This PDF file contains the front matter associated with SPIE Proceedings Volume 8221, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

A new fiber-based imaging system has been incorporated into a modifie artificia eye for direct measurement of the thermal lensing effect induced by an infrared laser (1319 nm) to correlate changes in the visible wavefront to visual distortions observed by human subjects. The response of a visible beam, 632 nm, was observed with respect to various exposures of the infrared light under different power levels and exposure durations. Infrared irradiance levels between 0.57 and 4.56 W • cm^-2 were used with exposure durations of 0.25, 0.50, 0.75, 1, and 2 seconds in order to observe the optimal level of radiant energy needed to bloom a visible beam at the retinal plane. Results show that deformation of the visible beam focused on the retina begins at irradiance levels of 2.28 W • cm^-2 with significan blurring (10 times larger than the original size) at 3.80 W • cm^-2. A maximum visible beam size at the retina is achieved with exposure durations of 0.75 seconds, and no observable change was reported for longer exposure durations. These results strongly correlate to the previously determined threshold for visual distortion in human subjects using infrared lasers of 2.98 W • cm^-2. Based on these results, the visible wavefront will need to expand four times its original size in order to overcome any accommodation effects and induce an observable visual disruption in human subjects.

We studied necrotic cell death effect on myocardial cells with photosensitizer existed outside the cells varying photosensitization reaction parameters widely in vitro. We have developed non-thermal ablator with the application of photosensitization reaction for atrial fibrillation. Since laser irradiation is applied shortly after photosensitizer injection, the photosensitization reaction is induced outside the cells. The interaction for the myocardial cells by the photosensitization reaction is not well understood yet on various photosensitization reaction parameters. Rat myocardial cells were cultured in 96 well plates for 7 days. The photosensitization reaction was applied with talaporfin sodium (NPe6) and the semiconductor laser of 663nm wavelength. The average drug light interval was set 8 mins. The photosensitizer concentration and radiant exposure were varied from 5 to 40 μg/ml and 1.2 to 60 J/cm², respectively. The well bottom was irradiated by the red laser with irradiance of 293 mW/cm². The photosensitizer fluorescence was monitored during the photosensitization reaction. Alive cell rate was measured by WST assay after 2 hours from the irradiation. In the case of the photosensitizer concentration of 10 μg/ml, the myocardial cells were almost alive even thought 60 J/cm² in the radiant exposure was applied. In the 15 μg/ml case, the alive cell rate was almost linear relation to the photosensitizer concentration and radiant exposure. We obtained that the threshold for myocardial cell necrosis on the photosensitizer concentration was around 15 μg/ml with 20 J/cm² in the radiant exposure. This threshold on the photosensitizer concentration was similar to the reported threshold for cancer therapy.

The spatial and temporal activation of NF-kB (p65) was monitored in the retina of a transgenic mouse model (cis-NFkB-EGFP) in vivo after receiving varying grades of laser induced thermal injury in one eye. Baseline images of the retinas from 26 mice were collected prior to injury and up to five months post-exposure using a Heidelberg Spectralis HRA confocal scanning laser ophthalmoscope (cSLO) with a spectral domain optical coherence tomographer (SDOCT). Injured and control eyes were enucleated at discrete time points following laser exposure for cryosectioning to determine localization of NF-kB dependent enhanced green fluorescent protein (EGFP) reporter gene expression within the retina using fluorescence microscopy. In addition, EGFP basal expression in brain and retinal tissue from the cis-NFkB-EGFP was characterized using two-photon imaging. Regions of the retina exposed to threshold and supra-threshold laser damage evaluated using fluorescence cSLO showed increased EGFP fluorescence localized to the exposed region for a duration that was dependent upon the degree of injury. Fluorescence microscopy of threshold damage revealed EGFP localized to the outer nuclear region and retinal pigment epithelial layer. Basal expression of EGFP imaged using two-photon microscopy was heterogeneously distributed throughout brain tissue and confined to the inner retina. Results show cis-NF-kB-EGFP reporter mouse can be used for in vivo studies of light induced injury to the retina and possibly brain injury.

Astrocyte, the most abundant cell type in the central nervous system, has been one of major topics in neuroscience. Even though many tools have been developed for the analysis of astrocyte function, there has been no adequate tool that can modulates astrocyte network without pharmaceutical or genetic interventions. Here we found that ultrashort pulsed laser stimulation can induce label-free activation of astrocytes as well as apoptotic-like cell death in a dose-dependent manner. Upon irradiation with high intensity pulsed lasers, the irradiated cells with short exposure time showed very rapid mitochondria fragmentation, membrane blebbing and cytoskeletal retraction. We applied this technique to investigate in vivo function of astrocyte network in the CNS: in the aspect of neurovascular coupling and blood-brain barrier. We propose that this noninvasive technique can be widely applied for in vivo study of complex cellular network.

