archives@tulane.edu / Pelvic organ prolapse (POP) is the descent of the pelvic organs. Quantifying composition in 3-D as opposed to traditional 2-D histologic analysis may reveal new information on vaginal microstructure to inform diagnostics and design criteria to improve interventions on POP. Dual-view inverted selective plane illumination microscopy (diSPIM) images a tissue in 3-D using fluorescent stains. The fluorescent stain TO-PRO-3 Iodide and Eosin (T&E) is a potential analog to Hematoxylin and Eosin (H&E) that can be used to acquire 3-D images. Therefore, the goal of this study was to validate T&E as an H&E fluorescent analog and to acquire 3-D images of the murine vagina using diSPIM with T&E staining to observe morphological changes throughout the vagina. Staining of murine samples with T&E and H&E generated very similar images, validating the use of T&E as a fluorescent analog to H&E. diSPIM imaging with T&E staining applied to murine vaginal samples at varying stages of pregnancy generated 3-D images from which 2-D slices could be isolated. These 2-D slices were analyzed by delineation and thickness measurements of their vaginal layers (epithelial, subepithelial, and muscularis layers). These thickness measurements showed changes in thicknesses across depths and across pregnancy status in the vagina, such as the thickening of the epithelial layer throughout pregnancy. These results highlighted the capability of diSPIM to reveal information on the vaginal microstructure throughout its depth. / 1 / Diego Gatica

The purpose of this experiment is to observe the diffusion coefficient of agarose solution as a function of temperature during the process of gel formation. The focus is on understanding how liquids become semi organized or semi-solid by monitoring dynamically with diffusion quantitative MRI the liquid-to-gel phase transition of pure agarose as a function of gel concentration. Four different concentrations of agarose solutions were allowed to cool down while scanning dynamically with 3 T MRI scanner (Achieva, Philips Medical Systems, Cleveland, OH) with diffusion qMRI, 70 dynamics with 56 seconds dynamic time. The 1%, 2%, 3%, and 4% agarose solutions were prepared by pouring agarose powder in distilled water and heating the solutions until they reached the boiling point ~80°C and completely dissolved. Then, scanning the phantoms dynamically as these cooled down immediately after preparation. A single axial slice diffusion-weighted-imaging turbo-spin-echo (DWI-TSE) pulse sequence was used. The diffusion versus time (temperature) curves of different agarose solutions show a distinct phase transition region characterized by a hump of increased diffusion. The diffusion coefficient as a function of time (temperature) curves of all the four concentrations shows similar behaviors with a phase transition characterized by a hump shaped at about 24 minutes at which time the gelation phase transition begins. These results may be useful for testing theoretical models of the NMR diffusion coefficient properties during liquids transforming to semi organized or semi solid

This study has been conducted for the purpose of investigating the systematic dose reduction of rectum and neurovascular bundles (NVBs) during treatment planning of the CyberKnifeTM prostate SBRT using CT-Based volumes versus MRI-based volumes. Three prostate cancer patients were Planned for the CyberKnifeTM prostate SBRT and they underwent computed tomography (CT) and magnetic resonance imaging (MRI) preplanning exams. The patients were positioned during both exams using an immobilizing device. A radiation oncologist and a radiologist delineated the prostate gland, intra-prostatic and peri-prostatic structures, and pelvic organs of interest in both CT and MRI images. The CT and MRI images were fused based on fuducial markers to accurately align the prostate. Radiation Therapy Oncology protocol RTOG 0938 was followed to meet the target volume (prostate plus margin) dose coverage requirement, and dose-volume constraints for organs at risk, including rectum, bladder, femoral heads, penile bulb, urethra, skin and NVBs. Radiation dose volume parameters were recorded for both volumes and compared. The preliminary result shows that the CT-based volumes were generally larger than MRI-based volumes of the prostate. Therefore, the CT-based volumes resulted in less accurate treatment planning and dose delivery to radiosensitive structures.

