Fully Ultrasound-Assisted Endovascular Aneurysm Repair: Preliminary Report.

BACKGROUND: Reducing fluoroscopy times and iodine contrast administration during endovascular repair (EVAR) of infrarenal aortic aneurysms remains a challenge. The purpose of this study is to evaluate the preliminary results of a fully ultrasound-assisted EVAR without iodine contrast administration. METHODS: Twenty-seven consecutive patients underwent an elective intravascular ultrasound (IVUS)-assisted EVAR with final contrast-enhanced ultrasound (CEUS) control of correct aneurysm exclusion. In no case intraprocedural injection of iodine contrast medium was performed. The primary study's end points were the overall duration of the procedure, duration of fluoroscopy, cumulative radiation dose, the length of intraoperative CEUS control, and the comparison of findings between intraoperative CEUS and computed tomography (CT) scan at 1 month. RESULTS: Mean duration of the procedure was 130 ± 35 min. Overall duration of fluoroscopy was 22 ± 18 min. Mean radiation dose was 66 mGy (range 24-82). The mean length of CEUS final control was 8 ± 2 min. No type I or type III endoleak was detected either at CEUS or at angio-CT scan at 1 month from EVAR. CEUS revealed a type II endoleak in 6 patients (22%), compared to 9 type II endoleaks (33%) detected at angio-CT scan 1 month after the procedure (P = 0.5). CONCLUSIONS: Fully ultrasound (IVUS and CEUS)-assisted EVAR is safe, feasible, and reliable, completely eliminating the need for iodine contrast medium and reducing the radiation exposure for both patients and surgeons.

The Underrated Role of Ultrasound in Peritoneal Dialysis.

Ultrasound is very effective in performing procedures and assessment of complications in peritoneal dialysis. The ultrasound examination can be applied for preoperative assessment, during the peritoneal catheter placement, for the detection and monitoring of infection, as well as for the evaluation of the catheter malfunction. Despite being not only a cost- and time-saving technique but also a bedside procedure, ultrasonography remains an underrated clinical tool in the field of peritoneal dialysis. This publication wants to explain and reinforce the clinical utility of US in PD and to expand the diagnostic equipment for the clinician.

3D-Arterial analysis software and CEUS in the assessment of severity and vulnerability of carotid atherosclerotic plaque: a comparison with CTA and histopathology.

PURPOSE: Our purpose is to assess Multiparametric Ultrasound (MPUS) efficacy for evaluation of carotid plaque vulnerability and carotid stenosis degree in comparison with Computed Tomography angiography (CTA) and histology. MATERIAL AND METHODS: 3D-Arterial Analysis is a 3D ultrasound software that automatically provides the degree of carotid stenosis and a colorimetric map of carotid plaque vulnerability. We enrolled 106 patients who were candidates for carotid endarterectomy. Prior to undergoing surgery, all carotid artery plaques were evaluated with Color-Doppler-US (CDUS), Contrast-Enhanced Ultrasound (CEUS), and 3D Arterial analysis (3DAA) US along with Computerized Tomographic Angiography (CTA) to assess the carotid artery stenosis degree. Post-surgery, the carotid specimens were fixed with 10% neutral buffered formalin solution, embedded in paraffin and used for light microscopic examination to assess plaque vulnerability morphological features. RESULTS: The results of the CTA examinations revealed 91 patients with severe carotid stenoses with a resultant diagnostic accuracy of 82.3% for CDUS, 94.5% for CEUS, 98.4% for 3DAA, respectively. The histopathological examination showed 71 vulnerable plaques with diagnostic accuracy values of 85.8% for CDUS, 93.4% for CEUS, 90.3% for 3DAA, 92% for CTA, respectively. CONCLUSIONS: The combination of CEUS and 3D Arterial Analysis may provide a powerful new clinical tool to identify and stratify "at-risk" patients with atherosclerotic carotid artery disease, identifying vulnerable plaques. These applications may also help in the postoperative assessment of treatment options to manage cardiovascular risks.

US-Elastography for Breast Lesion Characterization: Prospective Comparison of US BIRADS, Strain Elastography and Shear wave Elastography.

