Perspectives and advances in optical elastography

In medicine, both pathological (e.g. cirrhosis) and non-pathological states (e.g. aging) can be characterized by changes in the mechanical properties of biological tissue. The use of optical techniques to measure and map the elastic properties of soft tissue, known as optical elastography, is an emergent field with applications in various clinical disciplines, including ophthalmology and dermatology. In this paper, a brief overview of optical elastography will be provided with a short taxonomy. Categories include appropriate types of tissue models (semi-infinite, single thin layer, composite stacks), clinical tasks (classification or estimation), and excitation modes (transient, continuous, quasi-static, or molecular shift). We will then discuss examples of current advances, including optical coherence elastography using reverberant shear wave fields and Brillouin microscopy. The examples will demonstrate how current and future techniques may address clinical needs. Advantages and disadvantages of these techniques will be presented, augmenting the framework of the categorization system. With emerging applications, the taxonomy may be expanded providing a roadmap to future techniques.