The impact of hepatocyte phase imaging from infancy to young adulthood in patients with a known or suspected liver lesion

Pediatric Hepatoblastoma After Neoadjuvant Chemotherapy: Diagnostic Performance of MR in Staging POSTTEXT and Vascular Involvement

BACKGROUND

The assessment of resectability after neoadjuvant chemotherapy of hepatoblastoma is dependent on Post-Treatment EXTENT of Disease (POSTTEXT) staging and its annotation factors P (portal venous involvement) and V (hepatic venous/inferior vena cava [IVC] involvement), but MR performance in assessing them remains unclear.

PURPOSE

To assess the diagnostic performance of contrast-enhanced MR imaging for preoperative POSTTEXT staging and diagnosing vascular involvement in terms of annotation factors P and V in pediatric hepatoblastoma following neoadjuvant chemotherapy.

STUDY TYPE

Retrospective.

SUBJECTS

Thirty-five consecutive patients (17 males, median age, 24 months; age range, 6-98 months) with proven hepatoblastoma underwent preoperative MR imaging following neoadjuvant chemotherapy.

FIELD STRENGTH/SEQUENCE

3.0 T; T2-weighted imaging (T2WI), T2WI with fat suppression, diffusion weighted imaging, radial stack-of-the-star/Cartesian 3D Dixon T1-weighted gradient echo imaging.

ASSESSMENT

Three radiologists independently assessed the POSTTEXT stages and annotation factors P and V based on the 2017 PRE/POSTTEXT system. The sensitivities and specificities were calculated for 1) diagnosing each POSTTEXT stage; 2) discrimination of stages III and IV (advanced) from those stages I and II (non-advanced) hepatoblastomas; and 3) annotation factors P and V. The combination of pathologic findings and surgical records served as the reference standard.

STATISTICAL TESTS

Sensitivity, specificity, Fleiss kappa test.

RESULTS

The sensitivity and specificity ranges for discriminating advanced from non-advanced hepatoblastomas were 73.3%-80.0% and 80.0%-90.0%, respectively. For annotation factor P, they were 66.7%-100.0% and 90.6%, respectively. For factor V, they were 75.0% and 67.7%-83.9%, respectively. There was excellent, substantial, and moderate agreement on POSTTEXT staging (Fleiss kappa = 0.82), factors P (Fleiss kappa = 0.64), and factors V (Fleiss kappa = 0.60), respectively.

DATA CONCLUSION

MR POSTTEXT provides reliable discrimination between advanced and non-advanced tumors, and MR has moderate to excellent specificity at identifying portal venous and hepatic venous/IVC involvement.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 3.

European Society of Pediatric Radiology survey of perioperative imaging in pediatric liver transplantation: (1) pre-transplant evaluation

BACKGROUND

Liver transplantation is the state-of-the-art curative treatment in end-stage liver disease. Imaging is a key element for successful organ-transplantation to assist surgical planning. So far, only limited data regarding the best radiological approach to prepare children for liver transplantation is available.

OBJECTIVES

In an attempt to harmonize imaging surrounding pediatric liver transplantation, the European Society of Pediatric Radiology (ESPR) Abdominal Taskforce initiated a survey addressing the current status of imaging including the pre-, intra-, and postoperative phase. This paper reports the responses on preoperative imaging.

MATERIAL AND METHODS

An online survey, initiated in 2021, asked European centers performing pediatric liver transplantation 48 questions about their imaging approach. In total, 26 centers were contacted and 22 institutions from 11 countries returned the survey. From 2018 to 2020, the participating centers collectively conducted 1,524 transplantations, with a median of 20 transplantations per center per annum (range, 8-60).

RESULTS

Most sites (64%) consider ultrasound their preferred modality to define anatomy and to plan surgery in children before liver transplantation, and additional cross-sectional imaging is only used to answer specific questions (computed tomography [CT], 90.9%; magnetic resonance imaging [MRI], 54.5%). One-third of centers (31.8%) rely primarily on CT for pre-transplant evaluation. Imaging protocols differed substantially regarding applied CT scan ranges, number of contrast phases (range 1-4 phases), and applied MRI techniques.

CONCLUSION

Diagnostic imaging is generally used in the work-up of children before liver transplantation. Substantial differences were noted regarding choice of modalities and protocols. We have identified starting points for future optimization and harmonization of the imaging approach to multicenter studies.

