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

How I Do It: Contrast-enhanced US Applications in Children

Contrast-enhanced US (CEUS) allows a detailed assessment of the tissue microvasculature after intravenous injection of contrast material. The use of CEUS also allows opacification of nonvascular hollow organs and fluid compartments after intracavitary instillation of dilute contrast material. This capability is far beyond that of grayscale and Doppler US techniques. The advantages of CEUS include its ease of use, high safety profile, and absence of ionizing radiation, making it an ideal tool for pediatric imaging. In 2016, the U.S. Food and Drug Administration approved CEUS for use in children for characterization of focal liver lesions and diagnosis of vesicoureteral reflux. Because the US contrast agent is distributed throughout the vascular pool, additional off-label imaging studies have focused on a variety of anatomic structures. This review of pediatric CEUS discusses the safety and technical aspects of CEUS, provides practical information on how to perform intravascular and intracavitary examinations, addresses the most common clinical applications of this method, and offers advice regarding the integration of CEUS into pediatric daily clinical practice.

Ultrasound innovations in abdominal radiology: techniques and clinical applications in pediatric imaging

Contrast-enhanced ultrasound, microvascular imaging, elastography, and fat quantification have varying degrees of utility, with some applications in the pediatric setting mirroring that in adults and having unique uses when applied to children in others. This review will present novel ultrasound technologies and the clinical context in which they are applied to the pediatric abdomen. New ultrasound technologies have a broad range of applications in clinical practice and represent a powerful diagnostic tool with the potential to replace other imaging modalities, such as magnetic resonance imaging and computed tomography, in specific cases.

Hepatocellular adenoma update: diagnosis, molecular classification, and clinical course

Hepatocellular adenomas (HCA) are acquired focal liver lesions, that occur mainly in young-to-middle-aged women who are on long-term estrogen-containing contraceptives or young men after prolonged use of anabolic steroids. Furthermore, distinct underlying diseases, such as obesity, metabolic dysfunction-associated steatotic liver disease, glycogen storage disease, etc. are considered risk factors. The 2017 Bordeaux classification, in particular Nault et al, divided HCAs into eight subtypes according to their pheno- and genotypic characteristics. This includes HCAs with hepatocyte-nuclear-factor (HNF1-alpha mutation), HCAs with β-catenin mutation, and HCAs without either of these genetic mutations, which are further subdivided into HCAs with and without inflammatory cells. HCAs should no longer be classified as purely benign without histologic workup since three of the eight subtypes are considered high-risk lesions, requiring adequate management: malignant transformation of the pure (ßex3-HCA) and mixed inflammatory/β-catenin exon 3 (ßex3-IHCA) adenomas, as well as potential bleeding of the sonic hedgehog HCA and pure (ßex7/8-HCA) and mixed inflammatory/β-catenin exon 7/8 (ßex7/8-IHCA). Elective surgery is recommended for any HCA in a male, or for any HCA exceeding 5 cm. Although MRI can classify up to 80% of adenomas, if findings are equivocal, biopsy remains the reference standard for adenoma subtype.

Review on Pediatric Malignant Focal Liver Lesions with Imaging Evaluation: Part I

Malignant focal liver lesions (FLLs) are commonly reported in adults but rarely seen in the pediatric population. Due to the rarity, the understanding of these diseases is still very limited. In children, most malignant FLLs are congenital. It is very important to choose appropriate imaging examination concerning various factors. This paper will outline common pediatric malignant FLLs, including hepatoblastoma, hepatocellular carcinoma, and cholangiocarcinoma and discuss them against the background of the latest knowledge on comparable/similar tumors in adults. Medical imaging features are of vital importance for the non-invasive diagnosis and follow-up of treatment of FLLs in pediatric patients. The use of CEUS in pediatric patients for characterizing those FLLs that remain indeterminate on conventional B mode ultrasounds may be an effective option in the future and has great potential to be integrated into imaging algorithms without the risk of exposure to ionizing radiation.

Pediatric Hepatocellular Adenomas: What Is Known and What Is New?