This thesis contributes to the solution of the inverse electromagnetic (EM) scattering problems arising in microwave imaging. A calibration technique based on measurements of specific objects is proposed and a fast quantitative imaging method based on such measurements is developed. The calibration measurements are performed on two known objects: the reference object representing the scatterer-free measurement and the calibration object representing a small scatterer embedded in the reference object. The inversion method does not need analytical or numerical approximations of the forward model as those are replaced by the measurement-based model. It is particularly valuable in short-range imaging, where analytical models of the incident field do not exist while the fidelity of the simulation models is often inadequate. In this thesis, it is demonstrated that the implementation of the calibration technique in the sensitivity-based imaging improves both the imaging efficiency as well as the image quality. A quantitative imaging method is further developed based on the calibration measurements where a direct inversion in real space is employed. The electrical properties of dielectric objects are reconstructed using a resolvent kernel in the forward model, which is extracted from the calibration measurements. The experimentally determined resolvent kernel inherently includes the particulars of the measurement setup, including all transmitting and receiving antennas. The inversion is fast, allowing for quasi-real-time image reconstruction. The theoretical limitations of the fast quantitative imaging method have been investigated and its performance with noisy data has been examined. It is found that the proposed method has limitations which are more flexible than those of the linear Born model. The method is also robust to random noise. Both the calibration technique and the fast quantitative imaging method are validated through synthetic, simulation and/or experimental examples. The proposed concept of experimentally derived resolvent kernel in the forward model is general and may be valuable in other imaging modalities such as ultrasound, photonic imaging, electrical-impedance tomography, etc. / Dissertation / Doctor of Philosophy (PhD)

Neck pain is a pervasive problem in the general population, especially in those working in vibrating environments, e.g. military troops and truck drivers. Previous studies showed neck pain was strongly associated with the degeneration of intervertebral disc, which is commonly caused by repetitive loading in the work place. Currently, there is no existing method to measure the in-vivo displacement and loading condition of cervical spine on the site. Therefore, there is little knowledge about the alternation of cervical spine functionality and biomechanics in dynamic environments. In this thesis, a portable ultrasound system was explored as a tool to measure the vertebral motion and functional spinal unit deformation. It is hypothesized that the time sequences of ultrasound imaging signals can be used to characterize the deformation of cervical spine functional spinal units in response to applied displacements and loading. Specifically, a multi-frame tracking algorithm is developed to measure the dynamic movement of vertebrae, which is validated in ex-vivo models. The planar kinematics of the functional spinal units is derived from a dual ultrasound system, which applies two ultrasound systems to image C-spine anteriorly and posteriorly. The kinematics is reconstructed from the results of the multi-frame movement tracking algorithm and a method to co-register ultrasound vertebrae images to MRI scan. Using the dual ultrasound, it is shown that the dynamic deformation of functional spinal unit is affected by the biomechanics properties of intervertebral disc ex-vivo and different applied loading in activities in-vivo. It is concluded that ultrasound is capable of measuring functional spinal units motion, which allows rapid in-vivo evaluation of C-spine in dynamic environments where X-Ray, CT or MRI cannot be used. / 2020-02-20T00:00:00Z

With the continual growth of the average age of the population and the global rise in obesity, it is important to investigate age related cognitive decline and its many related risk factors. Alzheimer’s Disease is the most common cause of dementia and has been linked to another inflammation-associated disease, atherosclerosis. In our lab’s recent findings, we have demonstrated this mechanistic link between inflammation and atherosclerosis with specialized pro-resolving mediators, such as lipoxin and resolvin found in Omega-3 fatty acids. Here we investigated the viability of our rabbit model of atherosclerosis as a model of Alzheimer’s Disease, in an effort to eventually test the impact of inflammation resolution as a treatment to AD. We developed and optimized an MRI protocol as a way to demonstrate and quantify the effect of vascular inflammation on a brain ex vivo in first a murine model of arterial stiffness. We then applied the refined protocol for use on our rabbit model of atherosclerosis. The mouse brains induced with arterial stiffness showed a significant increase of cerebral microbleeds (indicators of cerebral amyloid angiopathy). Some of the rabbit brains used for this study were found to be preserved for too long but found good images in recently harvested and perfused rabbit brains. While the our findings are currently inconclusive, this thesis proposes a novel method for investigating the mechanistic and synergistic link between inflammation, atherosclerosis, and Alzheimer’s Disease.

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