Zona Pellucida (ZP), the outer protective layer of mammalian eggs, is composed of glycoproteins that can be dissolved by temperature elevation. The kinetics of this thermo-dissolution process can play an important role in understanding... more
Zona Pellucida (ZP), the outer protective layer of mammalian eggs, is composed of glycoproteins that can be dissolved by temperature elevation. The kinetics of this thermo-dissolution process can play an important role in understanding the mechanism of photothermolysis by a laser. While a temperature of around 70 degrees Celsius has been previously reported as the critical dissolution temperature for the
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Since it is difficult to measure the temperature in the small focused area of the laser-irradiated zona pellucida, we have developed a model to characterize the temperature field associated with this process which uses optical properties... more
Since it is difficult to measure the temperature in the small focused area of the laser-irradiated zona pellucida, we have developed a model to characterize the temperature field associated with this process which uses optical properties of water and measured beam profiles. In this presentation, we use this model to examine the temperature field for laser irradiation conditions which result
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Laser drilling of the zona pellucida of the mammalian egg can be achieved using a continuous wave 1.48 micrometers diode laser because of high absorption coefficient of water at this wavelength. Effect of increase in temperature of the... more
Laser drilling of the zona pellucida of the mammalian egg can be achieved using a continuous wave 1.48 micrometers diode laser because of high absorption coefficient of water at this wavelength. Effect of increase in temperature of the medium on the holes produced by the laser is studied. A threshold temperature is identified and its relation to the radial temperature
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The Theoretical study of thermal damage processes in laser irradiated tissue provides further insight into the design of optimal coagulation procedures. Controlled laser coagulation of tissue was studied theoretically using a finite... more
The Theoretical study of thermal damage processes in laser irradiated tissue provides further insight into the design of optimal coagulation procedures. Controlled laser coagulation of tissue was studied theoretically using a finite element method with a modulating laser heat source to simulate feedback controlled laser delivery with a constant surface temperature. The effects of uncertainty in scattering and absorption properties of the tissue, thermal denaturation induced changes in optical properties, and surface convection were analyzed. Compared to a single pulse CW irradiation in which a doctor would presumably stop CW laser delivery after noticing some effect such as vaporization or carbonization, the constant surface temperature scenario provided a better overall control over the coagulation process. In particular, prediction of coagulative damage in a constant temperature scenario was less sensitive to uncertainties in optical properties and their dynamic changes during the course of coagulation. Also, subsurface overheating under surface convective conditions could be compensated for under constant temperature irradiation by lowering the surface temperature.
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ABSTRACT
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We have investigated the possibility of using diffuse reflectance polarimetry to detect changes caused by different molecular compounds and concentrations in tissue-simulating phantoms. The effects of glucose, B-alanine and l-lysine at... more
We have investigated the possibility of using diffuse reflectance polarimetry to detect changes caused by different molecular compounds and concentrations in tissue-simulating phantoms. The effects of glucose, B-alanine and l-lysine at different concentrations in turbid media have been investigated separately. This approach is based on the effect of optical properties on the polarization state of light. The results show that this method has potential for determining changes in molecular concentrations in highly scattering biological media from polarization images.
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Laser removal of dental hard tissue has been proposed as a replacement for or augmented approach to the dental handpiece. The main limitation for widespread usage of lasers in dentistry has been inefficient ablation of dental hard tissue,... more
Laser removal of dental hard tissue has been proposed as a replacement for or augmented approach to the dental handpiece. The main limitation for widespread usage of lasers in dentistry has been inefficient ablation of dental hard tissue, accompanied by potential laser-induced damage to the surrounding tissue. The research focuses on a novel approach for enhancement of tissue ablation and confinement of laser interaction to a small tissue volume by controlled placement of an exogenous dye on the enamel surface. Studies were done with both pulsed alexandrite and pulsed Nd:YAG lasers, with indocyanine green and India ink, respectively, used as photo-absorbers. These dye-enhanced laser processes demonstrated the feasibility of this technique for cavity preparation. While control studies produced little or no appreciable crater, average preparation depth for the dye-enhanced ablation was from 1 to 1.5 mm, with a diameter of approximately 0.6 mm. Knoop hardness measurements show that, su...