Current understanding and classification of pediatric hepatocellular adenomas (HCA) are largely based on adult data. HCAs are rare in children and, unlike in adults, are often seen in the context of syndromes or abnormal background liver. Attempts to apply the adult classification to pediatric tumors have led to several "unclassifiable" lesions. Although typically considered benign, few can show atypical features and those with beta-catenin mutations have a risk for malignant transformation. Small lesions can be monitored while larger (>5.0 cm) lesions are excised due to symptoms or risk of bleeding/rupture, etc. Management depends on gender, age, underlying liver disease, multifocality, size of lesion, histologic subtype and presence of mutation, if any. In this review, we summarize the data on pediatric HCAs and highlight our experience with their diagnosis and management.

Utility of the pediatric liver contrast-enhanced ultrasound criteria in differentiating malignant and benign multifocal lesions

BACKGROUND

The pediatric liver contrast-enhanced ultrasound (CEUS) criteria were developed to improve the diagnostic performance of CEUS in differentiating pediatric benign and malignant liver lesions. However, the diagnostic performance of CEUS in the evaluation of multiple focal liver lesions in the pediatric population has not yet been fully evaluated.

OBJECTIVE

To evaluate the diagnostic performance of the pediatric liver CEUS criteria in differentiating benign and malignant multifocal liver lesions in children.

MATERIALS AND METHODS

From April 2017 to September 2022, the CEUS characteristics of multifocal liver lesions in patients < 18 years were analyzed. Lesions classified as CEUS-1, CEUS-2 or CEUS-3 were considered benign and lesions classified as CEUS-4 or CEUS-5 were considered malignant. The diagnostic performance of the pediatric liver CEUS criteria (i.e. sensitivity, specificity, positive predictive value [PPV], negative predictive value [NPV] and accuracy) was assessed.

RESULTS

After exclusion, 21 patients (median age, 36.0 months; range, 1.0-204 months; 7 boys) were included. There were significant differences in the serum alpha fetoprotein level (P= 0.039) and the presence of washout (P < 0.001) between children with malignant and benign lesions. The sensitivity, specificity, PPV, NPV and accuracy of the pediatric liver CEUS criteria were 100.0% (10/10), 90.9% (10/11), 90.9% (10/11), 100.0% (10/10) and 95.2% (20/21), respectively.

CONCLUSION

The pediatric liver CEUS criteria had excellent diagnostic performance in differentiating benign and malignant multifocal liver lesions in children.

Incidental Findings in Pediatric Patients: How to Manage Liver Incidentaloma in Pediatric Patients

The World Federation for Ultrasound in Medicine and Biology (WFUMB) is addressing the issue of incidental findings (IFs) with a series of publications entitled "Incidental imaging findings-the role of ultrasound". IFs in the liver of newborns and children are rare and much less commonly encountered than in adults; as a result, they are relatively much more frequently malignant and life-threatening, even when they are of benign histology. Conventional B-mode ultrasound is the well-established first line imaging modality for the assessment of liver pathology in pediatric patients. US technological advances, resulting in image quality improvement, contrast-enhanced ultrasound (CEUS), liver elastography and quantification tools for steatosis have expanded the use of ultrasound technology in daily practice. The following overview is intended to illustrate incidentally detected liver pathology covering all pediatric ages. It aims to aid the examiner in establishing the final diagnosis. Management of incidentally detected focal liver lesions (FLL) needs to take into account the diagnostic accuracy of each imaging modality, the patient's safety issues (including ionizing radiation and nephrotoxic contrast agents), the delay in diagnosis, the psychological burden on the patient and the cost for the healthcare system. Moreover, this paper should help the pediatric clinician and ultrasound practitioner to decide which pathologies need no further investigation, which ones require interval imaging and which cases require further and immediate diagnostic procedures.

Imaging strategy for focal nodular hyperplasia in children: long-term experience from two specialist European centres

BACKGROUND

Focal nodular hyperplasia (FNH) in children is a rare but benign tumour, which must be differentiated from malignant entities to avoid unnecessary treatment, leading to potential morbidity.

OBJECTIVES

To provide data on imaging findings of these lesions with a suggested algorithm for diagnosis, sampling and follow-up.

MATERIALS AND METHODS

This retrospective review evaluated imaging of all patients diagnosed with FNH in two tertiary referral centres in Europe between 1975 and 2018.

RESULTS

One hundred and four patients with 137 tumours were reviewed. The mean age at presentation was 8.2 years. The median tumour size was 5 cm (range: 0.3-29 cm). Multiple lesions were seen in 16.3% of patients. The male-to-female ratio was 1:2.

