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

Quantitative Liver Imaging in Children

ABSTRACT

In children and adults, quantitative imaging examinations determine the effectiveness of treatment for liver disease. However, pediatric liver disease differs in presentation from liver disease in adults. Children also needed to be followed for a longer period from onset and have less control of their bodies, showing more movement than adults during imaging examinations, which leads to a greater need for sedation. Thus, it is essential to appropriately tailor and accurately perform noninvasive imaging tests in these younger patients. This article is an overview of updated imaging techniques used to assess liver disease quantitatively in children. The common initial imaging study for diffuse liver disease in pediatric patients is ultrasound. In addition to preexisting echo analysis, newly developed attenuation imaging techniques have been introduced to evaluate fatty liver. Ultrasound elastography is also now actively used to evaluate liver conditions, and the broad age spectrum of the pediatric population requires caution to be taken even in the selection of probes. Magnetic resonance imaging (MRI) is another important imaging tool used to evaluate liver disease despite requiring sedation or anesthesia in young children because it allows quantitative analysis with sequences such as fat analysis and MR elastography. In addition to ultrasound and MRI, we review quantitative imaging methods specifically for fatty liver, Wilson disease, biliary atresia, hepatic fibrosis, Fontan-associated liver disease, autoimmune hepatitis, sinusoidal obstruction syndrome, and the transplanted liver. Lastly, concerns such as growth and motion that need to be addressed specifically for children are summarized.

Guide to use of ferumoxytol for hepatic vascular assessment as part of dual contrast MRI

Magnetic resonance imaging (MRI) assessment of hepatic vasculature can be challenging in the setting of liver disease and liver lesions. The widely used hepatobiliary contrast agent gadoxetate is an extracellular contrast agent that provides excellent soft tissue characterization but has limitations as a vascular contrast agent. Ferumoxytol is an iron oxide nanoparticle with superparamagnetic properties that can be used as blood pool contrast agent to provide dedicated vascular assessment. We provide a detailed protocol for evaluation of pediatric liver vasculature using ferumoxytol, after imaging of the parenchyma with gadoxetate. We provide multiple examples and discuss practical considerations when incorporating ferumoxytol into practice.

Influence of age on gadoxetic acid disodium-induced transient respiratory motion artifacts in pediatric liver MRI

PURPOSE

Gd-EOB-DTPA-enhanced liver MRI is frequently compromised by transient severe motion artifacts (TSM) in the arterial phase, which limits image interpretation for the detection and differentiation of focal liver lesions and for the recognition of the arterial vasculature before and after liver transplantation. The purpose of this study was to investigate which patient factors affect TSM in children who undergo Gd-EOB-DTPA-enhanced liver MRI and whether younger children are affected as much as adolescents.

METHODS

One hundred and forty-eight patients (65 female, 83 male, 0.1-18.9 years old), who underwent 226 Gd-EOB-DTPA-enhanced MRIs were included retrospectively in this single-center study. The occurrence of TSM was assessed by three readers using a four-point Likert scale. The relation to age, gender, body mass index, indication for MRI, requirement for sedation, and MR repetition was investigated using uni- and multivariate logistic regression analysis.

RESULTS

In Gd-EOB-DTPA-enhanced MRIs, TSM occurred in 24 examinations (10.6%). Patients with TSM were significantly older than patients without TSM (median 14.3 years; range 10.1-18.1 vs. 12.4 years; range 0.1-18.9, p<0.001). TSM never appeared under sedation. Thirty of 50 scans in patients younger than 10 years were without sedation. TSM were not observed in non-sedated patients younger than 10 years of age (p = 0.028). In a logistic regression analysis, age remained the only cofactor independently associated with the occurrence of TSM (hazard ratio 9.152, p = 0.049).

CONCLUSION

TSM in Gd-EOB-DTPA-enhanced liver MRI do not appear in children under the age of 10 years.

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.

Advances in Diagnostic Imaging in Pediatric Gastroenterology

PURPOSE OF REVIEW

The purpose is to provide a review of cross-sectional imaging updates in the assessment of gastrointestinal diseases, relevant to clinical practice and research.

RECENT FINDINGS

New magnetic resonance imaging contrast agents (Eovist) are taken up by hepatocytes and excreted via the biliary tree. As such, a lesion will retain contrast only if hepatocytes are present, which aids in refining the differential diagnosis. Magnetic resonance enterography is a method for non-invasively diagnosing and following various GI conditions, predominantly inflammatory bowel disease. Contrast-enhanced ultrasound uses gas-filled microbubbles providing superb temporal resolution most notably in the arterial phase, which aids in differentiating lesions. Elastography is a new technique which assesses stiffness of liver for evaluating fibrosis. These new techniques provide more accurate diagnoses and information, often limiting ionizing radiation exposure from other modalities. While ultrasound will still remain the initial imaging modality, familiarity with these other options is valuable for appropriate pathology workup.

Rate of gadoxetate disodium (Eovist®) induced transient respiratory motion in children and young adults

BACKGROUND

Gadoxetate disodium (Eovist®, Bayer Healthcare, Wayne, NJ) is the preferred MR contrast agent for pediatric hepatobiliary imaging. A known limitation of this contrast agent is transient severe respiratory artifacts during arterial phase imaging, and some adult studies have raised caution against its use for evaluation of arterial enhancing lesions. The reported rate of transient severe breathing motion is 5-22% in adult studies. This study seeks to evaluate the frequency of transient severe respiratory motion secondary to gadoxetate disodium in a pediatric cohort.

MATERIALS AND METHODS

This is a retrospective, IRB-approved study with informed consent waiver. The radiology information system of a children's hospital was searched to identify all MRI studies performed with gadoxetate disodium during January 2016-June 2018. Two readers independently evaluated all phases of a dynamic liver protocol for respiratory motion artifact on a 5-point scale (1 none, 2 mild, 3 moderate, 4 severe-still diagnostic, 5 extreme-not diagnostic). Average scores of the 2 readers for each phase were used for analyses. Transient severe respiratory motion was defined as an increase in artifact score of ≥ 1.5 from pre-contrast to arterial phase that returned to < 3 in equilibrium phase of imaging.

RESULTS

The study cohort consisted of 140 cases (60% female), age range: 1 month-23 years (median 13 years). 102/140 scans were performed non-sedated. Mean respiratory motion score for each phase of scan for the entire cohort were pre-contrast: 2.23, arterial: 2.56, portal venous: 2.39, and equilibrium: 2.31. Transient severe respiratory motion was seen in 8 non-sedated cases and in 0 sedated cases. The rate of transient severe respiratory motion in a non-sedated pediatric cohort was estimated at 7.84% (8/102 cases).

CONCLUSION

The rate of transient severe respiratory motion in the non-sedated pediatric population is in the lower end of the range reported in adults. Transient severe respiratory motion is not observed in sedated patients.

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.