A tailored passive driver for liver MRE in pediatric patients.

Objectives: Magnetic resonance elastography (MRE) is increasingly used in the pediatric population for diagnosis and staging of liver fibrosis. However, the MR-compatible driver and sequences are usually those used for adult patients. Our feasibility study aimed to adapt the standardized adult MRE passive driver and vibrational parameters to a pediatric population. Methods: We designed an elliptic passive driver shaped on a torus equipped with an elastic membrane and adapted to children's morphologies. As a first step, eight children (aged 8-18 years) were enrolled in a prospective pilot study aiming to determine the threshold vibrational amplitude for MRE using a custom passive driver, based on phase aliasing assessment and the occurrence of signal void artifacts on magnitude MR images. In the second step, the practicality and the consistency of the custom driver were assessed in a further 11 pediatric patients (aged 7-18 years). In the third step, we compared our custom driver vs. the commercial driver on six adult volunteers, in terms of the reliable region of interest area within the acquired MRE slices, the shear wave maps' quality, and measured stiffness values obtained. Results: Based on pediatric patient data, the threshold vibrational amplitude expressed as percentage of maximum output was found to be 0.4 and 1.1 times the body weight (kg) at 40 and 60 Hz frequencies, respectively. In comparison to the commercial passive driver, the custom driver improved threefold the contact with the body surface, also enabling a more comfortable examination as self-assessed by the volunteers. Conclusions: Our custom driver was more comfortable for the volunteers and was able to generate more homogenous shear waves, yielding larger usable hepatic area, and more reliable stiffness values.

Features of Nodules in Explants of Children Undergoing Liver Transplantation for Biliary Atresia.

(1) Background: In patients with biliary atresia (BA) liver nodules can be identified either by pre-transplant imaging or on the explant. This study aimed to (i) analyze the histopathology of liver nodules, and (ii) to correlate histopathology with pretransplant radiological features. (2) Methods: Retrospective analysis of liver nodules in explants of BA patients transplanted in our center (2000−2021). Correlations with pretransplant radiological characteristics, patient age at liver transplantation (LT), time from Kasai hepatoportoenterostomy (KPE) to LT, age at KPE and draining KPE. (3) Results: Of the 63 BA-patients included in the analysis, 27/63 (43%) had nodules on explants. A majority were benign macroregenerative nodules. Premalignant (low-grade and high-grade dysplastic) and malignant (hepatocellular carcinoma) nodules were identified in 6/63 and 2/63 patients, respectively. On pretransplant imaging, only 13/63 (21%) patients had liver nodules, none meeting radiological criteria for malignancy. The occurrence of liver nodules correlated with patient age at LT (p < 0.001), time KPE-LT (p < 0.001) and draining KPE (p = 0.006). (4) Conclusion: In BA patients, pretransplant imaging did not correlate with the presence of liver nodules in explants. Liver nodules were frequent in explanted livers, whereby 25% of explants harboured malignant/pre-malignant nodules, emphasizing the need for careful surveillance in BA children whose clinical course may require LT.

Acoustic radiation force impulse imaging: normal values of spleen stiffness in healthy children.

BACKGROUND: Acoustic radiation force impulse (ARFI) imaging is a noninvasive ultrasound elastography technique for evaluating tissue stiffness. The association of liver and spleen stiffness provides additional information in the assessment of portal hypertension. The technique and normal values of spleen stiffness by point shear wave elastography (p-SWE) in pediatrics have not been well documented. OBJECTIVE: Our aim is to describe the feasibility and normal ARFI elastography values in the spleen for healthy children and to compare measurements in two different probe positions (the axial and sagittal planes). MATERIALS AND METHODS: Spleen p-SWE using ARFI values were measured with a 6C1 probe in 102 healthy children (age range: 8 weeks to 17 years) divided into four age groups. An average of nine (standard deviation: two) spleen stiffness measurements were taken during free breathing in each plane (axial and sagittal). The impact of age and measurement plane in the spleen was analyzed using multivariate models. RESULTS: There was no significant difference in spleen stiffness values taken at different ages, with an average of the medians of 2.43±0.31 m/s. There was no significant difference based on probe orientation: sagittal plane (median: 2.46±0.29 m/s) and axial plane (median: 2.43±0.32 m/s) with Student's t-test P=0.18. The mean depth of measurement varied between 2.3 cm and 3.7 cm, according to age. CONCLUSION: Normal spleen stiffness values using ARFI imaging in children do not vary with age and correspond to a median of 2.43 m/s. No significant difference was found when using different probe positions.