CONCLUSION

FNH with typical features on imaging can be safely followed up once the diagnosis has been established. The use of contrast-enhanced ultrasound and magnetic resonance imaging allows accurate characterisation in most cases. Histological sampling is only advised when there is diagnostic doubt. Atypical arterial enhancement of FNH should prompt the search for a congenital portosystemic shunt.

Microvascular Flow Imaging: A State-of-the-Art Review of Clinical Use and Promise

Vascular imaging with color and power Doppler is a useful tool in the assessment of various disease processes. Assessment of blood flow, from infarction and ischemia to hyperemia, in organs, neoplasms, and vessels, is used in nearly every US investigation. Recent developments in this area are sensitive to small-vessel low velocity flow without use of intravenous contrast agents, known as microvascular flow imaging (MVFI). MVFI is more sensitive in detection of small vessels than color, power, and spectral Doppler, reducing the need for follow-up contrast-enhanced US (CEUS), CT, and MRI, except when arterial and venous wash-in and washout characteristics would be helpful in diagnosis. Varying clinical applications of MVFI are reviewed in adult and pediatric populations, including its technical underpinnings. MVFI shows promise in assessment of several conditions including benign and malignant lesions in the liver and kidney, acute pathologic abnormalities in the gallbladder and testes, and superficial lymph nodes. Future potential of MVFI in different conditions (eg, endovascular repair) is discussed. Finally, clinical cases in which MVFI correlated and potentially obviated additional CEUS, CT, or MRI are shown.

Diagnostic accuracy of three-dimensional contrast-enhanced ultrasound for focal liver lesions: A protocol for systematic review and meta-analysis

BACKGROUND

Contrast-enhanced ultrasound (CEUS) examination is a well-established technique for this purpose with several unique advantages. It is a real-time technology with high temporal resolution. With its unique ability to detect microvascular perfusion, it helps in better characterization of FLL.[1-4] Three-dimensional (3D) CEUS with quantitative analysis is updated in recent years. 3D-CEUS is a new ultrasonic diagnostic technique, which can observe the nourishing vessels of lesions from multiple angles. Previous studies showed that 3D-CEUS can detect tumor nourishing vessels to differentiate benign from malignant focal liver lesions (FLLs). However, the results of these studies have been contradictory. Therefore, this meta-analysis tested the hypothesis that 3D-CEUS is accurate in distinguishing benign and malignant FLLs.

METHODS

We will search PubMed, Web of Science, Cochrane Library, and Chinese biomedical databases from their inceptions to the April 30, 2021, without language restrictions. Two authors will independently carry out searching literature records, scanning titles and abstracts, full texts, collecting data, and assessing risk of bias. Review Manager 5.2 and Stata14.0 software will be used for data analysis.

RESULTS

This systematic review will determine the accuracy of 3D-CEUS in the differential diagnosis between benign and malignant FLLs.

CONCLUSION

Its findings will provide helpful evidence for the accuracy of 3D-CEUS in the differential diagnosis between benign and malignant FLLs.

SYSTEMATIC REVIEW REGISTRATION

INPLASY202150096.

Contrast-enhanced ultrasound: a comprehensive review of safety in children

Contrast-enhanced ultrasound (CEUS) has been increasingly used in pediatric radiology practice worldwide. For nearly two decades, CEUS applications have been performed with the off-label use of gas-containing second-generation ultrasound contrast agents (UCAs). Since 2016, the United States Food and Drug Administration (FDA) has approved the UCA Lumason for three pediatric indications: the evaluation of focal liver lesions and echocardiography via intravenous administration and the assessment of vesicoureteral reflux via intravesical application (contrast-enhanced voiding urosonography, ceVUS). Prior to the FDA approval of Lumason, numerous studies with the use of second-generation UCAs had been conducted in adults and children. Comprehensive protocols for clinical safety evaluations have demonstrated the highly favorable safety profile of UCA for intravenous, intravesical and other intracavitary uses. The safety data on CEUS continue to accumulate as this imaging modality is increasingly utilized in clinical settings worldwide. As of August 2021, 57 pediatric-only original research studies encompassing a total of 4,518 children with 4,906 intravenous CEUS examinations had been published. As in adults, there were a few adverse events; the majority of these were non-serious, although very rarely serious anaphylactic reactions were reported. In the published pediatric-only intravenous CEUS studies included in our analysis, the overall incidence rate of serious adverse events was 0.22% (10/4,518) of children and 0.20% (10/4,906) of all CEUS examinations. Non-serious adverse events from the intravenous CEUS were observed in 1.20% (54/4,518) of children and 1.10% (54/4,906) of CEUS examinations. During the same time period, 31 studies with the intravesical use of UCA were conducted in 12,362 children. A few non-serious adverse events were encountered (0.31%; 38/12,362), but these were most likely attributable to the bladder catheterization rather than the UCA. Other developing clinical applications of UCA in children, including intracavitary and intralymphatic, are ongoing. To date, no serious adverse events have been reported with these applications. This article reviews the existing pediatric CEUS literature and provides an overview of safety-related information reported from UCA uses in children.

