In this study, we have developed a high performance multi-photon microscopic system to perform second- harmonic (SH) imaging on a tooth and a KTP crystal . The high sensitivity of the system allows acquisition rate of 300 seconds/frame with resolution at 512¡Ñ512 pixels. The surface SH signal generated from the tooth and the KTP crystal is also carefully verified through micro-spectroscopy, polarization rotation and wavelength tuning. In this way, we can ensure the authenticity of the signal. KTP crystal and the enamel that encapsulates the dentine is known to possess highly ordered structures. The anisotropy of the structure is revealed in the microscopic SH images of the tooth and the KTP crystal samples.

In this study, we have successfully developed a high performance transmission mode Laser scanning for SHG imaging. This setup is capable of acquiring images of size 512¡Ñ512 pixels at a rate of 5.4 seconds/frame. The of samples can thus be imaged, which reflects the samples¡¦ structure and symmetry.

Around 80% of women experience vaginal tears during labor when the diameter of the vagina must increase from ~2.5 cm to ~9.5 cm to allow the passage of a full-term baby. Vaginal tears vary from superficial cuts of the mucosal lining to tears propagating through the entire vaginal wall and into the surrounding tissues and organs. Complications associated with vaginal tears include postpartum hemorrhaging, fecal incontinence, urinary incontinence, and dyspareunia. Beyond the agonizing pain, these complications are emotionally and psychologically traumatic for women. Prevention, evaluation, and treatment of vaginal tears and subsequent conditions are limited due to the lack of studies examining the mechanical behavior of the pelvic floor tissues. Therefore, the mechanical response of healthy and torn vaginal tissue is investigated here to establish quantitative metrics for maternal healthcare. Toward this end, swine and rat vaginal tissue is subjected to biaxial loads until tearing to reveal its mechanical properties. The resulting large inhomogeneous deformations are measured by the digital image correlation optical method to calculate material strain. The influence of these strains near to and far from the immediate vicinity of the tears on the tearing behavior is studied. Coupling mechanisms of the mechanical properties in the circumferential and axial directions as well as their effect on the nature of tear resistance is studied. Collagen fibers, the component within tissue responsible for its strength under tension, are imaged using a multiphoton microscopy technique known as second-harmonic generation imaging to investigate the change in organization with mechanical loading. Furthermore, imaging is performed in the near-regions of tears to reveal the relationship between collagen fibers and tearing resistance. The data collected through these studies provide new knowledge on the nonlinear elastic behavior of vaginal tissue, the geometrical and micro-structural characteristics of tears, and the mechanisms that contribute to the formation and propagation of tears. The mechanical properties and tearing mechanisms of vaginal tissue will be crucial in developing new prevention and treatment methods for maternal trauma following childbirth. Episiotomy, late-term stretching, surgical treatment with graft materials and other protocols will all benefit from a mechanically-informed perspective. It is our hope that this work will raise awareness to the serious complexities of pelvic floor trauma and encourage a more refined and systematic approach to the inspection, imaging, and treatment of all vaginal tears following delivery. This work was supported in part by the National Science Foundation fund #1511603 and the Institute for Critical Technology and Sciences at Virginia Tech. / Doctor of Philosophy / Every year nearly three million women give birth vaginally with 80% experiencing vaginal tears. These injuries sustained during delivery vary with severity and are associated with several conditions, including pelvic floor disorders. These disorders are a set of long-term conditions of the pelvic region presently affecting one-fourth of adult women in the United States. Pelvic floor disorders are: pelvic organ prolapse - a pelvic organ such as the uterus "falls" from its natural position, urinary incontinence - difficulty controlling urination, and fecal incontinence - difficulty controlling bowel movements. Pelvic floor disorders lower the quality of life for women not only physically due to pain and daily discomfort, but also mentally as the disorders are generally perceived as an embarassing and private matter. The pelvic floor represents a complex system of muscles, organs, and support structures that work together to ensure everything stays in place and is functioning properly. Injury to any of these structures poses the risk of developing a disorder. As a central supporting organ, injuries to the vagina may be particularly worrisome. Surprisingly, little is known about the magnitude of forces and/or stretching that is placed on the pelvic floor during delivery, how much force and/or stretching is required for an injury, or how various injuries relate to future complications. The goal of this research is to describe how much the normal, healthy vagina stretches to various forces including forces that will result in injuries. The research further examines the stretching of injured vaginas to quantify any observable differences due to this injury. Finally, the relationships between the biological components of the vagina, such as collagen, and the forces placed on the vagina are examined. The result of this work will provide doctors and engineers with guidelines for understanding the conditions that produce vaginal injuries. The relationships examined between the tissue makeup and forces exerted onto the tissue may also aid in identifying any irregularities that would place a woman at risk for injury. Many of the medical procedures surrounding childbirth as well as surgical treatment for pelvic floor disorders will benefit from knowing how far the vagina can stretch before being injured. It is our hope that this work will raise awareness to the serious complexities of pelvic floor injuries and encourage a more refined and systematic approach to the inspection, imaging, and treatment of all vaginal tears following delivery. This work was supported in part by the National Science Foundation fund #1511603 and the Institute for Critical Technology and Sciences at Virginia Tech.

<div>Vibrational spectroscopic imaging has become an emerging platform for chemical visualization of biomolecules and materials in complex systems. For over a century, both Raman and infrared spectroscopy have demonstrated the capability to recognize molecules of interest by harnessing the characteristic features from molecular fingerprints. With the recent development of hyperspectral vibrational spectroscopy imaging, which records the chemical information without sacrificing the spatial-temporal resolution, numerous discoveries has been achieved in the field of molecular and cellular biology. Despite the ability to provide complimentary chemical information to Raman-based approaches, infrared spectroscopy has not been extensively applied in routine studies due to several fundamental limitations: 1). the poor spatial resolution; 2). inevitable strong water absorption; 3). lack of depth resolution.</div><div>Mid-infrared photothermal (MIP) microscopy overcame all the above mentioned problems and for the first time, enabled depth-resolved in vivo infrared imaging of live cells, microorganisms with submicrometer spatial resolution. The development of epi-detected MIP microscopy further extends its application in pharmaceutical and materials sciences. With the deployment of difference frequency generation and other nonlinear optical techniques, the spectral coverage of the MIP microscopy was significantly enhanced to enable chemical differentiation in complex systems across the broad mid-infrared region. In addition to the efforts to directly improve the performance of MIP microscopy, a novel quantitative phase imaging approach based on polarization wavefront shaping via custom-designed micro-retarder arrays was developed to take advantage of the highly sensitive phase measurement in combination with the photothermal effect. Besides, the extended depth-of-field and multifocus imaging enabled by polarization wavefront shaping could both improve the performance of MIP microscopy for volumetric imaging.</div>