PURPOSE: To evaluate the diagnostic performance of strain elastography (SE) and 2 D shear wave elastography (SWE) and SE/SWE combination in comparison with conventional multiparametric ultrasound (US) with respect to improving BI-RADS classification results and differentiating benign and malignant breast lesions using a qualitative and quantitative assessment. MATERIALS AND METHODS: In this prospective study, 130 histologically proven breast masses were evaluated with baseline US, color Doppler ultrasound (CDUS), SE and SWE (Toshiba Aplio 500 with a 7-15 MHz wide-band linear transducer). Each lesion was classified according to the BIRADS lexicon by evaluating the size, the B-mode and color Doppler features, the SE qualitative (point color scale) and SE semi-quantitative (strain ratio) methods, and quantitative SWE. Histological results were compared with BIRADS, strain ratio (SR) and shear wave elastography (SWE) all performed by one investigator blinded to the clinical examination and mammographic results at the time of the US examination. The area under the ROC curve (AUC) was calculated to evaluate the diagnostic performance of B-mode US, SE, SWE, and their combination. RESULTS: Histological examination revealed 47 benign and 83 malignant breast lesions. The accuracy of SR was statistically significantly higher than SWE (sensitivity, specificity and AUC were 89.2 %, 76.6 % and 0.83 for SR and 72.3 %, 66.0 % and 0.69 for SWE, respectively, p = 0.003) but not higher than B-mode US (B-mode US sensitivity, specificity and AUC were 85.5 %, 78.8 %, 0.821, respectively, p = 1.000). CONCLUSION: Our experience suggests that conventional US in combination with both SE and SWE is a valid tool that can be useful in the clinical setting, can improve BIRADS category assessment and may help in the differentiation of benign from malignant breast lesions, with SE having higher accuracy than SWE.

TIRADS, SRE and SWE in INDETERMINATE thyroid nodule characterization: Which has better diagnostic performance?

PURPOSE: To assess Strain Ratio (SRE) and Shear Wave Elastography (SWE) accuracy alone and with TIRADS classification, for the risk stratification of indeterminate thyroid nodules. MATERIALS AND METHODS: 128 Patients with 128 indeterminate nodules candidates for thyroidectomy underwent preoperative staging neck ultrasound and were classified according to K-TIRADS score. After TIRADS evaluation, semi-quantitative (SRE) and quantitative (SWE expressed in kPa) elastosonography were performed and relative diagnostic performances, alone and in combination, were compared through ROC curves analysis. In order to maximize the SRE and SWE sensitivity and specificity, their cut-off values were calculated using the Liu test. Bonferroni test was used to evaluate statistically significant differences with a p value < 0.05. RESULTS: Sensitivity, specificity, PPV and NPV were, respectively, 71.4%, 82.4%, 62.5%, 87.5% for K-TIRADS baseline US, 85.7%, 94.1%, 85.7%, 94.1% for SRE and 57.1%, 79.4%, 53.3%, 81.8% for SWE (kPa expressed). SRE evaluation showed the best diagnostic accuracy compared to the SWE (kPa expressed) (p < 0.05) and to the K-TIRADS (p > 0.05). The association of SRE with conventional ultrasound with K-TIRADS score increased sensitivity (92.9% vs 71.4%) but decreased the specificity than conventional US alone (76.5% vs 82.4%). CONCLUSION: Strain Elastosonography can be associated with K-TIRADS US examination in the thyroid nodule characterization with indeterminate cytology; in fact, adding the SRE to K-TIRADS assessment significantly increases its sensitivity and negative predictive value. However, further multicenter studies on larger population are warranted.

Prospective Evaluation of Semiquantitative Strain Ratio and Quantitative 2D Ultrasound Shear Wave Elastography (SWE) in Association with TIRADS Classification for Thyroid Nodule Characterization.

PURPOSE: To evaluate the diagnostic performance of strain ratio elastography (SRE) and shear wave elastography (SWE) alone and in combination with Thyroid Imaging Reporting and Data System (TIRADS) classification parameters to improve differentiation between benign and malignant thyroid nodules. MATERIALS AND METHODS: In this prospective study benign (n = 191) and malignant (n = 52) thyroid nodules were examined with high-resolution ultrasound (US) features using the TIRADS lexicon and SRE semiquantitative and SWE quantitative findings using histology or cytology as the gold standard with a 12-month follow-up. Sensitivity (Se), specificity (Sp) and the area under the ROC curve (AUROC) were used to evaluate the diagnostic performance of each feature and combinations of the methods. RESULTS: TIRADS score showed a sensitivity of 59.6 %, a specificity of 83.8 % with an AUROC of 0.717, a PPV of 50.0 % and an NPV of 88.4 %. SRE yielded the highest performance with a sensitivity of 82.7 %, a specificity of 92.7 % with AUROC of 0.877, a PPV 75.4 % and an NPV of 95.2 %. SWE (kPa) had a sensitivity and specificity of 67.3 % and 82.7 %, respectively, with an AUROC of 0.750, a PPV of 51.5 % and an NPV of 90.3 %. Differences were significant for SRE only but not for SWE. CONCLUSION: Ultrasound elastography may improve thyroid nodule discrimination. In particular, SRE has a better performance than TIRADS classification, while their combination improves sensitivity.

