Doctor of Philosophy, Case Western Reserve University, 2024, EECS - Electrical Engineering

Quantitative Magnetic Resonance Imaging (qMRI) is a powerful tool for detecting biochemical abnormalities without harmful ionizing radiation and invasive procedure, which can significantly enhance early disease diagnosis and progression monitoring compared to standard morphological MRI. Osteoarthritis is a disease significantly impacting joint function, mobility, and quality of life, often leading to chronic pain and reduced physical activity. Despite the significant impact, the disease lacks sensitive biomarker that can detect and track the disease progression from an early stage which can help improve patient outcomes and develop effective treatment for the disease. qMRI, due to its sensitivity to biochemical properties, provide multiple candidates that may serve as imaging biomarkers for OA. Among them, T2 and T1ρ have advantage of not requiring special coil nor contrast agent. However, challenges need to be addressed to expand the accessibility of the technique and successful translation to be used in large scale clinical trials and in clinical practice. In this study, novel quantitative T2 and T1ρ acquisition techniques were developed to enhance reliability and enable faster acquisition.

Committee: Xiaojuan Li (Advisor); Mark Griswold (Committee Member); Xin Yu (Committee Member); Cenk Cavusoglu (Committee Chair) Subjects: Biomedical Engineering; Electrical Engineering

PhD, University of Cincinnati, 2024, Engineering and Applied Science: Mechanical Engineering

One of the largest sources of uncertainty in the calculation of stopping power ratios for use in proton radiotherapy is the measurement of Hounsfield Units (HU) for the determination of electron density. The primary source of this uncertainty is due to the relative difference in scatter between the patient and electron density calibration phantoms. In this dissertation, I will show how anatomy adaptive CT number to electron density calibration curves can improve the accuracy of stopping power ratio tabulations for proton radiation therapy dosimetry. We will generate new curves by measuring realistic (anthropomorphic) phantoms, fabricated using realistic tissue equivalent materials that accurately represent the internal structure and tissue types of the pelvis. The goal of this research is to use the new realistic anthropomorphic phantoms to evaluate how patient scatter affects measured electron density curves.

Committee: Henry Spitz Ph.D. (Committee Chair); Jay Kim Ph.D. (Committee Member); Michael Lamba Ph.D. (Committee Member); Bruce Mahoney (Committee Member); Peter Sandwall Ph.D M.A B.A. (Committee Member); Michael Alexander-Ramos Ph.D. (Committee Member); Sam Glover Ph.D. (Committee Member) Subjects: Nuclear Physics

Master of Science, The Ohio State University, 2024, Vision Science

Purpose: Spaceflight Associated Neuro-ocular Syndrome (SANS) is experienced by astronauts in microgravity and is characterized by a hyperopic shift, globe flattening, optic disc edema and choroidal folds. The pathophysiology of SANS is not yet known, but it is thought to be caused by the loss of ground-based hydrostatic pressure gradient, which results in a head-ward fluid shift. It has been recently hypothesized that this fluid shift elicits congestion of the orbital fat. Thyroid eye disease (TED) may be a novel terrestrial analog to SANS because the physical manifestations in both pathologies can be similar. The purpose of this study is to assess the performance of an established magnetic resonance imaging (MRI) sequence to measure fat/water fractions in the orbit, first in phantoms and then in one initial TED subject. Methods: Fat-water fractions in orbital phantoms were quantified using a q-Dixon Multi-Echo Chemical Shift Encoded MRI at 3 Tesla. Images were acquired in triplicate to evaluate test-retest reliability, as well as in 3 orientations. The first subject with TED was enrolled, provided informed consent, and triplicate orbital images were acquired. These images were processed with the imaging software ImageJ and orbital fat volume and fat fraction measurements were obtained from selected orbital fat. Results: The MRI sequence measured fat-fraction in the phantom models with good accuracy, and there was a strong linear association in all three positions between measured fat values and true fat values (R2 = 0.9978). The sequence was found to be repeatable, with good test-retest reliability between the positions and with triplicate acquisitions. Preliminary results for the initial TED subject show successful procurement of overall average fat-fraction (approximately 43% fat in the right orbit and 42% in the left orbit). Statistical analysis suggests generally good agreement between the triplicate scans, with low coefficient of variation in both orbits (open full item for complete abstract)

