International Delphi Study to Develop Standardized Quality Criteria and a Rating Tool for Liver CEUS Image Quality Assessment. (ICON LiverCEUS)

Delphi Study on Quality Indicators for CEUS Imaging of the Liver Using SonoVue® Contrast Agent

This study aims to establish international consensus-based quality criteria for contrast-enhanced ultrasound (CEUS) examinations of the liver and to develop a standardized tool for assessing CEUS image quality. CEUS is an established imaging technique used in clinical practice for the characterization and assessment of focal liver lesions and other liver abnormalities. Despite its increasing use, there are currently no universally accepted or validated standards for evaluating the quality and reproducibility of CEUS examinations.

The primary objective of this project is therefore to identify robust and clinically relevant quality indicators for liver CEUS examinations through an international Delphi consensus process. The study focuses specifically on CEUS examinations performed in adult patients using the ultrasound contrast agent SonoVue®.

The project is divided into two work packages (WP). In Work Package 1 (WP1), the study team will first conduct a structured review of the available literature and discuss potential CEUS quality criteria within the research group. Based on this process, an initial catalogue of quality indicators relating to technical, procedural, and imaging characteristics relevant to liver CEUS examinations will be developed.

These proposed criteria will subsequently be evaluated through a multi-round Delphi process involving an international and interdisciplinary panel of experienced CEUS users and experts. A minimum of 20 panellists will participate across all Delphi rounds. Participants will rate their level of agreement with each proposed quality criterion using a 7-point Likert scale and may suggest additional criteria where appropriate. Newly proposed criteria supported by more than 10% of participants will be included in subsequent Delphi rounds.

During each round, panellists will receive anonymised feedback summarising the responses of the group and will be invited to re-evaluate the relevance of the proposed criteria. This iterative process will continue for at least three rounds or until predefined consensus criteria are achieved. Consensus will be defined as at least 70% agreement with a rating of 6 or higher on the Likert scale.

In Work Package 2 (WP2), the consensus-based quality criteria identified in WP1 will be operationalised into a comprehensive and standardized rating scale for CEUS image quality assessment. Individual criteria will be grouped into broader domains and transformed into practical assessment items and prompts. The resulting rating tool will then be circulated among all Delphi panel members for final review and feedback to ensure clarity, applicability, and international usability.

The overall goal of this study is to improve standardization, quality assurance, and reproducibility in liver CEUS examinations. The developed consensus criteria and rating scale may support clinical practice, future research studies, multicentre collaborations, and educational initiatives by enabling more consistent evaluation of CEUS image quality across institutions and countries.

Study Overview

• Status: Recruiting
• Conditions: Liver; Ultrasonic Diagnosis; Contrast Enhanced Ultrasound

Detailed Description

Contrast-enhanced ultrasound (CEUS) is an established and widely used imaging modality for the evaluation of focal liver lesions and other hepatic abnormalities. It plays an increasingly important role in clinical diagnostics due to its real-time imaging capability, safety profile, and broad availability. Despite its clinical relevance, there is currently no internationally standardised definition of adequate CEUS image quality, and no validated criteria exist for its objective assessment. As a result, interpretation and perceived diagnostic quality of CEUS examinations may vary considerably between operators, institutions, and healthcare systems.

The aim of this study is to develop internationally agreed, consensus-based quality criteria for adequate CEUS image quality in liver examinations and to translate these criteria into a standardised rating tool. The overall objective is to improve the reproducibility, comparability, and standardisation of CEUS examinations in both clinical practice and research settings.

To achieve this, the study is structured into two work packages (WP). Work Package 1 (WP1) focuses on identifying and refining relevant quality criteria for CEUS of the adult liver through an international Delphi consensus process.

Work Package 2 (WP2) focuses on clustering the agreed criteria into overarching domains and developing a structured rating scale for practical application.

