Kunal Mitra

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Papers by Kunal Mitra

NIRS-based noninvasive cerebrovascular regulation assessment

Clinical and Translational Neurophotonics; Neural Imaging and Sensing; and Optogenetics and Optical Manipulation, 2016

Alterations to cerebral blood flow (CBF) have been implicated in diverse neurological conditions,... more Alterations to cerebral blood flow (CBF) have been implicated in diverse neurological conditions, including mild traumatic brain injury, microgravity induced intracranial pressure (ICP) increases, mild cognitive impairment, and Alzheimer’s disease. Near infrared spectroscopy (NIRS)-measured regional cerebral tissue oxygen saturation (rSO2) provides an estimate of oxygenation of the interrogated cerebral volume that is useful in identifying trends and changes in oxygen supply to cerebral tissue and has been used to monitor cerebrovascular function during surgery and ventilation. In this study, CO2-inhalation-based hypercapnic breathing challenges were used as a tool to simulate CBF dysregulation, and NIRS was used to monitor the CBF autoregulatory response. A breathing circuit for the selective administration of CO2-compressed air mixtures was designed and used to assess CBF regulatory responses to hypercapnia in 26 healthy young adults using non-invasive methods and real-time sensors. After a 5 or 10 minute baseline period, 1 to 3 hypercapnic challenges of 5 or 10 minutes duration were delivered to each subject while rSO2, partial pressure of end tidal CO2 (PETCO2), and vital signs were continuously monitored. Change in rSO2 measurements from pre- to intrachallenge (ΔrSO2) detected periods of hypercapnic challenges. Subjects were grouped into three exercise factor levels (hr/wk), 1: 0, 2:>0 and <10, and 3:>10. Exercise factor level 3 subjects showed significantly greater ΔrSO2 responses to CO2 challenges than level 2 and 1 subjects. No significant difference in ΔPETCO2 existed between these factor levels. Establishing baseline values of rSO2 in clinical practice may be useful in early detection of CBF changes.

Parametric Studies of Retinal Strain Distribution due to Repair Stent Using Finite Element Modelling

Biomedical Engineering, 2016

Transient radiation modeling of short-pulse laser detection of tumors in animal model

Circuits, Systems and Computers, 1977. Conference Record. 1977 11th Asilomar Conference on

The objective of this paper is to perform a comprehensive experimental and numerical analysis of ... more The objective of this paper is to perform a comprehensive experimental and numerical analysis of the short pulse laser interaction with tissue medium with the goal of tumor / cancer diagnostics. For a short pulse laser source, the shape of the output signal is a function of the optical properties of the medium and hence the scattered temporal optical signal helps in understanding of the medium characteristics. In this paper the scattered reflected optical signals from the tissue medium are modeled using the transient radiative transport equation (RTE) solved by the discrete ordinates technique. In vivo imaging was performed on anaesthetized rats with tumorogenic agents injected inside skin tissues and on anaesthetized mouse with mammary tumors. The numerical results are compared with the experimental data to validate the model and demonstrate the feasibility of the time-resolved technique in detecting tumors in animal model.

Temperature Distribution in Tissue Medium During Short Pulse Laser Irradiation of Tumors

Bio Heat Transfer, 2006

The objective of this paper is to analyze the temperature distributions and heat affected zone in... more

Thermal Assessment of Ablation Limit of Subsurface Tumor During Focused Ultrasound and Laser Heating

Journal of Thermal Science and Engineering Applications, 2015

Theoretical study on the thermal assessment of two types of tumor ablation techniques, viz., focu... more Theoretical study on the thermal assessment of two types of tumor ablation techniques, viz., focused laser for ablating skin lesion and focused high-frequency ultrasound for ablating breast tumor has been presented in this article. Estimation of temperature rise and the induced thermal damage in the skin using laser heating have been done by integrating the bioheat transfer, the laser-light attenuation, and the thermal damage models. Further, ultrasound heating of deep seated tumor within the breast has been implemented to estimate the temperature rise and the induced thermal damage by combining the bioheat transfer, the vascularized, the pressure wave, and the thermal damage models. The theoretical models for skin, breast, and blood vessels have been constructed based on the anatomical details, thermophysical, optical, and acoustic properties available in the literature. The study indicates that the focused ultrasound heating can selectively raise the temperature of the tissue abov...

