# Ultrasound Elastography: Methods, Clinical Applications, and Limitations: A Review Article
## 1 Introduction  
Ultrasound is a form of imaging that utilizes sound waves at high frequencies. The primary purpose of this function, like other imaging techniques, is to generate visual representations of internal organs and structures within the body [1; 2; 3]. Typically, clinicians employ it to observe the heart, blood vessels, kidneys, liver, and other organs. In addition, ultrasonography is employed to visualize the fetus during the course of the pregnancy. Images can offer useful insights for identifying and treating a diverse range of diseases and conditions. Typically, ultrasound tests are conducted using an external sonar instrument. Nevertheless, certain ultrasound tests necessitate the insertion of a device into your body [4; 5]. In the beginning of the 1990s, the idea of transient tissue elasticity and stiffness aiding in the detection of diseases originated, denoted as ultrasound elastography (USE) [6; 7; 8; 9]. The scope of uses for elasticity imaging (EI) in medical diagnosis and therapy monitoring is continuously expanding. Recent publications have provided extensive data indicating that the shear elasticity modulus of tissue is a highly variable physical property. It is also extremely responsive to alterations in tissue structure that occur during normal and abnormal biological processes. It is remarkable that this comprehension emerged only approximately two decades ago. The fact that the qualitative assessment of tissue elasticity through manual palpation has been extensively used since ancient times and continues to be employed today makes it particularly astonishing. Elastic moduli are regarded asfundamental parameters when describing non-biological materials. An engineer cannot conceive of designing a machine or any other construction without conducting a quantitative evaluation of the mechanical properties of the components and materials employed. Given the fact that different pathologies vary in tissue structure, a change in stiffness can lead to various diseases, such as liver-cirrhosis-associated fibrosis, cancerous pathology, and arteriosclerosis-associated calcification [10; 11; 12; 13]. CT and MRI are commonly utilized for disease detection; however, ultrasound elastography is still the best technique to observe changes in tissue elasticity and stiffness. Moreover, ultrasound elastography is used to image tissue stiffness, using the acquired information to enhance disease diagnosis accuracy, aid in early disease detection, and monitor the response to treatments like chemotherapy. Although it may reflect qualitative changes even when morphological changes are not visible, tissue stiffness measurement has the following clinical applications: (a) early detection and differential diagnosis of diseases; (b) improvement in accuracy for diagnosing diseases involving fibrosis, such as cancer, chronic hepatitis, and atherosclerosis; (c) evaluation of the response to treatments, such as rituximab [10; 14; 15; 16; 17]. Medical practitioners throughout history have acquired knowledge about tissue biology by using diagnostic palpation, a physical examination technique that identifies alterations in mechanical tissue properties. Alterations in tissue mechanics often accompany common disease processes such as fibrosis, inflammation, and neovascularization. However, using diagnostic palpation to assess the stiffness of tissue can be an effective method of detecting tumors, but it is restricted to parts of the body that are accessible to the physician's hand. Therefore, the physician can assess these changes using innovative ultrasonic elastography techniques. Conventional ultrasound (US), which also applies to USE, offers the advantage of being an inexpensive, adaptable, and widely available modality that can be used at the bedside. In recent years, USE has been researched for a number of clinical applications, and it has even been included in clinical practice for certain applications. Some examples of these applications include the evaluation of liver fibrosis and the characterization of breast lesions.