Imaging of pediatric liver tumors: A COG Diagnostic Imaging Committee/SPR Oncology Committee White Paper

Primary hepatic malignancies are relatively rare in the pediatric population, accounting for approximately 1%-2% of all pediatric tumors. Hepatoblastoma and hepatocellular carcinoma are the most common primary liver malignancies in children under the age of 5 years and over the age of 10 years, respectively. This paper provides consensus-based imaging recommendations for evaluation of patients with primary hepatic malignancies at diagnosis and follow-up during and after therapy.

Liver cirrhosis in children - the role of imaging in the diagnostic pathway

Liver cirrhosis in children is a rare disease with multifactorial causes that are distinct from those in adults. Underlying reasons include cholestatic, viral, autoimmune, hereditary, metabolic and cardiac disorders. Early detection of fibrosis is important as clinical stabilization or even reversal of fibrosis can be achieved in some disorders with adequate treatment. This article focuses on the longitudinal evaluation of children with chronic liver disease with noninvasive imaging tools, which play an important role in detecting cirrhosis, defining underlying causes, grading fibrosis and monitoring patients during follow-up. Ultrasound is the primary imaging modality and it is used in a multiparametric fashion. Magnetic resonance imaging and computed tomography are usually applied second line for refined tissue characterization, clarification of nodular lesions and full delineation of abdominal vessels, including portosystemic communications.

Liver magnetic resonance imaging: how we do it

Magnetic resonance imaging is used for evaluating focal liver lesions, hepatic vascular diseases, biliary diseases and diffuse liver diseases in children. MRI examinations take a long time, often requiring sedation or anesthesia in smaller children. This makes it essential to understand the concepts and technique necessary to obtain an optimal examination for answering the clinical question while minimizing the need for sedation/anesthesia. We discuss key concepts including appropriate sequence selection, choice of contrast media, dynamic imaging, phases of contrast enhancement and protocol organization.

Magnetic resonance imaging of pediatric liver tumors

Liver tumors in children can be benign or malignant. Although several clinical factors are important in the evaluation of these lesions, MRI is particularly important for lesion characterization and tumor staging. In children, use of a hepatobiliary contrast agent is recommended to evaluate a known or suspected liver lesion. In this review, we discuss the most common benign and malignant pediatric liver tumors, including vascular tumors, mesenchymal hamartoma, focal nodular hyperplasia, hepatocellular adenoma, hepatoblastoma, hepatocellular carcinoma, fibrolamellar hepatocellular carcinoma, undifferentiated embryonal sarcoma and metastases, with emphasis on relevant clinical information and imaging appearance at MRI using hepatobiliary agents.

Surgical Resection of Hepatoblastoma: Factors Affecting Local Recurrence

INTRODUCTION

 This study aimed to investigate potential factors contributing to local recurrence after surgical resection of hepatoblastoma (HB).

MATERIALS AND METHODS

 This retrospective study involving all patients with HB who underwent nontransplant surgery at our tertiary center between July 2007 and July 2018. Data were analyzed regarding microscopic surgical resection margin, tumor multifocality and extracapsular tumor extension in correlation with local recurrence. These relations were assessed by logistic regression.

RESULTS

 The study included 133 patients with a median age of 1.3 years (range: 0.5-12.8 years). They were classified into 99 cases (74.44%) standard risk and 34 cases (25.56%) high risk. Delayed surgical resection was adopted in all patients. Follow-up to July 2019 revealed that 23 patients (23/133, 17.3%) developed local recurrence, whereas the remaining 110 were locally disease free. Microscopic positive margin (R1) was detected in 29 patients, 8 of them had local recurrence (p = 0.097). Regarding tumor multifocality, there were 12 patients who had multifocal lesions, 3 of them developed local recurrence (p = 0.459). Forty-four patients had extracapsular tumor extension in their pathological reports, 12 of them had local recurrence (p = 0.032).

CONCLUSION

 Extracapsular tumor extension was a significant prognostic factor of local recurrence after surgical resection of HB. R1 margin does not necessarily require a second resection, and it could achieve accepted results when combined with adjuvant platinum-based chemotherapy. However, patients who are not eligible for surgical resection must be transferred for primary transplantation to obtain favorable outcome.

Intravenous gadolinium-based hepatocyte-specific contrast agents (HSCAs) for contrast-enhanced liver magnetic resonance imaging in pediatric patients: what the radiologist should know

Hepatocyte-specific contrast agents (HSCAs) are a group of intravenous gadolinium-based MRI contrast agents that can be used to characterize hepatobiliary pathology. The mechanism by which these agents are taken up by hepatocytes and partially excreted into the biliary tree improves characterization of hepatic lesions and biliary abnormalities relative to conventional extracellular gadolinium-based contrast agents (GBCAs). This manuscript presents an overview of HSCA use in pediatric patients with the intent to provide radiologists a guide for clinical use. We review available HSCAs and discuss dosing and age specifications for use in children. We also review various hepatic and biliary indications for HSCA use in children, with emphasis on the imaging characteristics distinct to HSCAs, as well as discussion of pitfalls one can encounter when imaging with HSCAs. Given the growing concern regarding gadolinium deposition in soft tissues and brain, we also discuss safety of HSCA use in children.