US Evaluation of Topical Hemostatic Agents in Post-Thyroidectomy.

BACKGROUND: the aim of this study was to describe the ultrasound appearance of topical hemostatics after thyroidectomy. METHODS: we enrolled 84 patients who were undergoing thyroid surgery and were treated with two types of topical hemostats, 49 with an absorbable hemostat of oxidized regenerated cellulose (Oxitamp®) and 35 with a fibrin glue-based hemostat (Tisseel®). All patients were examined using B-mode ultrasound. RESULTS: In 39 patients of the first group (approximately 80%), a hemostatic residue was detected and in some cases confused with a native gland residue, or with cancer recurrence in oncological patients. No residue was detected in patients in the second group. The main ultrasound characteristics of the tampon were analyzed and arranged according to predefined patterns, and suggestions to recognize it and avoid wrong diagnoses were provided. A part of the group of patients with tampon residue was re-evaluated after 6-12 months, ensuring that the swab remained for months after the maximum resorption time declared by the manufacturer. CONCLUSIONS: with equal hemostatic effectiveness, the fibrin glue pad is more favorable in the ultrasound follow-up because it creates reduced surgical outcomes. It is also important to know and recognize the ultrasound characteristics of oxidized cellulose-based hemostats in order to reduce the number of diagnostic errors and inappropriate diagnostic investigations.

Liver Transplant Imaging prior to and during the COVID-19 Pandemic.

BACKGROUND: The suspension of the surgical activity, the burden of the infection in immunosuppressed patients, and the comorbidities underlying end-stage organ disease have impacted transplant programs significantly, even life-saving procedures, such as liver transplantation. METHODS: A review of the literature was conducted to explore the challenges faced by transplant programs and the adopted strategies to overcome them, with a focus on indications for imaging in liver transplant candidates. RESULTS: Liver transplantation relies on an appropriate imaging method for its success. During the Coronavirus Disease 2019 (COVID-19) pandemic, chest CT showed an additional value to detect early signs of SARS-CoV-2 infection and other screening modalities are less accurate than radiology. CONCLUSION: There is an emerging recognition of the chest CT value to recommend its use and help COVID-19 detection in patients. This examination appears highly sensitive for liver transplant candidates and recipients, who otherwise would have not undergone it, particularly when asymptomatic.

Contrast-Enhanced Ultrasound (CEUS) in the Evaluation of Renal Masses with Histopathological Validation-Results from a Prospective Single-Center Study.

BACKGROUND: To evaluate the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in characterizing between malignant and benign renal lesions confirmed by histological examination. METHODS: Overall, 110 patients, for a total of 118 renal masses previously identified at CT and MRI underwent CEUS. An expert radiologist evaluated morphological, qualitative and quantitative parameters. Acquired data were analyzed to assess the value of each parameter to differentiate between malignant and benign lesions. RESULTS: Histological results of 118 renal masses showed 88 (75%) malignant lesions and 30 (25%) benign lesions. Among morphological features, inhomogeneous echogenicity was the best predictor of malignancy depicting a sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 76%, 76%, 88% and 57%, respectively. Among qualitative parameters, the most reliable parameter was the presence of pseudo-capsule. Here, sensitivity, specificity, positive PPV and NPV were 85%, 86%, 94% and 71%, respectively. Among quantitative parameters, the most reliable parameters were peak intensity (PI) and the area under the (AUC) with sensitivity, specificity, PPV and NPV values of 94%, 92%, 96% and 87% and 99%, 92%, 97% and 97%, respectively. Finally, the most reliable parameters were combined to distinguish between benign and malignant lesions. The best combination obtained was restricted to CEUS parameters (PI and AUC). Here, sensitivity, specificity, PPV, NPV and accuracy rate were 93%, 100%, 100%, 83% and 93%, respectively. CONCLUSIONS: CEUS increases the US accuracy to discriminate between benign and malignant renal lesions.

US-Elastography With Different Techniques for Thyroid Nodule Characterization: Systematic Review and Meta-analysis.