The effect of femtosecond laser radiation provided by the Erbium fiber laser with the pulse duration of 10^-13 s, peak and average power of 6,0±0,3 kW and 1,26±0,15 mW, respectively, wavelength λ of 1,55 μm has been studied in the experiments on rat ascitic ovarian tumor cell in vitro. Irradiation has been performed at the average intensity of 0,033±0.002 mW/cm² at two expositions under femtosecond laser radiation of 600 and 900 s. The membrane topology and rigidity of the cancer cells have been estimated with the Scanning probe microscopy (SolverPro, NT-MDT, Russia). Besides, the viability and apoptosis of the cancer cells have been estimated. Free-radical processes and antioxidant enzyme activity have been studied in cancer cell lysate. Femtosecond laser irradiation was established to increases the activity of the "Lipoperoxidation - antioxidants" system in neoplasm, enhance the apoptosis, decrease the viability, and change cancer cell membrane topology and rigidity in vitro depending on the energy density of the irradiation.

The aim of the study was to find a relationship between laser power, exposure time, ablation efficiency and temperature increase during laser brain ablation by Thulium fiber laser. The thermal effects of the 1940-nm Tm-fiber laser on the brain tissue was also investigated in terms of ablation efficiency. These experiments are very important in order to model temperature increase-ablation efficiency during lasing with different power and exposure time. 4-5 mm coronal sections were taken from lamb brains. Laser was applied at cortical and subcortical tissue with 0-0.1 mm distance, in both continuous and pulsed modes with 400 mW and 600 mW which were chosen by a predosimetric study. In continuous and pulse mode doses were changed with exposure time and on-off cycle respectively, in order to achive the tissue to absorb same energy. During lasing temperature increases were recorded by a thermoprobe (thermoprobe is a system which a 300 micrometer fiber was embedded into a thermocouple). The radius of ablation and coagulation for each laser application was recorded by a microscope. By calculating ablation efficiency (100xablation/calculation radius) the appropriate laser doses were determined for both cortical and subcortical tissue. The maximum ablation efficiency for cortical and subcortical tissue in both continous and pulsed mode was found for 600 mW. Ablation efficiencies for continuous mode was superior than the pulsed mode for all laser doses which were studied. Temperature increases showed a significant differences for continuous and pulse mode operating systems and effect the ablation efficiencies.

Laser ablation therapy combined with photodynamic therapy (PDT) is studied for treatment of advanced cancers. The clinical outcome of PDT may be improved by the accurate knowledge about the light distribution within tissue. Optical properties [absorption coefficient (μ_a), scattering coefficient (μ_s), anisotropy factor (g), refractive index, etc.] of tissues help us realizing a light propagation through the tissue. It is important to understand of the effect of laser coagulation formed by laser ablation to PDT. The aim of this study is to estimate of influence of coagulated region to PDT for effective PDT combined laser ablation therapy. We evaluated the optical property of mouse tumor tissue in native and coagulated state using a double integrating sphere system and an inverse Monte Carlo method in the wavelength range from 350 to 1000 nm. After laser ablation, the μ_a and reduced scattering coefficient spectra of coagulated tissues were increased in the wavelength range from 350 to 1000 nm. The optical penetration depth of coagulated tissues is 1.2-2.9 times lower than the native state in the wavelength range from 350 to 1000 nm. The intensity of the light energy inside the coagulated tissue falls to about 60% of its original value at the end of coagulated layer. The evaluation of light energy distribution by the determination of the tissues optical properties could be useful for optimization of the treatment procedure in combined laser ablation with PDT.

In this paper, a novel photo-acoustic technique modality utilizing a frequency- modulated Q-switch Nd:YAG laser at 1064 nm and coherent frequency domain signal processing is introduced for impulse and frequency responses of biological tissues. We present a photoacoustic technique to monitor the temporal behavior of temperature and pressure in an excised sample of human teeth after either a single laser pulse or during multiple laser pulses at pulse repetition frequencies (PRF) from 5 Hz to 100 Hz. Knowledge of the dynamic characteristics of structural elements often means the difference between normal and abnormal tissue. The determination of the resonance characteristics of structures is termed "modal analysis." The results of our study suggest that it is possible to identify the impulse, frequency response and resonance modes of simplified human teeth. This data provided a powerful tool to differentiate between normal and decay teeth.

