointense observations on gadoxetate disodium–enhanced MRI can improve sensitivity in the diagnosis of HCC without a significant difference in specificity. Key Points: • Modified nonrim arterial phase hyperenhancement (APHE), extended application of subtraction arterial phase imaging for T1 hypo- or isointense observation, outperforms conventional nonrim APHE. • The LR-5 category with modified nonrim APHE provided better sensitivity in diagnosing HCC than the LR-5 with conventional APHE, without a significant decrease in specificity. [ABSTRACT FROM AUTHOR]

Background: Radiation dose reduction is a major concern in patients who undergo computed tomography (CT) to follow liver and renal abscess. Objectives: The purpose of this study is to investigate the feasibility of ultralow-dose CT with iterative reconstruction (IR) to follow patients with liver and renal abscess. Methods: This prospective study included 18 patients who underwent ultralow-dose CT with IR to follow abscesses (liver abscesses in 10 patients and renal abscesses in 8 patients; ULD group). The control group consisted of 14 patients who underwent follow-up standard-dose CT for liver abscesses during the same period. The objective image noise was evaluated by measuring standard deviation (SD) in the liver and subcutaneous fat to select a specific IR for qualitative analysis. Two radiologists independently evaluated subjective image quality, noise, and diagnostic confidence to evaluate abscess using a five-point Likert scale. Qualitative parameters were compared between the ULD and control groups with the Mann-Whitney U test. Results: The mean CT dose index volume and dose length product of standard-dose CT were 8.7 ± 1.8 mGy and 555.8 ± 142.8 mGy·cm, respectively. Mean dose reduction of ultralow-dose CT was 71.8% compared to standard-dose CT. After measuring SDs, iDose level 5, which showed similar SD to standard-dose CT in both the subcutaneous fat and liver (P = 0.076, and P = 0.124), was selected for qualitative analysis. Ultralow-dose CT showed slightly worse subjective image quality (P < 0.001 for reader 1, and P = 0.005 for reader 2) and noise (P = 0.004 for reader 1, and P = 0.001 for reader 2) than standard-dose CT. However, the diagnostic confidence of ultralow-dose CT for evaluating abscess was comparably excellent to standard-dose CT (P = 0.808 for reader 1, and P = 0.301 for reader 2). Conclusions: Ultralow-dose CT with IR can be used in the follow-up of liver and renal abscess with comparable diagnostic confidence. [ABSTRACT FROM AUTHOR]

Acute myocardial infarction (AMI) is lethal and causes myocardial necrosis via time-dependent ischemia due to prolonged occlusion of the infarct-related artery. No effective therapy or potential therapeutic targets can prevent myocardial ischemia/reperfusion (I/R) injury. Targeted temperature management (TTM) may reduce peri-infarct regions by inhibiting the extracellular release of high mobility group box-1 (HMGB1) as a primary mediator of the innate immune response. We used a rat left anterior descending (LAD) coronary artery ligation model to determine if TTM at 33°C and 36°C had similar myocardial protective effects. Rats were divided into sham, LAD I/R+37°C normothermia, LAD I/R+33°C TTM, and LAD I/R+36°C TTM groups (n = 5 per group). To verify the cardioprotective effect of TTM by specifically inhibiting HMGB1, rats were assigned to sham, LAD I/R, and LAD I/R after pre-treatment with glycyrrhizin (known as a pharmacological inhibitor of HMGB1) groups (n = 5 per group). Different target temperatures of 33°C and 36°C caused equivalent reductions in infarct volume after myocardial I/R, inhibited the extracellular release of HMGB1 from infarct tissue, and suppressed the expression of inflammatory cytokines from peri-infarct regions. TTM at 33°C and 36°C significantly attenuated the elevation of cardiac troponin, a sensitive and specific marker of heart muscle damage, after injury. Similarly, glycyrrhizin alleviated myocardial damage by suppressing the extracellular release of HMGB1. TTM at 33°C and 36°C had equivalent myocardial protective effects by similar inhibiting HMGB1 release against myocardial I/R injury. This is the first study to suggest that a target core temperature of 36°C is applicable for cardioprotection. [ABSTRACT FROM AUTHOR]