Committee: Phillip Yuhas (Advisor); Jennifer Fogt (Committee Member); Nicklaus Fogt (Committee Member); Cynthia Roberts (Advisor) Subjects: Medical Imaging; Medicine; Ophthalmology

Doctor of Philosophy (PhD), Wright State University, 2023, Engineering PhD

Blood flow dynamics plays a critical role in maintaining tissue health, as it delivers nutrients and oxygen while removing waste products. It is especially important when there is a disruption in cerebral autoregulation due to trauma, which can induce ischemia or hyperemia and can lead to secondary brain injury. Thus, there is a need for noninvasive techniques that can allow continuous monitoring of blood flow during intervention. Optical techniques have become increasingly practical for measuring blood flow due to their non-invasive, continuous, and relatively lower-cost nature. This research focused on developing a low-cost, scalable optical technique for measuring blood flow by implementing speckle contrast optical spectroscopy using a fiber-camera-based approach. This technique is particularly well-suited for measuring blood flow in deep tissues, such as the brain, which is challenging to access using traditional optical methods. A two-channel continuous wave speckle contrast optical spectroscopy device was developed, and the device was rigorously tested using phantoms. Then, it is applied to monitor blood flow changes in the brain following traumatic brain injury (TBI) in mice. The results indicate that trauma-induced significant blood flow decreases consistent with the recent literature. Overall, this approach provides noninvasive continuous measurements of blood flow in preclinical models such as traumatic brain injury.

Committee: Ulas Sunar Ph.D. (Advisor); Tarun Goswami Ph.D. (Committee Member); Keiichiro Susuki Ph.D. (Committee Member); Robert Lober M.D., Ph.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Biophysics; Engineering; Optics

Master of Science, The Ohio State University, 2021, Health and Rehabilitation Sciences

Manuscript 1: Methodology Dependent Variation in Volumetric Bone Mineral Density Calculation throughout the Body Introduction: Bone quality assessment using quantitative computed tomography (QCT) may provide a more in-depth and accurate assessment of osteoporosis and fracture risk than dual-energy x-ray absorptiometry (DXA). However, QCT methodologies utilizing single-scan calibration curves may not account for differential x-ray attenuation caused by the patient which may influence calculated volumetric bone mineral density (vBMD) and skew bone quality and fracture risk assessment. Methodology: Clinical CT scans were conducted on 50 male post-mortem human subjects with phantom calibration rods throughout the scan. Height and weight were collected to determine subject BMI. Hounsfield units (HU) from skeletal volumes of interest (VOIs) were collected from the lumbar spine and left femoral neck, humerus, radius, tibia, and calcaneus. The femoral neck was segmented into trabecular (Tb), cortical (Ct) and Total (Tb and Ct) VOI's, the lumbar spine and the calcaneus consisted of Tb and Total VOIs, and the humerus, radius, and tibia were assessed for Ct bone. HU from each VOI was converted to vBMD using both a general scan specific (Gen.) calibration curve constructed from phantom rods within the CT slices of the lumbar region and location specific (LS) calibration curves constructed from phantom rods in slices for each of the skeletal VOIs. Results: Significant variation in vBMD calculated from Gen. and LS calibration curves was observed in the femoral neck, calcaneus, and tibia in all skeletal compartments 15 (p<0.01). However, no significant differences were observed in any of the lumbar spine, humerus, or radius VOIs (p>0.01). Additionally, BMI was not able to explain variation in vBMD values at any site (p>0.01). Conclusions: Using a single calibration curve to calculate vBMD in other anatomical locations, may skew bone quality and differential fracture risk ass (open full item for complete abstract)

Committee: Randee Hunter PhD (Advisor); Amanda Agnew PhD (Committee Member); Jun Zhang PhD (Committee Member) Subjects: Anatomy and Physiology; Biomedical Research; Health; Health Care

Master of Sciences, Case Western Reserve University, 2019, Biomedical Engineering

