TITLE: "The Physics and Analysis of Non-invasive Optical Imaging"

SPEAKER: Professor Hanli Liu

TIME: Thursday Oct. 9, 2003 at 4 PM

PLACE: George P. Williams, Jr. Lecture Hall, (Olin 101)

When tissues are illuminated with optical light, it will be either absorbed by various tissue chromophores or highly scattered by tissue cells and intracellular organelles. Recent development on optical imaging and spectroscopy of tissues affords new techniques for low-cost, portable, and real-time clinical monitoring and diagnosis of tissue/tumor properties, structures, and functions.

Theoretical basis for the photon migration techniques is the diffusion approximation to photon transport theory when the source-detector separation is on the order of centimeters. Technically, three classes of devices using pulsed, intensity-modulated, and continuous-wave (cw) light can be coupled to the tissues under study with optical fibers. The measurements from any of the three instruments lead to in vivo determination of absorption (&mu_a) and scattering (&mu_s') properties of the tissues, resulting in quantification of tissue physiological/functional properties. Furthermore, recent studies show that inverse calculations of &mu_s' from Mie theory permit determination of sizes and distributions of the effective scatterers inside the tissue at the cellular or sub-cellular level. These quantified parameters may serve as functional signatures/markers to identify tissue structures or to diagnose cancers. Several in vivo examples of using such optical means will be presented, showing a significant value of optical imaging/sensing to clinical applications.

Technical issues concerning the reconstruction of both absorption and scattering images and the uniqueness of the solution of the inverse problem will also be discussed.