Magnetic resonance imaging-based risk factors of hepatocellular carcinoma after direct-acting antiviral therapy: A multicenter observational study.

AIM: To determine risk factors associated with hepatocellular carcinoma (HCC) development following direct-acting antiviral (DAA) therapy. METHODS: We enrolled patients with chronic hepatitis C who underwent direct-acting antiviral therapy and achieved sustained virologic response at 12 weeks between 2012 and 2018. Subsequently, patients were followed up. The primary endpoint was the development of HCC or the date of the last follow up when the absence of HCC was confirmed. Uni- and multivariate Cox proportional hazards models were used to identify factors contributing to HCC development, including gadoxetic acid-enhanced magnetic resonance imaging findings. The cumulative incidence rates of HCC development were calculated using the Kaplan-Meier method, and differences between groups were assessed using the log-rank test. RESULTS: The final study cohort comprised 482 patients (median age 70.5 years; 242 men). The median follow-up period was 36.8 months. Among 482 patients, 96 developed HCC (19.9%). The 1-, 3-, and 5-year cumulative rates of HCC development were 4.9%, 18.6%, and 30.5%, respectively. Multivariate analysis revealed that age, male sex, history of HCC, and hepatobiliary phase hypointense nodules without arterial phase hyperenhancement were independent risk factors significantly associated with HCC development (p < 0.001-0.04). The highest risk group included patients with both a history of HCC and the presence of hepatobiliary phase hypointense nodules without arterial phase hyperenhancement (the 1- and 3-year cumulative HCC development rates were 14.2% and 62.2%, respectively). CONCLUSION: History of HCC and presence of hepatobiliary phase hypointense nodules without arterial phase hyperenhancement were strong risk factors for HCC development following direct-acting antiviral therapy.

Early diagnosis of hepatic inflammation in Japanese nonalcoholic fatty liver disease patients using 3D MR elastography.

BACKGROUND: The damping ratio (DR) and the loss modulus (G″) obtained by 3D MR elastography complex modulus analysis has been reported recently to reflect early intrahepatic inflammation, and is expected to be a noninvasive biomarker of inflammation in nonalcoholic fatty liver disease (NAFLD). However, the role of the DR and the G″ in Japanese NAFLD patients remains unclear. METHODS: We enrolled 39 Japanese patients with NAFLD who underwent liver biopsy and 3D MR elastography within 1 month and analyzed the association between DR, G″, and histological activity. RESULTS: Regarding DR, no evident correlation was observed between the DR and histological activity (p = 0.14) when patients with all fibrosis stages were included. However, when patients were restricted up to stage F2 fibrosis, the association of the DR and inflammation became significant, the DR increasing with the degree of activity (p = 0.02). Among the constituents of fibrosis activity, ballooning correlated with the DR (p < 0.01) while lobular inflammation did not. Regarding G″, it was correlated with histological activity (p < 0.01), ballooning (p < 0.01), and lobular inflammation (p < 0.01) in patients with all fibrosis stages and in patients up to F2 fibrosis (p = 0.03 for activity and p = 0.04 for ballooning). The best cutoff value of DR for hepatitis activity in patients within the F2 stage was 0.094 (area under the receiver operating characteristic curve 0.775, 95% CI: 0.529-1.000) and G″ was 0.402 (area under the receiver operating characteristic curve 0.825, 95% CI: 0.628-1.000). CONCLUSIONS: The DR and G″ reflected the histological activity in Japanese patients with NAFLD during the early stage, indicating these values for noninvasive diagnosis of inflammation in Japanese patients with NAFLD.

Clinical Practice Guidelines for Hepatocellular Carcinoma: The Japan Society of Hepatology 2021 version (5th JSH-HCC Guidelines).

The fifth version of the Clinical Practice Guidelines for Hepatocellular Carcinoma was revised by the Japan Society of Hepatology, according to the methodology of evidence-based medicine and partly to the Grading of Recommendations Assessment, Development and Evaluation system, which was published in October 2021 in Japanese. In addition to surveillance-diagnostic and treatment algorithms, a new algorithm for systemic therapy has been created, as multiple drugs for hepatocellular carcinoma can be currently selected. Here, new or revised algorithms and evidence on which the recommendations are based are described.

MRI-Based Quantitative R2* Mapping at 3 Tesla Reflects Hepatic Iron Overload and Pathogenesis in Nonalcoholic Fatty Liver Disease Patients.