The main goal of this thesis is to develop a flexible and body-conformal sensor for vascular access stenosis characterization. Vascular accesses are monitored through physical examination by medical personnel. These examinations are time consuming and subjective, thus creating a challenge for long term monitoring and an opportunity for automated analysis. In our method, we record phonoangiograms from vascular access phantoms through a custom-made flexible array of piezoelectric sensors. These signals are processed through an autoregressive bruit- enhancing filter which used a nonlinear, sub-band frequency-domain linear prediction approach to amplify the systolic pulses of the blood flow and associated stenosis related turbulence while attenuating inter-pulse intervals and artifacts due to ambient noise. Features like auditory spectral centroid (ASC) and auditory spectral flux (ASF) are extracted from the wavelet coefficients which are computed over 6 octaves with 12 voices/octave, starting at scale 3. Finally, we show that this piezoelectric sensor in combination with signal processing techniques can i) localize stenosis within 1 cm of the actual location, and ii) differentiate the degree of stenosis into three grades (mild, moderate and severe) in vitro. These results were confirmed with statistical analysis and the performance of the extracted features was also tested with a threshold-based stenosis detection classifier to mimic a clinical screening scenario aimed at identifying at-risk patients.

Committee: Soumyajit Mandal PhD (Committee Chair); Dominique Durand PhD (Committee Member); Colin Drummond PhD (Committee Member); Steve Majerus PhD (Committee Member) Subjects: Biomedical Engineering; Biomedical Research

Master of Science in Biomedical Engineering (MSBME), Wright State University, 2019, Biomedical Engineering

Neurovascular coupling is an important concept that indicates the direct link between neuronal electrical firing with the vascular hemodynamic changes. Functional Near Infrared Spectroscopy (fNIRS) can measure changes in cerebral vascular parameters of oxy-hemoglobin and deoxyhemoglobin concentrations and thus can provide neuronal activity through neurovascular coupling. Currently many commercial fNIRS devices are available, but they are limited by the number of channels (usually having only 8 detectors), which can limit the sensitivity, contrast, and resolution of imaging. High-density imaging can improve sensitivity, contrast, and resolution by providing many measurements and averaging the signals originating from the target cerebral focus area compared to background tissue. Here a multi-channel, low-cost, high-density imaging system based on scientific CMOS (Complementary Metal-Oxide-Semiconductor) detector will be presented. The CMOS camera is fiber-coupled such that on one end fibers are focused on the pixels on the CMOS camera, which allows individual pixels (or binned sub-pixels) to act as detectors, while the other end of the fibers can be positioned on a wearable optical probe. After the device details, I will show the device validation using a series of the dynamic flow phantom experiments mimicking the brain activation and finally human motor cortex experiments (finger tapping experiments). The results demonstrate that this system can obtain high-density data sets with higher contrast and resolution. This wearable, high-density optical neuroimaging technology is expected to find many applications including pediatric neuroimaging at clinics and assessing human cognitive performance.

Committee: Ulas Sunar Ph.D. (Advisor); Keiichiro Susuki Ph.D. (Committee Member); Tarun Goswami Ph.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Engineering; Optics

Doctor of Philosophy, Case Western Reserve University, 2019, Physics

Magnetic Resonance Imaging (MRI) has become an important imaging method in the field of medical diagnostics and therapy due to its soft tissue contrast and use of non-ionizing radiations (unlike CT and X-ray). However, MRI also presents a number of safety issues including RF induced heating created by the interaction of the RF electromagnetic fields with human tissue and possible medical implants. A particular and important concern arises in the presence of any electrically conducting implant within the imaging specimen. The coupling between the conducting implants and RF electromagnetic fields produces relatively strong electrical currents within the implant and surrounding tissue which lead to ohmic heating and possibly unsafe temperature rises that damage tissue. One type of implant, and the focus of this thesis, are Stereo-electroencephalography (SEEG) electrodes. The SEEG electrodes are partially inserted into the brain of epilepsy patients for the localization and monitoring of focal epileptic zones. The electrical contacts on the SEEG electrode within the brain are connected via signal wires to external instrumentation to monitor the electrical activity in the brain. In this work, we study the RF induced heating due to the SEEG electrodes using both experimental measurements and numerical simulations. As a means for improved understanding of RF heating with implants containing both internal and external conductors, and to help validate the agreement between simulations and experiment, studies were first performed with a single insulated conducting copper wire using an MRI phantom. The benchmark for characterizing the level of RF heating was the temperature rise within the phantom and near the implants. These studies were then extended to include an 8 contact SEEG electrode, and then configurations with multiple wires and multiple SEEG electrodes. The results of the study demonstrate the importance of the length of the SEEG electrode and the signal wire (open full item for complete abstract)