Background: Thyroid nodules are frequent in adult population and thyroid cancer incidence has increased dramatically over the past three decades. The aim of this systematic review and meta-analysis was to evaluate the US-Elastosonography (USE) diagnostic performance in assessing the thyroid nodules malignancy risk. Methods: PubMed and Embase databases were searched from January 2011 to July 2021. We extracted data from selected studies and calculated the overall diagnostic accuracy of qualitative USE, semi-quantitative USE and quantitative USE. Summary receiver operating characteristic (ROC) curve was elaborated to show the results. All statistical tests were performed using Metadisc and Medcal software package. Results: Finally 72 studies with 13,505 patients and 14,015 thyroid nodules (33% malignant) undergoing elastography were included. The pooled sensitivity, specificity and AUC were 84%, 81%, and 0.89 respectively for qualitative USE; 83%, 80%, and 0.93 for semi-quantitative USE and 78%, 81% and 0.87, for quantitative USE. The qualitative and semiquantitative USE present very similar diagnostic accuracy values and both better than the quantitative USE. Conclusions: USE is a useful imaging tool for thyroid nodule characterization. In accordance with recent guidelines and meta-analyses, the USE could be used daily in thyroid nodule malignancy risk stratification. Systematic Review Registration: PROSPERO: CRD42021279257.

The Role of CEUS in the Evaluation of Thyroid Cancer: From Diagnosis to Local Staging.

Ultrasound often represents the first diagnostic step for thyroid nodule evaluation in clinical practice, but baseline US alone is not always effective enough to achieve thyroid nodule characterization. In the last decades new ultrasound techniques, such as CEUS, have been introduced to evaluate thyroid parenchyma as recommended by EFSUMB guidelines, for use in clinical research field, although its role is not yet clear. Several papers show the potential utility of CEUS in the differential diagnosis of benign and malignant thyroid nodules and in the analysis of lymph node involvement in neoplastic pathology. Therefore, we carried out an evaluation of the literature concerning the role of CEUS in three specific areas: the characterization of the thyroid nodule, the evaluation of minimally invasive treatment and loco-regional staging of the lymph node in proven thyroid cancer. According to evidence reported, CEUS can also play an operative role in nodular thyroid pathology as it is able to guide ablation procedures on thyroid nodule and metastatic lymph nodes, to assess the radicality of surgery, to evaluate disease relapse at the level of the margins of ablated regions and to monitor the clinical evolution of necrotic areas in immediate post-treatment setting.

Preoperative Multiparametric Ultrasound and Fine Needle Aspiration Cytology evaluation of parotid gland tumors: which is the best technique?

AIMS: To evaluate the pre-surgical diagnostic value of Multiparametric Ultrasound (MPUS) and Fine Needle Aspiration Cytology (FNAC) in differentiating parotid gland tumors, comparing the results with histology. MATERIALS AND METHODS: The study enrolled 84 patients with parotid gland lesions surgically treated in a single tertiary center and evaluated by MPUS. Each patient underwent FNAC. Histological examination was considered the gold standard. RESULTS: Histology identified 62 benign tumors and 22 malignancies. In the differential diagnosis between malignant and benign lesions, B-mode Ultrasound (US), Color-Doppler US, Contrast-Enhanced US (CEUS), Elastography (USE) and FNAC showed the following values of sensitivity: 82%, 81%, 86%, 77%, 73% respectively; specificity: 97%, 61%, 95%, 71%, 97% respectively; PPV: 90%, 43%, 86%, 50%, 89% respectively; NPV: 93%, 90%, 95%, 88%, 91% respectively; and accuracy: 89%, 71%, 90%, 78%, 84% re-spectively. CONCLUSIONS: CEUS proved to be a valid and accurate method for identifying malignant tumors of parotid gland; the combination of B-mode US with CEUS showed similar diagnostic accuracy, but better sensitivity than CEUS taken alone. USE did not improve the diagnostic performance of the B-mode US, alone or in association with CEUS; however, it revealed the highest diagnostic accuracy in the differentiation between benign lesions. FNAC demonstrated lower values in comparison with CEUS and with USE. Therefore, according to our study, MPUS could be proposed as a valid alternative to FNAC.

Role of multiparametric ultrasound in testicular focal lesions and diffuse pathology evaluation, with particular regard to elastography: Review of literature.

