Endoscopic ultrasound (EUS) elastography is an imaging procedure used for the visualization of tissue elasticity during usual EUS examinations. EUS elastography can be accomplished real-time with state-of-the-art ultrasound systems, with the images being represented in transparent color superimposed on the conventional gray-scale B-mode scans. The aim of this review was to introduce the potential range of applications of EUS elastography. EUS elastography might be useful for the differentiation of benign and malignant lymph nodes, with a qualitative pattern analysis and a quantitative histogram analysis of the color images being used to adequately classify the lesions. Mapping of the tissue elasticity distribution might be useful for the differential diagnosis of focal pancreatic masses, especially in the setting of chronic pancreatitis where the accuracy of EUS-guided fine needle aspiration is also low. EUS elastography might also enhance the detection and differentiation of various solid tumors (adrenal tumors, submucosal tumors, etc.) situated nearby the gastrointestinal tract. Routine use of EUS elastography thus offers supplemental information that enhances conventional EUS imaging, with a possible decrease in the number of unnecessary EUS-FNA procedures used for tissue confirmation. However, future enhancements of the EUS elastography technology, as well as prospective, randomized studies will probably establish the clinical impact of dynamic elasticity imaging. Key words Elastography- endoscopic ultrasound- lymph nodes-

RECHERCHES Elastographie par ondes de cisaillement

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Abstract—Ethanol-induced hepatic lesions were investigated in swine for in vivo use as a strain imaging animal model. Lesions (n � 25) were induced by injecting ethanol (doses 0.33 to 2.0 mL) directly into the surgically exposed liver at depths of 12, 15 or 25 mm. Lesions were imaged with a modified HDI 1000 scanner (Philips Medical Systems, Bothell, WA, USA). The elastograms (n � 91) characterized lesions as being areas harder than the surrounding soft hepatic tissue. Elastographic lesion sizes and the corresponding injected ethanol dose used to induce the lesions were shown to be statistically significant (r 2 � 0.22; p � 0.029) using a linear regression analysis. Additionally, lesion depth was shown to be statistically insignificant (r 2 < 0.12; p> 0.10) when regressed against elastographic lesion size. An analysis of elastographic and gross pathology lesion sizes indicated no correlation (r 2 < 0.01; p � 0.973). Subsequently, lesion types were sorted by size and regression lines were computed from quasilinear regions of the corresponding run charts. Trend lines indicate a four-to-three size relationship between the selected elastographic and pathology lesion sizes. Comparison of elastogram lesion sizes from two independent observers using a paired t-test resulted in no statistically significant difference (p � 0.14). In conclusion, ethanol-induced hepatic lesions in swine is a suitable animal model for evaluation of strain-based imaging systems, due to the ease of generation and repeatability. (E-mail:

Abstract: From times immemorial manual palpation served as a source of information on the state of soft tissues and al-lowed detection of various diseases accompanied by changes in tissue elasticity. During the last two decades, the ancient art of palpation gained new life due to numerous emerging elasticity imaging (EI) methods. Areas of applications of EI in medical diagnostics and treatment monitoring are steadily expanding. Elasticity imaging methods are emerging as com-mercial applications, a true testament to the progress and importance of the field. In this paper we present a brief history and theoretical basis of EI, describe various techniques of EI, analyze their advan-tages and limitations, and overview main clinical applications. We present a classification of elasticity measurement and imaging techniques based on the methods used for generating a stress in the tissue (external mechanical force, internal ul-trasound radiation force, or an internal endogenous force), and measurement of the tissue response. The measurement method can be performed using differing physical principles including magnetic resonance imaging (MRI), ultrasound imaging, X-ray imaging, optical and acoustic signals. Until recently, EI was largely a research method used by a few select institutions having the special equipment needed to perform the studies. Since 2005 however, increasing numbers of mainstream manufacturers have added EI to their ultra-

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