Committee: Michael Martens Prof. (Advisor) Subjects: Biomedical Engineering; Biomedical Research; Physics

Master of Science, Miami University, 2018, Physics

This thesis presents data from a series of experiments that investigate the ability of laser speckle contrast imaging (LSCI) to sense changes in flow in turbid media. I first provide a theoretical overview and a description of the experimental approach used in this flow imaging technique. Experimental validation of the technique's ability to sense induced changes in blood flow in the human forearm is demonstrated. Then, the technique's sensitivity to buried flow in controlled optical phantoms is examined. It is shown that the buried depth and optical properties of the media surrounding flow impact the measured flow indices. Lastly, a study shows how the polarization state of the imaged light impacts the flow measurements as a function of the buried depth and rate of the flow. The results demonstrate that the measurements are dependent on the flow rates and optical properties of the sample as well as the imaging setup used to capture the speckle.

Committee: Karthik Vishwanath (Advisor); Paul Urayama (Committee Member); E. Carlo Samson (Committee Member) Subjects: Biomedical Research; Biophysics; Medical Imaging; Optics; Physics

Doctor of Philosophy (PhD), Wright State University, 2015, Engineering PhD

The sampling of three dimensional (3D) mesoscale microstructural data is typically prescribed using simple rules, likely resulting in data under- or oversampling depending on the measurement(s) of interest. The first part of this work investigates one approach for determining a minimally sufficient sampling scheme for 3D microstructural data, using computer-generated phantoms of polycrystalline grain microstructures. Sources of error that are observed experimentally are modeled using phantoms, in order to determine the effect that errors have on the microstructural statistic(s)-of-interest. Minimally-sufficient sampling schemes are then established based on a required accuracy in the microstructural statistic(s). The characterization error modeling framework is subsequently demonstrated on experimentally-derived statistics from high resolution 3D serial sectioning data, in order to inform future experiments on the same material. The second part of this work lends the aforementioned approach to the additive manufacturing (AM) of Ti-6Al-4V. Statistical analysis and virtual modeling tools developed herein are used to analyze alpha and beta phase microstructures in two thin-walled Ti-6Al-4V samples. Ultimately, this research aims to provide a virtual modeling framework for analyzing uncertainty in microstructural characterization, and to produce an offering of novel solutions for addressing current issues associated with rapid qualification methods for AM of Ti-6Al-4V components.

Committee: Nathan Klingbeil Ph.D. (Advisor); Ramana Grandhi Ph.D. (Committee Member); Raghu Srinivasan Ph.D., P.E. (Committee Member); Michael Uchic Ph.D. (Committee Member); Jaimie Tiley Ph.D., P.E. (Committee Member); Peter Collins Ph.D. (Committee Member) Subjects: Aerospace Materials; Materials Science; Mechanical Engineering

PhD, University of Cincinnati, 2014, Engineering and Applied Science: Nuclear and Radiological Engineering

The following work describes investigations of spatial dosimetry using laser-induced fluorescence of a radio-fluorogenic detector embedded within water-equivalent media. The chemical composition of a gelatin-based coumarin-3-carboxylic acid detector was investigated and dose response characterized. Violet diode (405nm) excitation sources were explored and laser-induced fluorescence (LIF) employed to obtain the pattern of fluorescent emission yielding images of the integrated spatial dose distribution. The design of a three-dimensional reader is proposed to provide a foundation for future work. Radio-fluorogenic processes create fluorescent products in response to ionizing radiation. Water radiolysis produced by ionizing radiation yields hydroxyl free radicals that readily hydroxylate coumarin-3-carboxylic acid to 7-hydroxy-coumarin-3-carboxylic acid, a derivative of umbelliferone. Umbelliferone is a known fluorophore, exhibiting peak excitation in the UV to near UV range of 365-405nm with a visible 445nm blue emission. Coumarin-3-carboxlyic acid has been studied in an aqueous gelatin matrix. The radio-fluorogenic coumarin-gelatin detector has been shown to respond to an absorbed dose of ionizing radiation in a measureable manner. The detector was studied with respect to concentration of gelatin and coumarin in the presence of pH buffers. Dose response of the detector was investigated with regard to ionizing radiation type, energy, and rate of irradiation. Results demonstrate a functional detector. Patterns of energy deposition were formed in response to ionizing radiation produced by a sealed-source of radioactive Ir-192 embedded in the gelatin matrix of the detector. Spatial distributions of absorbed dose were recorded and analyzed as a function of fluorescent emission. The distribution of energy deposition was imaged with LIF excitation by a divergent beam of 405nm light and determined by analysis of digital image pixel intensity values displaying the (open full item for complete abstract)

