SIAD (Societé d'Imagerie Abdominale et Digestive) and
AFEF (Association Française pour l'Etude du Foie) best
practice position paper on the implementation of
ultrasound elastography in clinical practice

Lucia Parlati, Christophe Aubé, Maité Lewin, Jérôme Boursier, Maxime Ronot, Anita Paisant

► To cite this version:

Lucia Parlati, Christophe Aubé, Maité Lewin, Jérôme Boursier, Maxime Ronot, et al. SIAD (Societé d'Imagerie Abdominale et Digestive) and AFEF (Association Française pour l'Etude du Foie) best practice position paper on the implementation of ultrasound elastography in clinical practice. Diagnostic and Interventional Imaging, 2025, 10.1016/j.diii.2025.03.010. hal-05084445

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## Recommendations

# SIAD (Société d'Imagerie Abdominale et Digestive) and AFEF (Association Française pour l'Etude du Foie) best practice position paper on the implementation of ultrasound elastography in clinical practice

<figure><img src="image_3.png" /></figure>

### ARTICLE INFO

**Keywords:**

Acoustic radiation force impulse imaging
(ARFI)

Delphi method

Elastography

Liver stiffness

Ultrasound elastography report

### ABSTRACT

**Purpose:** The diagnosis of liver fibrosis is critical in managing chronic liver diseases. The EASL guidelines now recognize ultrasound elastography as a valuable, non-invasive method for assessing liver fibrosis. However, there is a lack of uniform use and reporting of the technique. The purpose of this position paper was to provide guidance on using ultrasound elastography techniques and interpreting results in clinical practice.

**Materials and methods:** A French national consensus panel of experts in radiology and hepatology, convened by SIAD (Société d'Imagerie Abdominale et Digestive) and AFEF (Association Française pour l'Etude du Foie), developed a position statement paper on best practices in ultrasound elastography. They were established using an online Delphi methodology that included an online panel discussion and item preparation. Consensus was achieved when ≥ 80 % of the participants agreed with a specific recommendation.

**Results:** The accuracy and reliability of ultrasound elastography results could be significantly affected by a variety of operator-related and patient-related factors. Standard recommendations have been established in two areas, including recommendations for measurements and factors affecting results and reliability, and guidelines for standardized reporting of ultrasound elastography results.

**Conclusion:** This position paper is a comprehensive and accessible guide for clinicians that outlines best practices and standardized protocols to improve the reliability of ultrasound elastography assessments.

## 1. Introduction

The diagnosis of liver fibrosis is critical in the management of chronic liver diseases, as its presence and stage correlate with patient prognosis. Liver biopsy and histopathological analysis remain the standard of reference for assessing liver fibrosis, but biopsy is invasive and suffers from sampling variability and suboptimal inter-observer reproducibility [1–3]. The 2021 EASL Clinical Practice Guidelines highlight the importance of non-invasive tests of liver lesions in primary care or outside of liver clinics, stating that non-invasive scores, serum markers, liver stiffness and imaging methods can identify advanced fibrosis in at-risk patients from low-prevalence populations significantly better than clinical acumen alone [4]. In particular, the EASL guidelines now recognize ultrasound elastography for the non-invasive assessment of liver fibrosis [4]. Given the widespread availability of ultrasound elastography on most current devices and its increasing use in clinical practice, the French Society of Abdominal and Digestive Imaging (SIAD, Société d'Imagerie Abdominale et Digestive) and the French Association for the Study of the Liver (AFEF, Association Française pour l'Etude du

Foie) initiated an expert position paper to provide guidance on the use of ultrasound elastography techniques and the interpretation of its results in clinical practice.

