CHAPTER 13: Optical Guidance for Therapeutic Interventions

There is increasing development and use of optics-based techniques for guiding therapeutic interventions, including in oncology. In the context of photodynamic medicine, fluorescence imaging in order to guide resection of solid tumors using the contrast provided by aminolevulinic acid-induced protoporphyrin IX has reached the stage of clinical adoption. Potential extensions include: the use of other fluorescent contrast agents (biomarker targeted or untargeted, passive or activatable and molecular or nanoparticle based); quantitative techniques and subsurface tumor localization; and the use of near-infrared-activated fluorophores in order to achieve greater tissue penetration and reduced tissue autofluorescence backgrounds. Several other optical techniques are also under development for tumor margin identification and surgical guidance, including optical coherence tomography, Raman spectroscopy, photoacoustic imaging and diffuse optical tomography, as well as multiplexed imaging using a variety of optically active nanoparticles. In addition to surgical guidance, optical techniques (including photodynamic-based techniques) are being explored for other interventional procedures, such as: detecting local infection and guiding debridement; defining the target volume for radiation treatments; tracking responses to chemotherapy by monitoring the tumor metabolic status; monitoring biophysical therapies such as photothermal ablation; and in photodynamic therapy itself in order to optimize and track treatment delivery and to monitor cell/tissue responses.