@phdthesis{bargo03b,
  author = {Paulo Bargo},
  title = {Optical measurements for quality control in photodynamic therapy},
  school = {Oregon Health \& Science University},
  year = {2003},
  abstract = {The evolution of Photodynamic Therapy (PDT) to a fully developed treatment modality requires the development of appropriate dosimetry to ensure proper quality control during treatments. The parameters measured for PDT quality control were the drug accumulation and the optical penetration depth. These methods were tested \textit{in vitro} in photochemical assays and in tissue simulating phantoms. Pilot clinical trials were conducted and \textit{in vivo} measurements were perform in patients undergoing endoscopic screening for esophageal diseases and photodynamic therapy of esophagus, lung, oral cavity and skin.\\[3mm] A system and model to measure the relative drug concentration \textit{in vivo} for patients undergoing endoscopic PDT are presented. Fluorescence measurements from tissue were corrected by the light transport of the excitation and emission light derived from Monte Carlo simulations. The mean error between the concentration determined from measurements in optical tissue simulating phantoms and was 10\%. The non-corrected relative fluorescence data showed differences of 2--3 fold when comparing samples with the same drug concentration but different optical properties. The range of concentrations measured for all patients span over 2 orders of magnitude highlighting the need of dosimetry in individual basis. \\[3mm] Blood perfusion was the main variable that affected the optical penetration depth of treatment light and the depth of treatment. The fraction of blood ranged from 0.1\% to 30\% and was typically greater for tumor tissue compared with normal tissue for a given patient. The increased blood fraction accounted for a higher absorption coefficient hence a reduced optical penetration depth in tumor tissue. Values of $\delta$ ranged from 1.3--3.6\,mm for the overall normal sites (mean$\pm$sd = 2.2$\pm$0.5\,mm) and from 0.6-3.6\,cm for the tumor sites (mean$\pm$sd = 1.6$\pm$0.7\,mm). \\[3mm] Models were developed to help understand light propagation from optical fibers to tissue and vice versa. These models were used to improve the development of instrumentation and to modify existing well-established theories to accurately interpret data.},
}