## 2. Current ultrasound elastography techniques

### 2.1. Principle of acoustic radiation force imaging

The term elastography describes techniques for measuring and visualizing the viscoelastic properties of tissues under mechanical stress. This article is restricted to ultrasound elastography. Traditionally, these methods are divided into static or near static techniques based on the qualitative visualization of tissue deformation (strain imaging), and dynamic methods, which allow quantification of biomechanical parameters. Acoustic radiation force imaging involves focusing an ultrasound beam for a few hundred microseconds at a given depth and then analyzing the mechanical response of the tissue to this stimulus. Due to the brevity of the mechanical vibrations, the excitation is polychromatic, generating both compression and shear waves that propagate through

**Abbreviations:** 2D-SWE, Two-dimensional shear-wave elastography; ARFI, Acoustic radiation force impulse; CVI, Content validity index; ICC, Intraclass correlation coefficient; IQR/M, Interquartile range/Median ratio; pSWE, Point shear-wave elastography.

https://doi.org/10.1016/j.diii.2025.03.010

Received 11 March 2025; Received in revised form 31 March 2025; Accepted 31 March 2025

Available online 9 April 2025

2211-5684/© 2025 The Authors. Published by Elsevier Masson SAS on behalf of Société française de radiologie. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
the medium. This technique does not allow the study of compression
wave propagation. Instead, it examines the properties of shear waves,
which provide real-time information about the viscoelastic character-
istics of the tissue.

The speed of shear wave propagation correlates with the elasticity of the tissue. Capturing and recording the displacements of this wave requires acquisition rates of several thousand images per second. The analysis of the deformation propagation velocity in the liver allows the determination of the Young's modulus (E) value (in kPa), which represents the stiffness of the liver. It expresses the density of the liver and the shear wave propagation velocity via the formula E = 3μ = 3ρVsw², where μ is the shear modulus of the liver, ρ is the liver density (1.063 kg/dm³), and Vsw is the shear-wave propagation speed (in m/s) [5]. Thus, the stiffer the medium, the faster the wave propagates, and vice versa.

## 2.2. Shear-wave elastography

Shear-wave elastography comprises two types of measurements: point measurements and multidimensional approaches.

### 2.2.1. Point shear-wave elastography

Point shear-wave elastography (pSWE) focuses ultrasounds (acoustic radiation force impulse, ARFI) at a certain depth within the tissues, creating a shear wave through the acoustic radiation force. Then, the average propagation speed of this wave is measured laterally within a region of interest. The measurement area in pSWE is small (approximately 1 × 0.5 cm) and cannot be modified in size, but the operator can choose its location. Indeed, pSWE is a unidimensional technique, but the measurement area can be positioned on a two-dimensional image [6]. The results are expressed in meters per second (m/s) or, more commonly, in kPa.

### 2.2.2. Two-dimensional shear-wave elastography

Two-dimensional shear-wave elastography (2D-SWE) extends the
measurement within a larger region by rapidly and sequentially moving
the ARFI (push) focus along a focal line. The result is the construction of
a shear-wave front that moves laterally within the tissue, the speed of

which is then measured. This process creates small shear-wave speed (SWS) image patches, which can be mosaicked to produce a larger planar image, known as a 2D-SWE elastogram. This latter is displayed in colour or grayscale and is either superimposed on the B-mode image (with adjustable transparency) or displayed separately, often side by side [7]. Thus, the elastogram provides a two-dimensional map of tissue stiffness, covering an area of approximately 2 × 2 cm (Fig. 1).

Within the elastogram, quantitative measurements can be performed by positioning one or more smaller regions of interest to sample the map. The advantage of the 2D-SWE technique over pSWE is that the operator can modify the size of these regions of interest and the elastogram itself. Another important aspect is the ability to perform retrospective measurements from saved images or cine-loops. The results are provided in kPa. For each stiffness measurement, the values obtained include the mean, median, standard deviation and minimum and maximum values.

# 3. Material and methods

## 3.1. Expert panel

The pilot group consisted of four expert radiologists from France (CA, ML, MR and AP, all specialists in hepatobiliary and gastrointestinal radiology with at least 10 years of experience in ultrasound elastography) and two hepatologists (LP and JB, the latter being a specialist in non-invasive tests of liver fibrosis). This team conducted an extensive review of the literature on elastography. Initially, the panel identified a preliminary list of key relevant topics or questions, which were categorized into two main sections: (i), recommendations for measurements and factors affecting results and reliability; and (ii), the structuring and standardization of reporting. Each section was then assigned to three experts, who performed an in-depth review of the literature and proposed corresponding statements. The modified Delphi method was applied to reach consensus and gather expert opinions [8]. After revisions, the manuscript received final approval from the SIAD and AFEF Executive Committees.