Evaluation and Management of the Child and Adult With Fontan Circulation: A Scientific Statement From the American Heart Association

It has been 50 years since Francis Fontan pioneered the operation that today bears his name. Initially designed for patients with tricuspid atresia, this procedure is now offered for a vast array of congenital cardiac lesions when a circulation with 2 ventricles cannot be achieved. As a result of technical advances and improvements in patient selection and perioperative management, survival has steadily increased, and it is estimated that patients operated on today may hope for a 30-year survival of >80%. Up to 70 000 patients may be alive worldwide today with Fontan circulation, and this population is expected to double in the next 20 years. In the absence of a subpulmonary ventricle, Fontan circulation is characterized by chronically elevated systemic venous pressures and decreased cardiac output. The addition of this acquired abnormal circulation to innate abnormalities associated with single-ventricle congenital heart disease exposes these patients to a variety of complications. Circulatory failure, ventricular dysfunction, atrioventricular valve regurgitation, arrhythmia, protein-losing enteropathy, and plastic bronchitis are potential complications of the Fontan circulation. Abnormalities in body composition, bone structure, and growth have been detected. Liver fibrosis and renal dysfunction are common and may progress over time. Cognitive, neuropsychological, and behavioral deficits are highly prevalent. As a testimony to the success of the current strategy of care, the proportion of adults with Fontan circulation is increasing. Healthcare providers are ill-prepared to tackle these challenges, as well as specific needs such as contraception and pregnancy in female patients. The role of therapies such as cardiovascular drugs to prevent and treat complications, heart transplantation, and mechanical circulatory support remains undetermined. There is a clear need for consensus on how best to follow up patients with Fontan circulation and to treat their complications. This American Heart Association statement summarizes the current state of knowledge on the Fontan circulation and its consequences. A proposed surveillance testing toolkit provides recommendations for a range of acceptable approaches to follow-up care for the patient with Fontan circulation. Gaps in knowledge and areas for future focus of investigation are highlighted, with the objective of laying the groundwork for creating a normal quality and duration of life for these unique individuals.

Respiratory motion in children and young adults undergoing liver magnetic resonance imaging with intravenous gadoxetate disodium contrast material

BACKGROUND

Gadoxetate disodium, utilized in hepatobiliary magnetic resonance (MR) imaging, has been associated with transient respiratory motion during the arterial phase in adults.

OBJECTIVE

The purpose of this study was to determine the presence and severity of this phenomenon in children imaged awake versus under general anesthesia.

MATERIALS AND METHODS

This retrospective cohort study was approved by the institutional review board; informed consent was waived. One hundred thirty exams of children ≤18 years old who underwent dynamic liver MR imaging with gadoxetate disodium between October 2010 and January 2018 were reviewed. Three pediatric radiologists scored respiratory motion artifacts on all imaging phases using a 5-point Likert scale. Differences in mean motion scores were assessed with analysis of variance and Tukey's multiple comparisons test, and multivariable regression was used to identify predictors of arterial phase motion in awake patients.

RESULTS

One hundred thirty patients (50% [n=65] female; mean age: 9.8±3.7 years, 48.5% [n=63] awake) were included. There were significant differences in mean motion scores between phases in the awake cohort (P<0.0001) but not in the general anesthesia cohort (P=0.051). In the awake cohort, arterial phase motion score (mean: 3.52±0.83) was significantly higher than mean motion score in all other phases (P≤0.0003). There were no significant patient-specific predictors of arterial phase motion score in the awake cohort.

CONCLUSION

Significantly increased arterial phase respiratory motion artifact in awake children undergoing dynamic liver MR imaging with gadoxetate disodium suggests that transient respiratory motion occurs in children. General anesthesia may suppress this phenomenon.

Contrast-enhanced ultrasound in the diagnosis of pediatric focal nodular hyperplasia and hepatic adenoma: interobserver reliability

BACKGROUND

Focal nodular hyperplasia and hepatic adenoma are rare liver tumors in which specific features on contrast-enhanced ultrasound (US) have been reported but are little known in children.

OBJECTIVE

To assess the interobserver agreement in diagnosing and differentiating focal nodular hyperplasia and hepatic adenoma in children using established adult contrast-enhanced US characteristics.