Globus pallidus MR signal abnormalities in children with chronic liver disease and/or porto-systemic shunting.

OBJECTIVES: Detection of subclinical hepatic encephalopathy in children is difficult. We aimed to assess the changes in imaging of the central nervous system in children with chronic liver disease using MR imaging, diffusion, and 1H -spectroscopy. METHODS: Forty three children with chronic liver disease and/or porto-systemic shunting (111.4±56.9 months) and 24 controls (72.0±51.8 months) underwent brain MRI/spectroscopy on a 1.5T to examine T1, T2, ADC, Cho/Cr, ml/Cr, Glx/Cr ratio spectroscopy in the globus pallidus. Patients were divided into 3 groups according to the ratios of globus pallidus/putamen T1 signal : isointense (i), hyperintense (h), much more hyperintense (h+). The relationship with clinical and biological data was analyzed. RESULTS: T1 signal intensity and ml/Cr were significantly different between controls and group h+ (p=0.001). ADC did not differ significantly between groups. Age correlated strongly with the presence of a T1 signal ratio (p > 0.001). There was no correlation between imaging findings and biological parameters. CONCLUSIONS: In children with chronic liver disease and/or porto-systemic shunting, the presence of a hyperintense T1 signal in the globus pallidus correlated strongly with age. Biological and clinical parameters were not predictive of these changes. MRI may become a useful screening tool for hepatic encephalopathy in children. KEY POINTS: • Children with chronic liver disease should undergo brain MRI during their follow-up • T1 hyperintensity of globus pallidus is suggestive of liver-related CNS involvement • MRS mI/Cr is decreased in children with chronic liver disease • Biological parameters (ammonium) were not predictive of hepatic encephalopathy • Duration of chronic liver disease may be causative the hepatic encephalopathy.

Whole-body MRI in children: Would a 3D STIR sequence alone be sufficient for investigating common paediatric conditions? A comparative study.

OBJECTIVES: To test the performance of a single 3D IR T2-Weighted sequence compared to a Whole-body MRI protocol including DWI, T1-Weighted and STIR 3D IR (3S) in a pediatric population. METHODS: Two radiologists (15 and 30 years of experience),reviewed WBMRIs: first the STIR alone and 2 weeks later the 3S protocol. The indications were variable. Only positive findings were explicitly reported. A third reader compared the results to gold standard (GS) exams specific for the pathology. Agreement between the two readers, sensitivity and positive predictive value of STIR were calculated. RESULTS: fifty-four WBMRIs were included (16 suspected child abuse, 8 chronic recurrent multifocal osteomyelitis (CRMO), 11 lymphomas, 4 osteosarcomas, 9 neuroblastomas, 6 histiocytosis). The mean age was 6 years 10 months, range: 1 month to 15 years. Agreement between readers was of 0.87 [0.82-0.91] for 3D STIR, and 0.89 [0.83-0.93] for the 3S protocol. For reader 1 sensitivity of 3D STIR was 81.6% and of 3S 81.0%. For reader 2 it was 74.1% for 3D STIR and 74.7% for 3S. For both readers and for both protocols, the positive predictive value (PPV) depended on the type of disease (for example 100% histocytosis and osteosarcomas, >90% for child abuse, >85% CRMO but <70% for lymphoma and neuroblastoma). CONCLUSIONS: Sensitivities were not different between the 2 protocols, for each reader and were different between the 2 readers for each protocol.

Prenatal imaging of congenital hepatic tumors: a report of three cases.