The photomechanical model of ablation of human tooth enamel is described in this work. It takes into account the structural peculiarities of enamel: free water in the enamel pores or cracks. We consider the photomechanical destruction of the enamel rods of hydroxyapatite by the pressure of water contained in the enamel pores and heated by laser radiation. This model takes into account attenuation by the Lambert-Beer law when radiation passes through the tissue and the fact that the tissue removal occurs when a unit volume of water was heated to the critical temperature. Decreasing logarithmic dependence of the enamel removal efficiency on the energy density was obtained as a result of the calculations. The shape of this function follows the shape of the experimental curve.

This paper investigates the feasibility of using terahertz pulsed imaging to detect breast cancer in a reflection imaging geometry. Spectroscopic terahertz data is used to simulate the reflected time domain response functions of healthy fibrous breast tissue and breast cancer tissue. Previously we have looked at the refractive index and absorption coefficient separately to characterize tissues. In this work we investigate their combined effects and identify parameters of the simulated reflected impulse response function and corresponding spectroscopic properties with a view to improving our ability to distinguish between the fibrous and cancer tissues in the breast.

In breast conservation surgery, surgeons attempt to remove malignant tissue along with a surrounding margin of healthy tissue. Subsequent pathological analysis determines if those margins are clear of malignant tissue, a process that typically requires at least one day. Only then can it be determined whether a follow-up surgery is necessary. This possibility of re-excision is undesirable in terms of reducing patient morbidity, emotional stress and healthcare. It has been shown that terahertz (THz) images of breast specimens can accurately differentiate between breast carcinoma, normal fibroglandular tissue, and adipose tissue. That study employed the Time-Domain Spectroscopy (TDS) technique. We are instead developing a new technique, Frequency-Domain Terahertz Imaging (FDTI). In this joint project between UMass/Amherst and UMass Medical School/Worcester (UMMS), we are investigating the feasibility of the FDTI technique for THz reflection imaging of breast cancer margins. Our system, which produces mechanically scanned images of size 2cm x 2cm, uses a THz gas laser. The system is calibrated with mixtures of water and ethanol and reflection coefficients as low as 1% have been measured. Images from phantoms and specimens cut from breast cancer lumpectomies at UMMS will be presented. Finally, there will be a discussion of a possible transition of this FDTI setup to a compact and inexpensive CMOS THz camera for use in the operating room.

Recent studies of the minute morphology of the skin by optical coherence tomography showed that the sweat ducts in human skin become helically shaped tubes in the Epidermis and are filled with an aqueous solution. When considered as entities embedded in a dielectric media, they resemble helical antennas. The spectral response obtained by our computer simulations coincides with the analytical prediction of antenna theory and support this hypothesis, if a fast enough current mechanism exists in the duct. In particular the strongest spectral response of the simulation was noted around the predicted frequencies (240 GHz and 380 GHz) for the respective normal and axial modes of the helical structure. Furthermore, circular dichroism of the reflected electromagnetic field is a characteristic property of such helical antennas and it was shown that it is indeed a characteristic of the simulation model. Fast proton hopping is posited as the current mechanism. Consequently experimental evidence is presented that the spectral response of the skin in the sub-Terahertz region is governed by the level of activity of the perspiration system. This in turn is moderated by the Sympathetic Nerve Response and is demonstrated by the correlation to physiological stress as manifested by the pulse rate and the systolic blood pressure. These physical relaxations are tonic in nature (lasting more than a minute). Could the phasic characteristic of emotional excitation also be evident in the reflection coefficient? By applying techniques borrowed from psychiatric science we hope to answer this point in our paper.

Biomolecules can exhibit low-lying vibrational modes in the THz region which are detectable in transmission given a strong molecular dipole moment and optical depth, and a spectrometer of adequate sensitivity. The nucleic acids are particularly interesting because of applications such as label-free gene assay, bio-agent detection, etc. However for nucleic acids, sample preparation and THz coupling are of paramount importance because of the strong absorption by liquid water and the small concentration of molecules present in physiological solutions. Concentration methods become necessary to make the THz vibrational modes detectable, either by concentrating the nucleic-acid sample itself in a small volume but large area, or by concentrating the THz radiation down to the volume of the sample. This paper summarizes one type of the first method: nanofluidic channel arrays for biological nucleic acids; and two types of the second method: (1) a circular-waveguide pinhole, and (2) a circular-waveguide, conical-horn coupling structure, both for DNA crystals. The first method has been demonstrated on a very short artificial nucleic acid [small-interfering (si) RNA (17-to-25 bp)] and a much longer, biological molecule [Lambda-phage DNA (48.5 kbp)]. The second method has been demonstrated on small (~100 micron) single crystals of DNA grown by the sitting-drop method.