MATERIALS AND METHODS

Thirty children with a definite or probable diagnosis of focal nodular hyperplasia or hepatic adenoma on magnetic resonance imaging (MRI)/histology who underwent contrast-enhanced US studies were included. Typical and additional contrast-enhanced US features of focal nodular hyperplasia and hepatic adenoma were included. The lesions were classified as definite/probable focal nodular hyperplasia, definite/probably hepatic adenoma or unclassified. The interobserver kappa of contrast-enhanced US characteristics was calculated.

RESULTS

Focal nodular hyperplasia and hepatic adenoma in children demonstrate contrast-enhanced US characteristics similar to those in adults. Among the nine lesions with confirmed histological diagnosis, correct diagnosis was made in 7 (77.8%) based on contrast-enhanced US criteria. Two lesions were unclassified by both observers due to a mixed arterial filling pattern. Interobserver kappa for contrast-enhanced US diagnosis was 0.64 (P<0.0001).

CONCLUSION

There is a good interobserver kappa for separating focal nodular hyperplasia from hepatic adenoma in children using established adult contrast-enhanced US features.

Hepatocyte-specific contrast media: not so simple

Hepatocyte-specific contrast media are gadolinium chelates that are taken up by hepatocytes and partially cleared via the biliary tree. The absence of lesional uptake of the contrast media in the hepatobiliary phase is a marker of either the absence of hepatocytes or of poorly functioning, neoplastic hepatocytes. Uptake of the contrast media in the hepatobiliary phase, whether equal to or greater than background liver, reflects the presence of hepatocytes but does not equate to absence of neoplasia. Accurate diagnosis of liver lesions utilizing hepatocyte-specific contrast media requires an understanding of the mechanisms of uptake and clearance of the contrast media to avoid misdiagnosis. In this review we discuss the mechanisms of hepatocellular transport of hepatocyte-specific contrast media and utilize an understanding of those mechanisms to discuss the imaging appearance of a subset of hepatocellular lesions that can be seen in the pediatric and young adult liver. We pay particular attention to lesions that appear iso- to hyperintense in the hepatobiliary phase but have the potential for adverse clinical outcomes. We also discuss strategies for identifying these lesions.

2017 PRETEXT: radiologic staging system for primary hepatic malignancies of childhood revised for the Paediatric Hepatic International Tumour Trial (PHITT)

Imaging is crucial in the assessment of children with a primary hepatic malignancy. Since its inception in 1992, the PRETEXT (PRE-Treatment EXTent of tumor) system has become the primary method of risk stratification for hepatoblastoma and pediatric hepatocellular carcinoma in numerous cooperative group trials across the world. The PRETEXT system is made of two components: the PRETEXT group and the annotation factors. The PRETEXT group describes the extent of tumor within the liver while the annotation factors help to describe associated features such as vascular involvement (either portal vein or hepatic vein/inferior vena cava), extrahepatic disease, multifocality, tumor rupture and metastatic disease (to both the lungs and lymph nodes). This manuscript is written by members of the Children's Oncology Group (COG) in North America, the International Childhood Liver Tumors Strategy Group (SIOPEL) in Europe, and the Japanese Study Group for Pediatric Liver Tumor (JPLT; now part of the Japan Children's Cancer Group) and represents an international consensus update to the 2005 PRETEXT definitions. These definitions will be used in the forthcoming Trial to Pediatric Hepatic International Tumor Trial (PHITT).

Practical use and pitfalls of hepatocyte-specific contrast agents (HSCAs) for pediatric hepatic and biliary magnetic resonance imaging

Magnetic resonance imaging is commonly used to evaluate for hepatic and biliary pathology in the pediatric population. Recently, there has been increased use of hepatocyte-specific contrast agents (HSCAs), such as Gadoxetate disodium in children. Traditionally, HSCAs have been used to characterize focal liver lesions. However, these agents can also be used to problem solve specific hepatic or biliary diagnostic dilemmas. The purpose of this manuscript is to review the practical uses of HSCA in children with both hepatic and biliary indications, and review the corresponding imaging findings. We will highlight the diagnostic uses of HSCA in children, as well as pitfalls encountered.

MRI of paediatric liver tumours: How we review and report

Liver tumours are fortunately rare in children. Benign tumours such as haemangiomas and cystic mesenchymal hamartomas are typically seen in infancy, often before 6 months of age. After that age, malignant hepatic tumours increase in frequency. The differentiation of a malignant from benign lesion on imaging can often negate the need for biopsy. Ultrasound is currently the main screening tool for suspected liver pathology, and is ideally suited for evaluation of hepatic lesions in children due to their generally small size. With increasing research, public awareness and parental anxiety regarding radiation dosage from CT imaging, MRI is now unquestionably the modality of choice for further characterisation of hepatic mass lesions.