Committee: Henry Spitz Ph.D. (Committee Chair); Henry Fenichel Ph.D. (Committee Member); William Connick Ph.D. (Committee Member); Howard Elson Ph.D. (Committee Member); Michael Lamba Ph.D. (Committee Member) Subjects: Nuclear Engineering

Master of Science (MS), Wright State University, 2010, Physics

Two primary accrediting bodies exist for magnetic resonance imaging systems: the American College of Radiology (ACR) and the Intersocietal Commission for the Accreditation of Magnetic Resonance Laboratories (ICAMRL), each of which defines specific standards for specific image quality criteria at which MRI images must be produced. An MRI clinic that wishes to show a commitment to image quality may do so by becoming accredited by one of these organizations of their choosing. The limits of these image criteria were compared to demonstrate the standards of each accrediting body. Images were produced that fell well within the standards of both accrediting organization, and subsequent images were produced at the limits of ACR and ICAMRL standards respectively. These images were first produced using a phantom to quantify a difference in criteria standards, then images were produced using a human patient to show a qualitative difference in criteria standards for clinical applications.

Committee: Brent Foy PhD (Advisor); Jason Parker PhD (Committee Member); Gary C. Farlow PhD (Committee Member) Subjects: Physics

PhD, University of Cincinnati, 2003, Medicine : Environmental Health Sciences

An anthropometric leg phantom developed at the University of Cincinnati (UC) was used to evaluate the effects that changes in leg position and variation between subjects has on in vivo x-ray fluorescence (XRF) measurements of stable lead in bone. The changes in leg position that were evaluated include changes in source-phantom distance ranging between 0.0 mm and 30.0 mm and phantom rotation over 40 degrees. Source-phantom distance was determined to have a significant effect on XRF measurement results particularly at source-phantom distances greater than 10.0 mm. Rotation of the leg phantom through 40 degrees was determined to have no significant effect on XRF measurement results. Between subject factors that were evaluated include bone calcium content and overlying tissue thickness. Bone calcium content was determined to have a significant effect on XRF measurements when measuring lead in micrograms per gram bone material. However, if measurement results of micrograms of lead per gram calcium (or per gram bone mineral) is used the normalization method makes the change in calcium content not significant. Overlying tissue thickness was determined to have no significant effect on XRF measurement results with tissue thickness ranging between 5.7 and 11.62 mm. The UC leg phantom was modified to include a fibula bone phantom so that the effect that the fibula has on XRF measurement results could be evaluated. The fibula was determined to have no significant effect on XRF measurement results and in the future need not be incorporated into in vivo XRF calibration phantoms. A knee phantom was also developed for purposes of calibrations of in vivo XRF measurement of lead in the patella. XRF measurement results using this phantom were compared to results of XRF measurements made using the plaster-of-Paris (POP) phantoms. A significant difference was observed between the normalized count rates of the two phantom types when either micrograms of lead per gram of bone material or (open full item for complete abstract)

Committee: Dr. C. Scott Clark (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2003, Business Administration

The primary goal of this research is to examine how consumers respond when their freedom to choose is constrained due to product unavailability. Reactance theory would suggest that restricting individuals' freedom of choice is likely to have an adverse effect, including lowered choice consistency caused by negative affect. The degree to which consumers will react adversely to product unavailability is likely to depend on how much freedom they expect prior to choice, and whether a choice constraint is perceived to be important to them. Managing consumers' expectations and perceptions in this regard represents an important challenge facing retailers. When should consumers be notified of a choice constraint, and what actions can be taken to minimize any detrimental effects on consumer choice and satisfaction? Two studies examine the role of psychological reactance in explaining consumer reaction to product unavailability. The first study establishes the importance of the timing of notification regarding product unavailability. Preference for the unavailable product is shown to moderate the relationship between the timing of notification and choice of the most similar alternative. The second study further explores the role of psychological reactance by examining the process by which consumers restore their freedom and reduce negative affect associated with product unavailability through the selection of another product. The theoretical contribution of this dissertation is to show how the timing of notification influences consumer choice and satisfaction. Past research argued that the presence of an unavailable alternative would increase the choice share of its most similar alternative due to consumers' cognitive biases, including loss aversion and similarity substitution. However, such cognitive accounts fail to fully explain why choice reverses when consumers are notified about product unavailability after they have made a choice. In addition, the existing accounts can (open full item for complete abstract)

