Thomas J. Farrell

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A model based upon steady-state diffusion theory which describes the radial dependence of diffuse reflectance of light from tissues is developed. This model incorporates a photon dipole source in order to satisfy the tissue boundary conditions and is suitable for either refractive index matched or mismatched surfaces. The predictions of the model were(More)
Using spatially resolved, steady state diffuse reflectometry, a directional dependence was found in the propagation of visible and near infrared light through human skin in vivo. The skin's reduced scattering coefficient mu(s)' varies by up to a factor of two between different directions of propagation at the same position. This anisotropy is believed to be(More)
Diabetics would benefit greatly from a device capable of providing continuous noninvasive monitoring of their blood glucose levels. The optical scattering coefficient of tissue depends on the concentration of glucose in the extracellular fluid. A feasibility study was performed to evaluate the sensitivity of the tissue reduced scattering coefficient in(More)
Singlet oxygen (¹O₂) direct dosimetry and photosensitizer fluorescence photobleaching are being investigated and applied as dosimetric tools during 5-aminolevulinic acid (ALA)-induced protophorphyrin IX (PpIX) photodynamic therapy (PDT) of normal skin and skin cancers. The correlations of photosensitizer fluorescence and singlet oxygen luminescence (SOL)(More)
A photon diffusion model has been developed to calculate the steady-state spatially resolved fluorescence from pencil beam excitation in layered tissue. The model allows the calculation of both the excitation reflectance and the fluorescence escape for an arbitrary continuous depth distribution of tissue optical properties and fluorophore concentration. The(More)
Photon diffusion theory was used to model photobleaching and tissue necrosis resulting from broad-beam therapeutic light irradiation of tissue containing a photosensitizer. The photosensitizer fluorescence signal at the tissue surface was simulated with both broad-beam and pencil-beam excitation. The relationship between the decreasing fluorescence signal(More)
We have examined the possibility of determining the optical properties of a two-layer medium by using a diffusion approximation radiation transport model [Appl. Opt. 37, 779 (1998)]. Continuous-wave and frequency-domain (FD) low-noise Monte Carlo (MC) data were fitted to the model. Marquardt-Levenberg and a simulated annealing algorithm were used and(More)
Most instruments used to measure tissue optical properties noninvasively employ data-analysis algorithms that rely on the simplifying assumption that the tissue is semi-infinite and homogeneous. The influence of a layered tissue architecture on the determination of the scattering and absorption coefficients has been investigated in this study. Reflectance(More)
Bone mineral mass measurements using dual photon absorptiometry rely on the assumption that fat thickness is constant within the region scanned by the photon beam. This assumption has been tested using both single and multiple slices from archived CT scans. In 26 patients, the difference in fat content between the bone and baseline measurement sites, the(More)
INTRODUCTION In this study, we investigated the effect of the 3-hydroxy-3-methylgutaryl-CoA reductase inhibitor lovastatin, as a sensitizer of lung cancer cells to ionizing radiation (IR). METHODS A549 lung adenocarcinoma cells were treated with 0 to 50 μM lovastatin alone or in combination with 0 to 8 Gy IR and subjected to clonogenic survival and(More)