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ABSTRACT Since it is difficult to measure the temperature in the small focused area of the laser-irradiated zona pellucida, we have developed a model to characterize the temperature field associated with this process which uses optical... more
ABSTRACT Since it is difficult to measure the temperature in the small focused area of the laser-irradiated zona pellucida, we have developed a model to characterize the temperature field associated with this process which uses optical properties of water and measured beam profiles. In this presentation, we use this model to examine the temperature field for laser irradiation conditions which result in a given hole size.
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Research Interests: Biomedical Engineering, Finite element method, Finite Element Analysis, Humans, Animals, and 12 moreLight, Temperature, Land Surface Temperature, Optical Properties, Mathematical Model, Radiation Effect, Burns, Surface Properties, Informing Science, Equipment Design, Electrical And Electronic Engineering, and *Hot Temperature
The role of optical properties in the distribution of laser light and the resulting thermodynamic processes in biological tissue is studied from a theoretical perspective. Light distribution is modeled by a discrete ordinate method and... more
The role of optical properties in the distribution of laser light and the resulting thermodynamic processes in biological tissue is studied from a theoretical perspective. Light distribution is modeled by a discrete ordinate method and heat transfer and ablation is modeled by an immobilized finite element method. The effect of parametric variation of absorption, scattering anisotropicity on the dynamics of the ablation process is examined. The manifestation of higher than the ablation threshold temperature in the subsurface tissue is observed and discussed. Results indicate significant differences in the ablation behavior which may have important clinical implications.
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The zona pellucida is the thick glycoprotein layer that surrounds and protects the female gamete. This layer plays an important part in mammalian reproduction. Here, the authors analyze a drilling process utilizing a 1.48 μm diode laser,... more
The zona pellucida is the thick glycoprotein layer that surrounds and protects the female gamete. This layer plays an important part in mammalian reproduction. Here, the authors analyze a drilling process utilizing a 1.48 μm diode laser, and they review their mathematical model of the deposition of laser energy. They also present their results from experiments in which they drilled
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A new optical probe which enables rapid and noninvasive measurement of the in vivo optical properties of tissues over a broad range of wavelengths is presented. The device was initially tested and calibrated in tissue-simulating phantoms... more
A new optical probe which enables rapid and noninvasive measurement of the in vivo optical properties of tissues over a broad range of wavelengths is presented. The device was initially tested and calibrated in tissue-simulating phantoms whose optical properties were known to be similar to those of biological media. The technique was then applied in vivo to measure the optical properties of canine and human prostates.
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The Texas Medical Center in Houston and the nearby UT Medical Branch at Galveston together constitute a major center of medical research activities. Laser applications in medicine are under development with the engineering assistance of... more
The Texas Medical Center in Houston and the nearby UT Medical Branch at Galveston together constitute a major center of medical research activities. Laser applications in medicine are under development with the engineering assistance of the colloborating engineering centers at Rice University, UT-Austin, and Texas A&M Univ. In addition, this collective is collaborating with the Naval Research Laboratory, where new developments in laser design are underway, in order to transfer promising new laser technology rapidly into the medical environment.
