Liver intravoxel incoherent motion diffusion-weighted imaging for the assessment of hepatic steatosis and fibrosis in children

AIM To evaluate the correlation between intravoxel incoherent motion(IVIM) diffusion-weighted imaging(DWI) parameters and the degree of hepatic steatosis and fibrosis in children.METHODS This retrospective study was approved by the institutional review board. The children(≤ 18 years) who underwent liver IVIM DWI with 8 b-values under the suspicion of hepatic steatosis or fibrosis from February 2013 to November 2016 were included. Subjects were divided into normal, fatty liver(FAT), and fibrotic liver(FIB) groups. The slow diffusion coefficient(D), fast diffusion coefficient(D*), perfusion fraction(f), and apparent diffusion coefficient(ADC) were measured. MR proton density fat fraction(PDFF), MR elastography(MRE), and IVIM values were compared.RESULTS A total of 123 children(median age of 12 years old, range: 6-18 years) were included, with 8 in the normal group, 93 in the FAT group, and 22 in the FIB group. The D* values were lower in the FIB group compared with those of the normal(P = 0.015) and FAT(P = 0.003) groups. The f values were lower in the FIB group compared with the FAT group(P = 0.001). In multivariate analyses, PDFF value was positively correlated with f value(β = 3.194, P < 0.001), and MRE value was negatively correlated with D* value(β =-7.031, P = 0.032). The D and ADC values were not influenced by PDFF or MRE value.CONCLUSION In liver IVIM DWI with multiple b-values in children, there was a positive correlation between hepatic fat and blood volume, and a negative correlation between hepatic stiffness and endovascular blood flow velocity, while diffusion-related parameters were not affected.

Predicting gastroesophageal varices through spleen magnetic resonance elastography in pediatric liver fibrosis

BACKGROUND A recent retrospective study confirmed that hepatic stiffness and splenic stiffness measured with magnetic resonance elastography(MRE) are strongly associated with the presence of esophageal varices. In addition, strong correlations have been reported between splenic stiffness values measured with MRE and hepatic venous pressure gradients in animal models. However, most studies have been conducted on adult populations, and previous pediatric MRE studies have only demonstrated the feasibility of MRE in pediatric populations, while the actual clinical application of spleen MRE has been limited.AIM To assess the utility of splenic stiffness measurements by MRE to predict gastroesophageal varices in children.METHODS We retrospectively reviewed abdominal MRE images taken on a 3 T system in pediatric patients. Patients who had undergone Kasai operations for biliary atresia were selected for the Kasai group, and patients with normal livers and spleens were selected for the control group. Two-dimensional spin-echo echoplanar MRE acquisition centered on the liver, with a pneumatic driver at 60 Hz and a low amplitude, was performed to obtain hepatic and splenic stiffness values. Laboratory results for aspartate aminotransferase to platelet ratio index(APRI) were evaluated within six months of MRE, and the normalized spleen size ratio was determined with the upper normal size limit. All Kasai group patients underwent gastroesophageal endoscopy during routine follow-up. The MannWhitney U test, Kendall's tau b correlation and diagnostic performance analysis using the area under the curve(AUC) were performed for statistical analysis.RESULTS The median spleen MRE value was 5.5 kPa in the control group(n = 9, age 9-18 years, range 4.7-6.4 kPa) and 8.6 kPa in the Kasai group(n = 22, age 4-18 years,range 5.0-17.8 kPa). In the Kasai group, the APRI, spleen size ratio and spleen MRE values were higher in patients with portal hypertension(n = 11) than in patients without(n = 11)(all P < 0.001) and in patients with gastroesophageal varices(n = 6) than in patients without(n = 16)(all P < 0.05), even though their liver MRE values were not different. The APRI(τ = 0.477, P = 0.007), spleen size ratio(τ = 0.401, P = 0.024) and spleen MRE values(τ = 0.426, P = 0.016) also correlated with varices grades. The AUC in predicting gastroesophageal varices was 0.844 at a cut-off of 0.65(100% sensitivity and 75% specificity) for the APRI,and 0.844 at a cut-off of 9.9 kPa(83.3% sensitivity and 81.3% specificity) for spleen MRE values.CONCLUSION At a cut-off of 9.9 kPa, spleen MRE values predicted gastroesophageal varices as well as the APRI and spleen size ratio in biliary atresia patients after the Kasai operation. However, liver MRE values were not useful for this purpose.

Contrast-enhanced ultrasonography for the evaluation of liver fibrosis after biliary obstruction

AIM:To investigate perfusion change in contrastenhanced ultrasonography(CEUS) to evaluate liver fibrosis based on biliary obstruction using an animal model.METHODS:New Zealand white rabbits(3-4 kg) underwent bile duct ligation to form a biliary obstruction model.We performed liver CEUS and laboratory tests on the day before the operation(day 0) and every 7 postoperative days until the rabbits were sacrificed.After CEUS,signal intensity of liver parenchyma with a time-intensity curve was analyzed.Perfusion parameters were automatically calculated from regionof-interests,including peak signal intensity,mean transit time,area under the curve and time to peak.Histological grades of liver fibrosis were assessed according to the Metavir score system immediately after sacrifice.Generalized estimating equations were used to analyze the association between liver fibrosis grades and perfusion parameters for statistical analysis.The perfusion parameters were measured on the last day and the difference between day 0 and the last day were evaluated.RESULTS:From the nine rabbits,histological grades of liver fibrosis were grade 1 in one rabbit,grade 2 and 3 in three rabbits each,and grade 4 in two rabbits.Among the four CEUS parameters,only the peak signal intensity measured on the last day demonstrated a significant association with liver fibrosis grades(OR =1.392,95%CI:1.114-1.741,P =0.004).The difference in peak signal intensity between day 0 and the last dayalso demonstrated an association with liver fibrosis(OR =1.191,95%CI:0.999-1.419,P =0.051).The other parameters tested,including mean transit time,area under the curve,and time to peak,showed no significant correlation with liver fibrosis grades.CONCLUSION:This animal study demonstrates that CEUS can be used to evaluate liver fibrosis from biliary obstruction using peak signal intensity as a parameter.