Using Gold Nanoparticles to Enhance the Contrast in Optical Imaging using Short-Pulse laser

Biomedical Optics and 3-D Imaging, 2012

ABSTRACT Intravenously administration of spherical gold nanoparticles, which accumulate in tumors... more

Tissue Response to Short Pulse Laser Irradiation

Heat Transfer and Fluid Flow in Biological Processes, 2015

The objective of this chapter is to analyze the transient temperature distribution in skin tissue... more The objective of this chapter is to analyze the transient temperature distribution in skin tissues due to short pulse laser irradiation. COMSOL Multiphysics, a finite element solver, is used to analyze the heat affected zone in a multilayer tissue geometry modeled by considering the embedded vasculature to account for the blood flow. Compared to the existing continuum model, the results predicted by the embedded vasculature simulations are in good agreement with the experimental temperature distribution measurements for experiments on live anesthetized mice. A parametric study has been performed to analyze the effects of varying blood flow velocities on the temperature distribution in tissues. Inclusion of embedded vascularity played a significant role in the analysis of short pulse laser-based therapy of soft tissues.

Transmission characteristics of an all-optical-waveguide biomedical system for x-ray delivery

Optical Fibers and Sensors for Medical Applications II, 2002

We have investigated the transmission characteristics of an alternative all-optical-waveguide sys... more

Non-destructive evaluation (NDE) of composites for marine structures: detecting flaws using infrared thermography (IRT)

Non-Destructive Evaluation (NDE) of Polymer Matrix Composites, 2013

Abstract: This chapter discusses the detection of flaws in marine structures using infrared (IR) ... more

Non-Destructive Detection of Defects in Composite Boat Hulls

Volume 9: Transportation Systems; Safety Engineering, Risk Analysis and Reliability Methods; Applied Stochastic Optimization, Uncertainty and Probability, 2011

ABSTRACT This paper demonstrates use of thermal imaging for nondestructive defect detection in a ... more ABSTRACT This paper demonstrates use of thermal imaging for nondestructive defect detection in a composite boat hull which covers a large area. There is a strong demand in the boat industry for a non-destructive method that can detect defects such as delamination, voids of air or fluid, cracks, acid, dry mat, and carbon fiber. These defects are always difficult to detect as they occur inside the walls of the boat. Currently, ultrasound and manual inspection methods are used to identify these defects. The manual checking technique is unscientific; furthermore the ultrasound method is not acceptable due to unsatisfactory results. Thermal imaging involves detecting infra-red radiation from a hot body; this is captured by a thermal imaging camera. A thermal heat gun is used to heat the walls of the boat hull. After heating for a specific time period, the walls of the boat start emitting radiation. Dry void attains the highest peak intensity value for short time heating followed by Acid. Other defects like carbon fiber, delamination, and dry mat took longer time to attain higher intensity value. The decay of radiations is also different for various types of defects. The maximum intensity decay occurs for dry void as compared to other defects. From the results obtained so far, it can be inferred that thermal imaging can distinctly differentiate the different kinds of defects, as well as the unaffected areas of the boat wall.

Short-Pulse Laser-Based System for Detection of Tumors: Administration of Gold Nanoparticles Enhances Contrast

Journal of Nanotechnology in Engineering and Medicine, 2012

The objective of this paper is to demonstrate the use of gold nanoparticles, which accumulate in ... more The objective of this paper is to demonstrate the use of gold nanoparticles, which accumulate in tumors due to the leakiness of tumor vasculature, as contrast agents for enhanced imaging in a time-resolved optical tomography system using short-pulse lasers for skin cancer detection in mouse model. It is found that intravenously administrated spherical gold nanoparticles broadened the temporal profile of reflected optical signals and enhanced the contrast between surrounding normal tissue and tumors. These results show that gold nanoparticles tuned to the wavelength of the laser can enhance the resolution and precision of laser-based cancer detection system.