Objective: To investigate the feasibility of using amide proton transfer (APT) magnetic resonance imaging (MRI) in the liver and to evaluate its ability to characterize focal liver lesions (FLLs).Methods: A total of 203 patients with suspected FLLs who underwent APT imaging at 3T were included. APT imaging was obtained using a single-slice turbo spin-echo sequence to include FLLs through five breath-holds, and its acquisition time was approximately 1 min. APT signals in the background liver and FLL were measured with magnetization transfer ratio asymmetry (MTRasym) at 3.5 ppm. The technical success rate of APT imaging and the reasons for failure to obtain meaningful MTRasym values were assessed. The Mann Whitney U test was used to compare MTRasym values between different FLLs.Results: The technical success rate of APT imaging in the liver was 62.1% (126/203). The reasons for failure were a too large B0 inhomogeneity (n = 43), significant respiratory motion (n = 12), and these two factors together (n = 22), respectively. Among 59 FLLs with analyzable APT images, MTRasym values were compared between 27 patients with liver metastases and 23 patients with hepatocellular carcinomas (HCCs). The MTRasym values of metastases were significantly higher than those of HCC (0.13 ± 2.15% vs. - 1.41 ± 3.68%, p = 0.027).Conclusions: APT imaging could be an imaging biomarker for the differentiation of FLLs. However, further technical improvement is required before APT imaging can be clinically applied to liver MRI.Key Points: • Liver APT imaging was technically feasible, but with a relatively low success rate (62.1%). • Liver metastases showed higher APT values than hepatocellular carcinomas. [ABSTRACT FROM AUTHOR]

Despite the clinical and genetic significance of macrotrabecular-massive hepatocellular carcinoma (MTM-HCC), its characteristics on imaging have not been described. This study aimed to characterise MTM-HCC on gadoxetic acid-enhanced MRI and to evaluate the diagnostic accuracy and prognostic value of these imaging characteristics. We enrolled 3 independent cohorts from 2 tertiary care centres. The 3 cohorts consisted of a total of 476 patients who underwent gadoxetic acid-enhanced MRI and surgical resection for treatment-naïve single HCCs. Independent review of histopathology and MRI by 2 reviewers was performed for each cohort, and inter-reader agreement was evaluated. Based on the result of MRI review in the training cohort (cohort 1), we developed 2 diagnostic criteria for MTM-HCC and evaluated their prognostic significance. The diagnostic performance and prognostic significance were validated in 2 validation cohorts (cohorts 2 and 3). We developed 2 diagnostic MRI criteria (MRIC) for MTM-HCC: MRIC-1, ≥20% arterial phase hypovascular component; MRIC-2, ≥50% hypovascular component and 2 or more ancillary findings (intratumoural artery, arterial phase peritumoural enhancement, and non-smooth tumour margin). MRIC-1 showed high sensitivity and negative predictive value (88% and 95% in the training cohort, and 88% and 97% in the pooled validation cohorts, respectively), whereas MRIC-2 demonstrated moderate sensitivity and high specificity (47% and 94% in the training cohort, and 46% and 96% in the pooled validation cohorts, respectively). MRIC-2 was an independent poor prognostic factor for overall survival in both training and pooled validation cohorts. Using gadoxetic acid-enhanced MRI findings, including an arterial phase hypovascular component, we could stratify the probability of MTM-HCC and non-invasively obtain prognostic information. Macrotrabecular-massive hepatocellular carcinoma (MTM-HCC) is a histopathologic subtype of HCC characterised by aggressive biological behaviour and poor prognosis. We developed imaging criteria based on liver MRI that could be used for the non-invasive diagnosis of MTM-HCC. HCCs showing imaging findings of MTM-HCC were associated with poor outcomes after hepatic resection. • Macrotrabecular-massive hepatocellular carcinoma (MTM-HCC) is an aggressive subtype of HCC. • We revealed gadoxetic acid-enhanced MRI findings related to MTM-HCC. • Using MRI findings, we could non-invasively stratify the probability of MTM-HCC. • HCC without an arterial phase hypovascular component is highly unlikely to be MTM-HCC. • MRI findings of MTM-HCC could be a useful prognostic factor after surgical resection. [ABSTRACT FROM AUTHOR]