European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB): An Update on the Pediatric CEUS Registry on Behalf of the "EFSUMB Pediatric CEUS Registry Working Group"

The European Federation of Ultrasound in Medicine and Biology (EFSUMB) created the "EFSUMB Pediatric Registry" (EFSUMB EPR) with the purpose of collecting data regarding the intravenous application of pediatric contrast-enhanced ultrasound (CEUS). The primary aim was to document the current clinical practice and usefulness of the technique and secondarily to assess CEUS safety in children. We issue the preliminary results of this database and examine the overall practice of CEUS in children in Europe.

Paediatric focal nodular hyperplasia: A case study of typical contrast-enhanced ultrasound findings with quantitative analysis and correlated with magnetic resonance imaging

INTRODUCTION

Focal nodular hyperplasia, a benign liver tumour, is the second most common focal benign liver lesion, after a cavernous haemangioma. Contrast-enhanced ultrasound is used increasingly for the diagnostic work up and follow-up of focal liver lesions in adults, but is particularly valuable in the paediatric population, with the ability to reduce radiation and the nephrotoxic contrast agents used in computed tomography or magnetic resonance imaging. Confident recognition of focal nodular hyperplasia is important; it is benign, usually asymptomatic, of no clinical significance, of no clinical consequence or malignant potential. We present a case of focal nodular hyperplasia of the liver with its characteristic findings on conventional ultrasound, contrast-enhanced ultrasound with quantitative analysis and correlated with magnetic resonance imaging.Case presentation: A 15-year-old female with right upper quadrant abdominal pain was referred for liver ultrasound. A focal liver lesion was detected on B-mode ultrasound examination, and colour Doppler demonstrated no specific features. Contrast-enhanced ultrasound examination demonstrated early arterial enhancement, with a characteristic spoke-wheel pattern, centrifugal uniform filling of the lesion on the late arterial phase and sustained enhancement on the portal venous phase. Quantitative contrast-enhanced ultrasound has been performed, showing a typical curve of enhancement, as well as characteristic parametric images, supporting the interpretation of contrast-enhanced ultrasound and assisting the diagnosis. Magnetic resonance imaging demonstrated a central T2 hyperintense scar and similar enhancement characteristics as contrast-enhanced ultrasound on T1 gadolinium-enhanced sequences.

CONCLUSION

Contrast-enhanced ultrasound is a useful technique for the differentiation of benign from malignant liver lesions and has the potential to establish the diagnosis of focal nodular hyperplasia, based on the enhancement pattern, which is similar to that observed on magnetic resonance imaging but can be better appreciated with superior temporal, contrast and spatial resolution of contrast-enhanced ultrasound.

Contrast-Enhanced Ultrasound in Children: Implementation and Key Diagnostic Applications

Contrast-enhanced ultrasound (CEUS) utilization is expanding rapidly, particularly in children, in whom the modality offers important advantages of dynamic evaluation of the vasculature, portability, lack of ionizing radiation, and lack of need for sedation. Accumulating data establish an excellent safety profile of ultrasound contrast agents in children. Although only FDA-approved for IV use in children for characterizing focal liver lesions and for use during echocardiography, growing off-label applications are expanding the diagnostic potential of ultrasound. Focal liver lesion evaluation is the most common use of CEUS, and the American College of Radiology Pediatric LI-RADS Working Group recommends including CEUS for evaluation of a newly discovered focal liver lesion in many circumstances. Data also support the role of CEUS in hemodynamically stable children with blunt abdominal trauma, and CEUS is becoming a potential alternative to CT in this setting. Additional potential applications that require further study include evaluation of pathology in the lung, spleen, brain, pancreas, bowel, kidney, female pelvis, and scrotum. This review explores the implementation of CEUS in children, describing basic principles of ultrasound contrast agents and CEUS technique and summarizing current and potential IV diagnostic applications based on pediatric-specific supporting evidence.