<figure><img src="image_4.png" /><figcaption>**Fig. 1.** Examples of two-dimensional shear-wave elastography elastograms show a normal liver (left) and the progressive evolution towards cirrhosis from left to right. This progression is indicated by a gradual increase in stiffness values (kPa) and a shift from blue to red (Liver stiffness values: A: 4.2 KPa, B: 12.6 KPa, C: 16.7 KPa, D: 81.1 KPa).</figcaption></figure>
## 3.2. Delphi panel

One month before the start of the first Delphi round, all panel participants were contacted and invited to take part in the project presentation. Participants were carefully chosen for the Delphi group based on established guidelines for forming such panels [8-9]. A diverse and representative group from France was invited. To prepare the participants, every participant was individually contacted to explain the project along with an explanatory email and relevant reference articles on elastography, which were shared with the group. The one-month interval was designed to allow participants ample time to reach out to the pilot group for clarifications or further explanations if needed. An online survey was developed for the first Delphi round [10] (Fig. 2).

Panelists were asked to rate each statement using a 5-point Likert scale, defined as follows: 5 = strongly agree, 4 = agree, 3 = neither agree nor disagree, 2 = disagree, and 1 = strongly disagree. This scale was chosen to ensure that the midpoint represented a neutral response. To avoid any potential misinterpretation, numerical values from 1 to 5 were included alongside the descriptive terms [11]. After each response, an open text box was provided for additional suggestions, including the suggestion of new statements.

## 3.3. Data analysis of the first Delphi round

After the first Delphi round, the pilot group of six members analyzed all results and comments. The content validity index (CVI) for each Likert-scale item was calculated for each statement [12]. The CVI interpretation was as follows: a CVI of 0.8 or higher indicated sufficient content validity; a CVI between 0.70 and 0.79 suggested that the item

needed revision; a CVI below 0.70 meant that the statement should be eliminated. The median score of each statement was then calculated, and a median < 4 was considered to indicate that the sentence needed revisions. All comments and suggestions from the open-text boxes were reviewed by the pilot group and processed as follows: (i), suggestions for textual clarifications and/or alterations were accepted if there was unanimous agreement among the group; (ii) suggestions that contradicted existing guidelines were rejected; (iii), suggestions regarding the content of a statement made by more than 10 % of participants were accepted; and (iv), suggestions made by less than 10 % of participants were rejected. Data were analyzed using SPSS software, version 15.0.

# 4. Results

## 4.1. General results

Of the 11 surveys sent to panelists, 11 complete responses (100 %) were received. The final panel included five radiologists (mean years of experience in abdominal ultrasound, 23.6 years) and six hepatogastroenterologists (mean years of experience in abdominal ultrasound, 25.3 years). All medians were = 5. All statements had a CVI > 0.8 and were accepted (Fig. 3). In addition, 18 % of the panelists requested an additional point in the comments section. This comment was considered by the pilot group and a new literature search was conducted. As no relevant study was found to support this point, the consultants with this proposal were contacted again and explained that this suggestion was not supported by the literature. The proposal was therefore rejected.

<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Flow-chart with the different steps of the Delphi study. CVI indicates content validity index.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>Fig. 3. Content validity index for each statement (Q1-Q15) of the first Delphi round.</figcaption></figure>

## 4.2. General results of the best practice position paper

The results are presented in a structured table (Table 1), offering a concise yet comprehensive summary of the statements evaluated by the Delphi panel. This approach ensures clarity and facilitates the interpretation of the panel's assessments, highlighting key insights and areas of consensus.

# 5. Recommendations for measurements and factors influencing results and reliability

## 5.1. How to perform measurements?

Patient preparation, imaging technique, and measurement recommendations for pSWE and 2D-SWE are the same. Moreover, the protocol recommended by the Society of Radiologists in Ultrasound (SRU)

<caption>**Table 1**
Summary of the recommendations for measurements and factors influencing ultrasound elastography results and reliability.</caption>

### Patient preparation

1. The patient should fast for at least four hours prior to examination.

2. The measurement should be performed between the ribs and the right liver, with the patient positioned in the supine or slight left lateral decubitus position (not > 30°) with the right arm extended.