Committee: Patricia West (Advisor) Subjects: Business Administration, Marketing

Master of Science (MS), Ohio University, 2007, Computer Science (Engineering)

This thesis presents implementation and evaluation of a multiple-points haptic rendering algorithm using the PHANToM haptic interface, in the context of our Virtual Haptic Back Project at Ohio University. This algorithm will increase realism in palpation with the Virtual Haptic Back and other virtual haptic palpation tasks when compared to the single point haptic rendering. The single-point haptic rendering cannot provide tool-object interactions in which more than one object is in contact simultaneously at different locations of the tool or finger. Since a single point does not represent the finger haptically well, this thesis uses a multiple-points probe. The multiple-points collision detection is computationally expensive and complicated than the single-point haptic rendering. This thesis constructs the volume object using a sphere. The center of this sphere is the original PHANToM position and the end-points consist of points on the sphere. The collision detection between these line segments and objects in the virtual scene is completed and a resultant force is displayed to the user. The multiple-points haptic rendering algorithm was integrated with simple haptic objects and with the complex Virtual Haptic Back. The multiple-points algorithm is made efficient using concepts such as rasterisation, hashing and spatial decomposition. Experiments have determined that multiple-points haptic rendering can improve the user's experience with virtual reality applications based on this first step in implementation and evaluation.

Committee: Robert Williams II (Advisor) Subjects: Computer Science

Master of Science (MS), Ohio University, 2005, Mechanical Engineering (Engineering)

This thesis presents implementation and evaluation of a haptic playback system using the PHANToM haptic interface, in the context of our Virtual Haptic Back Project at Ohio University. Playback has the potential to improve virtual palpatory diagnosis training by allowing students to follow and feel an expert's motions in virtual reality prior to performing their own palpatory tasks. We have two types of playback system. The first type is called ‘Combined Playback System' and the second one is called ‘Two Mode Playback System'. In the first type we have a combined position and force playback. In the second type of playback system, in mode 1 the human is passive and experiences position playback of the expert's tactile examination via the PHANToM with a PD position controller. In mode 2 the human traces the expert's path actively through visual cues. Mode 2 enables the haptics model so that the trainee feels approximately what the expert did in the original task. Both playback systems are evaluated. Our experiments show that if both playback modes of the ‘Two Mode Playback System' are used together, trainees follow the expert's path with lesser position error than the other group, which doesn't do mode 1 training.

Committee: Robert Williams (Advisor) Subjects: Engineering, Mechanical

Master of Science in Biomedical Sciences (MSBS), University of Toledo, 2010, College of Medicine

The purpose of this study was to develop and report on the implementation and IMRT quality assurance plan delivery verification using a Spiral phantom. The phantom utilizes a cylindrical solid water system with a machined spiral trajectory for insertion of film. Several analyses were performed on various IMRT treatment plans comparing predicted planar fluence dose and measured dose using radiochromic film. A solid water cylindrical IMRT phantom manufactured by GAMMEX which has been machined creating a spiral cavity for placement of radiochromic film (GAFCHROMIC® EBT2) was employed for IMRT plan QA. This spiral phantom is implemented to measure data in a three dimensional (3D) subspace which was not previously demonstrated. The patient treatment plan with predicted planar and volumetric isodose distributions were obtained in Pinnacle treatment planning software (TPS). The patient treatment planning data using a CT data set was then projected onto the spiral phantom in the TPS where planar dose files were generated using a scripting file. The measured data was obtained upon successful delivery of the intended treatment plan with a linear accelerator on the spiral phantom with radiochromic film in place. Comparison of the predicted and measured data provides a quantitative and qualitative assessment and validation of the intended treatment when delivered as planned. The films were subsequently scanned and the measured dose data from the delivered plan were compared with the planar fluence dose maps generated in Pinnacle using RIT113 software. Schematic isodose overlays, vertical and horizontal dose profiles as well as IMRT distance to agreement (DTA) analysis of the predicted and measured dose distributions were shown to be in great accord with one another. One can easily see the value of this phantom as a quantitative and qualitative IMRT plan analysis tool.

