Rajan Gurjar

Detection of preinvasive cancer cells

More than 85% of all cancers originate in the epithelium that lines the internal surfaces of organs throughout the body. Although these are readily treatable provided they are diagnosed in one of the preinvasive stages, early lesions are often almost impossible to detect. Here we present a new optical-probe technique based on light-scattering spectroscopy that is able to detect precancerous and early cancerous changes in cell-rich epithelia.

Imaging human epithelial properties with polarized light-scattering spectroscopy

Biomedical imaging with light-scattering spectroscopy (LSS) is a novel optical technology developed to probe the structure of living epithelial cells in situ without need for tissue removal. LSS makes it possible to distinguish between single backscattering from epithelial-cell nuclei and multiply scattered light. The spectrum of the single backscattering component is further analyzed to provide quantitative information about the epithelial-cell nuclei such as nuclear size, degree of pleomorphism, degree of hyperchromasia and amount of chromatin. LSS imaging allows mapping these histological properties over wide areas of epithelial lining. Because nuclear enlargement, pleomorphism and hyperchromasia are principal features of nuclear atypia associated with precancerous and cancerous changes in virtually all epithelia, LSS imaging can be used to detect precancerous lesions in optically accessible organs.

Measuring cellular structure at submicrometer scale with light scattering spectroscopy

We present a novel instrument for imaging the angular distributions of light backscattered by biological cells and tissues. The intensities in different regions of the image are due to scatterers of different sizes. We exploit this to study scattering from particles smaller than the wavelength of light used, even when they are mixed with larger particles. We show that the scattering from subcellular structure in both normal and cancerous human cells is best fitted to inverse power-law distributions for the sizes of the scattering objects, and propose that the distribution of scattering objects may be different in normal versus cancerous cells.

Quantitative Analysis of Mucosal Tissues in Patients Using Light Scattering Spectroscopy

We presented two approaches for separating a diffusive component of the backscattered signal originated in deep tissue layers and a non-diffusive single backscattering component which backscattered from a thin epithelial layer. Both approaches can be effective and have their advantages and disadvantages. The modeling technique can provide important information about hemoglobin concentration, oxygenation, and average scattering properties of the mucosal tissue. On the other hand, when applied to new tissues, it has to be adjusted to take into account tissue morphology. Also, the polarization technique can be very robust and more effective in background removal. However, it lacks extracting capabilities of the modeling technique. Both techniques can be quite valuable and compliment each other in a future clinical device.

Imaging and measurement of cell structure and organization with submicron accuracy using light scattering spectroscopy

Light scattering spectroscopy (LSS) is a promising optical technique developed for quantitative characterization of tissue morphology as well as in vivo detection and diagnosis of disease such as early cancer. LSS employs a wavelength dependent component of light scattered by epithelial cells and other tissues to obtain information about subcellular structure. We present two novel modalities of LSS, LSS imaging and scattering angle sensitive LSS (a/LSS). LSS imaging provides quantitative information about the epithelial cell nuclei, such as nuclear size, degree of pleomorphism, hyperchromasia, and amount of chromatin. It allows mapping these histological properties over wide areas of epithelial lining. We show that LSS imaging can be used to detect precancerous lesions in optically accessible organs. Using a/LSS, which enables characterization of tissue components with sizes smaller than the wavelength of light, we show that the number of subcellular components with the sizes between 30 nm and few microns scales with the size according to an inverse power-law. We show that the size distribution exponent is an important parameter characterizing tissue organization, for example the balance between stochasticity and order, and has a potential to be applicable for early cancer diagnosis and characterization.

Sensing vascularization of ex-vivo produced oral mucosal equivalent (EVPOME) skin grafts in nude mice using optical spectroscopy

Repair of soft tissue defects of the lips as seen in complex maxillofacial injuries, requires pre-vascularized multi-tissue composite grafts. Protocols for fabrication of human ex-vivo produced oral mucosal equivalents (EVPOME) composed of epithelial cells and a dermal equivalent are available to create prelaminated flaps for grafting in patients. However, invivo assessment of neovascularization of the buried prelaminated flaps remains clinically challenging. Here, we use diffuse reflectance spectroscopy (DRS) and diffuse correlation spectroscopy (DCS) to non-invasively quantify longitudinal changes in the vessel density and blood-flow within EVPOME grafts implanted in the backs of SCID mice and subsequently to determine the utility of these optical techniques for assessing vascularization of implanted grafts. 20 animals were implanted with EVPOME grafts (1x1x0.05 cm3) in their backs. DRS and DCS measurements were obtained from each animal both atop the graft site and far away from the graft site, at one week post-implantation, each week, for four consecutive weeks. DRS spectra were analyzed using an inverse Monte Carlo model to extract tissue absorption and scattering coefficients, which were then used to extract blood flow information by fitting the experimental DCS traces. There were clear differences in the mean optical parameters (averaged across all mice) at the graft site vs. the off-site measurements. Both the total hemoglobin concentration (from DRS) and the relative blood flow (from DCS) peaked at week 3 at the graft site and declined to the off-site values by week 4. The optical parameters remained relatively constant throughout 4 weeks for the off-site measurements.

