title: Reconstruction of hemodynamics and sensitizer distributions during interstitial PDT using spectroscopy with linear light sources.
abstract: Light dosimetry for photodynamic therapy requires a knowledge of the optical absorption spectrum of the tissue being treated Here, we present a theoretical and experimental analysis of the capabilities of a system using interstitial linear light sources ranging in length from 2 to 5 cm to illuminate the tissue interstitially, and isotropic point-like detectors to measure the resulting diffusely transmitted light. The sources and detectors are translated in transparent plastic catheters under the control of a motorized positioning system designed for interstitial measurements in the prostate. The light source is a quartz-tungsten-halogen (QTH), and the spectrally resolved detection is accomplished using a CCD-based grating spectrometer. The data are analyzed using an approximation to the radiative transport equation, assuming homogeneous scattering and heterogeneous absorption spectra Absorption spectra are reconstructed independently for individual source-detector channel pairs. Sequential reconstruction can then be used to create a 3-dimensional reconstruction. The results of simulated data, measurements made in multi-component phantoms, and synthetic data reconstructed fromin vivomeasurements made with point sources demonstrate the feasibility of this method.
authors.affiliation: Dept. of Radiation Oncology, University of Pennsylvania, 3400 Spruce St., Philadelphia, PA USA 19104.
authors.forename: Jarod C
authors.initials: JC
authors.lastname: Finlay
authors.affiliation: Dept. of Radiation Oncology, University of Pennsylvania, 3400 Spruce St., Philadelphia, PA USA 19104.
authors.forename: Ken
authors.initials: K
authors.lastname: Wang
authors.affiliation: Dept. of Radiation Oncology, University of Pennsylvania, 3400 Spruce St., Philadelphia, PA USA 19104.
authors.forename: Yida
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Dept. of Radiation Oncology, University of Pennsylvania, 3400 Spruce St., Philadelphia, PA USA 19104.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Zhu
keywords:  Photodynamic therapy ;  dosimetry ;  optical properties 