Although the importance of water for bio-materials have been believed, even the amount of hydration water have not been defined. Despite picosecond time scale of the collective dynamics of bulk water, past studies for the hydration state of solute with using NMR or neutron scattering have measured water dynamics only in nanosecond time scale and have defined only the strongly perturbed water as the hydration water. However, it is expected that much more slightly perturbed water exist near the solute surfaces. To define precisely the hydration state of lipid bilayer, which is the basic structure of biomembrane, including slightly perturbed water, we have used terahertz time-domain spectroscopy, with which picosecond dynamics of water can be measured. By comparing the terahertz results with the structural information of the lipid/water system obtained by X-ray scattering, it is concluded that there is a long-range hydration layer on the surface of lipid membrane on up to 4-5 water layers (1 nm) [1], which is 5 time as much as that in the previous reports by NMR or neutron scattering. Our results indicates that the hydration water is important for the self-assembly of biomolecules because its length scale is comparable to that of some interactions such as van der Waals interaction.

Recently in phototherapy the use of diodes and broadband light devices instead of lasers was suggested for economical and practical reasons. It has been argued that lasers have no preference over diodes since they lose their coherency and polarization once penetrating into biological tissues. In this talk we have for the first time experimentally validated the conditions that affect the polarization state of light when laser illumination is propagated through a biological tissue with and without a flow. In additional we will present physical modeling showing that illuminating a flow in a medium with linear polarized light can be highly correlated to the direction and rate of the flow through that medium.

Computer simulations of light transport in multi-layered turbid media are an effective way to theoretically investigate light transport in tissue, which can be applied to the analysis, design and optimization of optical coherence tomography (OCT) systems. We present a computationally efficient method to calculate the diffuse reflectance due to ballistic and quasi-ballistic components of photons scattered in turbid media, which represents the signal in optical coherence tomography systems. Our importance sampling based Monte Carlo method enables the calculation of the OCT signal with less than one hundredth of the computational time required by the conventional Monte Carlo method. It also does not produce a systematic bias in the statistical result that is typically observed in existing methods to speed up Monte Carlo simulations of light transport in tissue. This method can be used to assess and optimize the performance of existing OCT systems, and it can also be used to design novel OCT systems.

We present a hybrid method to speed up the Monte Carlo simulation of diffuse reflectance from a multi-layered tissue model with finite-size tumor-like heterogeneities. The proposed method consists of two steps. In the first step, a set of photon trajectory information generated from a baseline Monte Carlo simulation is utilized to scale the exit weight and exit distance of survival photons for the multi-layered tissue model by using a multiple scaling method. In the second step, another set of photon trajectory information including the locations of all collision events from the baseline simulation and the scaling result obtained from the first step are employed by the perturbation Monte Carlo method to estimate diffuse reflectance from the multi-layered tissue model with tumor-like heterogeneities. Our method is demonstrated to be able to shorten simulation time by several orders of magnitude. Moreover, this hybrid method works for a larger range of probe configurations and tumor models compared to the scaling method or the perturbation method alone.

Coherent Raman scattering (CRS) spectroscopy is explored as a tool for obtaining localized temperature measurements. A single femtosecond oscillator is used to pump a photonic crystal fiber to provide a broadband Stokes pulse. The CRS signals from the broad OH-stretching modes between 3000 and 3700 cm^-1 are recorded for water at different temperatures. The shapes of these two modes are shown to correlate with water temperature. As a multi-wave process, excitation is limited to only the focal volume giving inherent spatial resolution that allows for mapping of the thermal profile. The local variation of temperature may be mapped so that the localized thermal response from directed energy exposure can be obtained. As these exposures typically have some thermal component, it is important to have a means of specifically characterizing the thermal effects. The thermal portion can then be decoupled from the other effects of the directed energy source so that the non-thermal components are better characterized.

Determination of tissue optical properties is important as it will lead to better design of optical diagnostic tools, improvement in laser therapy, photo dynamic therapy dosimetry, drug pharmacokinetics, etc. We have developed a theoretical model for OCT signal using Monte Carlo simulation that allows us to fit values extracted from the OCT signal, namely, reflectance, ρ, and the total optical attenuation coefficient, μt, to obtain optical properties of tissue (scattering coefficient, μs, and anisotropy factor, g). Using this method we have extracted optical properties of different tissue types, e.g., skin, muscle, liver, and brain of mouse.