Objective: To investigate if size measurements of liver observations is more variable in the arterial phase as suggested by LI-RADS and assess potential higher instability in categorization in this particular phase. Secondarily, to assess inter- and intra-reader agreement for size across phases. Materials and methods: Patients with liver cirrhosis who underwent multi-arterial phase MRI between 2017 and 2018 were retrospectively selected. Three radiologists measured liver observations in each phase, independently, in a random order. Mean size between early and late arterial phases (AP), 2, 3 and 10 min delay and the number of observations crossing the LI-RADS size thresholds (10 and 20 mm) per phase were compared using McNemar's test. Reader agreement was evaluated using intraclass correlation coefficient (ICC) and bootstrap-based comparisons. Bonferroni's correction was applied to pairwise comparisons. Results: 94 observations (LR-3, LR-4, LR-5, and LR-M) were included. Mean sizes (mm) were late AP: 19.9 (95% CI 17.2, 24.2), 2 min delay: 19.8 (95% CI 17.1, 24.0), 3 min delay: 19.8 (95% CI 17.2, 24.0), 10 min delay: 20.2 (95% CI 17.5, 24.5) (p = 0.10–0.88). There was no difference between phases in number of observations that could have changed category due to variability in size (p = 0.546–1.000). Inter- and intra-reader agreement was excellent (ICC = 0.952–0.981). Conclusion: Measurements of focal liver observations were consistent across all post-contrast imaging phases and we found no higher instability in LI-RADS category in any particular phase. Inter- and intra-reader agreement for size was excellent for each phase. Based on these findings, size measurement could be allowed on any post-contrast phase, including the arterial phase, if deemed appropriate by the radiologist. [ABSTRACT FROM AUTHOR]

Background & aims: Contrast‐enhanced ultrasound (CEUS) Liver Imaging Reporting and Data System (LI‐RADS) is a comprehensive system for standardizing CEUS at high risk for hepatocellular carcinoma (HCC). We performed a meta‐analysis to determine the diagnostic performance of the CEUS LR‐5 for HCC and the pooled proportions of HCCs in each CEUS LI‐RADS category. Methods: We searched multiple databases for studies reporting the diagnostic accuracy of the CEUS LI‐RADS. Random‐effects model was used to determine summary estimates of the diagnostic performance of CEUS LR‐5 and the pooled proportions of HCCs in each CEUS LI‐RADS category. Risk of bias and concerns regarding applicability were evaluated with the Quality Assessment of Diagnostic Accuracy Studies‐2 tool. Results: Eleven studies were included in the final analysis, which consisted of 5535 observations with 3983 HCCs. The pooled per‐observation sensitivity and specificity of the CEUS LR‐5 for diagnosing HCC were 69% (95% confidence interval [CI], 64%–73%) and 92% (95% CI, 83%–96%) respectively. The pooled proportions of HCCs were 0% (95% CI, 0‐0%) for LR‐1, 1% (95% CI, 0%–4%) for CEUS LR‐2, 26% (95% CI, 14%–39%) for CEUS LR‐3, 77% (95% CI, 68%–86%) for CEUS LR‐4, 97% (95% CI, 95%–98%) for CEUS LR‐5, 57% (95% CI, 44%–69%) for CEUS LR‐M and 100% (95% CI, 93%–100%) for CEUS LR‐5V or TIV. Conclusions: The CEUS LR‐5 category showed moderate sensitivity and high specificity for diagnosing HCC. The proportion of HCCs was higher in the higher CEUS LI‐RADS categories. [ABSTRACT FROM AUTHOR]

