ABSTRACT
The principle of diffuse optical tomography (DOT) can be illustrated as shown in Figures 1.1 and 1.2. Using breast imaging as an example, an array of optic bers typically arranged along a circular path is attached to the surface of the breast (Figure 1.1). A light beam from a source (typically a diode laser) is delivered via source optic bers to one point at the breast surface (left, Figure 1.2). Light is multiply scattered due to various cellular structures in tissue, and some are absorbed by chromophores such as hemoglobin and water molecules. The surviving photons, after often millions of times scattering, are received by multiple detection optic bers placed along the boundary (left, Figure 1.2). The received signals are then sent to a data acquisition system for output. The data collection is not considered complete until the light beam is sequentially delivered to all the preselected points along the boundary (left, Figure 1.2). A complete set of data collected is nally input into a reconstruction algorithm that is able to produce a spatial distribution of tissue absorption and scattering coefcients (middle and right, Figure 1.2). Because tumors or different structures in tissue absorb and scatter photons differently, tissue absorption and scattering coefcients are two fundamental imaging parameters in DOT.