High reliability, miniature personal hypoxia monitoring system

In this work, we present research performed towards the realization of a hypoxia monitor that can detect the onset of hypoxia within a minute with very low false positive and false negative rates. We report the development of the next-generation hypoxia monitor with the capability to simultaneously detect various physiological parameters that change in response to reduced oxygen availability and identify the onset of hypoxia based on the changes in their cross-correlation signals. Significant improvements are obtained over the conventional techniques that are used currently to measure some of the physiological parameters including blood oxygen saturation and blood flow velocity. We demonstrate that a simple patch geometry holding three LEDs and two single photon sensitive detectors can be used to simultaneously obtain the heart rate, respiratory rate, blood flow velocity and blood oxygen saturation levels and in less than one minute analyze their cross-correlation signals to identify the onset of hypoxia from the more benign auto-regulatory response to stress.

Diffuse optical monitoring of peripheral tissues during uncontrolled internal hemorrhage in a porcine model

Reliable, continuous and noninvasive blood flow and hemoglobin monitoring in trauma patients remains a critical, but generally unachieved goal. Two optical sensing methods - diffuse correlation spectroscopy (DCS) and diffuse reflectance spectroscopy (DRS) - are used to monitor and detect internal hemorrhage. Specifically, we investigate if cutaneous perfusion measurements acquired using DCS and DRS in peripheral (thighs and ear-lobe) tissues could detect severe hemorrhagic shock in a porcine model. Four animals underwent high-grade hepato-portal injury in a closed abdomen, to induce uncontrolled hemorrhage and were subsequently allowed to bleed for 10 minutes before fluid resuscitation. DRS and DCS measurements of cutaneous blood flow were acquired using fiber optical probes placed on the thigh and earlobe of the animals and were obtained repeatedly starting from 1 to 5 minutes pre-injury, up to several minutes post shock. Clear changes were observed in measured optical spectra across all animals at both sites. DCS-derived cutaneous blood flow decreased sharply during hemorrhage, while DRS-derived vascular saturation and hemoglobin paralleled cardiac output. All derived optical parameters had the steepest changes during the rapid initial hemorrhage unambiguously. This suggests that a combined DCS and DRS based device might provide an easy-to-use, non-invasive, internal-hemorrhage detection system that can be used across a wide array of clinical settings.

Foliage penetrating airborne ladar for surface situation awareness

A field test of an airborne foliage penetrating (FOPEN) ladar system was recently conducted in order to assess the utility of FOPEN ladar for surface situation awareness applications. The FOPEN ladar system was flown over staged targets embedded in a woodland area with vegetation typical of a forest environment. This paper presents data that demonstrates the ability to detect man-made objects such as trucks, tents, and tarps embedded in this vegetation through exploitation by human analysts, as well as an initial evaluation of automated 3D object detection, specifically through the sum of absolute difference (SAD) approach. Many governmental and aid agencies often requires actionable information in a rapid timeframe, we additionally consider two candidate CONOPS that might be employed by such an end user for both tactical and strategic use cases.

Extracting optical properties of turbid media using radially and spectrally resolved diffuse reflectance

Extraction of optical absorption and scattering coefficients from experimental measurements of spatially and/or spectrally resolved diffuse reflectance typically requires that measurements made on unknown samples be calibrated using those made on reference phantoms with well characterized optical properties. Here, we derive the optical scattering and absorption spectra of a solid homogenous resin-phantom using two analytical methods: radially resolved diffuse reflectance (RRDR) based fitting and spectrally resolved diffuse reflectance (SRDR) based fitting. Radially resolved data was acquired using a fabricated probe holder which connected one source fiber to 7 detector fibers with distances ranging between 1.65 to 12.5 mm. Each detector fiber was connected to a spectrometer and spectra ranging 450 to 800 nm were measured when a broadband halogen lamp was used as the source. Diffusion theory based, as well as scaled Monte Carlo based models were used to fit the spectrally and radially resolved reflectance (on a per wavelength basis) to derive the absorption and scattering spectra of the solid phantom. To assess the accuracy of these derived absorption and scattering properties, they were used as reference measurements to reconstruct the optical properties of liquid phantoms, with well-determined absorption and scattering. Reference optical properties determined using the SRDR methods were more accurate in reconstructing the optical properties in liquid phantoms. However, RRDR methods are useful to obtain a spectral profile of the absorption coefficient of an unknown media, for subsequent analyses using SRDR.