Liver Tumours in Children: The Hepatologist's View

ABSTRACT

Diagnostic and therapeutic innovations have changed the way we now approach liver tumours in children and adolescents. Novel imaging tools, increasing awareness, and surveillance has led to early diagnosis of benign and malignant liver tumours. Multidisciplinary interventions have favourably altered the natural course in some liver tumours. The role of liver transplantation is expanding and has become fully integrated into today's therapeutic algorithms. Transarterial locoregional and ablation therapies have been successful in adults and are being explored in children to facilitate resectability and improve outcome. For the first time, North American, Japanese, and European experts have designed a global trial to optimize management of malignant liver tumours and aim to find signature molecular profiles that will translate to individualised treatment strategies.This article aims to offer an overview of recent advances in our understanding of liver tumours in children. It focuses on the paediatric hepatologist's view and their role in the multidisciplinary management of benign and malignant liver tumours.

Development of a pediatric liver CEUS criterion to classify benign and malignant liver lesions in pediatric patients: a pilot study

OBJECTIVES

To analyze the contrast-enhanced ultrasound (CEUS) characteristics of pediatric patients with focal liver lesions (FLLs) and develop a pediatric liver CEUS criterion to improve the diagnostic performance of CEUS in differentiating pediatric benign and malignant liver lesions.

METHODS

Between March 2011 and May 2020, patients < 18 years who underwent CEUS were retrospectively evaluated. The CEUS characteristics of FLLs were analyzed. A pediatric liver CEUS criterion categorized as CEUS-1 to CEUS-5 was developed. The diagnostic performance of the criterion (i.e., sensitivity, specificity, PPV, and NPV) was assessed. Chi-square and Mann-Whitney tests were used.

RESULTS

After exclusion, the study included 130 lesions (mean diameter, 7.1 cm; range, 0.8-17.0 cm) from 130 patients (mean age, 36.0 months; range, 0.03-204.0 months; 74 boys). Hyperenhancement with washout in patients < 5 years or with early washout (≤ 45 s) was used to predict hepatoblastoma, with a sensitivity and specificity of 90.7% (95% confidence interval [CI]: 77.9%, 97.4%) and 93.6% (95% CI: 84.3%, 98.2%), respectively. Peripheral discontinuous globular hyperenhancement was used to diagnose hemangioma, with a sensitivity and specificity of 84.6% (95% CI: 65.1%, 95.6%) and 100% (95% CI: 95.4%, 100.0%), respectively. The rates of malignancies within the pediatric liver CEUS-1, CEUS-2, CEUS-3, CEUS-4, and CEUS-5 categories were 0.0%, 0.0%, 5.6%, 50.0%, and 96.1%, respectively. Besides, the incidences of hepatoblastoma in pediatric liver CEUS-3, CEUS-4, and CEUS-5 were 5.6%, 16.7%, and 67.5%, respectively.

CONCLUSIONS

The pediatric liver CEUS criterion is useful in differentiating benign focal liver lesions from malignancies, especially hepatoblastoma from hemangioma.

KEY POINTS

• Hyperenhancement with washout in patients <v5 years or with early washout (≤ 45 s) were used to predict hepatoblastoma, with a sensitivity and specificity of 90.7% and 93.6%. • Peripheral discontinuous globular hyperenhancement was used to diagnose hemangioma, with a sensitivity and specificity of 84.6% and 100.0%. • The rates of malignancies within the pediatric liver CEUS-1, CEUS -2, CEUS-3, CEUS-4, and CEUS-5 categories were 0.0%, 0.0%, 5.6%, 50.0%, and 96.1%, respectively.