The generalization of screening pregnancy ultrasound (US) studies has increased the detection of congenital tumors, including hepatic masses. In these cases, prenatal MRI is often used as a complementary imaging study. We present three cases of congenital hepatic tumors-two hemangiomas and one hamartoma-detected in utero and followed up in our institution. The retrospective analysis of their US and MRI prenatal imaging findings shows significant overlapping, indicating that the characterization of congenital hepatic tumors based exclusively on imaging findings is challenging.

Acoustic radiation force impulse sonography in assessing children with biliary atresia for liver transplantation.

BACKGROUND: Children with biliary atresia are prone to developing progressive hepatic fibrosis and biliary cirrhosis following the Kasai operation. The only treatment is liver transplantation. OBJECTIVE: To assess liver fibrosis by acoustic radiation force impulse elastography (ARFI) in children who had Kasai operation, with the goal of identifying an ARFI value cut-off for children requiring liver transplantation. MATERIALS AND METHODS: Of the 32 post-Kasai children included, 19 were transplanted or listed for transplantation (group A), while 13 were not on the list during their follow-up (group B). We recorded biopsies, blood samples and ARFI values over time, including at Kasai operation and at transplantation. We estimated an association between groups and continuous variables using generalized estimating equations, and we compared categorical variables using the Fisher exact test. RESULTS: Portal hypertension signs were similar in both groups, whereas ARFI values were higher in group A (mean±standard deviation=3.3±1.2 m/s) than in group B (2.0±0.7 m/s; P=.0003). Eighteen of 19 (94.7%) children in group A and 6/13 (46.2%) children in group B presented with two consecutive ARFI values ≥2 m/s (sensitivity=7%, specificity=53.8%; P=0.003). CONCLUSION: We found that children who were transplanted had two consecutive ARFI values ≥2 m/s during follow-up. ARFI for evaluation of post-Kasai liver fibrosis may assist the long-term assessment of biliary atresia and may even guide treatment decisions.

Portal Vein Embolization Before Extended Hepatectomy in a Toddler With Mesenchymal Hamartoma.

Portal vein embolization is widely used to induce hypertrophy of the future liver remnant before extended hepatectomy, decreasing the risk of postoperative liver failure. However, this percutaneous procedure has not been previously reported in a young child. The present report describes the case of a 14-month-old patient with a large multifocal mesenchymal hamartoma of the entire right liver, successfully resected after induction of future liver remnant hypertrophy by portal vein embolization.

Contribution of acoustic radiation force impulse (ARFI) elastography to the ultrasound diagnosis of biliary atresia.

BACKGROUND: Children with biliary atresia rapidly develop liver fibrosis secondary to inflammatory destruction of the biliary tract. Noninvasive detection of liver fibrosis in neonatal/infantile cholestasis is an additional criterion for the diagnosis of biliary atresia, leading to prompt surgical exploration. OBJECTIVE: To assess the value of US with acoustic radiation force impulse (ARFI) elastography to detect biliary atresia in the workup of neonatal/infantile cholestasis. MATERIALS AND METHODS: In this retrospective study, 20 children with cholestasis suspected of having biliary atresia were investigated by US and ARFI. We evaluated the association between US findings and the diagnosis of biliary atresia and with two scores of liver fibrosis obtained from liver biopsy. RESULTS: In univariate analyses, gallbladder size, triangular cord sign, spleen size and ARFI values were found to be associated with biliary atresia, though only the triangular cord sign remained significant when elevated gamma glutamyltransferase (GGT) was included as a predictor. In contrast, spleen size and ARFI correlated with the degree of liver fibrosis on biopsy (r > 0.70, P < 0.001), which remained significant when gamma glutamyltransferase elevation was included as a predictor. CONCLUSION: The addition of ARFI to a standard abdominal US in the initial workup of the neonate with possible infantile cholestasis can provide reliable information on liver fibrosis and help in the diagnosis of biliary atresia.

Concomitant septic arthritis and osteomyelitis of the hip in young children; a new pathophysiological hypothesis suggested by MRI enhancement pattern.