BACKGROUND: The role of hepatic iron overload (HIO) in nonalcoholic fatty liver disease (NAFLD) pathogenesis has not been fully elucidated. PURPOSE: This study aimed to investigate the effect of HIO and examine the diagnostic usefulness of magnetic resonance imaging (MRI)-based R2* quantification in evaluating hepatic iron content (HIC) and pathological findings in NAFLD. STUDY TYPE: Prospective and retrospective. POPULATION: A prospective study of 168 patients (age, 57.2 ± 15.0; male/female, 80/88) and a retrospective validation study of 202 patients (age, 57.0 ± 14.4; male/female, 113/89) with liver-biopsy-confirmed NAFLD were performed. FIELD STRENGTH/SEQUENCE: 3 T; chemical-shift encoded multi-echo gradient echo. ASSESSMENT: Using liver tissues obtained by liver biopsy, HIC was prospectively evaluated in 168 patients by atomic absorption spectrometry. Diagnostic accuracies of HIC and R2* for grading hepatic inflammation plus ballooning (HIB) as an indicator of NAFLD activity were assessed. STATISTICAL TESTS: Student's t-test and analysis of variance (ANOVA) with Scheffe's multiple testing correction for univariate comparisons; multivariate logistic analysis. P-value less than 0.05 is statistically significant. RESULTS: HIC was significantly correlated with HIB grades (r = 0.407). R2* was significantly correlated with HIC (r = 0.557) and HIB grades (r = 0.569). R2* mapped an area under the receiver operating characteristic (AUROC; 0.774) for HIC ≥808 ng/mL (median value) with cutoff value of 62.5 s-1 . In addition, R2* mapped AUROC of HIB for grades ≥3 was 0.799 with cutoff value of 58.5 s-1 . When R2* was <62.5 s-1 , R2* correlated weakly with HIC (r = 0.372) as it was affected by fat deposition and did not correlate with HIB grades (P = 0.052). Conversely, when R2* was ≥62.5 s-1 , a significant correlation of R2* with HIC (r = 0.556) and with HIB grades was observed (P < 0.0001) with being less affected by fat deposition. DATA CONCLUSION: R2* ≥ 62.5 s-1 is a promising modality for non-invasive diagnosis of clinically important high grades (≥3) of HIB associated with increased HIC. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 2.

Computed Tomography Findings of Emergency Cases Resulting From Fish Bone Ingestion.

Fish bones are some of the most commonly ingested foreign bodies. In most cases, fish bone ingestion is asymptomatic, and the bones are expelled from the body spontaneously. Otherwise, patients with fish bone ingestion can present to the emergency department with nonspecific symptoms. Fish bones can become impacted in various part of the body. Even in cases that are initially asymptomatic after ingestion, serious complications may develop at a later stage. Computed tomography (CT) plays an important role in the diagnosis of fish bone ingestion because it is the most sensitive modality for detecting these foreign bodies. It is important to be familiar with CT findings to detect ingested fish bones and the related complications and to direct further management of the condition.

Diffusion-weighted MRI-based Virtual Elastography for the Assessment of Liver Fibrosis.

Background Diffusion-weighted (DW) MRI-based elastography has recently been proposed for noninvasive liver fibrosis staging but requires evaluation in a larger number of patients. Purpose To compare DW MRI and MR elastography for the assessment of liver fibrosis. Materials and Methods In this retrospective study, patients underwent MR elastography and DW MRI between November 2017 and April 2018. Shear modulus measured by MR elastography (µMRE) was obtained in each patient from regions of interest placed on liver stiffness maps by two independent readers. Shifted apparent diffusion coefficient (ADC) was calculated from DW MRI (b = 200 and 1500 sec/mm2) and converted to DW MRI-based virtual shear modulus (µDiff). MRI-based liver fibrosis stages were estimated from µMRE and µDiff values (F0-F4) and serum fibrosis markers were assessed. Statistical analyses included Bland-Altman plots, Bayesian prediction, and receiver operating characteristic analyses. Results Seventy-four patients (mean age, 68 years ± 9 [standard deviation]; 45 men) were evaluated. Interreader coefficient of reproducibility was 0.86 kPa for DW MRI and 1.2 kPa for MR elastography. Strong correlation between shifted ADC and µMRE was observed (r2 = 0.81; P < .001), showing high agreement between µMRE and µDiff values (mean difference, -0.02 kPa ± 0.88; P < .001). DW MRI-based fibrosis staging agreed with MR elastography-based staging in 55% of patients (41 of 74) and within one stage difference in 35% of patients (26 of 74). Binarization into insignificant (F0-F1) and significant fibrosis (F2-F4) showed agreement in 85% of patients (63 of 74; κ = 0.85). Compared with serum markers (area under the receiver operating characteristic curve [AUC], 0.50-0.69), µDiff showed better performance in discriminating fibrosis stages F0-F2 from F3-F4 (AUC, 0.79; 95% confidence interval: 0.69, 0.90), whereas serum markers showed slightly better results for F0-F1 versus F2-F4 differentiation (fibrosis stages were estimated by using MR elastography). Combining DW MRI with serum markers provided a trend toward highest discriminative performance (AUC, µDiff + aspartate aminotransferase-to-platelet radio index: F0-F1 vs F2-F4, 0.81 [95% confidence interval: 0.69, 0.93], P = .17; F0-F2 vs F3-F4, 0.83 [95% confidence interval: 0.74, 0.92], P = .07; and AUC µDiff + Fibrosis 4 score: F0-F1 vs F2-F4, 0.78 [95% confidence interval: 0.64, 0.92], P < .30; F0-F2 vs F3-F4, 0.81 [95% confidence interval: 0.71, 0.91], P = .08). Conclusion MR elastography and diffusion-weighted (DW) MRI-based estimation of liver fibrosis stage showed high agreement. DW MRI shows potential as an alternative to MR elastography for noninvasive fibrosis staging without the need for mechanical vibration setup. © RSNA, 2020 Online supplemental material is available for this article.