Objectives: Contrast-induced acute kidney injury (CI-AKI) is one of the leading causes of new-onset renal failure in hospitalized patients. Statin has been evaluated for its protective effect against CI-AKI but rarely in patients receiving intravenous (IV) administrations of iodine-based contrast media for enhanced computed tomography (CT).Methods: In total, 12,371 patients who underwent contrast-enhanced abdominopelvic CT were retrospectively reviewed and stratified into statin users and statin nonusers. Subgroup analyses comparing high-intensity statins with low- to moderate-intensity statins were conducted within statin users and similar comparisons were performed within statin users stratified based on baseline eGFR.Results: Overall, CI-AKI events did not occur less in statin users compared with non-statin users (p = 0.342). Within statin users, CI-AKI events did not decrease in high-intensity statin users compared with low- to moderate-intensity statin users (p = 0.355). Moreover, no significant difference in CI-AKI events was found between high-intensity statin users and low- to moderate-intensity statin users even after stratifying the patients with baseline eGFR.Conclusions: Collectively, statin was not significantly associated with the risk of CI-AKI events in patients undergoing contrast-enhanced abdominopelvic CT and high-intensity statins did not show significant association with CI-AKI over low- to moderate-intensity statins in the subgroup analysis.Key Points: • Statin is not associated with risk of CI-AKI events in patients undergoing intravenous administration of contrast-enhanced CT. • CI-AKI incidence among high-intensity statin users was not significantly different from that of low- to moderate-intensity statin users. [ABSTRACT FROM AUTHOR]

[Display omitted] Although the use of iodinated contrast agents is sometimes unavoidable for accurate diagnosis, contrast-induced acute kidney injury (CI-AKI) is a possible complication of its administration. The pathogenesis of CI-AKI has not been fully elucidated, but oxidative stress is thought to be a major factor. Sestrin2 plays an important role in cellular and mitochondrial homeostasis by regulating oxidative stress. In this study, we aimed to investigate whether recombinant adenovirus containing sestrin2 (RS) can attenuate CI-AKI by reducing oxidative stress in a CI-AKI mice model. Our results showed that RS decreases oxidative stress, pro-inflammatory cytokines (TNF-α, IL-1α, IL-1β and IL-6) and apoptosis (Bax/Bcl2 and cleaved caspase-3) in the CI-AKI model. Additionally, RS alleviated mitochondrial damage, as evidenced by morphological changes, are restored ATP synthesis. Furthermore, RS administration resulted in a decrease in mitochondrial fission marker (Drp1) that was increased in the CI-AKI model, while the mitochondrial fusion marker (Mfn2) increased, indicating a restoration of mitochondrial dynamics. Decreased relative blood volume, as evaluated on computed tomography (CT), significantly increased compared to the CI-AKI group after RS administration. Finally, renal injury markers such as Kim-1, Ngal, IL-18 also decreased and kidney function was preserved with RS. These results suggested that RS can mitigate the deterioration of renal function in CI-AKI model. [ABSTRACT FROM AUTHOR]