<title>A concept for early cancer detection and therapy</title>

Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems XIII, 2003

Early detection and treatment of breast cancer is least costly in terms of dollars, morbidity and... more Early detection and treatment of breast cancer is least costly in terms of dollars, morbidity and mortality. With new early detection x-ray technology, tumors can be found, diagnosed and treated at a much smaller size than is currently possible. This paper proposes the development of a high resolution, high quality imaging system. It is a laser-driven x-ray system with time-gated detection that removes scattering noise in the image and produces resolution on the order of 10 μm. This higher resolution and higher image quality will enable the detection of one or two millimeter tumors hopefully detecting them before metastasis. We also propose that tumor detection should be followed by an immediate needle-directed, optical fiber biopsy to instantly determine if cancer is present and, if present, the tumor should immediately be given a lethal treatment of laser or x-radiation through the same needle using fiber optics or hollow waveguides. This technology will help prevent multiple interventions resulting in both the lowest overall cost and a more efficacious therapy. The approach can be stopped at the first negative (benign) indication and will help forestall repeated examination as well as reduce patient anxiety.

<title>Calculation of signals for oceanographic lidar</title>

Advances in Laser Remote Sensing for Terrestrial and Hydrographic Applications, 1998

This paper calculates signal levels that would be obtained from oceanographic lidar by solving th... more This paper calculates signal levels that would be obtained from oceanographic lidar by solving the one-dimensional transient radiative transfer equation for remote sensing. As an example, detection of fish schools is considered. In this technique a pulsed laser is directed into the ocean, and the time-dependent back-scattered flux is measured at different locations. A large number of parameters such as the spatial and temporal variability of optical properties within the ocean, ocean depth, type of ocean water, and presence of biological matters can significantly affect the radiative transport through oceans. But since the emphasis of the work is on the scattering phenomenon, important parameters associated with it, namely the scattering albedo and scattering phase function distribution, are considered in detail.

Comparison of Experimental and Numerical Temperature Distributions in Tissues During Short Pulse Laser Irradiation Using Focused Beam

Heat Transfer, Volume 1, 2006

The objective of this work is to perform experimental measurements validated with numerical model... more The objective of this work is to perform experimental measurements validated with numerical modeling results for analyzing the temperature distributions and heat affected zone during short pulse laser irradiation of tissues using focused beam. A Q-switched laser is used as a radiation source. A threelayered tissue phantom model of skin consisting of epidermis, dermis, and fatty tissues is first considered for model validation. Tumors are simulated with inhomogeneities embedded inside the tissue phantoms. Experiments are next conducted with freshly excised skin tissue samples from mice and finally on live anaesthetized mice to consider the bulk effect of convective heat transfer due to blood flow. Experimental measurements of axial and radial temperature distributions for all the cases are compared with numerical modeling results obtained using Pennes' bio-heat transfer equation coupled with either traditional Fourier parabolic or non-Fourier hyperbolic heat conduction formulatio...

Non-Thermal Dental Ablation Using Ultra-Short Pulsed Near Infrared Laser

ASME 2007 Summer Bioengineering Conference, 2007

Ultra-short pulsed lasers are known for their ability to precisely machine materials including hu... more Ultra-short pulsed lasers are known for their ability to precisely machine materials including human hard and soft tissues while minimizing the amount of thermal energy deposited to the surroundings. Non-thermal ablation produced by ultra-short pulsed lasers in the femtosecond to picosecond range is very effective for dental applications. As shown in Figure 1, most decay occurs in the dentin, which is found between the outer surface (enamel) and the inner region containing the nerve endings (pulp) [1]. Caries removal and the preparation of cavities in dentistry are primarily performed by the use of mechanical drills. The current techniques are invasive and cause patient discomfort. Due to the vibrations of the drills it is necessary to use local anesthetic for the majority of dental procedures. A continuous water spray is used in conjunction with the drills to balance the temperature rise produced by mechanical vibrations. Drills are somewhat limited in precision causing a large amount of healthy tooth to be lost during any restoration process. Replacing a multitude of mechanical tools with one non-invasive, accurate and painless laser treatment will be a huge advancement to the current dental techniques.Copyright © 2007 by ASME

Analysis of Short Pulse Radiation Transport Through Tissues for Tumor Detection

Heat Transfer, Part B, 2005

The objective of this paper is to perform a comprehensive experimental and numerical study to ana... more The objective of this paper is to perform a comprehensive experimental and numerical study to analyze short pulse laser propagation through animal tissue samples and phantoms with inhomogeneities imbedded in them. Initially a parametric study of different absorption and scattering coefficients of the tissue phantoms and of inhomogeneities imbedded in them, size and location of the inhomogeneities is performed in order to optimize the time resolved optical detection scheme. Tissues can be modeled primarily as having two main layers- ...