Nevertheless the cost, length of imaging time and perceived complexity of a paediatric liver MR study can be intimidating to the general radiologist and referring clinician. This article outlines standard MR sequences utilised, reasons for their utilisation, types of mixed hepatocyte specific/extracellular contrast agents employed and imaging features that aid the interpretation of paediatric liver lesions. The two commonest paediatric liver malignancies, namely hepatoblastoma and hepatocellular carcinoma are described. Differentiation of primary hepatic malignancies with metastatic disease and mimickers of malignancy such as focal nodular hyperplasia (FNH) and hepatic adenomas are also featured in this review..

Imaging should aim to clarify the presence of a lesion, the likelihood of malignancy and potential for complete surgical resection. Reviewing and reporting the studies should address these issues in a systematic fashion whilst also commenting upon background liver parenchymal appearances. Clinical information and adequate patient preparation prior to MR imaging studies help enhance the diagnostic yield.

Safety and Efficacy of Gadoxetate Disodium-Enhanced Liver MRI in Pediatric Patients Aged >2 Months to <18 Years-Results of a Retrospective, Multicenter Study

PURPOSE

To assess the safety and efficacy of gadoxetate disodium–enhanced liver MR imaging in pediatric patients.

MATERIAL AND METHODS

Retrospective, multicenter study including pediatric patients aged >2 months to <18 years who underwent contrast-enhanced liver MRI due to focal liver lesions. A single intravenous bolus injection of 0.025 to 0.05 mmol/kg body weight of gadoxetate disodium was administered. Adverse events (AEs) up to 24 hours after injection were recorded and a one-year follow-up was conducted for all serious and unexpected AEs. Efficacy was defined based on the additional diagnostic information obtained from the combined (pre- and postcontrast) image sets as compared with the precontrast image sets by blinded reading.

RESULTS

A total of 52 patients for safety and 51 patients for efficacy analyses were evaluated. Twenty-two patients (42.3%) reported a total of 51 serious AEs (SAEs) and one AE after one year. No SAE or AE was related to gadoxetate disodium injection. Gadoxetate disodium–related effects on vital signs were not seen. Additional diagnostic information was obtained for 86.3% of patients. The three most improved efficacy variables were lesion-to-background contrast, lesion characterization, and improved border delineation in 78.4%, 76.5%, and 70.6% of patients, respectively.

CONCLUSION

Gadoxetate disodium in pediatric patients did not raise any clinically significant safety concern. Contrast enhancement provided additional clinically relevant information.

Magnetic resonance imaging of primary pediatric liver tumors

Although primary hepatic neoplasms are less common than other intra-abdominal tumors in children, these neoplasms are a significant source of morbidity and mortality in the pediatric population. MRI is increasingly relied upon in the diagnostic evaluation of these lesions, both before and after treatment, and familiarity with the MRI findings associated with these neoplasms is a must for pediatric radiologists. Advances in MRI technology, particularly the advent of hepatocyte-specific gadolinium-based MRI contrast agents, have allowed for accurate characterization of several types of hepatic neoplasms on the basis of imaging appearance. In this review, we provide an overview of the approach to imaging hepatic neoplasms in children using MRI, including a sample imaging protocol. We also discuss the relevant clinical features and MRI findings of the most clinically relevant entities, including their appearance on post-contrast imaging using hepatocyte-specific gadolinium-based MRI contrast agents.

Current role of body MRI in pediatric oncology

Magnetic resonance imaging (MRI) plays an important role in the imaging of children with non-central nervous system malignancies, and it is increasingly replacing or complementing CT in many cases. MRI has several advantages over CT, including superior contrast resolution as well as superior tissue characterization with the use of novel pulse sequences and functional or organ-specific contrast agents. In addition, the lack of ionizing radiation - an important consideration in children - allows for multiphase dynamic post-contrast imaging, which can be useful for lesion detection and characterization. Several challenges remain in the performance of MRI in pediatric oncology patients, including the frequent need for sedation or anesthesia in young children because of long imaging times, as well as the suboptimal imaging of the lungs in the evaluation for pulmonary metastatic disease. However, despite these challenges, with continued improvements in MRI image quality and the development of novel sequences, contrast agents and quantitative imaging techniques, MRI is expected to play an ever increasing role in the imaging of pediatric oncology patients.