Pharmacokinetics of Ferumoxytol in the Abdomen and Pelvis: A Dosing Study with 1.5- and 3.0-T MRI Relaxometry.

Background The off-label use of ferumoxytol (FE), an intravenous iron preparation for iron deficiency anemia, as a contrast agent for MRI is increasing; therefore, it is critical to understand its pharmacokinetics. Purpose To evaluate the pharmacokinetics of FE in the abdomen and pelvis, as assessed with quantitative 1.5- and 3.0-T MRI relaxometry. Materials and Methods R2*, an MRI technique used to estimate tissue iron content in the abdomen and pelvis, was performed at 1.5 and 3.0 T in 12 healthy volunteers between April 2015 and January 2016. Volunteers were randomly assigned to receive an FE dose of 2 mg per kilogram of body weight (FE2mg) or 4 mg/kg (FE4mg). MRI was repeated at 1.5 and 3.0 T for each volunteer at five time points: days 1, 2, 4, 7, and 30. A radiologist experienced in MRI relaxometry measured R2* in organs of the mononuclear phagocyte system (MPS) (ie, liver, spleen, and bone marrow), non-MPS anatomy (kidney, pancreas, and muscle), inguinal lymph nodes (LNs), and blood pool. A paired Student t test was used to compare changes in tissue R2*. Results Volunteers (six female; mean age, 44.3 years ± 12.2 [standard deviation]) received either FE2 mg (n = 5) or FE4 mg (n = 6). Overall R2* trend analysis was temporally significant (P < .001). Time to peak R2* in the MPS occurred on day 1 for FE2mg and between days 1 and 4 for FE4mg (P < .001 to P < .002). Time to peak R2* in non-MPS anatomy, LNs, and blood pool occurred on day 1 for both doses (P < .001 to P < .09). Except for the spleen (at 1.5 T) and liver, MPS R2* remained elevated through day 30 for both doses (P = .02 to P = .03). Except for the kidney and pancreas, non-MPS, LN, and blood pool R2* returned to baseline levels between days 2 and 4 at FE2mg (P = .06 to P = .49) and between days 4 and 7 at FE4mg (P = .06 to P = .63). There was no difference in R2* change between non-MPS and LN R2* at any time (range, 1-71 sec-1 vs 0-50 sec-1; P = .06 to P = .97). Conclusion The pharmacokinetics of ferumoxytol in lymph nodes are distinct from those in mononuclear phagocyte system (MPS) organs, parallel non-MPS anatomy, and the blood pool. © RSNA, 2019 Online supplemental material is available for this article.

Predicting Patients With Insufficient Liver Enhancement in the Hepatobiliary Phase Before the Injection of Gadoxetic Acid: A Practical Approach Using the Bayesian Method.