Purpose: This paper proposes a sinogram‐consistency learning method to deal with beam hardening‐related artifacts in polychromatic computerized tomography (CT). The presence of highly attenuating materials in the scan field causes an inconsistent sinogram that does not match the range space of the Radon transform. When the mismatched data are entered into the range space during CT reconstruction, streaking and shading artifacts are generated owing to the inherent nature of the inverse Radon transform Methods: The proposed learning method aims to repair inconsistent sinogram by removing the primary metal‐induced beam hardening factors along the metal trace in the sinogram. Taking account of the fundamental difficulty in obtaining sufficient training data in a medical environment, the learning method is designed to use simulated training data and a patient's implant type‐specific learning model is used to simplify the learning process. Results: The feasibility of the proposed method is investigated using a dataset, consisting of real CT scans of pelvises containing simulated hip prostheses. The anatomical areas in training and test data are different, in order to demonstrate that the proposed method extracts the beam hardening features, selectively. The results show that our method successfully corrects sinogram inconsistency by extracting beam hardening sources by means of deep learning. Conclusion: This paper proposed a deep learning method of sinogram correction for beam hardening reduction in CT for the first time. Conventional methods for beam hardening reduction are based on regularizations, and have the fundamental drawback of being not easily able to use manifold CT images, while a deep learning approach has the potential to do so. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the diagnostic value of the T1 bright appendix sign for the diagnosis of acute appendicitis in pregnant women.Material and Methods: This retrospective study included 125 pregnant women with suspected appendicitis who underwent magnetic resonance (MR) imaging. The T1 bright appendix sign was defined as a high intensity signal filling more than half length of the appendix on T1-weighted imaging. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the T1 bright appendix sign for normal appendix identification were calculated in all patients and in those with borderline-sized appendices (6-7 mm).Results: The T1 bright appendix sign was seen in 51% of patients with normal appendices, but only in 4.5% of patients with acute appendicitis. The overall sensitivity, specificity, PPV, and NPV of the T1 bright appendix sign for normal appendix diagnosis were 44.9%, 95.5%, 97.6%, and 30.0%, respectively. All four patients with borderline sized appendix with appendicitis showed negative T1 bright appendix sign.Conclusion: The T1 bright appendix sign is a specific finding for the diagnosis of a normal appendix in pregnant women with suspected acute appendicitis.Key Points: • Magnetic resonance imaging is increasingly used in emergency settings. • Acute appendicitis is the most common cause of acute abdomen. • Magnetic resonance imaging is widely used in pregnant population. • T1 bright appendix sign can be a specific sign representing normal appendix. [ABSTRACT FROM AUTHOR]

Objectives: To assess whether gadoxetic acid-enhanced MRI could be used as a prognostic factor for intrahepatic mass-forming cholangiocarcinomas (IMCCs).Methods: Forty-one patients with pathologically proven IMCCs who underwent preoperative gadoxetic acid-enhanced MRI were included. The signal intensity of the IMCCs on hepatobiliary phase (HBP) MRI was qualitatively analyzed by two radiologists, and categorized into intermediate or hypointense groups. Analysis of clinicopathological prognostic factors and correlations of imaging and histology were also performed. Survival time and time to recurrence (TTR) were analyzed.Results: Of the 41 IMCCs, 23 were in the intermediate group and 18 were in the hypointense group on HBP MRI. IMCCs in the intermediate group were associated with shorter survival time (P = 0.048) and TTR (P = 0.002) than the IMCCs of the hypointense group. Only the intermediate group on HBP MRI had a significantly shorter TTR on multivariate analysis (P = 0.012). The IMCCs of the intermediate group showed a tendency for more abundant tumour fibrous stroma than those of the hypointense group (P = 0.027).Conclusions: The enhancement of IMCCs on HBP gadoxetic acid-enhanced MRI appears to correlate with tumour aggressiveness and outcomes due to the tumour fibrous stromal component. Thus, HBP images could be a useful prognostic factor for IMCCs after surgery.Key Points: • The enhancement of IMCCs on HBP correlates with the tumour fibrous stroma. • The enhancement of IMCCs on HBP MRI appears to correlate with prognosis. • Gadoxetic acid-enhanced MRI is helpful for predicting prognosis of IMCCs after surgery. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the appropriateness of follow-up with only non-enhanced CT (NECT) in patients with gastrointestinal cancer. Subjects and Methods: This retrospective study included 323 patients with colorectal and gastric cancer who underwent two consecutive CT examinations (CT1 and CT2), including non-contrast and portal venous phase CT images, with an interval of 1 year. Patients were divided into 2 groups: Group A included patients with no hepatic metastasis on CT1 and with or without newly developed metastasis on CT2 to evaluate the diagnostic performance of NECT for detecting newly developed hepatic metastasis; Group B included patients with known hepatic metastasis both on CT1 and CT2 to evaluate the accuracy of NECT for the assessment of hepatic metastasis based on RECIST criteria (version 1.1). Contrast-enhanced CT (CECT) images were considered as reference standards. Results: Group A included 172 patients (M:F = 107:65; mean age, 62.6 years). Among them, 57 patients had 95 metastases (mean size, 2.2 ± 1.3 cm). Per patient and per lesion sensitivity for diagnosing newly developed hepatic metastasis was 56.1–66.7% and 52.6–56.8%, respectively. In terms of small metastases (<1.5 cm), per lesion sensitivity was significantly decreased to 28.1–34.4% (P < 0.05). Metastasis size measurements were significantly smaller on NECT (P < 0.001) compared with reference standards. In Group B, the accuracy of response evaluation based on RECIST criteria was 65.6–72.2%. Conclusions: NECT showed inadequate diagnostic performances in both detecting newly developed hepatic metastasis and evaluating the response of hepatic metastasis based on RECIST criteria. [ABSTRACT FROM AUTHOR]