BACKGROUND: In children, septic arthritis (SA) of the hip is either primary or concomitant with acute haematogenous osteomyelitis (AHO). However, seldom, patients with isolated SA at presentation, may later show osteomyelitis in the metaphysis. The aim of this study was to elaborate a physiopathological hypothesis based on the peculiar MRI findings to explain the onset of AHO after SA. METHODS: Cases of acute infection of the hip admitted between January 2010 and December 2013 were retrospectively reviewed to assess radiographic and MRI features, as well as bacteriological findings. Only children with isolated SA were included in this study, whereas cases of concomitant SA and AHO at presentation were excluded. RESULTS: Ten patients met the inclusion criteria. Six (1-11 months) demonstrated, on the initial MRI, decreased perfusion on gadolinium enhanced fat-suppressed T1-weighted sequence of the femoral epiphysis and developed one month later metaphyseal AHO. Four (5-14 years) did not show decreased perfusion and did not develop AHO on follow-up. The type of germ involved influenced neither the type of enhancement pattern nor the outcome. CONCLUSIONS: Age under one year and decreased perfusion of the affected femoral epiphysis increases the risk of secondary AHO. Our study is the first report in human medicine supporting the physiopathological hypothesis described by Alderson et al. in an animal model: primary infection can originally affect the joint, then penetrate the epiphyseal cartilage, and finally spread into the metaphyseal region through transphyseal vessels present only in the first 12/18 months of life.

Microstructural changes in thickened corpus callosum in children: contribution of magnetic resonance diffusion tensor imaging.

BACKGROUND: Thickened corpus callosum is a rare finding and its pathophysiology is not well known. An anomalous supracallosal bundle has been depicted by fiber tracking in some cases but no diffusion tensor imaging metrics of thickened corpus callosum have been reported. OBJECTIVE: To use diffusion tensor imaging (DTI) in cases of thickened corpus callosum to help in understanding its clinical significance. MATERIALS AND METHODS: During a 7-year period five children (ages 6 months to 15 years) with thickened corpus callosum were studied. We determined DTI metrics of fractional anisotropy (FA), mean diffusivity, and axial (λ1) and radial (λ2, λ3) diffusivity and performed 3-D fiber tracking reconstruction of the thickened corpus callosum. We compared our results with data from the literature and 24 age-matched controls. RESULTS: Brain abnormalities were seen in all cases. All children had at least three measurements of corpus callosum thickness above the 97th percentile according to age. In all children 3-D fiber tracking showed an anomalous supracallosal bundle and statistically significant decrease in FA (P = 0.003) and λ1 (P = 0.001) of the corpus callosum compared with controls, but no significant difference in mean diffusivity and radial diffusivity. CONCLUSION: Thickened corpus callosum was associated with abnormal bundles, suggesting underlying axonal guidance abnormality. DTI metrics suggested abnormal fiber compactness and density, which may be associated with alterations in cognition.

Acoustic radiation force impulse (ARFI) elastography for the noninvasive diagnosis of liver fibrosis in children.

BACKGROUND: Acoustic radiation force impulse (ARFI) imaging) is correlated with histopathological findings using METAVIR and semiquantitative scoring system (SSS) criteria for liver fibrosis. OBJECTIVE: To compare acoustic radiation force impulse imaging with biopsy results in the evaluation of liver fibrosis in children. MATERIALS AND METHODS: Children with chronic liver disease and healthy children underwent acoustic radiation force impulse imaging liver measurements. ARFI gives a shear-wave velocity corresponding to tissue elasticity. In 39 children with liver disease, the values obtained were correlated with biopsy results. Receiver-operating characteristic (ROC) curves were used to determine the reliability of ARFI in estimating liver fibrosis in children. RESULTS: ARFI mean value was 1.12 in the healthy group and 1.99 in children with chronic liver disease. ROC curves show that an ARFI cutoff of 1.34 m/s is predictive of both METAVIR and SSS scores with a sensitivity of SSS > 2:0.85; METAVIR > F0:0.82. A cutoff of 2 m/s yielded a sensitivity of 100% to detect SSS > 4 or METAVIR > F2. CONCLUSION: Acoustic radiation force impulse imaging is a reliable, noninvasive and rapid method to estimate moderate to severe liver fibrosis in children. It might prove useful to clinicians for fibrosis monitoring in children with liver disease and postpone the time of liver biopsy.