BACKGROUND: Gadoxetic acid-enhanced hepatobiliary phase (HBP) is useful in liver MRI, but sometimes shows insufficient liver enhancement. There is no established method to predict insufficient liver enhancement before the contrast injection. PURPOSE: To reveal the utility of the Bayesian method for predicting patients with insufficient liver enhancement in the gadoxetic acid-enhanced HBP. STUDY TYPE: Retrospective. SUBJECTS: In all, 576 patients with chronic liver disease. FIELD STRENGTH/SEQUENCE: 3T/3D gradient-echo T1 -weighted imaging and MR elastography (MRE). ASSESSMENT: The patients were divided into two groups: insufficient and sufficient liver enhancement in HBP according to the liver-to-portal vein signal intensity ratio. Various parameters, including liver function tests and liver stiffness by MRE, were evaluated as predictors of insufficient liver enhancement. STATISTICAL TESTS: We used Chi-square/Student's t-test/logistic regression analysis to determine independent associates, and Bayes' theorem to estimate the probability of insufficient (or sufficient) liver enhancement. The feasibility of Bayesian prediction of insufficient liver enhancement was tested by leave-one-out cross-validation to calculate sensitivity and specificity for single variables and combinations of some variables in all patients and in a subpopulation showing a confidence level of >80%. RESULTS: Independent associates of insufficient liver enhancement in HBP included: serum albumin (odds ratio [OR] = 4.82, P < 0.001), total bilirubin (OR = 0.30, P < 0.00), platelet count (OR = 1.54, P < 0.00), and liver stiffness by MRE (OR = 0.59, P < 0.00). The accuracy of Bayesian prediction of insufficient liver enhancement was 80.9% (466/576) for the single parameter of albumin and 79.0% (455/576) for total bilirubin, and was increased to 85.2% (487/576) for a combination of albumin, total bilirubin, and liver stiffness. In patients who showed a confidence level of >80%, the accuracy was 89.0% (439/493) for the above combination. DATA CONCLUSION: Bayesian prediction was useful to predict patients with insufficient enhancement by combining serum liver function tests and liver stiffness by MRE. LEVEL OF EVIDENCE: 3 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:62-69.

MRI-based risk factors of hepatocellular carcinoma in patients with chronic liver disease: A prospective observational study.

BACKGROUND: MR-based metrics, including hepatobiliary phase (HBP) hypointense nodules without arterial phase hyperenhancement (APHE), and liver stiffness as measured by MR elastography are useful markers to stratify the risk of hepatocellular carcinoma (HCC) development in chronic liver disease patients. However, prospective studies are needed to clarify their utility. PURPOSE: To perform a risk analysis of HCC development in chronic liver disease patients, with a focus on MR-based biomarkers. STUDY TYPE: Prospective. SUBJECTS: Consecutive 110 cirrhotic patients (61 males, 49 females) without a history of HCC who matched the inclusion criteria. FIELD STRENGTH/SEQUENCE: 3T/3D gradient-echo T1 -weighted images and MR elastography. ASSESSMENT: Patients underwent MRI for HCC screening and attended follow-up appointments every 3 months. The primary endpoint was the development of hypervascular HCC. Patients were classified according to the presence of an HBP hypointense nodule without APHE (if present in the liver, the patient was classified in nonclean liver group; if absent, clean liver group), and stiffness value on MR elastography (soft liver, <4.0 kPa; stiff liver, ≥4.0 kPa) at the initial examination. STATISTICAL TESTS: Risk factors were identified in univariate and multivariate Cox regression models. Incidence rates of HCC development were evaluated using the Kaplan-Meier method. RESULTS: Patients were classified into clean-liver (n = 76) and nonclean-liver groups (n = 34), and into soft-liver (n = 53) and stiff-liver groups (n = 45). During the follow-up period (median, 21.0 months), 16 patients developed hypervascular HCC. Patients in the nonclean-liver group showed a higher incidence of hypervascular HCC than those in the clean-liver group (3-year HCC incidence rates: 50.4% and 5.7%, respectively; P < 0.05). A nonclean liver was independently associated with hypervascular HCC development (hazard ratio, 18.75; 95% confidence interval, 4.83-128.63; P < 0.0001), but stiff liver was not (1.91; 0.66-6.23; P = 0.23). DATA CONCLUSION: An HBP hypointense nodule without APHE observed on a gadoxetic acid-enhanced MR image is a strong indicator of subsequent development of hypervascular HCC in patients with chronic liver disease. LEVEL OF EVIDENCE: 2 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:389-396.

Influence of Age on Global and Regional Brain Stiffness in Young and Middle-Aged Adults.