Backgrounds & Aims The aim of this study is to evaluate the prognostic significances of not only the initial and the best response during repeated transarterial chemoembolization (TACE) for hepatocellular carcinoma (HCC), but if eligible, also the time point of achieving treatment responses. Methods Three hundred and fourteen treatment-naïve patients with well-preserved liver function undergoing TACE were recruited. Treatment responses were assessed using modified Response Evaluation Criteria in Solid Tumors. Overall survival (OS) was analyzed using Kaplan–Meier methods, and Cox regression analysis was performed for multivariate analysis. Results After adjusting other variables, objective response (complete response [CR] and partial response [PR]) as the initial response (adjusted hazard ratio [HR] 0.410) and the best response (adjusted HR 0.335) had independent prognostic significances for OS, respectively (both p <0.001). Objective responders as the initial response had the longest OS, followed by patients who subsequently achieved objective response after at least two sessions and those who did not achieve objective response during treatment course eventually (52.6, 27.0, and 10.8 months, respectively; log-rank test, p <0.001). Likewise, patients with CR as the initial response had the longest OS, followed by those who subsequently achieved CR after at least two sessions and those who achieved PR as the best response (70.2, 40.6, and 23.0 months, respectively; log-rank test, p <0.001). Large (>5 cm) and multiple (⩾4) tumors were independently associated with failure to achieve CR after the initial TACE (both p <0.05). Conclusion Both the initial and the best response predicts OS effectively. However, achievement of treatment response at an early time point is still the most robust predictor for favorable outcomes. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate feasibility of radiation dose reduction by optimal phase selection of computed tomography (CT) in patients who visited the emergency department (ED) for abdominal pain.Methods: We included 253 patients who visited the ED for abdominal pain. They underwent multiphasic CT including precontrast, late arterial phase (LAP), and hepatic venous phase (HVP). Three image sets (HVP, precontrast + HVP, and precontrast + LAP + HVP) were reviewed. Two reviewers determined the most appropriate diagnosis with five-point confidence scale. Diagnostic performances were compared among image sets by weighted-least-squares method or DeLong's method. Linear mixed model was used to assess changes of diagnostic confidence and radiation dose.Results: There was no difference in diagnostic performance among three image sets, although diagnostic confidence level was significantly improved after review of triphasic images compared with both HVP images only or HVP with precontrast images (confidence scale, 4.64 ± 0.05, 4.66 ± 0.05, and 4.76 ± 0.04 in the order of the sets; overall P = 0.0008). Similar trends were observed in the subgroup analysis for diagnosis of pelvic inflammatory disease and cholecystitis.Conclusions: There is no difference between HVP-CT alone and multiphasic CT for the diagnosis of causes of abdominal pain in patients admitted to the ED without prior chronic disease or neoplasia.Key Points: • There was no difference in diagnostic performance of HVP CT and multiphasic CT. • The diagnostic confidence level was improved after review of the LAP images. • HVP CT can achieve diagnostic performance similar to that of multiphasic CT, while minimizing radiation. [ABSTRACT FROM AUTHOR]

