| It is well known that changes in the mechanical properties of tissues are correlated with the presence of disease. In the eye for example, the vitreous body undergoes dramatic changes in mechanical properties during age related degradation. These changes may play a significant role in the formation of a variety of diseases, including retinal detachment and nuclear sclerotic cataracts. However, vitreous degradation cannot currently be quantified.; The work presented here aims to develop a non-invasive experimental system called Kinetic Acoustic Vitreoretinal Examination (KAVE), which may be used to detect and quantify mechanical changes of the vitreous body. KAVE uses acoustic radiation force as a means to produce small, localized displacements within the vitreous. Returning echoes are processed using ultrasonic motion tracking algorithms so that the response of the tissue to the induced radiation force can be evaluated. By repeating this process at a number of locations, images depicting viscoelastic properties of the vitreous body can be formed.; In vivo experiments were conducted using a modified Philips SONOS 5500 imaging system employing a 5 MHz linear array probe. Displacements ranging between 14 and 240 microns were observed within the vitreous body at an acoustic power output that falls within current Food and Drug Administration (FDA) limits for ophthalmic ultrasound imaging. Through the combination of appropriate mechanical modeling and signal processing, it was possible to generate images depicting a series of viscoelastic parameters, such as relative elasticity, relative viscosity, and time constant.; The preliminary results of this work show that KAVE is able to quantify mechanical properties of the vitreous body in vivo within current FDA constraints. The availability of such a technology could dramatically improve diagnostic capabilities, as well as aid the planning of appropriate treatment, thus protecting patient vision while controlling health care costs. |
