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T. Joshua Pfefer - IEEE Xplore Author Profile

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We have investigated the potential for contrast-enhanced near-infrared fluorescence imaging of tissue on a mobile phone platform. Charge-coupled device- and phone-based cameras were used to image molded and three-dimensional-printed tissue phantoms, and an ex vivo animal model. Quantitative and qualitative evaluations of image quality demonstrate the viability of this approach and elucidate variat...Show More
Time-resolved fluorescence (TRF) measurements of biological tissue provide chemical and structural information useful for detecting subtle disease processes, including cancers originating in mucosal tissues. A number of techniques for analyzing such TRF measurements exist, but they have not yet been compared to determine which of them can provide the greatest sensitivity to differences between a T...Show More
In order to facilitate rapid simulation of reflectance spectroscopy for biological tissue, we have derived convolution equations needed to apply the condensed Monte Carlo (MC) modeling approach to single illumination-detection fiber probes. This approach was validated against a standard MC model, and then implemented to perform three computationally demanding tasks. First, by performing simulation...Show More
Fluorescence spectroscopy systems designed for clinical use commonly employ fiberoptic probes to deliver excitation light to a tissue site and collect remitted fluorescence. Although a wide variety of probes have been implemented, there is little known about the influence of probe design on light propagation and the origin of detected signals. In this study, we examined the effect of optical fiber...Show More
Infrared laser ablation of urinary calculi was investigated as a function of wavelength to determine the relation of ablation threshold fluences, ablation depths, and optical absorption. A simple photothermal ablation model was employed to examine this relationship. Human urinary calculi composed of >95% uric acid, >95% cystine, >95% calcium oxalate monohydrate (COM), and >90% magnesium ammonium p...Show More
A transient two-dimensional optical-thermal model that accounts for dynamic changes in optical and thermal properties with temperature was developed to investigate the mechanisms leading to thermal damage during laser tissue soldering. The model was implemented using the electrical circuit simulator simulation program with integrated circuit emphasis (SPICE). Electrical analogies for the optical a...Show More
Information regarding energy deposition during laser irradiation of structurally complex biological tissue is needed to understand and improve the results of clinical procedures. A modular adaptive geometry numerical model capable of simulating the propagation of laser light in a wide variety of multiple component tissues has been developed and tested. A material grid array is generated by assigni...Show More