In contrast to patients with underlying cancer or chronic disease, injury patients are relatively young, and can be expected to live their natural lifespan if injuries are appropriately treated. Multiple and repeated diagnostic scans might be performed in these patients during admission. Nevertheless, radiation exposure in injury patients has been overlooked and underestimated because of the emergent nature of such situations. Therefore, we tried to assess the cumulative effective dose (cED) of injury patients in the emergency department. We included patients who visited the emergency department (ED) of a single tertiary hospital due to injury between February 2010 and February 2011. The cED for each patient was calculated and compared across age, sex and injury mechanism. A total of 11,676 visits (mean age: 28.0 years, M:F = 6,677:4,999) were identified. Although CT consisted of only 7.8% of total radiologic examinations (n=78,025), it accounted for 87.1% of the total cED. The mean cED per visit was 2.6 mSv. A significant difference in the cED among injury mechanisms was seen (p<0.001) and patients with traffic accidents and fall down injuries showed relatively high cED values. Hence, to reduce the cED of injury patients, an age-, sex- and injury mechanism-specific dose reduction strategy should be considered. [ABSTRACT FROM AUTHOR]

Abstract: Background: To evaluate hepatocellular carcinoma (HCC) that developed in patients with no evidence of a tumor during a prior ultrasound (US) performed within 1 year of the diagnosis. Methods: We retrospectively analyzed data for 100 consecutive patients with liver cirrhosis who had undergone US within 1 year prior to HCC diagnosis and who showed no liver lesions on the previous US. Size and T stage of HCC were assessed as well as whether patients met surgical criteria for liver transplantation as HCC treatment [Milan or University of California at San Francisco (UCSF) criteria]. Results: The mean interval between the negative and diagnostic scans was 5 months, 13 days. HCC presented as a single nodule in 69 patients (size, 0.8–8.0cm), as two or more nodules in 18 patients, and as the diffuse form of HCC in 13 patients. HCC presented as a small tumor (<3cm) in 48 patients. T stages were: T1 in 26 patients, T2 in 45, T3 in 18, and T4 in 11. The Milan criteria were met in 79 patients. Eighty-five patients fulfilled the UCSF. Conclusion: Patients may present with advanced HCC, even if sonographic findings were negative within 1 year prior to diagnosis. [Copyright &y& Elsevier]

Objective: To assess whether reticular hypointensity on hepatobiliary phase images of gadoxetic acid-enhanced magnetic resonance imaging (EOB-MRI) is a diagnostic finding of sinusoidal obstruction syndrome (SOS) in patients with hepatic metastases who have undergone chemotherapy. Methods: We retrospectively analysed EOB-MRI of 42 patients who had undergone chemotherapy before hepatic resection of colorectal hepatic metastases. Two radiologists, who were unaware of whether or not the patients had SOS, reviewed the hepatobiliary phase images to determine the presence of hypointense reticulation in the liver using a 5-point scale. The sensitivity, specificity and area under the receiver operating characteristics curve (A) were calculated for each reviewer. Results: The sensitivity, specificity and A for the diagnosis of SOS were 75%, 100% and 0.957 for reader 1 and 75%, 96.2% and 0.936 for reader 2, respectively. In one patient who received a false-positive diagnosis by one reader, there was sinusoidal fibrosis on histological examination, but not diagnostic for SOS. False-negative diagnosis occurred in four patients for both readers; histology of these patients showed minimal and localised sinusoidal congestion and fibrosis. Conclusions: Reticular hypointensity on hepatobiliary phase images of EOB-MRI is highly specific for the diagnosis of SOS in patients with treated colorectal hepatic metastases. Key Points: • Gadoxetic acid enhanced magnetic resonance imaging (EOB-MRI) can identify the sinusoidal obstruction syndrome (SOS) • The diagnosis can be achieved with high specificity and good interobserver agreement. • SOS typically demonstrates diffuse hypointensity on hepatobiliary phase images on EOB-MRI. • EOB-MRI may be falsely negative in patients with minimal degree of SOS. [ABSTRACT FROM AUTHOR]