### Measurement technique

3. The intercostal space should be as open as possible to avoid lateral artifacts from rib shadows in the image.

4. Measurements should be taken during neutral apnea (neither inhalation nor forced expiration).

5. The axis of the ultrasound beam must be perpendicular to the liver capsule.

6. Adequate hepatic imaging in B-mode is a prerequisite for proper measurement.

7. Measurements should be taken in an area free of large blood vessels or focal lesions.

### Measurement quality criteria

8. The measurement area (pSWE) or the elastogram (2D-SWE) should be positioned parallel to the liver capsule, at least 1.5-2 cm below, to avoid reverberation artifacts.

9. The maximum measurement depth is 6-8 cm.

10. Measurements are taken directly within the measurement area (pSWE) or using regions of interest placed within the elastogram (2D-SWE).

11. Measurements by regions in 2D-SWE should be performed after temporal and spatial stabilization of the elastogram.

### Conditions that affect diagnostic performance

12. The following conditions increase liver stiffness measured by elastography: acute hepatitis, obstructive cholestasis, hepatic congestion, and infiltrative liver diseases. In the presence of these confounding factors, the relationship between ultrasound elastography values and the degree of fibrosis is confounded, and thus, other tools should be used for assessment.

### How to evaluate the reliability of measurements?

13. When manufacturers provide quantitative quality criteria (e.g., R2 or stability index) or visual criteria (e.g., wave propagation map), they should be followed.

14. For pSWE, ten measurements must be obtained. The final liver stiffness result should be expressed as the median of those measurements. The reliability criterion is the interquartile range/median ratio (IQR/M), and the result should be interpreted based on the obtained stiffness value (Table 2).

15. For 2D-SWE, at least three reliable measurements must be obtained. The reliability criterion for each measurement is its coefficient of variation (standard deviation/mean), and the result should be interpreted based on the obtained stiffness value (Table 3). The final liver stiffness result is the average of the three reliable measurements.

2D SWE indicates two-dimensional shear-wave elastography; IQR/M indicates ratio between the interquartile range and the median; pSWE indicates point shear-wave elastography.

R² (coefficient of determination) indicates the goodness of fit of the elasticity model and shows how well the data fit the regression model. A greater R² (closer to 1) indicates more reliable measurements. The stability index assesses the consistency of elastography measurements across frames or acquisitions. A higher stability index indicates less variability and more reproducible results.
consensus, that of the European Federation of Societies for Ultrasound in Medicine and Biology, and the guidelines of the World Federation for Ultrasound in Medicine and Biology are similar [13,14]. The protocol includes: (i), instructing the patient to fast for at least four hours before the examination; (ii), positioning the patient in a supine position or slight left lateral decubitus (no > 30°), with their right hand placed above their head (the intercostal space should be as open as possible to avoid lateral artifacts from rib shadows in the image); (iii), performing measurements between the ribs and in the right liver; (iv), aligning the ultrasound beam perpendicular to the hepatic capsule; (v), ensuring a high-quality B-mode image free of artifacts [15]; (vi), correctly positioning the measurement zone: parallel to the hepatic capsule, the upper part placed 1.5-2 cm below the hepatic capsule to avoid reverberation artifacts; (vii), avoiding placing large vessels or focal structures within the measurement zone; (viii), taking measurements directly within the measurement area (pSWE) or using regions of interest placed within the elastogram (2D-SWE); and (ix), performing measurements by regions in 2D-SWE after temporal and spatial stabilization of the elastogram.