BACKGROUND: An understanding of potential age-related changes in brain stiffness and its regional variation is important for further clinical application of MR elastography. PURPOSE: To investigate the effect of age on global and regional brain stiffness in young and middle-aged adults. STUDY TYPE: Prospective. SUBJECTS: Fifty subjects with normal brains and aged in their 20s, 30s, 40s, 50s, or 60s (five men, five women per decade). FIELD STRENGTH/SEQUENCE: 3.0T MRI and elastography with a vibration frequency of 60 Hz. ASSESSMENT: Stiffness was measured in nine brain regions (cerebrum, temporal lobes, sensorimotor areas, frontotemporal composite region, deep gray matter and white matter (deep GM/WM), parietal lobes, occipital lobes, frontal lobes, and cerebellum) using an atlas-based region-of-interest approach. The influence of age on regional brain stiffness was evaluated. STATISTICAL TESTS: Multiple linear regression analysis, followed by Dunnett's multiple comparisons test, using subjects in their 20s as controls. RESULTS: Following adjustment for sex, multiple linear regression revealed a significant negative correlation between age and stiffness of the cerebrum (P < 0.0001), temporal lobes (P < 0.0001), sensorimotor areas (P < 0.0001), frontotemporal composite region (P < 0.0001), deep GM/WM (P = 0.0028), parietal lobes (P < 0.0001), occipital lobes (P = 0.0055), and frontal lobes (P < 0.0001). Dunnett's multiple comparison test showed that the stiffness of the sensorimotor areas, frontotemporal composite region, and frontal lobes was significantly decreased in subjects in their 40s (P < 0.0367), 50s (P < 0.0001), and 60s (P < 0.0001), while that of the cerebrum, temporal lobes, and parietal lobes was significantly decreased only in subjects in their 50s (P < 0.0012) and 60s (P < 0.0031) when compared with the controls. DATA CONCLUSION: There is an age-related decrease in brain stiffness that varies across the different regions. LEVEL OF EVIDENCE: 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:727-733.

Distinguishing intrahepatic mass-forming biliary carcinomas from hepatocellular carcinoma by computed tomography and magnetic resonance imaging using the Bayesian method: a bi-center study.

OBJECTIVES: To determine imaging hallmarks for distinguishing intrahepatic mass-forming biliary carcinomas (IMBCs) from hepatocellular carcinoma (HCC) and to validate their diagnostic ability using Bayesian statistics. METHODS: Study 1 retrospectively identified clinical and imaging hallmarks that distinguish IMBCs (n = 41) from HCC (n = 247) using computed tomography (CT) and magnetic resonance imaging (MRI). Study 2 retrospectively assessed the diagnostic ability of these hallmarks to distinguish IMBCs (n = 37) from HCC (n = 111) using Bayesian statistics with images obtained from a different institution. We also assessed the diagnostic ability of the hallmarks in the patient subgroup with high diagnostic confidence (≥ 80% of post-test probability). Two radiologists independently evaluated the imaging findings in studies 1 and 2. RESULTS: In study 1, arterial phase peritumoral parenchymal enhancement on CT/MRI, delayed enhancement on CT/MRI, diffusion-weighted imaging peripheral hyperintensity, and bile duct dilatation were hallmarks indicating IMBCs, whereas chronic liver disease, non-rim arterial phase hyperenhancement on CT/MRI, enhancing capsule on CT/MRI, and opposed-phase signal drop were hallmarks indicating HCC (p = 0.001-0.04). In study 2, Bayesian statistics-based post-test probability combining all hallmark features had a diagnostic accuracy of 89.2% (132/148) in distinguishing IMBCs from HCC for both readers. In the high diagnostic confidence subgroup (n = 120 and n = 124 for readers 1 and 2, respectively), the accuracy improved (95.0% (114/120) and 93.5% (116/124) for readers 1 and 2, respectively). CONCLUSIONS: Combined interpretation of CT and MRI to identify hallmark features is useful in discriminating IMBCs from HCCs. High post-test probability by Bayesian statistics allows for a more reliable non-invasive diagnosis. KEY POINTS: • Combined interpretation of CT and MRI to identify hallmark features was useful in discriminating intrahepatic mass-forming biliary carcinomas from hepatocellular carcinoma. • Bayesian method-based post-test probability combining all hallmark features determined in study 1 showed high (> 90%) sensitivity and specificity for distinguishing intrahepatic mass-forming biliary carcinomas from hepatocellular carcinoma. • If the post-test probability or the confidence was ≥ 80% when combining the imaging features of CT and MRI, the high specificity of > 95% was achieved without any loss of sensitivity to distinguish hepatocellular carcinoma from intrahepatic mass-forming biliary carcinomas.

Gadoxetate disodium-related event during image acquisition: a prospective multi-institutional study for better MR practice.