Fourier Transform Infrared Spectroscopy (FTIR) is a very sensitive tool which is capable of providing strong insight on structural and functional changes in lipids and proteins induced by laser radiation. In the present work cockroach nervous tissue and chitin from tibia region are irradiated with Nd: YAG laser (λ= 1064 nm, Power =150mW) via fiber optics (Numerical aperture=0.22, diameter = 8 μ). Nd: YAG laser exposure time is varied from 10 sec to 50 sec for nervous tissue and chitin. FTIR (Fourier Transform Infra Red spectra) of cockroach nervous tissue and chitin are compared before and after laser irradiation. The FTIR spectrum of non irradiated cockroach nervous tissue shows clearly the peaks due to O-H (Carboxylic acid), C=O (Amide I), C=C (Aromatic), N=0 (Nitro), C-H (Alkenes), CH (Aromatics). FTIR Spectra of non irradiated cockroach chitin clearly shows O-H (Carboxylic acid), C=O (Carbonyl stretch), C=C (Aromatic), N=O (Nitro), C-O, (anhydrides), C-H (Alkenes stretch) group. FTIR spectra of laser radiated nervous tissue from cockroach tibia and chitin shows significant changes in transmittance for O-H, C=O, C=C, C-H, N=O, C-O and C-H groups. The percentage transmittance increases for O-H, C=C group for exposure time 10sec, 40sec and 50 sec for nervous tissue. The percentage transmittance increases for O-H, C=C group for exposure time 10sec, 20sec, 30sec and 40 sec for chitin. The study shows clearly that FTIR spectroscopy of nervous tissue can reveal the interactions between infrared laser light and nervous tissue.

The backscattered fraction of laser incident beam from the biological tissues depends on their composition, leading to change in their optical properties. The tissue models consist of heart tissue as the base embedded with adipose and spleen tissues at various depths from the tissues surface Monte Carlo simulation is carried out to detect the changes in back-scattered fraction (BSF) at various locations on the tissue surface. The BSF is increased and decreased with the presence of adipose and spleen tissues located at various depths, respectively. The location of these is carried by construction of the BSF images by scanning at various locations. From the variation in images the location and type of abnormality is determined. Thus this study provides the possibility of detection of various changes in tissue composition

Safe exposure limits for directed energy sources are derived from a compilation of known injury thresholds taken primarily from animal models and simulation data. The summary statistics for these experiments are given as exposure levels representing a 50% probability of injury, or ED50, and associated variance. We examine biological variance in focal geometries and thermal properties and the influence each has in singlepulse ED50 threshold studies for 514-, 694-, and 1064-nanometer laser exposures in the thermal damage time domain. Damage threshold is defined to be the amount of energy required for a retinal burn on at least one retinal pigment epithelium (RPE) cell measuring approximately 10 microns in diameter. Better understanding of experimental variance will allow for more accurate safety buffers for exposure limits and improve directed energy research methodology.

In this research, we present the first MPI-CUDA implementation of Finite-Difference Time-Domain (FDTD) discretization of Maxwell's equations in dispersive media that uses the MPI API to assign each CPU node its share of the computational domain and GPUs to their corresponding CPU threads. By taking advantage of the CUDA programming model, we present a unique implementation of the FDTD scheme that exploits the memory hierarchy of GPUs, including the global, texture, and shared memory. This enables us to tackle problems that are otherwise computationally prohibitive. Practical results will be presented along with a measure of speedup factors achieved when using multiple GPU processors.

We studied an optical interaction on an optical window and blood boundary during the CW laser irradiation in 660 nm band until blood charring occurrence. We previously reported that a pre-charring optical behavior may be detected by diffuse-reflected-light power time-history. The aim of this study is to measure absorption coefficient (μa) and reduced scattering coefficient (μ's) of a blood model to explain this pre-charring optical behavior. The blood model sandwiched between 2 glass slides to simulate the interface between blood and the optical window was used. A double integrating sphere system was constructed. The red laser in 660 nm band was irradiated to the sandwiched blood model. Fourty W/cm² in irradiance was used as the maximum irradiance during irradiation via the laser catheter in vivo. μa and μ's in the irradiated laser wavelength were measured continuously until blood charring occurrence using inverse adding doubling analysis. Continuous μa increase of 5-10% from the initial value until charring was observed. Decrease of μ's with 8-10% during 15-30 s before charring following broad peak was obtained. We think these μa and μ's changes may explain the pre-charring optical behavior detected by the diffuse-reflected-light power time-history in our reported study.