## Recommendations

### Patient preparation

* The patient should fast for at least four hours before the examination. (Delphi CVI: 1)

* The measurement should be performed between the ribs and the right liver, with the patient positioned in the supine or slight left lateral decubitus position (not > 30°) with the right arm extended. (Delphi CVI: 1)

### Measurement procedures

* The intercostal space should be as open as possible to avoid lateral artifacts from rib shadows in the image. (Delphi CVI: 1)

* The axis of the ultrasound beam must be perpendicular to the liver capsule. (Delphi CVI: 1)

* Adequate hepatic imaging in B-mode is a prerequisite for proper measurement. (Delphi CVI: 1)

* Measurements should be taken in an area free of large blood vessels or focal liver lesions. (Delphi CVI: 1)

### Measurement quality criteria

* The measurement area (pSWE) or the elastogram (2D-SWE) should be positioned parallel to the liver capsule, at least 1.5-2 cm below, to avoid reverberation artifacts. (Delphi CVI: 0.91)

* Measurements are made directly within the measurement area (pSWE) or using regions of interest placed within the elastogram (2D-SWE). (Delphi CVI: 1)

* Measurements by regions in 2D-SWE should be performed after temporal and spatial stabilization of the elastogram. (Delphi CVI: 1)

## 5.2. Which factors influence measurement reproducibility?

The different ultrasound elastography techniques show very good intra- (intraclass correlation coefficient, ICC > 0.90) and inter-observer reproducibility (ICC > 0.80) when following the recommended guidelines [5]. Measurements are not affected by patient age or sex. However, measurements taken in the subxiphoid area of the left liver tend to overestimate the actual values (likely due to greater probe compression and/or the transmission of cardiac pulsations) and should be avoided [16]. Factors affecting reproducibility are operator-related or patient-related.

For the pSWE technique, operator experience does not affect performance [17]. For the 2D-SWE technique, there is a learning curve, and reproducibility is better among experts. Nonetheless, results remain very good among non-expert operators (ICC > 0.90) [18]. At least one study reported that operators reach maximum performance after one year of

regular practice or about 100 examinations [19].

With regard to patient-related factors, the variability of measurements increases in overweight/obese patients or those with advanced liver fibrosis [20,21]. The percentage of unreliable measurements also increases with the skin-to-liver capsule distance up to 50 % if that distance is > 3 cm [21]. Performing measurements during forced inspiration influences the variability of the measurements (increasing values by +13 %) [22]. Therefore, the measurement should be performed during a short apnoea in a neutral position (neither inspiration nor deep expiration) and with strict adherence to the previously described examination conditions. The ultrasound waves used to create the measurements are attenuated at greater depths. The threshold for unreliability is approximately 6-8 cm below the skin. In contrast, the lowest measurement variability is found 4-5 cm below the skin (convex probe) [23]. Therefore, this depth should be preferred.

## Recommendations

* Measurements should be performed during neutral apnoea (neither inhalation nor forced expiration). (Delphi CVI: 1)

* The maximum measurement depth is 6-8 cm. (Delphi CVI: 1)

## 5.3. Which factors influence diagnostic performance?

In addition to those influencing reproducibility, factors also affect diagnostic performance [14]. These latter confounding factors can disrupt the relationship between the measurement expressed in kPa or m/s and the degree of hepatic fibrosis. Most studies have been performed using vibration-controlled transient elastography (VCTE™, Echosens or FibroScan®, Echosens), but the results are applicable to other elastography techniques. These factors include: (i), hepatic inflammation (serum transaminases > 5 N) [24,25]; (ii), obstructive cholestasis [26]; (iii), hepatic congestion (particularly heart failure and certain hepatic vascular diseases) [27]; (iv), acute hepatitis [28]; and (v), infiltrative liver diseases (e.g., lymphoma, amyloidosis, or extra-medullary hematopoiesis) [14]. Ultrasound elastography should yield other fibrosis assessment tools in the presence of these factors. Ultrasound elastography can be reconsidered for fibrosis evaluation after one to four weeks of abstinence in cases of acute alcoholic hepatitis [29]. Theoretically, the presence of steatosis should not influence the measurement results [16]. However, some studies have suggested it may do so nonetheless [13]. Therefore, it is preferable to interpret results with caution in cases of severe steatosis [13,16].

## Recommendations

* The following conditions increase liver stiffness as measured by ultrasound elastography: acute hepatitis, obstructive cholestasis, hepatic congestion, and infiltrative liver disease. In the presence of these confounding factors, the relationship between ultrasound elastography values and the degree of fibrosis is confounded, and thus, other tools should be used for assessment. (Delphi CVI: 0.91)

## 5.4. How to assess measurement reliability?

In addition to the standardized measurement acquisition conditions described above and the control of reproducibility and performance factors, the quality and reliability criteria of the measurements themselves must also be taken into account in order to guarantee the results obtained.