PURPOSE: To acknowledge the facts of gadoxetate disodium-related events in Japan and to achieve better MR practice by analyzing large cohort data with various MR parameters. MATERIALS AND METHODS: This prospective multi-institutional study included 1993 patients (1201 men, mean age 66.4 ± 12.8 years), who received dynamic MRI with gadoxetate disodium (gadoxetate group, n = 1646) or extracellular gadolinium-based contrast agents (other-GBCAs group, n = 347) between January and November 2016. Recorded data covered adverse reactions including dyspnea, breath-hold failure during acquisition, respiratory artifacts rated with a four-point scale, and MR parameters. We compared data between the two groups in whole cohort and age-, gender-, and institution-matched subcohort using χ2 test (n = 640). Logistic regression model was used to reveal independent associates of substantial artifacts in arterial phase imaging. RESULTS: Transient dyspnea rarely occurred in gadoxetate or other-GBCAs group (both < 1%). Gadoxetate group (vs other-GBCAs group) showed higher rates of breath-hold failure (whole cohort, 18.2% vs 7.7%, p < 0.001; subcohort, 17.6% vs 6.3%, p < 0.001) and substantial artifacts in arterial phase (7.2% vs 2.2%, p = 0.001; 7.4% vs 1.7%, p = 0.001). With single arterial phase protocol, substantial artifacts under gadoxetate were independently associated with age (odds ratio [OR] = 1.04, p < 0.001), hearing difficulty (OR = 2.92, p = 0.008), breath-hold practice required (OR = 1.61, p = 0.039), and short acquisition time (OR = 0.43, p = 0.005). Multiple arterial phase acquisition did not reduce the incident rate of substantial artifacts. CONCLUSION: Gadoxetate disodium was associated with breath-hold failure and substantial artifacts in arterial phase imaging, but not with dyspnea in Japan. Shorter acquisition time should be used to sustain image quality in gadoxetate disodium-enhanced arterial phase imaging. KEY POINTS: • Gadoxetate disodium administration leads to breath-hold failure and substantial imaging artifacts in arterial phase MRI in Japan. • Contrast agent-induced dyspnea in arterial phase and adverse reactions are rare in Japan, without showing differences between gadoxetate disodium or other extracellular gadolinium-based contrast agents. • Shorter acquisition time significantly reduces gadoxetate-induced imaging artifacts in the arterial phase.

Diagnostic Performance of the Support Vector Machine Model for Breast Cancer on Ring-Shaped Dedicated Breast Positron Emission Tomography Images.

OBJECTIVE: The aim of this study was to evaluate the diagnostic ability of support vector machine (SVM) for early breast cancer (BC) using dedicated breast positron emission tomography (dbPET). METHODS: We evaluated 116 abnormal fluorodeoxyglucose (FDG) uptakes less than 2 cm on dbPET images in 105 women. Fluorodeoxyglucose uptake patterns and quantitative PET parameters were compared between BC and noncancer groups. Diagnostic accuracy of the SVM model including quantitative parameters was compared with that of visual assessment based on FDG-uptake pattern. RESULTS: Age, maximum standardized uptake value, peak standardized uptake value, total lesion glycolysis, metabolic tumor volume, and lesion-to-contralateral background ratio were significantly different between BC and noncancer groups. Area under the curve, sensitivity, specificity, and accuracy for FDG-uptake pattern of visual assessment were 0.77, 0.57, 0.77, and 0.71, respectively; those of an SVM model including age, maximum standardized uptake value, total lesion glycolysis, and lesion-to-contralateral background ratio were 0.89, 0.94, 0.77, and 0.85, respectively. CONCLUSIONS: Support vector machine showed high diagnostic performance for BC using dbPET.

Imaging Findings of Acute Abdomen due to Complications of Meckel Diverticulum.

Meckel diverticulum is the most common and well-known congenital anomaly of the digestive system. Although most cases are asymptomatic, Meckel diverticulum can have a variety of complications, including gastrointestinal bleeding as a result of peptic ulceration, diverticulitis, and small bowel obstruction. Although the radiologic findings of these complications have been reported, they are difficult to diagnose preoperatively because Meckel diverticulum is a small entity. Computed tomography and scintigraphy play an important role in the diagnosis of Meckel diverticulum and its complications. It is important to be familiar with the radiologic features of acute abdomen due to complications of Meckel diverticulum to be able to manage the condition appropriately.

Four-dimensional Flow MRI as a Marker for Risk Stratification of Gastroesophageal Varices in Patients with Liver Cirrhosis.

