Thesis Committee

Keith Paulsen, Ph.D. (Chair)

Frederic Leblond, Ph.D.

David Roberts, M.D.

Chad Kanick, Ph.D.

Abstract

In neurosurgical tumor resection, the current standard is to use pre-operative MR image combined with tracking equipment to provide a map for intraoperative guidance. This technology has improved surgical outcomes, but is limited by deformation of the brain during the surgery. A potential supplement to image-guidance is fluorescence-guidance. To date, ALA is being researched as a technique to guide tumor resection by inducing the accumulation of the endogenous fluorophore PpIX. Most research has focused on the use of blue light excitation of PpIX to visual the tumor. However, due to the high attenuation of blue light by in vivo chromophores, such as oxy- and deoxy-hemoglobin, only the top layer of cells emits the fluorescence and is subject to masking by blood in the surgical field of view. This issue is particularly a problem at the end of the resection, when the surgeon believes that the tumor is removed, but there is a possibility that residual tumor is several millimeters beneath the surface. PpIX also has an absorption band in the near infrared (NIR), where the absorption due to blood is orders of magnitude lower. The light transport in this region can be approximated as diffuse since the optical scattering is much higher than the absorption. The goal of this project is to utilize diffuse light models to estimate the location, depth, and size of the fluorescent inclusion based upon surface measurements of the fluorescence emission spectrum. The techniques will be optimized first in phantoms, verified in animal tumor models, and tested in human cases.