Liver stiffness and perfusion changes for hepatic sinusoidal obstruction syndrome in rabbit model

BACKGROUND Hepatic sinusoidal obstruction syndrome(SOS)is caused by damage to hepatic sinusoidal endothelial cells that results in fibrous obliteration of intrahepatic venules and necrosis of hepatocytes.Currently the diagnosis is primarily based on nonspecific clinical features and invasive liver biopsy.Therefore,noninvasive imaging methods are required for the early diagnosis and severity assessment of hepatic SOS.AIM To determine the effectiveness of supersonic shear wave imaging(SSI)and dual energy computed tomography(DECT)for diagnosing hepatic SOS using a rabbit model.METHODS Among nine New Zealand white rabbits(3-4 kg,male),three in control group ingested normal saline for 20 d and six in the SOS group ingested 6-thioguanine(5 mg/kg/d)for 20 d.Liver stiffness was measured using SSI on days 0,3,10,and 20.On the same days,liver perfusion was evaluated from virtual monochromatic images of 55 keV and iodine map using DECT.Morphologic changes in the liver were assessed using CT.Final pathology scores were compared between the two groups.Liver stiffness and perfusion parameters were compared according to the groups,days,and pathology scores.RESULTS Final pathology scores were significantly higher in the SOS than the control group(median 22 vs 2,P=0.024).No gross morphologic changes were seen in livers.Liver stiffness,Hounsfield Unit values,and iodine concentrations were higher in the SOS compared to the control group on days 10 and 20(all,P≤0.007).Compared to day 0,liver stiffness and perfusion parameters were higher on day 20 in the SOS group(all,P≤0.001).Correlation coefficients for liver stiffness(r=0.635),Hounsfield Unit values(r=0.587),and iodine concentration(r=0.611)with final pathology scores were positive without significance(all,P>0.05).CONCLUSION Liver stiffness and perfusion parameters were significantly increased in the livers of a rabbit SOS model.SSI and DECT might aid in early diagnosis of hepatic SOS.

Hepatic fat quantification magnetic resonance for monitoring treatment response in pediatric nonalcoholic steatohepatitis

AIM: To evaluate the possibility of treatment effect monitoring using hepatic fat quantification magnetic resonance(MR) in pediatric nonalcoholic steatohepatitis(NASH).METHODS: We retrospectively reviewed the medical records of patients who received educational recommendations and vitamin E for NASH and underwent hepatic fat quantification MR from 2011 to 2013.Hepatic fat fraction(%) was measured using dual- and triple-echo gradient-recalled-echo sequences at 3T.The compliant and non-compliant groups were compared clinically,biochemically,and radiologically.RESULTS: Twenty seven patients(M:F = 24:3; mean age: 12 ± 2.3 years) were included(compliant group = 22,non-compliant = 5).None of the baseline findings differed between the 2 groups,except for triglyceride level(compliant vs non-compliant,167.7 mg/d L vs 74.2 mg/d L,P = 0.001).In the compliant group,high-density lipoprotein increased and all other parameters decreased after 1-year follow-up.However,there were various changes in the non-compliant group.Dualecho fat fraction(-19.2% vs 4.6,P < 0.001),tripleecho fat fraction(-13.4% vs 3.5,P < 0.001),alanine aminotransferase(-110.7 IU/L vs-10.6 IU/L,P = 0.047),total cholesterol(-18.1 mg/d L vs 3.8 mg/d L,P = 0.016),and triglyceride levels(-61.3 mg/d L vs 11.2 mg/d L,P = 0.013) were significantly decreased only in the compliant group.The change in body mass index and dual-echo fat fraction showed a positive correlation(ρ = 0.418,P = 0.030).CONCLUSION: Hepatic fat quantification MR can be a non-invasive,quantitative and useful tool for monitoring treatment effects in pediatric NASH.

Extragastrointestinal stromal tumor presenting as a scrotal mass： an unusual case

We describe an unusual case of extragastrointestinal stromal tumor （EGIST） presenting as a scrotal mass. A 71- year-old man presented with a gradually enlarging scrotal mass with a 20-year duration. Physical examination re vealed a huge （as large as volleyball）, round, nontender mass occupying the whole scrotum, which was resected completely. Clinical and radiological findings did not comply with any other primary site disease. Under histological examination, the tumor showed a spindle cell pattern with low cellularity, absence of necrotic and mitotic features. Immunohistochemical anlaysis revealed the tumor reactive for CD117 and CD34, while negative for smooth muscle actin, desmin and S-100 protein. To our knowledge, this is the first reported case of an EGIST involving the scrotum.