All manufacturers provide reliability criteria based on technical data. These include the stability index (SI) for SSI (Aixplorer, SuperSonic Imagine), the confidence map for ElastQ (Epiq series, Philips Healthcare), and the reliability measurement index (RMI) for S-shearwave (HS70 A, RS80 A, Samsung Medison). These reliability criteria, as defined by the manufacturers, must be adhered to, but they may not be sufficient on their own. Indeed, additional reliability criteria based on measurements and their results have been developed and published.
They vary depending on the technique being used and must also be applied.

### 5.4.1. Reliability criteria with point shear-wave elastography

The validated and commonly used reliability criterion in pSWE is the same as for VCTE: the ratio between the interquartile range and the median of the ten obtained measurements (IQR/M). A study evaluating the VTQ technique (Siemens Healthineers, Germany) defined three categories of reliability (i.e., unreliable, reliable, and very reliable examinations) (Table 2) [30]. To our knowledge, no reliability factors for other pSWE devices have been described. However, by extension, an IQR/M ratio ≤ 30% from a series of ten measurements can be used for all pSWE devices. Almost all devices equipped with an elastography module based on the pSWE technique are able to calculate the IQR/M ratio automatically.

### 5.4.2. Reliability criteria with two-dimensional shear-wave elastography

The criteria described and used for VCTE and pSWE apply entirely to the 2D-SWE technique. In the literature, the IQR/M values associated with obtaining reliable measurements vary from IQR/M < 50% to < 20% [31,32].

The coefficient of variation (CV, standard deviation/mean) has been proposed as superior to the IQR/M ratio for the Aixplorer device [33, 34]. The advantage of this criterion is that it benefits from the 2D technique by considering the measurements of each pixel in the region of interest (the standard deviation and the mean). The criterion validates each independent measurement rather than a set of measurements. By interpreting the result (kPa) according to the CV, two reliability categories are defined for each measurement: unreliable and reliable (Table 3). Obtaining three reliable measurements according to these criteria and averaging them is sufficient for a result with maximum performance [33]. This reliability criterion is automatically calculated on the new devices the manufacturer sells. However, its use remains limited as it has not yet been implemented by other manufacturers using the 2D-SWE technique. Thus, as of this writing, the calculation must be done manually for non-Aixplorer or older Aixplorer devices in parallel with the measurement.

#### Recommendations

* When vendors provide quantitative quality criteria (e.g., R2 or stability index) or visual criteria (e.g., wave propagation map), they should be followed. (Delphi CVI: 1)

* For pSWE, ten measurements must be obtained. The final liver stiffness result should be expressed as the median of these measurements. The reliability criterion is the interquartile range/median ratio (IQR/M), and the result should be interpreted based on the obtained stiffness value (see Table 2). (Delphi CVI: 0.91)

* For 2D-SWE, at least three reliable measurements must be obtained. The reliability criterion for each measurement is its coefficient of variation (standard deviation/mean), and the result should be interpreted based on the obtained stiffness value (see Table 3). The

<table><caption>**Table 2**
Point shear-wave elastography reliability criteria.</caption><thead><tr><th rowspan="2">IQR/M ratio *</th><th colspan="3">Median of the ten obtained measurements</th></tr><tr><th>&lt; 1.37 m/s</th><th>1.37-1.86 m/s</th><th>≥ 1.87 m/s</th></tr></thead><tbody><tr><td>&lt; 0.15</td><td>Very reliable</td><td>Very reliable</td><td>Very reliable</td></tr><tr><td>0.15-0.34</td><td>Reliable</td><td>Reliable</td><td>Reliable</td></tr><tr><td>≥ 0.35</td><td>Reliable</td><td>Unreliable</td><td>Unreliable</td></tr></tbody></table>

IQR/M indicates interquartile range/median ratio. The reliability of the liver stiffness result is assessed using the criteria presented in the table.

*IQR/M ratio is calculated from values expressed in m/s and adapted from a study conducted with the Virtual Touch quantification (VTQ) technique (Siemens Healthineers) [30]. Ten measurements are taken, and the median (M) and the interquartile range (IQR) are calculated.

