  Induction of thermal damage to tissue through delivery of microwave energy is
frequently applied in surgery to destroy diseased tissue such as cancer cells.
Minimization of unwanted harm to healthy tissue is still achieved subjectively,
and the surgeon has few tools at their disposal to monitor the spread of the
induced damage. This work describes the use of optical methods to monitor the
time course of changes to the tissue during delivery of microwave energy in the
porcine liver. Multispectral imaging and diffuse reflectance spectroscopy are
used to monitor temporal changes in optical properties in parallel with thermal
imaging. The results demonstrate the ability to monitor the spatial extent of
thermal damage on a whole organ, including possible secondary effects due to
vascular damage. Future applications of this type of imaging may see the
multispectral data used as a feedback mechanism to avoid collateral damage to
critical healthy structures and to potentially verify sufficient application of
energy to the diseased tissue.