BACKGROUND: Ultrasound is the main requested technique for the assessment of traumatic, vascular, neoplastic, and inflammatory testicular pathology. Moreover, the role of ultrasound has broadened over the years along with the introduction of new techniques, such as contrast enhanced ultrasound and ultrasound elastography. OBJECTIVE: An updated representation of the pre-existing Literature evidence for multiparametric ultrasound imaging with particular regard to elastography, in the evaluation of focal and diffuse testicular pathologies, has been presented. METHODS: The search was performed in PubMed, Cochrane, EMBASE, Web of Science and Scopus databases from the earliest available article (1977) until January 2021. Based on the evidence of the Literature, the current role of US imaging for focal and diffuse testicular pathologies has been reported and illustrated, with emphasis on examination technique, classification, and pitfalls. RESULTS: Multiparametric Ultrasound has a recognized role for testicle focal and diffuse disease. Elastography is nowadays recognized as an essential part of the multiparametric ultrasound examination. However, in the setting of testicular pathology this method showed some promising results in the setting of varicocoele and for focal lesions characterization. In the remaining field its role is still under debate. DISCUSSION: B-mode ultrasound and color Doppler ultrasound have been for a long time the diagnostic gold standard for testicular pathologies. The introduction of both contrast enhanced ultrasound and elastography in the last two decades has brought to the emergence of the multiparametric ultrasound concept. These methods are currently able to increase diagnostic confidence especially for testicular lesions characterization, with different relevance depending on the pathology under consideration. CONCLUSION: Multiparametric ultrasound testis assessment, with specific regard to elastography is nowadays recommended for focal and diffuse disease evaluation. Further and larger studies are however needed to validate these results and to understand if the role of elastography in testicular pathology may be broadened.

Thyroid Nodule Characterization: How to Assess the Malignancy Risk. Update of the Literature.

Ultrasound (US) is the first imaging modality for thyroid parenchyma evaluation. In the last decades, the role of ultrasound has been improved with the introduction of new US software, such as contrast-enhanced ultrasound (CEUS) and US-elastography (USE). USE is nowadays recognized as an essential part of the multiparametric ultrasound (MPUS) examination, in particular for the indeterminate thyroid nodule with possible fine-needle aspiration cytology (FNAC) number reduction; even if further and larger studies are needed to validate it. More controversial is the role of CEUS in thyroid evaluation, due to its high variability in sensitivity and specificity. Semi-automatic US systems based on the computer-aided diagnosis (CAD) system are producing interesting results, especially as an aid to less experienced operators. New knowledge on the molecular mechanisms involved in thyroid cancer is allowing practitioners to identify new genomic thyroid markers that could reduce the number of "diagnostic" thyroidectomies. We have therefore drawn up an updated representation of the current evidence in the literature for thyroid nodule multiparametric ultrasound (MPUS) evaluation with particular regard to USE, the US CAD system and CEUS.

Can strain US-elastography with strain ratio (SRE) improve the diagnostic accuracy in the assessment of breast lesions? Preliminary results.

PURPOSE: To assess the diagnostic value of strain ratio elastography (SRE), a semiquantitative elastosonographic method based on the displacement of the tissue from an external source (manual compression with the transducer), as compared and in combination with conventional ultrasound for the differentiation of breast lesions. METHODS: One hundred and eighty-two patients with breast lesions consecutively underwent B-mode, color Doppler US, and strain US-elastography. Each lesion was classified according to the BI-RADS lexicon by evaluating the size, the B-mode, and color Doppler features and then evaluated by SRE. Histology proven by biopsy was used as the gold standard and the patients with malignant lesions subsequently underwent operations. The diagnostic performance of each method was assessed with 2 × 2 contingency tables and ROC curve analysis. To maximize the SRE sensitivity and specificity, the SRE cut-off value was calculated using the Youden test. RESULTS: Histological examination revealed 66 benign and 116 malignant breast lesions. The conventional ultrasound showed sensitivity and specificity for the differentiation of benign and malignant lesions of 86.2% and 75.8%, respectively. Similar results were found for strain US-elastography with a cut-off of 2.49, with sensitivity and specificity of 89.7% and 72.7%, respectively. The association of conventional ultrasound with the SRE value increased the sensitivity (98.3%) but decreased the specificity compared with conventional US alone (63.6%). CONCLUSION: Strain US-elastography can be associated with BI-RADS US examination. According to our preliminary results, it helped increase the sensitivity although it decreased the specificity. However, further multicenter studies on a larger population are warranted.

Narrative review of multiparametric ultrasound in parotid gland evaluation.