Ultra-short pulsed laser tissue ablation using focused laser beam

Optical Interactions with Tissue and Cells XIX, 2008

ABSTRACT Short pulse lasers are used for a variety of therapeutic applications in medicine. Recen... more ABSTRACT Short pulse lasers are used for a variety of therapeutic applications in medicine. Recently ultra-short pulse lasers have gained prominence due to the reduction in collateral thermal damage to surrounding healthy tissue during tissue ablation. In this paper, ultra-short pulsed laser ablation of mouse skin tissue is analyzed by assessing the extent of damage produced due to focused laser beam irradiation. The laser used for this study is a fiber-based desktop laser (Raydiance, Inc.) having a wavelength of 1552 nm and a pulse width of 1.3 ps. The laser beam is focused on the sample surface to a spot size on the order of 10 microns, thus producing high peak intensity necessary for precise clean ablation. A parametric study is performed on in vitro mouse tissue specimens and live anaesthetized mice with mammary tumors through variation of laser parameters such as time-averaged laser power, repetition rate, laser scanning rate and irradiation time. Radial temperature distribution is measured using thermal camera to analyze the heat affected zone. Temperature measurements are performed to assess the peak temperature rise attained during ablation. A detailed histological study is performed using frozen section technique to observe the nature and extent of laser-induced damages.

<title>Novel modeling techniques for tumor diagnostics using pulsed laser sources</title>

Biomedical Diagnostic, Guidance, and Surgical-Assist Systems IV, 2002

In this paper, a two-dimensional transient radiation transport algorithm is developed to analyze ... more In this paper, a two-dimensional transient radiation transport algorithm is developed to analyze short pulse laser transport through a tissue medium having tumors and inhomogeneities imbedded in it. Short pulse probing techniques have distinct advantages over conventional very large pulse width or cw lasers primarily due to the additional information conveyed about the tissue interior by the temporal variation of the observed signal. The distinct feature is the multiple scattering induced temporal signatures that persists for time periods greater than the duration of the source pulse and is a function of the source pulse width, the scattering/absorbing properties and nature of the medium, the location in the medium where the properties undergo changes. A wide range of parameters such as tissue and tumor size, scattering/absorbing properties and phase function of tissues and tumors, tumor location, laser beam diameter will affect the temporal and spatial distribution of the reflected and transmitted optical signals. The goal is to perform a parametric study in order to gain insight about laser-tissue interaction characteristics with the goal to detect tumors.

Optical Performance of a Hybrid Nano-Polymer Solar Cell

Volume 6: Energy Systems: Analysis, Thermodynamics and Sustainability, 2007

Solar energy harvesting is one of the most fundamental solutions to the energy crisis; photovolta... more Solar energy harvesting is one of the most fundamental solutions to the energy crisis; photovoltaics are the best way to achieve it. Organic based photovoltaics have potential for application as a renewable source of energy. It is cost-effective, light weight, simple and economical to fabricate. Introduction of nanomaterials into polymers is very promising for enhancing photovoltaic conversion efficiency and can potentially improve photochemical and environmental stability. The objective of this paper is to investigate the influence of the nanocomposite film morphology on the optical performance of the hybrid nano-polymer solar cell. The efficiency of such hybrid solar cell depends mainly on the exciton dissociation efficiency and charge mobility. The exciton dissociation efficiency can be improved by increasing the interfacial area between the nanoparticles and polymer. Charge mobility can be improved by proper distribution of nanoparticles in polymer to form better percolation pat...

Transport through Core-Shell Fibrous Biomaterials and Biological Systems

Core-shell fiber systems are three-component porous media with numerous applications in various f... more Core-shell fiber systems are three-component porous media with numerous applications in various fields, primarily in biomedical and biological systems and processes. Their effective diffusivity, viscous permeability, thermal and electrical conductivity, dielectric constant, refractive index and magnetic permeability are key transport parameters affecting the performance of such media in most applications. Nonetheless, there have been no theoretical or experimental results reported