EBUS strain elastography for predicting lymph node malignancy: standardization of assessment technique

Introduction: In intrathoracic lung cancer staging, PET-CT and EBUS lymph node ultrasound characteristics are used to guide aspiration in lung cancer. In order to predict malignancy in lymph nodes, ultrasound characteristics can be used in adjunct to PET-CT. A new ultrasound technique termed strain elastography has become available in EBUS and indirectly measures tissue elasticity. The elastography assessment however lacks standardization. Methods: We systematically compared different EBUS-strain elastography (SE) assessment strategies in 120 lymph nodes of 63 patients with lung cancer. Two qualitative visual analogue scale strain scores and two semi-quantitative strain elastography measurements (strain histogram and strain ratio) were acquired using Pentax-Hitachi platform. Technical considerations for using EBUS-SE as clinical diagnostic tool are identified to introduce a standardized operating procedure for SE assessment for daily clinical use and research. Results: We identified sources of artefacts, anatomical structures, amount of axial deformation, energy absorption, ROI size selection, and software preset settings as technical limitations of influence on reproducibility of EBUS strain elastography assessment. Conclusion: We found that the mean strain histogram technique is the most robust, objective and reproducible technique. But the endoscopist needs to be aware of technological bounderies and pitfalls for EBUS-SE to be applied in daily clinical practice. When addressed, adding the EBUS-SE mean histogram has additional predictive value in both imaging suspicious and imaging normal lymph nodes, with stiffer lymph nodes being more likely malignant (Respiration DOI:10.1159/000494143).