Disorders affecting parotid gland represent a heterogeneous group comprising congenital, inflammatory and neoplastic diseases which show a focal or diffuse pattern of appearance. The differentiation of neoplastic from non-neoplastic conditions of parotid glands is pivotal for the diagnostic imaging. Frequently there is evidence of overlapping between the clinical and the imaging appearance of the various pathologies. The parotid gland is also often object of study with the combination of different techniques [ultrasound-computed tomography-magnetic resonance imaging (US-CT-MRI), ex.]. Compared to other dominant methods of medical imaging, US has several advantages providing images in real-time at lower cost, and without harmful use of ionizing radiation and of contrast enhancement. B-mode US, and the microvascular pattern color Doppler are usually used as first step evaluation of parotid lesions. Elastography and contrast-enhanced US (CEUS) has opened further possible perspectives to improve the differentiation between benign and malignant parotid lesions. The characterization of the parotid tumors plays a crucial role for their treatment planning and for the prediction of possible surgical complications. We present, here an updated review of the most recurrent pathologies of parotid gland focusing on the diagnostic power of multiparametric US including CEUS and ultrasound elastography (USE); limitations, advantages and the main key-points will be presented.

Computer-aided diagnostic system for thyroid nodule sonographic evaluation outperforms the specificity of less experienced examiners.

PURPOSE: Computer-aided diagnosis (CAD) may improve interobserver agreement in the risk stratification of thyroid nodules. This study aims to evaluate the performance of the Korean Thyroid Imaging Reporting and Data System (K-TIRADS) classification as estimated by an expert radiologist, a senior resident, a medical student, and a CAD system, as well as the interobserver agreement among them. METHODS: Between July 2016 and 2018, 107 nodules (size 5-40 mm, 27 malignant) were classified according to the K-TIRADS by an expert radiologist and CAD software. A third-year resident and a medical student with basic imaging training, both blinded to previous findings, retrospectively estimated the K-TIRADS classification. The diagnostic performance was calculated, including sensitivity, specificity, positive and negative predictive values, and the area under the receiver operating characteristic curve. RESULTS: The CAD system and the expert achieved a sensitivity of 70.37% (95% CI 49.82-86.25%) and 81.48% (61.92-93.7%) and a specificity of 87.50% (78.21-93.84%) and 88.75% (79.72-94.72%), respectively. The specificity of the student was significantly lower (76.25% [65.42-85.05%], p = 0.02). CONCLUSION: In our opinion, the CAD evaluation of thyroid nodules stratification risk has a potential role in a didactic field and does not play a real and effective role in the clinical field, where not only images but also specialistic medical practice is fundamental to achieve a diagnosis based on family history, genetics, lab tests, and so on. The CAD system may be useful for less experienced operators as its specificity was significantly higher.

Median nerve evaluation by shear wave elastosonography: impact of "bone-proximity" hardening artifacts and inter-observer agreement.

PURPOSE: Peripheral nerves frequently travel close to the bone surface and are, therefore, prone to elastosonographic "bone-proximity" hardening artifacts. The impact of these artifacts on quantitative measurements of median nerve stiffness performed by shear wave elastosonography has not been explored. Our aim was to assess normal median nerve stiffness values at various locations. MATERIALS AND METHODS: Thirty-six healthy volunteers (24 women and 12 men) aged between 25 and 40 years were evaluated. Two operators performed the evaluation: one expert (6 years of ultrasound experience) and one inexperienced operator (6 months' experience). The nerve was sampled in cross-section at three different locations: mid-forearm, immediately before the carpal tunnel and within the tunnel. The ultrasound scanner was equipped with a 14-MHz linear probe. The Shear Wave module was activated in one-shot mode. Measurements were performed using a ROI corresponding to the diameter of the nerve. RESULTS: The mean values of stiffness of the medial nerve were 32.26 kPa ± 18.60 within the carpal tunnel, 22.20 kPa ± 9.84 at the carpal tunnel inlet and 7.62 kPa ± 7.38 in the forearm. Inter-observer agreement assessed using the intraclass correlation coefficient (ICC) was "moderate" within the carpal tunnel (ICC = 0.44), "moderate" at the carpal tunnel inlet (ICC = 0.41) and "fair" in the forearm (ICC = 0.38). CONCLUSIONS: The stiffness of the median nerve progressively increases in its distal portions, where the nerve approaches the bone surface. Inter-observer agreement was generally good (from fair to moderate).