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Optical properties of biological tissue can change as a result of thermal denaturation due to temperature rise; a familiar example is whitening observed in cooking egg-white. Changes in optical properties with temperature have been... more
Optical properties of biological tissue can change as a result of thermal denaturation due to temperature rise; a familiar example is whitening observed in cooking egg-white. Changes in optical properties with temperature have been reported in the literature. Temperature rise due to laser irradiation is a function of the optical properties of tissue which themselves are a function of temperature
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The purpose of this research was to gain better insight into the processes involved in ablation of biological media by continuous wave (CW) laser irradiation. In all experiments, a high-speed video camera and infrared camera were used... more
The purpose of this research was to gain better insight into the processes involved in ablation of biological media by continuous wave (CW) laser irradiation. In all experiments, a high-speed video camera and infrared camera were used simultaneously to observe and correlate the mechanical and thermal events associated with CW argon laser irradiation of various substances (porcine aortae, collagen fibers, and polyacrylamide control samples). Lateral temperature histories of rod specimens after ablation onset demonstrate the fact that the highest temperature achieved in each medium is located some distance along its axis rather than at the ablation front itself. Surface temperature recordings of tissue slabs describe the explosive nature of CW laser ablation of soft biological media, and threshold surface temperatures for argon CW laser ablation of various media were established. Fast video imaging reveals the dehydration, bubble formation, explosive events, subsequent boiling of remaining liquid, and eventual burning of the media corresponding to the thermal events recorded.
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The Er:YAG laser ablation of hard dental tissues and artificial dental stones was studied. The hole depth after ablation was measured as a function of pulse energy and pulse number. The dental gypsum products allowed systematic study of... more
The Er:YAG laser ablation of hard dental tissues and artificial dental stones was studied. The hole depth after ablation was measured as a function of pulse energy and pulse number. The dental gypsum products allowed systematic study of how pulse energy, pulse number, and water content affected ablation. The studies on human teeth compared teeth stored in saline vs teeth
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Page 1. Diffusely Backscattered Polarized Light Mueller Matrix Imaging of a Turbid Medium Brent D. Cameron Biomedical Engineering Program, Texas A&M University College Station, Texas 77843-3120 MJ Rakovic Center ...
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This paper presents a novel computer procedure for correlating intravascular ultrasound- (WLJS) images with their corresponding locations on contrast angiograms, and dkpfaying both images in a side by side format. Modeh with artificial... more
This paper presents a novel computer procedure for correlating intravascular ultrasound- (WLJS) images with their corresponding locations on contrast angiograms, and dkpfaying both images in a side by side format. Modeh with artificial plaques located at various sites were created in order to assess the accuracy of the procedure in-vitro. The error obtained was small and not Likely to have
Experiments in dog and rat liver compared the 805-nm wavelength of the diode laser and the 1064-nm wavelength of the Nd:YAG laser. (1) The major optical differences are in the absorption. The optical properties of dog liver were... more
Experiments in dog and rat liver compared the 805-nm wavelength of the diode laser and the 1064-nm wavelength of the Nd:YAG laser. (1) The major optical differences are in the absorption. The optical properties of dog liver were determined by integrating sphere experiments. The scattering coefficients were similar at both wavelengths, but the absorption was 3.5-fold greater for the diode
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Effects of temperature on the near-infrared spectroscopic measurement of glucose. [Proceedings of SPIE 3253, 41 (1998)]. Byungjo Jung, Michael J. McShane, Sohi Rastegar, Gerard L. Cote. Abstract. The noninvasive monitoring ...