In WP1, a preliminary set of potential quality indicators will be generated based on a structured literature review and expert discussion within the study team. These indicators will reflect technical, procedural, and image-related aspects of liver CEUS examinations. The most commonly applied CEUS context, adult liver imaging, will serve as the clinical focus of the study. An international panel of CEUS experts will be recruited based on defined expertise criteria, including extensive clinical experience in ultrasound and CEUS, training involvement, and scientific contribution to the field. Approximately 35 experts will be invited to participate in the first Delphi round, with an expected final panel size of at least 20 participants across all rounds.

The Delphi process will consist of three iterative survey rounds. In each round, participants will rate their agreement with predefined statements describing potential quality criteria using a 7-point Likert scale ranging from "completely disagree" to "completely agree," with an additional option for "outside of my expertise." Participants may also suggest additional criteria in the first round. Free-text responses will be systematically analysed, categorised, and included in subsequent rounds if supported by at least 10% of participants.

After each round, anonymised aggregated feedback will be provided to participants, including summary statistics such as median scores, interquartile ranges, and agreement rates. Participants will then be asked to reconsider and, if appropriate, revise their ratings in light of group responses. Consensus will be defined a priori as at least 70% of panellists rating a criterion as "agree" or "completely agree." Criteria not reaching consensus after repeated rounds will be revised or excluded according to predefined rules.

WP2 will translate the final consensus-based criteria into a structured rating scale for assessing CEUS image quality. The agreed criteria will be organised into overarching domains reflecting key dimensions of image quality. Within each domain, individual criteria will serve as structured prompts to guide evaluation. The resulting scale will be designed to be practical and reproducible and will use a simplified scoring system for domain-level assessment. Depending on the Delphi findings, non-imaging or technical aspects may be included as a separate domain.

The draft rating scale will be reviewed by the Delphi panel participants who completed all rounds. They will be asked to evaluate agreement with each domain and with the overall structure of the scale using a structured binary response format, with optional qualitative feedback. If predefined acceptance thresholds are not met, an additional revision round will be conducted.

Data analysis will include descriptive statistics for each criterion, including median and interquartile range, as well as calculation of agreement proportions. Responses indicating "outside of my expertise" will be treated as missing data and excluded from statistical calculations. Criteria will be evaluated against predefined consensus thresholds to determine inclusion, revision, or exclusion across Delphi rounds.

The final outcome of this study will be an internationally derived consensus set of quality criteria for liver CEUS examinations and a structured, standardised rating tool for assessing CEUS image quality. This framework is intended to support improved quality assurance, enhance reproducibility, and facilitate harmonisation of CEUS practice across institutions and countries in both clinical and research contexts.

• Study Type: Observational
• Enrollment (Estimated): 35

Contacts and Locations

• Study Contact: Name: Robin Walter, MD; Phone Number: +41 79 844 71 34; Email: robin.walter@unibe.ch
• Study Contact Backup: Name: Fabian M Föhrenbacher, MD; Phone Number: +41 78 313 77 08; Email: fabi.foehri@web.de

Study Locations

• Switzerland
  • Bern, Switzerland, 3007
    • Recruiting
    • University of Bern
    • Contact: Robin Walter, MD; Phone Number: +41 79 844 7134; Email: robin.walter@unibe.ch
    • Principal Investigator: Robin Walther, MD
    • Sub-Investigator: Michael Harris, MD et MME
    • Sub-Investigator: Christoph Dietrich, MD et Prof.
    • Sub-Investigator: Fabian Föhrenbacher, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

The study population consists of internationally recognised CEUS experts from radiology and internal medicine with extensive clinical and scientific experience in ultrasound diagnostics. Participants are recruited from multiple countries to form an interdisciplinary expert panel.

Inclusion requires expertise comparable to DEGUM Level III, including substantial ultrasound experience, regular performance of CEUS examinations, and involvement in CEUS training and/or research.

Approximately 35 experts will be invited for the first Delphi round, with at least 20 expected to complete all rounds. The purposive sampling approach ensures a highly specialised panel aimed at achieving expert consensus rather than statistical representativeness.

