Abstract

Optical imaging techniques can be combined with standard imaging technologies such as computed tomography (CT) and magnetic resonance (MR) imaging to allow measurement of signals pertaining to the molecular components of tissue. Some of the more promising approaches to image-guided spectroscopy rely upon inelastic scattering or fluorescence phenomena, which directly sample molecular contrast. Measurement of these molecular signal changes can then allow for diagnostic determination of tissue function or disease status in vivo. Molecular signal measurement often requires small tissue thickness and high signal intensity, yet when utilized with tomographic recovery it is often feasible to detect even lower signals at deep tissue depths. In this work, the range of useful signals and concentrations possible for molecular sensing with image-guidance are identified.

In order to better understand the advantages and disadvantages of each possible tomographic signal, a series of experiments have been conducted in tissue phantoms as well as animals. Three imaging signals have been explored in detail: 1) Raman, 2) surface enhanced Raman and 3) molecular fluorescence. Previous work has shown, that with the combination of optical measurements and spatial information garnered from CT or MR scans, a higher level of contrast-to-background could be obtained. These gains in signal will be verified for these imaging methods. At the culmination of this proposed work, we will be able to compare the signal strength and contrast of each imaging type with respect to the biologically relevant molecular signals necessary to allow for a linear response in imaging.