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Profiles of light, temperature, and thermal damage distributions in tissue based on measured optical properties are examined theoretically for high power diode laser (810 nm) and Nd:YAG laser 1064 nm). Generally higher absorption and... more
Profiles of light, temperature, and thermal damage distributions in tissue based on measured optical properties are examined theoretically for high power diode laser (810 nm) and Nd:YAG laser 1064 nm). Generally higher absorption and effectively lower optical penetration has been experimentally observed at the wavelength of diode laser as compared to that of Nd:YAG laser. Results of this study indicate
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Optical properties of biological tissue can change as a result of thermal denaturation due to temperature rise; a familiar example is whitening observed in cooking egg-white. Changes in optical properties with temperature have been... more
Optical properties of biological tissue can change as a result of thermal denaturation due to temperature rise; a familiar example is whitening observed in cooking egg-white. Changes in optical properties with temperature have been reported in the literature. Temperature rise due to laser irradiation is a function of the optical properties of tissue which themselves are a function of temperature
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ABSTRACT Factors that have limited the acceptance of optical spectroscopy methods for non-invasive blood glucose sensing include signal variations due in part to changes in the skin tissue optics between patients, the lack of a repeatable... more
ABSTRACT Factors that have limited the acceptance of optical spectroscopy methods for non-invasive blood glucose sensing include signal variations due in part to changes in the skin tissue optics between patients, the lack of a repeatable pathlength inherent in using diffusely reflected photon approaches, temperature variations on the skin, and the pressure with which a probe is applied to the skin surface. Unfortunately, most previous approaches to non-invasive glucose sensing have failed to address these important issues. In this work, we developed a novel skin port sensor (SPS) which eliminates the effect of skin optics by using a stable, infection-free, dermal implant to provide a skinless window into the body. Our implant is designed to provide a fixed optical pathlength as well as features to minimize temperature and pressure variations. Preliminary experiments in a pig model demonstrate both a stable biological seal at the transcutaneous interface as well as ingrowth of vascular containing granulation tissue within the sensing chamber. Furthermore, optical spectra acquired from the port demonstrate changes in glucose signatures related to concentration changes induced in the blood. Our novel SPS may provide the necessary platform for successful implementation of an optical approach to in vivo glucose sensing.
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5-Aminolevulinic acid-induced protoporphyrin IX is a promising photosensitizer that could enhance the spectroscopic contrast between normal and diseased oral tissues. Knowledge of the pharmacokinetics and effects on tissue type are... more
5-Aminolevulinic acid-induced protoporphyrin IX is a promising photosensitizer that could enhance the spectroscopic contrast between normal and diseased oral tissues. Knowledge of the pharmacokinetics and effects on tissue type are important for diagnostic and therapeutic procedures. Dogs randomly were administered five doses of 5-aminolevulinic acid: 5, 25, 50, 75, and 100 mg/kg. The fluorescence was recorded from buccal mucosa, gums, tongue, and facial skin using a fiberoptic probe connected to an optical multichannel analyzer. Blood samples were collected for hematologic and serum biochemical analysis. Pharmacokinetic parameters of interest were estimated using a compartmental model. Protoporphyrin fluorescence at all sites reached a peak in 2-6 hours, and returned to baseline in 24-31 hours, depending on the dose. Plasma protoporphyrin peaked earlier than oral tissues. The rate of synthesis of protoporphyrin, and its conversion to heme products are dose dependent. Different tissues have different pharmacokinetic response.
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A Monte Carlo simulation of photon propagation through human skin and interaction with a subcutaneous fluorescent sensing layer is presented. The algorithm will facilitate design of an optical probe for an implantable fluorescent sensor,... more
A Monte Carlo simulation of photon propagation through human skin and interaction with a subcutaneous fluorescent sensing layer is presented. The algorithm will facilitate design of an optical probe for an implantable fluorescent sensor, which holds potential for monitoring many parameters of biomedical interest. Results are analyzed with respect to output light intensity as a function of radial distance from source, angle of exit for escaping photons, and sensor fluorescence (SF) relative to tissue autofluorescence (AF). A sensitivity study was performed to elucidate the effects on the output due to changes in optical properties, thickness of tissue layers, thickness of the sensor layer, and both tissue and sensor quantum yields. The optical properties as well as the thickness of the stratum corneum, epidermis, (tissue layers through which photons must pass to reach the sensor) and the papillary dermis (tissue distal to sensor) are highly influential. The spatial emission profile of the SF is broad compared that of the tissue fluorescence and the ratio of sensor to tissue fluorescence increases with distance from the source. The angular distribution of escaping photons is more concentrated around the normal for SF than for tissue AF. The information gained from these simulations will be helpful in designing appropriate optics for collection of the signal of interest.