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Changes in tissue elasticity are generally correlated with its pathological state. In many cases, despite the difference in elasticity, the small size of a lesion or its location deep in the body preclude its detection by palpation. In general, such a lesion may or may not possess echogenic properties that would make it ultrasonically detectable. Elastography is an ultrasonic method for imaging the elasticity of compliant tissues. The method estimates the local longitudinal strain of tissue elements by ultrasonically assessing the one dimensional local displacements. This information can be combined with first order theoretical estimates of the local stress to yield a quantitative measure of the local elastic properties of tissue. The elasticity information is displayed in the form of a gray scale image called an elastogram. An experimental system for elastography in phantoms based on a single element transducer has been described previously [1]. Here we introduce a new elastography system based on a linear array transducer that is suitable for in vivo scanning. We describe tissue mimicking phantom experiments and preliminary in vivo breast and muscle elastograms confirming the feasibility of performing elastography in vivo. An elastogram of a breast containing an 8 mm palpable cancer nodule clearly shows the lesion. Elastograms and their corresponding sonograms show some similarities and differences in the depiction of tissue structures.

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EMB alone is not sufficient for screening women for PMB. TVS appears to be more sensitive than is EMB for the detection of abnormalities, particularly those outside the endometrium. For these reasons, TVS should be the initial screening test when examining women with PMB.

This monograph presents a tutorial review of the current state-of-the-art in ultrasonic attenuation estimation in reflection. Clinical indications which provide the motivation for attempting in vivo attenuation estimation are discussed. Frequency and time domain techniques and their respective tradeoffs and problems are presented. Finally, current clinical results obtained with the various techniques are summarized and further areas of study are suggested.