In turn, elastography measures the state of rigidity or elasticity of an internal tissue by sending mechanical waves (like a small blow) through them and detecting the shape and speed at which the vibration is transmitted in the different layers of the body. To “see” how this vibration is transmitted, other techniques capable of showing us the inside of the body are used, such as an ultrasound wave from ultrasound or a ray of light if the eye is being studied, so that it can be detected (through of the variations in the received signals) how the mechanical disturbance is transmitted inside the body.
In the case of the study of an eye, the mechanical disturbance can be a simple puff of air.

Two different types of materials being measured by elastography.

Beginnings of the technique

Historically, elastography was first implemented in imaging modalities such as magnetic resonance imaging (MRE) and ultrasound (USE) (with millimeter-scale image resolution) demonstrating extensive capabilities in generating 2D and 3D elasticity maps.
Later, optical coherence tomography (OCT) was developed, which uses infrared light to pass through the transparent parts of the eye and also different layers of the retina, reflecting part of each layer in order to provide information about the eye with a micrometric image resolution ( ∼3–10 μm) and a retinal penetration depth of 1 or 2 mm. This technique made possible the first implementation of elastography in OCT, also called optical coherence elastography (OCE).

This optical coherence tomography technology makes it possible to measure the vibration suffered by the tissues when receiving the mechanical wave with a sub-nanometric sensitivity, so that with a small external disturbance the system can be used to provide not only structural images of the internal tissues as in an ultrasound, but can detect its properties of elasticity or hardness.

Future challenges of elastography

The article explains that in order to improve the conclusions about the data received, it is necessary to understand even better the elastic properties of the tissues of the body, and in this area there is work to be done due to the complexity of some tissues, such as zones between two tissues without a well-defined boundary such as the corneoscleral boundary in the eye, effects of anisotropy, viscoelasticity like liver or non-linearity such as the increased stiffness of the cornea when it is stretched.

In addition, a lot of research is being done on the ways to send that wave that generates the elastic vibration of the tissues, there are those based on light, sound, air, electromagnetic or displacement pulses, there are those with contact or without contact such as blowing, and within them the vibration can be sent in many different ways to achieve different results or work better on different tissues or to avoid possible damage, infection and discomfort to the patient.