Pediatric Primary Hepatic Tumors: Diagnostic Considerations

The liver is the third most common site of abdominal tumors in children. This review article aims to summarize current evidence surrounding identification and diagnosis of primary hepatic tumors in the pediatric population based upon clinical presentation, epidemiology, and risk factors as well as classical imaging, histopathological, and molecular diagnostic findings. Readers will be able to recognize the features and distinguish between benign and malignant hepatic tumors within different age groups.

Contrast-enhanced ultrasound of the small organs in children

In pediatric and adult populations, intravenous contrast-enhanced ultrasound (CEUS) remains off-label for imaging of organs other than the liver and heart. This limited scope inhibits potential benefits of the new modality from a more widespread utilization. Yet, CEUS is potentially useful for imaging small organs such as the thyroid gland, lymph nodes, testes, ovaries and uterus, with all having locations and vasculature favorable for this type of examination. In the adult population, the utility of CEUS has been demonstrated in a growing number of studies for the evaluation of these small organs. The aim of this article is to present a review of pediatric CEUS of the thyroid gland, lymph nodes, testes, ovaries and uterus as well as to draw from the adult literature indications for possible applications in children.

Contrast-enhanced ultrasound of benign and malignant liver lesions in children

Contrast-enhanced ultrasound (CEUS) is increasingly being used in children. One of the most common referrals for CEUS performance is characterization of indeterminate focal liver lesions and follow-up of known liver lesions. In this setting, CEUS is performed with intravenous administration of ultrasound contrast agents (UCAs). When injected into a vein, UCA microbubbles remain confined within the vascular network until they dissipate. Therefore, visualization of UCA within the tissues and lesions corresponds to true blood flow. CEUS enables continuous, real-time observation of the enhancement pattern of a focal liver lesion, allowing in most cases for a definite diagnosis and obviating the need for further cross-sectional imaging or other interventional procedures. The recent approval of Lumason (Bracco Diagnostics, Monroe Township, NJ) for pediatric liver CEUS applications has spurred the widespread use of CEUS. In this review article we describe the role of CEUS in pediatric liver applications, focusing on the examination technique and interpretation of main imaging findings of the most commonly encountered benign and malignant focal liver lesions. We also compare the diagnostic performance of CEUS with other imaging modalities for accurate characterization of focal liver lesions.

Guidelines and Good Clinical Practice Recommendations for Contrast Enhanced Ultrasound (CEUS) in the Liver - Update 2020 - WFUMB in Cooperation with EFSUMB, AFSUMB, AIUM, and FLAUS

The present, updated document describes the fourth iteration of recommendations for the hepatic use of contrast enhanced ultrasound (CEUS), first initiated in 2004 by the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB). The previous updated editions of the guidelines reflected changes in the available contrast agents and updated the guidelines not only for hepatic but also for non-hepatic applications.The 2012 guideline requires updating as previously the differences of the contrast agents were not precisely described and the differences in contrast phases as well as handling were not clearly indicated. In addition, more evidence has been published for all contrast agents. The update also reflects the most recent developments in contrast agents, including the United States Food and Drug Administration (FDA) approval as well as the extensive Asian experience, to produce a truly international perspective.These guidelines and recommendations provide general advice on the use of ultrasound contrast agents (UCA) and are intended to create standard protocols for the use and administration of UCA in liver applications on an international basis to improve the management of patients.

Guidelines and Good Clinical Practice Recommendations for Contrast-Enhanced Ultrasound (CEUS) in the Liver-Update 2020 WFUMB in Cooperation with EFSUMB, AFSUMB, AIUM, and FLAUS

The present, updated document describes the fourth iteration of recommendations for the hepatic use of contrast-enhanced ultrasound, first initiated in 2004 by the European Federation of Societies for Ultrasound in Medicine and Biology. The previous updated editions of the guidelines reflected changes in the available contrast agents and updated the guidelines not only for hepatic but also for non-hepatic applications. The 2012 guideline requires updating as, previously, the differences in the contrast agents were not precisely described and the differences in contrast phases as well as handling were not clearly indicated. In addition, more evidence has been published for all contrast agents. The update also reflects the most recent developments in contrast agents, including U.S. Food and Drug Administration approval and the extensive Asian experience, to produce a truly international perspective. These guidelines and recommendations provide general advice on the use of ultrasound contrast agents (UCAs) and are intended to create standard protocols for the use and administration of UCAs in liver applications on an international basis to improve the management of patients.