Near Infrared (NIR) extinction measurements can be used to determine the cerebral hemodynamics of adult patients. To be able to interpret and verify measurement data, it is necessary to know the three-dimensional light intensity distribution in the human head. This light intensity map can advantageously be created by numerical simulations. Such simulations of light intensity in the head are complex, since the light is crossing several tissue types with very distinct optical properties. The Monte-Carlo method proved to represent a reliable tool for simulation of light intensity in turbid media. The desired result of a Monte-Carlo simulation is the spatially resolved average light intensity, which has to be derived from the statistical output of the Monte- Carlo simulation. We propose a novel analysis method which directly tracks the intensity based on a linedrawing algorithm to attain a 3D intensity map of the whole computational domain. The proposed method largely operates independently of the underlying Monte-Carlo algorithm itself. The algorithm is verified through comparison with analytical approximations of the Radiative Transport Equation. As a challenging example, the simulation of the light intensity distribution inside the human head based on segmented MRI data is presented.

Little numerical analysis has been done on in vivo vascular fluorescence imaging. Here, we use a 3D fluorescence Monte Carlo model to evaluate a microvasculature geometry obtained via two-photon microscopy. We found that a bulk-vascularization assumption does not pro- vide an accurate picture of penetration depth of the collected fluorescence signal. Instead the degree of absorption difference between extravascular and intravascular space, and the degree of stokes shift must be taken into account to determine the depth distribution. Additionally, we found that using targeted illumination can provide for superior surface vessel sensi- tivity over wide-field illumination, with small area detection offering an even greater amount of sensitivity to surface vasculature. Depth sensitivity can be enhanced by either increasing the detector area or increasing the illumination area. Finally, we see that excitation wavelength and vessel size can affect intra-vessel sampling distribution, as well as the amount of signal that originates from inside the vessel under targeted illumination conditions.

Optical imaging through biological tissue has the significant problems of scattering which degrades the image resolution and quality. Research has shown that Angular Domain Imaging (ADI) improves image quality by filtering out the scattered light in the biological tissue images based on the angular direction of photons. The advantage of this technique is that it is independent of the wavelength, coherent, pulse, or duration compared to OCT or time domain. This allows us to couple ADI with conventional fluorescence imaging technique. Previous work was creating test media by varying Intralipid/water concentration to produce different scattering levels. This showed difficulties in producing a consistent scattering medium in liquid states. Hence, ideally we want a reusable solid medium which has a stable scattering characteristic. Our target is to investigate fluorescence ADI on skin with cancerous collagen tissue where healthy collagen fluoresces while the cancerous collagen tissue does not. To mimic the characteristic of skin, a solid scattering medium over a patterned fluorescence material with non-emitting structures is created. We used a solid agar medium, or a transparent polymer, infused with Intralipid at different concentrations, as the scattering medium. The solid media with similar scattering characteristic of skin (μs = 20cm^-1, g = 0.85) is placed on top of a fluorescence plastic (415nm excitation, ≈ 530nm emission) which is patterned by strips of non-emitting structures (200-400μm). Using small apertures with acceptance angles of 0.171° a distance away from the solid scattering medium, these non-emitting structures are detectable at shallow scattering tissue depth (1-2mm).

The Radial Angular Filter Array (RAFA) is a novel optical filter consisting of a radially-distributed series of micromachined channels with a focal length of a few millimeters. The RAFA filters photons passing through the focal point according to the propagation direction and has proven to be capable of collecting the angular distribution and the spectral information of photons simultaneously and non-invasively, which allows angle-resolved spectroscopic measurement of a turbid medium. To explore the feasibility of using this device to characterize the optical abnormalities in human tissues, we tested the performance of an angle-resolved RAFA-based spectroscopy system to detect absorption targets embedded within a tissue-mimicking phantom. The body of the phantom was made of 0.1% Intralipid^TM/agarose gel (7 mm in thickness) and the targets were spherical (1.5 mm in radius) and contained 10 μM Indocyanine Green (ICG). The illumination source was a broadband near infrared (NIR) collimated beam. Photons were angularly filtered by the RAFA and spectrally resolved by a pushbroom spectrometer. The experimental results confirmed that the RAFA preferentially filtered photons that carried absorption and scattering information of the embedded targets.