Purpose To assess the feasibility of four-dimensional (4D) flow MRI as a noninvasive imaging marker for stratifying the risk of variceal bleeding in patients with liver cirrhosis. Materials and Methods This study recruited participants scheduled for both liver MRI and gastroesophageal endoscopy. Risk of variceal bleeding was assessed at endoscopy by using a three-point scale: no varices, low risk, and high risk requiring treatment. Four-dimensional flow MRI was used to create angiograms for evaluating visibility of varices and to measure flow volumes in main portal vein (PV), superior mesenteric vein, splenic vein (SV), and azygos vein. Fractional flow changes in PV and SV were calculated to quantify shunting (outflow) from PV and SV into varices. Logistic analysis was used to identify the independent indicator of high-risk varices. Results There were 23 participants (mean age, 52.3 years; age range, 25-75 years), including 14 men (mean age, 51.7 years; age range, 25-75 years) and nine women (mean age, 53.2 years; age range, 31-72 years) with no varices (n = 8), low-risk varices (n = 8), and high-risk varices (n = 7) determined at endoscopy. Four-dimensional flow MRI-based angiography helped radiologists to view varices in four of 15 participants with varices. Independent indicators of high-risk varices were flow volume in the azygos vein greater than 0.1 L/min (P = .034; 100% sensitivity [seven of seven] and 62% specificity [10 of 16]) and fractional flow change in PV of less than 0 (P < .001; 100% sensitivity [seven of seven] and 94% specificity [15 of 16]). Conclusion Azygos flow greater than 0.1 L/min and portal venous flow less than the sum of splenic and superior mesenteric vein flow are useful markers to stratify the risk of gastroesophageal varices bleeding in patients with liver cirrhosis. © RSNA, 2018 Online supplemental material is available for this article.

Linear gadolinium-based contrast agent (gadodiamide and gadopentetate dimeglumine)-induced high signal intensity on unenhanced T1 -weighted images in pediatric patients.

BACKGROUND: Recent studies of adults have found an association between hyperintensity of the dentate nucleus (DN) and globus pallidus (GP) on T1 -weighted images (T1 WI) and a history of linear gadolinium-based contrast agent (GBCA) administration. Several reports have also focused on this phenomenon in pediatric patients; however, data in the current literature remains limited. PURPOSE/HYPOTHESIS: To evaluate the associations between DN and GP T1 -signal increase and previous administration of linear GBCAs in pediatric patients. STUDY TYPE: Single-center, retrospective, cross-sectional study. POPULATION: We included pediatric patients with histories of ≥5 linear GBCA (gadodiamide and gadopentetate dimeglumine) administrations (the "≥5 Linear GBCA administrations" group), 1-4 administrations (the "1-4 Linear GBCA administrations" group), and no history of GBCA administration (the "No GBCA administration" group). Each group included 42 patients. Therefore, 126 patients (male:female, 72:54; median age, 16 [range, 4-18] years) were included in this study. FIELD STRENGTH/SEQUENCE: 1.5T/ Spin-echo unenhanced T1 -weighted imaging. ASSESSMENT: Unenhanced T1 -weighted images were quantitatively analyzed by two radiologists. The DN-to-pons and GP-to-thalamus signal intensity ratios (DN-to-pons and GP-to-thalamus ratios, respectively) were compared. STATISTICAL TESTS: Wilcoxon test with the Bonferroni correction and intraclass correlation coefficients. RESULTS: The DN-to-pons ratio increased as the number of GBCA administrations increased (P < 0.0063). The GP-to-thalamus ratio of the "≥5 Linear GBCA administrations" group was significantly higher than those of the other two groups (P < 0.0001). The GP-to-thalamus ratio of the "1-4 Linear GBCA administrations" group did not differ significantly from that of the "No GBCA administration" group (P = 1.000). The DN-to-pons and GP-to-thalamus ratios' interobserver intraclass correlation coefficients were excellent (0.8236) and good (0.6738), respectively. DATA CONCLUSION: High signal intensities in the DN and GP on T1 WI were associated with previous linear GBCA administration in pediatric patients. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1046-1052.

Magnetic resonance elastography can predict development of hepatocellular carcinoma with longitudinally acquired two-point data.