<table><caption>**Table 3**
Two-dimensional shear-wave elastography reliability criteria.</caption><thead><tr><th rowspan="2">Coefficient of variation of the measurement</th><th colspan="3">Result of a liver stiffness measurement (kPa)</th></tr><tr><th>&lt; 8.8</th><th>8.8-11.9</th><th>≥ 12</th></tr></thead><tbody><tr><td>&lt; 0.10</td><td>Reliable</td><td>Reliable</td><td>Reliable</td></tr><tr><td>0.10-0.24</td><td>Reliable</td><td>Reliable</td><td>Unreliable</td></tr><tr><td>&gt; 0.24</td><td>Reliable</td><td>Unreliable</td><td>Unreliable</td></tr></tbody></table>

Adapted from a study conducted with the SSI technique (Aixplorer, Supersonic Imaging) [33]. The result and the coefficient of variation (CV = SD/mean) of liver stiffness are recorded for each measurement. The reliability of each result is assessed using the criteria indicated in the table. The final liver stiffness result corresponds to the average of three reliable measurements.

final liver stiffness result is the average of the three reliable measurements. (Delphi CVI: 0.82)

## 6. Guidelines for standardized reporting

### 6.1. What should be included in an ultrasound elastography report?

The ultrasound device and technique used (pSWE or 2D-SWE), the measurement conditions (patient fasting, measurement site), the factors limiting the measurements (skin-to-measurement distance, artifacts, or inability to achieve neutral apnea), and the known factors influencing performance (acute hepatitis, obstructive cholestasis, hepatic congestion, or infiltrative liver disease) should be noted. The report should also state the number of measurements obtained, the resulting liver stiffness measurement, and the reliability criteria of the examination.

Ten measurements are required for pSWE. The final liver stiffness result should be expressed as the median of these measurements. The reliability criterion is IQR/M and the result should be interpreted based on the stiffness value obtained (Table 2). For 2D-SWE, at least three reliable measurements must be obtained. The reliability criterion for a measurement is its coefficient of variation (standard deviation/mean), and the result should be interpreted based on the stiffness value obtained (Table 3). The final liver stiffness result is the average of the three reliable measurements. A result ≤ 7 kPa can be considered normal. Stiffness values > 7 kPa can be considered abnormal, but should not be interpreted as a stage of liver fibrosis. An example of a standard ultrasound elastography report is shown in Fig. 4.

## 7. Conclusion

Elastography has emerged as an important non-invasive technique for the assessment of liver fibrosis and portal hypertension; however, the accuracy and reliability of elastography measurements can be significantly affected by a variety of operator and patient-related factors. It is important to follow specific guidelines to ensure that these measurements are consistent and reliable. These include recommendations for patient preparation, positioning, technical aspects of the procedure, and the need for operators to be adequately trained and experienced. This position paper is intended to serve as a comprehensive and accessible guide for clinicians, outlining best practices and standardized protocols to improve the reliability of elastography assessments.

### Human rights

Not relevant to position statement papers/guidelines.

### Informed consent and patient details

Not relevant to position statement papers/guidelines.
<table><tr><td>Indication for the examination with mention of the clinical context:</td></tr></table>

Ultrasound machine used:

Date of commissioning:

Technique used:

<figure><img src="image_7.png" /></figure>

pSWE

<figure><img src="image_8.png" /></figure>

2D-SWE

<table><tr><td><strong>Measurement conditions:</strong><br>☐ Fasting<br>☐ Right intercostal space<br>☐ Number of measurements:</td><td><strong>Factors limiting the measurements:</strong><br>☐ No ☐ Yes<br>If yes, specify (e.g., skin-to-measurement distance, inability to achieve neutral apnoea, artefacts):</td></tr></table>

<table><tr><td colspan="2"><strong>Presence of factors influencing diagnostic performance</strong></td></tr><tr><td>☐ No</td><td>If yes, specify (e.g., acute hepatitis, obstructive cholestasis, hepatic congestion, infiltrative liver disease):</td></tr><tr><td>☐ Yes</td><td></td></tr></table>