As a model for laser exposure of the iris during femtosecond corneal surgery, we simulated the temperature rise in porcine cadaver iris during direct illumination by the femtosecond laser. The temperature increase induced by a 60 kHz iFS Advanced Femtosecond Laser (AMO Inc., Santa Ana, CA) in porcine cadaver iris was simulated using COMSOL (Comsol Inc., Burlington, MA) finite element software. Temperature increases up to 2.45 °C (corresponding to 2 μJ laser pulse energy and 24 second illumination) were observed in the porcine cadaver iris from the simulation with little variation in temperature profiles compared with specimens for the same laser energy illumination in experiment. : The commercial iFS Advanced Femtosecond Laser operating with pulse energies at approximately the lower limit of the range evaluated in this study would be expected to result in a 1.23 °C temperature increase and, therefore, does not present a safety hazard to the iris.

In laser medicine, the accurate knowledge about the optical properties (absorption coefficient; μ_a, scattering coefficient; μ_s, anisotropy factor; g) of laser irradiated tissues is important for the prediction of light propagation in tissues, since the efficacy of laser treatment depends on the photon propagation within the irradiated tissues. Thus, it is likely that the optical properties of tissues at near-ultraviolet, visible and near-infrared wavelengths will be more important due to more biomedical applications of lasers will be developed. For improvement of the laser induced thermotherapy, the optical property change during laser treatment should be considered in the wide wavelength range. For estimation of the optical properties of the biological tissues, the optical properties measurement system with a double integrating sphere setup and an inverse Monte Carlo technique was developed. The optical properties of chicken muscle tissue were measured in the native state and after laser coagulation using the optical properties measurement system in the wavelength range from 350 to 2100 nm. A CO₂ laser was used for laser coagulation. After laser coagulation, the reduced scattering coefficient of the tissue increased. And, the optical penetration depth decreased. For improvement of the treatment depth during laser coagulation, a quantitative procedure using the treated tissue optical properties for determination of the irradiation power density following light penetration decrease might be important in clinic.

Chemotherapy is a standard treatment for metastatic cancer. However drug toxicity limits the dosage that can safely be used, thus reducing treatment efficacy. Drug carrier particles, like liposomes, can help reduce toxicity by shielding normal tissue from drug and selectively depositing drug in tumors. Over years of development, liposomes have been optimized to avoid uptake by the Reticuloendothelial System (RES) as well as effectively retain their drug content during circulation. As a result, liposomes release drug passively, by slow leakage, but this uncontrolled drug release can limit treatment efficacy as it can be difficult to achieve therapeutic concentrations of drug at tumor sites even with tumor-specific accumulation of the carriers. Lipid membranes can be photochemically lysed by both Type I (photosensitizer-substrate) and Type II (photosensitizer-oxygen) reactions. It has been demonstrated in red blood cells (RBCs) in vitro that these photolysis reactions can occur in two distinct steps: a light-initiated reaction followed by a thermally-initiated reaction. These separable activation steps allow for the delay of photohemolysis in a controlled manner using the irradiation energy, temperature and photosensitizer concentration. In this work we have translated this technique from RBCs to liposomal nanoparticles. To that end, we present in vitro data demonstrating this delayed bolus release from liposomes, as well as the ability to control the timing of this event. Further, we demonstrate for the first time the improved delivery of bioavailable cargo selectively to target sites in vivo.

Scattering of photons in biological imaging is a known factor of degrading image resolution and quality. Angular Domain Imaging (ADI) is a technique which utilizes the angular distribution of photons to filter out multiple-scattering photons and accept only photons with small angular deviation from their original trajectories. The advantage of ADI is that it does not require a high optical quality, coherent, or pulsed source to acquire quality image. Initial experiments with Spatialfrequency Filter (SFF) ADI on simple liquid scattering test phantom showed good results as it can image through media with scattering ratio (SR) of 106:1. Previous work with complex 3D aquatic species eliminated scattering but showed optical interference patterns from the coherent laser sources. With SFF ADI, our target is to image through a complex 3D scattering structure with multilayer of different refractive indices and scattering coefficient from an Intralipid-infused polymer/agar, and a small species called Branchiostoma lanceolatum, a lancelet that is 5-8cm long and ~5mm thick. To remove interference, several narrow wavelength-band LEDs were used as illumination sources with one peaks at 630nm and the other peaks at 415nm. The LEDs are collimated and illuminates the 3D structure/lancelet in a water-filler container while a SFF removes the scattered photons before the imager. This allows us to reduce the optical interference and to study the impact of switching from coherent laser source into an incoherent narrow wavelength-band source. Hence, it allows us to investigate the enhancement of imaging the internal structures using the incoherent narrow wavelength-band source.

