EUS elastography: Is it replacing or supplementing tissue acquisition?

摘要

Despite improvements in image quality and resolution, one of the major drawbacks of pancreatic EUS is the limited ability to determine the benign or malignant nature of solid lesions. In this context, EUS may guide FNA for cytological or histological diagnosis. EUS-FNA, however, may provide false-negative results for malignancy, may be unfeasible because of technical problems or interposed malignant tissue and vascular structures, and is associated with a small, but not insignificant, morbidity. As a result of efforts to overcome these limitations, most recent US image processors provide elastography, a technique that allows the imaging and quantifying of the hardness of lesions with dedicated software. The principle of EUS elastography is based on the assumption that compression of a target tissue by an echoen-doscopic probe produces a smaller strain (ie, displacement of one tissue structure by another) in hard tissue than in soft tissue. Thus, by calculating the elasticity of tissue, it is possible to differentiate benign (soft) tissue from malignant (hard) tissue. The recent introduction of second-generation EUS elastography allows quantitative analysis of tissue stiffness; the simplest of these methods uses the ratio of the elasticity of a given mass to that of a selected reference region within adjacent soft tissue, the so-called strain ratio. The most significant advantage of EUS elastography is that it can be performed in real time during a diagnostic examination with immediate information provided to the endosonographer that can affect the patient's management by delineation of a lesion and more precise targeting of FNA, without need for extensive training or costly devices or software.