## IF pSWE TECHNIQUE:

### Result

Median of the ten obtained measurements:

<figure><img src="image_9.png" /></figure>

IQR/M ratio:

<figure><img src="image_10.png" /></figure>

## IF 2D-SWE TECHNIQUE:

<table><thead><tr><th></th><th>Average stiffness (kPa)</th><th>Coefficient of variation</th></tr></thead><tbody><tr><td>Measurement 1</td><td></td><td></td></tr><tr><td>Measurement 2</td><td></td><td></td></tr><tr><td>Measurement 3</td><td></td><td></td></tr><tr><td><strong>Average of the three valid measurements:</strong></td><td style="background-color: #D3D3D3;">--.-- kPa</td><td></td></tr></tbody></table>

<table><tr><td>Conclusion:</td><td>Reliable / Unreliable examination<br>Normal liver stiffness (≤ 7 kPa) / Elevated liver stiffness (>7 kPa)</td></tr></table>

<caption>Fig. 4. Template for standard ultrasound elastography report.</caption>

## Funding

This work did not receive any grant from funding agencies in the public, commercial, or not-for-profit sectors.

## Author contributions

All authors attest that they meet the current International Committee of Medical Journal Editors (ICMJE) criteria for Authorship.

## CRediT authorship contribution statement

**Lucia Parlati:** Conceptualization, Investigation, Writing – original draft, Writing – review & editing. **Christophe Aubé:** Conceptualization, Investigation, Writing – review & editing. **Maïté Lewin:** Conceptualization, Investigation, Writing – review & editing. **Jérôme Boursier:** Conceptualization, Investigation, Writing – review & editing. **Maxime Ronot:** Conceptualization, Investigation, Writing – review & editing. **Anita Paisant:** Conceptualization, Investigation, Writing – original draft, Writing – review & editing.
Declaration of competing interest

Christophe Aubé and Anita Puisant declare Scientific collaboration with Supersonic Imagine and Siemens. The other authors have no conflicts of interest to disclose in relation with this article.

Acknowledgements

The authors thank M. Kevin Erwin, for professional English translation.

The authors wish to thank Edouard Bardou-Jacquet (Université de Rennes & CHU de Rennes, France), Christophe Bureau (Université Paul Sabatier & CHU de Toulouse, France), Laurent Castera (Université Paris Cité & Hôpital Beaujon, Paris, France), Charlotte Costentin (Université de Grenoble Alpes & CHU de Grenoble, France), Marco Dioguardi Burgio (Université Paris-Cité & Hôpital Beaujon, Paris, France) Jérôme Lebigot (CHU d'Anger, France) and Arthur Lecharpentier (CHU d'Anger, France) as members of the Delphi Pannel Group.

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Lucia Parlati<sup>a,b,*,c</sup>, Christophe Aubé<sup>c,d</sup>, Maïté Lewin<sup>c,f</sup>, Jérôme Boursier<sup>c,g</sup>, Maxime Ronot<sup>b,i</sup>

Anita Puisant<sup>c,d</sup> Collaborative authors (Delphi Panel Group)

<sup>a</sup> Université Paris Cité, Institut Cochin, CNRS, INSERM, Paris 75014, France

<sup>b</sup> Department of Hepatology, Hôpital Cochin, AP-HP, Paris 75014, France

<sup>c</sup> Laboratoire HIFIH, Université d'Angers, SFR ICAT 4208, Angers 49000, France

<sup>d</sup> Department of Radiology, CHU Angers, Angers 49000, France

<sup>e</sup> Department of Radiology, Hôpital Paul Brousse, AP-HP, Villejuif 94804, France

<sup>f</sup> Faculté de Médecine, Université Paris Saclay, Le Kremlin-Bicêtre 94270, France

<sup>g</sup> Department of Hepato-Gastroenterology and Digestive Oncology, CHU Angers, Angers 49000, France

<sup>h</sup> Department of Radiology, Hôpital Beaujon, AP-HP. Nord, Clichy 92118, France

<sup>i</sup> Université Paris-Cité, UMR 1149, CRI, Paris 75018, France

* Corresponding author.

E-mail address: lucia.parlati@aphp.fr (L. Parlati).