We compared the isotropic and anisotropic diffuse models in retrieving the optical properties in fibrous samples from time-resolved reflectance measurements. A Monte Carlo model was used to simulate light propagation in a fibrous tissue consisting of aligned cylinders and spherical particles. Using the anisotropic diffuse model, the reduced scattering coefficients for both cylinder and background can be derived from a single time-resolved reflectance measured perpendicularly to the fiber direction. Using isotropic diffuse solution, these parameters can be derived from two measurements both parallel and perpendicular to the fiber direction. The simulation results also indicate that the derived optical properties are correct only for fibrous samples with small fiber diameter. For large fiber diameters, the reduced scattering coefficient of fibers needs to be corrected by fiber-size dependent factor. Overall, the isotropic diffuse model produced better results than the anisotropic model.

Human (and other mammals) would secrete cerumen (ear wax) to protect the skin of the ear canal against pathogens and insects. The studies of biodiversity of pathogen in human include intestine microbe colony, belly button microbe colony, etc. Metals such as zinc and iron are essentials to bio-molecular pathways and would be related to the underlying pathogen vitality. This project studies the biodiversity of cerumen via its metal content and aims to develop an optical probe for metal content characterization. The optical diffusion mean free path and absorption of human cerumen samples dissolved in solvent have been measured in standard transmission measurements. EXFAS and XANES have been measured at Brookhaven Synchrotron Light Source for the determination of metal contents, presumably embedded within microbes/insects/skin cells. The results show that a calibration procedure can be used to correlate the optical diffusion parameters to the metal content, thus expanding the diagnostic of cerumen in the study of human pathogen biodiversity without the regular use of a synchrotron light source. Although biodiversity measurements would not be seriously affected by dead microbes and absorption based method would do well, the scattering mean free path method would have potential to further study the cell based scattering centers (dead or live) via the information embedded in the speckle pattern in the deep-Fresnel zone.

Certain phytonutrients are known to confer protection and immunosuppression against radiation insults. Radiation-induced reactive oxygen species (ROS) can either lead to the destruction of normal tissue cells, or induce tumor radioresistance by activating ROS scavenging proteins. To identify whether the triterpene phytonutrient, ursolic acid, reduces radiation-induced damage in normal cells and promotes the apoptosis of malignant cells, we investigated the biologic mechanisms and effect of radiation-cell interaction with or without treatment with ursolic acid in human skin melanoma cells (ATCC CRL-11147^TM) and transformed human retinal pigment epithelial (hTERT-RPE) cells. UV-VIS light was employed to investigate the efficacy of ursolic acid in altering cellular viability by modulations of p53 and NF-κB p65 signaling. Cell response was investigated by changes in proliferative activity and free radical generation assessed by 2',7'-dichlorofluorescin liquid chromatography. Ursolic acid pretreatment strongly increased the level of p53 and decreased the level of phosphorylated p65 leading to enhanced cell death of skin melanoma cells in response to UV-VIS exposure. In contrast, ursolic acid appeared to downregulate p53 levels without disturbing NF-κB activation along with an increase of oxidative stress in hTERT-RPE cells. These findings indicate that ursolic acid may beneficially increase the radiosensitivity of tumor cells while potentiating a photoprotective effect on benign cells through differential effects on the NF-κB and p53 signaling pathways.

Terahertz time-domain spectroscopy (THz-TDS) is an effective technique to probe the intermolecular and collective vibrational modes of biological macromolecules at THz frequencies. To date, the vast majority of spectroscopic studies have been performed on dehydrated biomolecular samples. Given the fact that all biochemical processes occur in aqueous environments and water is required for proper protein folding and function, we hypothesize that valuable information can be gained from spectroscopic studies performed on hydrated biomolecules in their native conformation. In this study, we used a THz-TDS system that exploits photoconductive techniques for THz pulse generation and freespace electro-optical sampling approaches for detection. We used the THz spectrometer to measure the time-dependent electric field of THz waves upon interaction with water, phosphate buffered saline (PBS), and collagen gels. By comparing these waveforms with references, we simultaneously determined each sample's index of refraction (n) and absorption coefficients (μa) as a function of frequency. Our data show that the properties we measure for the water, PBS and collagen are comparable to those reported in the literature. In the future, we plan to examine the effect that both temperature and pH have on the optical properties of other biological macromolecules. Studies will also be performed to compare our results to those generated using molecular dynamics simulations.