Description

Inclusion Criteria:

• At least 6 years of active experience in ultrasound diagnostics in internal medicine, radiology, or a related clinical field
• Independent performance of at least 5,000 ultrasound examinations Participation in structured CEUS training
• Performance of at least 800 ultrasound examinations per year in routine clinical practice
• Either: at least 100 independently performed CEUS examinations per year or more than 700 CEUS examinations in total
• Regular participation in ultrasound-related meetings, case reviews, or quality assurance activities within their institution
• Scientific involvement in CEUS, demonstrated by at least one peer-reviewed publication and/or active engagement in CEUS education or training
• Signing the consent form of the participants

Exclusion Criteria:

• Failure to meet the inclusion criteria

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
How many proposed contrast-enhanced ultrasound (CEUS) quality criteria achieve expert consensus, defined as ≥70% of panellists assigning a score of 6 ("agree") or 7 ("completely agree") on a 7-point Delphi Likert scale, by the end of Round 3?	The number of proposed CEUS quality criteria that achieve predefined consensus after completion of the Delphi process. Consensus is defined as ≥70% of participating experts assigning a score of 6 ("agree") or 7 ("completely agree") on a 7-point Likert scale evaluating the statement: "This criterion indicates adequate quality of a CEUS examination." The rating is based on a 7-point Likert scale from 1 (strongly disagree) to 7 (strongly agree). Higher scores indicate stronger agreement that the criterion reflects adequate CEUS image quality.	Completion of Delphi Round 3 (within six months)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
What percentage of experts assigns a score of 6 or 7 on the 7-point Delphi Likert scale to each proposed CEUS quality criterion across the Delphi rounds?	For each proposed quality criterion, the percentage of participating experts assigning a rating of 6 ("agree") or 7 ("completely agree") on the 7-point Likert scale will be calculated and reported. The rating is based on a 7-point Likert scale from 1 (strongly disagree) to 7 (strongly agree). Higher scores indicate stronger agreement that the criterion reflects adequate CEUS image quality.	After each Delphi round (within six months)
What are the median ratings for each proposed CEUS quality criterion on the 7-point Delphi Likert scale across the Delphi rounds?	Median expert rating for each proposed CEUS quality criterion. Responses marked as "Outside of my expertise" will be excluded from calculation. The rating is based on a 7-point Likert scale from 1 (strongly disagree) to 7 (strongly agree). Higher scores indicate stronger agreement that the criterion reflects adequate CEUS image quality.	After each Delphi round (within six months)
What are the interquartile ranges (IQRs) of expert ratings for each proposed CEUS quality criterion on the 7-point Delphi Likert scale across the Delphi rounds?	Interquartile range (IQR) of expert ratings for each proposed CEUS quality criterion. Lower IQR values indicate greater agreement among panellists. The rating is based on a 7-point Likert scale from 1 (strongly disagree) to 7 (strongly agree). Higher scores indicate stronger agreement that the criterion reflects adequate CEUS image quality.	After each Delphi round (within six months)
How many quality domains are incorporated into the final CEUS image quality rating scale derived from the consensus-based criteria?	Total number of domains derived from consensus-based CEUS quality criteria and incorporated into the final rating scale developed in Work Package 2.	Following completion of Work Package 2 (within six months)
What percentage of Experts Approving the Final Contrast-Enhanced Ultrasound Image Quality Rating Scale Using Binary Agreement Responses?	Percentage of Delphi panellists who completed all Delphi rounds and respond "Yes" to the question: "Do you agree this rating scale covers the important aspects to rate adequate CEUS image quality?" The survey is conducted using a binary response scale (Yes/No). Higher percentages indicate greater acceptance of the final rating scale.	Final rating scale evaluation survey (within six months)

Collaborators and Investigators

• Sponsor: University of Bern
• Investigators: Study Chair: Robin Walter, University of Bern

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): September 30, 2026
• Study Completion (Estimated): September 30, 2026

Study Registration Dates

• First Submitted: May 20, 2026
• First Submitted That Met QC Criteria: June 12, 2026
• First Posted (Actual): June 18, 2026

Study Record Updates

• Last Update Posted (Actual): June 18, 2026
• Last Update Submitted That Met QC Criteria: June 12, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Quality Indicators of Liver CEUS
• Other Study ID Numbers: Delphi on CEUS: Req-2025-01086

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No