Inflammatory myofibroblastic tumor of the lung: a rare cause of atelectasis in children.

Although rare, inflammatory myofibroblastic tumor is the most common primary lung mass in children. We report the case of an 11-year-old boy investigated for persistent cough and dyspnea with complete left lung atelectasis mimicking pneumonia. CT and MRI showed an endobronchial mass of the left main bronchus. The boy underwent endoscopic resection of the tumor and histology was in favor of an inflammatory myofibroblastic tumor of the lung. This diagnosis should be suspected in children with recurrent pneumonia. The prognosis is good after complete resection.

Acoustic radiation force impulse imaging-normal values of liver stiffness in healthy children.

BACKGROUND: Acoustic radiation force impulse imaging (ARFI) is a recent ultrasound technique to assess tissue stiffness. OBJECTIVE: Our aim was to describe the feasibility and to define normal ARFI values in liver in children. MATERIALS AND METHODS: ARFI values were measured in 103 children (ages 2 weeks to 17 years) divided into four age groups, at a minimum depth of 3 cm. In 20 children, measurements were done at 3-, 4- and 5-cm depth in the liver to assess the suitability of measurement location. The impact of age groups and of depth groups was examined using multilevel models. The precision of the measurements was determined using intraclass correlation coefficient (ICC). RESULTS: There was no statistical difference between measurements taken at different ages, with a mean propagation velocity of 1.12 m/s (range: 0.73 to 1.45 m/s). There was no significant difference according to the depth of the regions of interest (up to 5 cm). The ICC was 0.77 (95% CI 0.69-0.83). CONCLUSION: ARFI is feasible in children at any age with an acceptable reliability. The depth of measurements in the liver seems to have no influence on test results. We set the standard ARFI elastography values for healthy liver in children.

Sinus pericranii: a scalp mass in a 6-month-old boy.

'Sinus pericranii' is an abnormal communication between the extracranial veins and the dural venous sinuses (usually the superior sagittal and the transverse sinuses). It is a rare childhood abnormality. We report a case of a 6-month-old boy presenting with a scalp swelling in the left parietal region. Ultrasound with color Doppler and MRI showed a dilated epicranial vein that communicated with the superior sagittal sinus. This anomalous venous connection is known as sinus pericranii. We describe the imaging findings, associated abnormalities and management of this rare vascular abnormality.

Look for the nerves! MR neurography adds essential diagnostic value to routine MRI in pediatric practice: a pictorial overview.

PURPOSE: This study aimed to assess the feasibility of magnetic resonance (MR) neurography in children, and the potential roles of diffusion-weighted imaging (DWI) and fiber-tracking (FT) techniques. METHODS: Five pediatric patients (age range: 6-12 years) underwent magnetic resonance imaging (MRI) for various clinical indications: neurogenic bladder (case 1); persistent hand pain following minor trauma (case 2); progressive atrophy of the lower left extremity muscles (case 3); bilateral hip pain (case 4); and palpable left supraclavicular mass (case 5). All studies were performed using a 1.5-T Avanto MRI scanner (Siemens, Erlangen, Germany). The protocol included 3D T2-weighted STIR and SPACE imaging, T1-weighted fat-saturation post-gadolinium imaging and diffusion tensor imaging (DTI) with tractography. ADC (N×10(-3) mm(2)/s) and FA values were calculated from regions of interest (ROIs) centered on the nerves. Nerve-fiber tracks were calculated using a fourth-order Runge-Kutta algorithm (NeuroD software). RESULTS: MR neurography allowed satisfactory visualization of all neural structures, and FA and ADC measurements were feasible. The final diagnoses were Tarlov cysts, median-nerve compression, sciatic perineurioma, Charcot-Marie-Tooth disease and plexiform neurofibroma in a patient with NF-1. DISCUSSION: FA and ADC measurements are of little value because of the lack of normal reference values. Nerve-fiber tractography (FT) may be of value in the characterization of tumor pathology, and is also helpful in the planning of surgical treatments. CONCLUSION: MR neurography is feasible in pediatric patients. However, a considerable amount of work has yet to be done to establish its role in the clinical management of the wide range of peripheral nerve diseases.