OBJECTIVE: To evaluate the usefulness of longitudinal observation of liver stiffness measured using magnetic resonance elastography (MRE) to stratify the risk of hepatocellular carcinoma (HCC) in patients with chronic liver disease. MATERIALS AND METHODS: We retrospectively reviewed data for 161 patients with chronic liver disease using the following inclusion criteria: two MRE examinations separated by at least a 12-month interval, no history of HCC, no development of HCC between the two examinations and availability of laboratory results. Liver stiffness was classified as low (< 3 kPa), moderate (3-4.7 kPa) or high (> 4.7 kPa). The patients were divided into three groups according to sequential changes in liver stiffness as follows: high on the first MRE (group A, n = 60), low on both MRE examinations (group C, n = 36) and other combinations (group B, n = 65). Cox analyses and Kaplan-Meier methods were used to determine the risk of developing HCC. RESULTS: Forty-seven patients (29.2%) developed HCC during follow-up (46.7% [28/60] in group A, 26.2% [17/65] in group B, and 5.6% [2/36] in group C). There was a significant difference in the rate of development of HCC between groups A (45.1%), B (26.1%) and C (12.4%) at 3 years (p = 0.0002). The independent risk factors for development of HCC were group A classification, age and a high alanine aminotransferase level (risk ratio 1.018-6.030; p = 0.0028-0.0268). CONCLUSION: Longitudinal observation of liver stiffness using MRE can stratify the risk of HCC during follow-up of chronic liver disease. KEY POINTS: • The results of MRE can stratify the risk for development of HCC during follow-up in patients with chronic liver disease. • Patients with chronic liver disease and high liver stiffness (> 4.7 kPa) on a previous MRE examination are at high risk for developing HCC, regardless of current liver stiffness. • Management of patients with chronic liver disease becomes more appropriate using longitudinally acquired two-point MRE data.

Unexpected Abnormal Uptake in the Breasts at Dedicated Breast PET: Incidentally Detected Small Cancers or Nonmalignant Features?

OBJECTIVE: The purposes of this study were to evaluate the diagnostic performance of dedicated breast PET (dbPET) in cases of unexpected uptake and to define parameters associated with malignancy. MATERIALS AND METHODS: There are two types of high-resolution dbPET systems. One has two platelike detectors that compress the breast. This study was conducted with the other type, on which the patient lies prone and the breast hangs through a ring without compression. In total, 627 consecutively registered women underwent 18F-FDG PET/CT and dbPET for pretherapeutic or posttherapeutic evaluation of breast cancer, prior suspicion of breast cancer, or cancer screening. Areas of abnormal FDG uptake, excluding known breast cancers, were analyzed. Uptake was morphologically categorized as focus, mass, or non-mass. Quantitative values were obtained, including the maximum standardized uptake value (SUVmax), peak SUV (SUVpeak), total lesion glycolysis (TLG), metabolic tumor volume (MTV), and lesion-to-background ratio (LBR). Clinical parameters were also assessed. Parameters were compared between breast cancer and noncancer groups; multivariate logistic regression analysis was performed. RESULTS: Of 40 instances of abnormal uptake, 13 were breast cancer. Morphologic features differed between cancer and noncancer groups (p = 0.0122). Among the cancers, 76.9% (10/13) had mass, 15.4% (2/13) had nonmass, and 7.7% (1/13) had focus uptake. Of noncancerous findings, 3.7% (1/27) were mass, 40.7% (11/27) nonmass, and 55.6% (15/27) focus uptake. SUVpeak (p = 0.0234), TLG (p = 0.0017), MTV (p = 0.004), and LBR (p = 0.0432) also differed between groups. Results of multivariate analysis indicated that morphologic category at dbPET was independently associated with malignancy. CONCLUSION: Morphologic features of abnormal uptake at dbPET are associated with breast cancer and may be useful for diagnosing lesions of unknown histologic composition.

Multiparameter estimation using multi-echo spoiled gradient echo with variable flip angles and multicontrast compressed sensing.

PURPOSE: To develop multiparameter mapping including T1 , R2*, and proton density fat fraction with a single breath-hold to evaluate liver disease and liver function. METHODS: A 6-echo spoiled gradient-echo sequence with dual flip angles was used to acquire a 12-set MRI volume data set. To shorten the scan time, undersampling and multicontrast compressed-sensing reconstruction were used. The scan time was 18 seconds. R2* and proton density fat fraction mapping were achieved by using the iterative least-squares method. T1 mapping was estimated using driven equilibrium single-pulse observation of T1 . Quantitative values were validated by performing phantom and volunteer studies. RESULTS: Statistical analysis showed that the quantitative values measured using the proposed methods agreed with those measured using conventional methods. T1 values of water proton measured by the proposed method in phantom and volunteer studies were in good agreement with those by MRS. CONCLUSION: The results showed that accurate quantitative mapping of T1 , R2*, and proton density fat fraction with a single breath-hold was achieved using our approach.