Cure of multifocal panhepatic hepatoblastoma: is liver transplantation always necessary?

PURPOSE: Multifocal panhepatic hepatoblastoma (HB) without extrahepatic disease is generally considered as an indication for total hepatectomy and liver transplantation. However, after initial chemotherapy, downstaging of the tumor sometimes allows complete macroscopic resection by partial hepatectomy. This procedure is no longer recommended because of the risk of persistent viable tumor cells in the hepatic remnant. We report our experience with conservative surgery in such cases. METHOD: Between 2000 and 2005, 4 children were consecutively referred to our unit with multinodular pan-hepatic HBs (classification PRETEXT IV of the International Society of Pediatric Oncology Liver Tumor Study Group SIOPEL). Three of them had extrahepatic disease at diagnosis. All patients were treated according to SIOPEL 3 and 4 protocols. RESULTS: Extrahepatic metastases were still viable in 2 of 3 patients after initial chemotherapy. These patients eventually died of tumor recurrence. In the 2 patients without residual extrahepatic disease, liver tumors had regressed, and complete macroscopic excision of hepatic tumor remnants could be achieved by conservative surgery. These 2 children are alive and well and free of tumor 7 years after diagnosis. CONCLUSIONS: Conservative surgery may be curative in some multinodular PRETEXT IV HB patients, with a good response to preoperative chemotherapy and complete excision of all macroscopic tumor remnants. However, because of the lack of reliable predictors of sterilization of the microscopic disease in the residual liver, with subsequent poor prognosis, total hepatectomy and liver transplantation remain currently recommended in patients with multinodular PRETEXT IV HB without extrahepatic disease, even though some of these children are probably overtreated.

[New developments in pediatric abdominal MRI]. / Evolution de l'imagerie abdomi- nale chez l'enfant: développement des applications en IRM.

Ultrasound is the first choice imaging modality in pediatric abdominal pathologies. In recent years, MRI is being increasingly used for complimentary information in the domain of GI and GU imaging as well as in biliary tract imaging. In the radiological workup of children, radiation issues as well as noninvasive techniques are important to consider in particular in young infants. A pediatric setting with specialized practitioners (to reassure the child and to sedate him if necessary) should be helpful in acquiring satisfying MR images even in small children.

Diffusion-weighted imaging findings in Perthes disease with dynamic gadolinium-enhanced subtracted (DGS) MR correlation: a preliminary study.

BACKGROUND: Legg-Calvé-Perthes disease (LCP) is necrosis of the proximal femoral epiphysis of vascular origin. Clinical course and outcome in LCP disease varies considerably between different patients. Earlier prognostic criteria than those offered by conventional radiography are necessary to identify children who require prompt surgical treatment. OBJECTIVE: To assess the significance of signal alteration on diffusion-weighted MR imaging (DWI MR) in LCP. MATERIALS AND METHODS: Twelve boys with unilateral LCP disease (Catterall grade 2 and 3), at the initial sclerotic stage and early fragmentation phase, underwent dynamic gadolinium-enhanced subtracted (DGS) and DWI MR. For DGS MR, the lateral pillar enhancement was recorded. For DWI imaging, we measured ADC values in the diseased and the unaffected epiphyses and metaphyses. Receiver operating characteristic curves were performed to analyze the performance of DWI in establishing agreement with the results of DGS MR, which is the gold standard for prognosis. RESULTS: Femoral epiphysis increased diffusivity was observed in the affected hip in all cases. Increased metaphysis diffusivity in the affected side was observed in all cases with absent lateral pillar enhancement at DGS MR. CONCLUSION: DWI seems to be a noninvasive means of distinguishing between Perthes disease with favourable and unfavourable prognosis.