Committee: E. Ishamael Parsai PhD (Committee Chair); David Pearson PhD (Committee Member); Diana Shvydka PhD (Committee Member) Subjects: Physics

Master of Science in Biomedical Engineering, Cleveland State University, 2011, Fenn College of Engineering

The mammalian left ventricle (LV) has two distinct motion patterns: wall thickening and rotation. The purpose of this study was to design and build a low-cost, non-ferromagnetic LV motion phantom, for use with cardiac magnetic resonance imaging (MRI), that is able to produce physiologically realistic LV wall thickening and rotation. Cardiac MRI is continuously expanding its range of techniques with new pulse sequences, including new tissue tagging techniques which allow intra-myocardial deformation to be visualized. An essential step in the development of new cardiac MRI techniques is validating their performance in the presence of motion. MRI-compatible dynamic motion phantoms are of substantial benefit in the development of cardiac specific-magnetic resonance imaging techniques. These phantoms enable the investigation of motion effects images by mimicking the three dimensional motion of the heart. To date, no single study has succeeded in duplicating both LV motion patterns, in an MRI-compatible cardiac motion phantom. In addition, a phantom that is 100% MRI-compatible with low cost to build would be desirable to researchers. We have built two MRI-compatible phantoms, housed within a common enclosure and each filled with MRI-visible dielectric gel (as a surrogate to myocardium),which model the wall thickening and rotation motions of the left ventricle independently. The wall motion phantom is pneumatic, driven by a custom non-ferromagnetic pump which cyclically fills and empties a latex balloon within the phantom. The rotation phantom is manually driven by a plastic actuator which rotates the phantom through a specified angular rotation. Each phantom also generates a TTL pulse for triggering the MRI scanner. Although this circuitry contains ferromagnetic materials, it can be located outside the scanner bore. The wall thickening motion phantom has been tested using segmented cine, real time cine and grid tagged MRI acquisition sequences. Results were significant wi (open full item for complete abstract)

Committee: Randolph Setser D.Sc (Advisor); Sandra Halliburton Ph.D. (Committee Member); George Chatzimavroudis Ph.D. (Committee Member) Subjects: Biomechanics; Biomedical Engineering; Biomedical Research; Engineering; Medical Imaging; Medicine

Doctor of Philosophy, Case Western Reserve University, 1993, Biomedical Engineering

A novel method for estimating the susceptibility of an object using the MRI field distortions in an external reference water bath next to the object is described. The field measurement is obtained using a MRI phase reconstruction from a Gradient Echo scan. A field model of an arbitrary object in a static magnetic field is discretely calculated using a Fourier convolution method from geometry determined from the magnitude reconstruction. Least squares estimation then yields the susceptibility of the object. Required (and proven) assumptions include; superposition, object homogeneity, negligible higher order field terms, field model accuracy, geometrical model accuracy and correlation of MRI FE phase to field distortion. MRI susceptometry estimation of in vitro phantoms yielded susceptibility estimates which correlated well with known values (r > 0.9975). This external reference bath MRI susceptometry method could be used to quantitate iron levels in iron overload patients. The errors which may occur in MRI susceptometry include field noise, and model errors including; outline error, outline shift, compartment inhomogeneity, volume error and unmodeled sources of field distort ion. Ultimately, the model errors can all be treated as unmodeled sources. Simulations and in vitro studies indicate that expected levels of field noise will not reduce the efficacy of the susceptibility estimations. However, unmodeled sources with relative strengths on the order of an unmodeled lung to a modeled liver of normal iron levels will reduce the efficacy of the fit (for a 22 patient in vivo experiment, r < 0.6). Filter application will alter the noise model, and improve the fit. Additionally, choosing the data set which lies closest to the organ of interest (i.e. the liver) will also improve the fit. With filtering and data set restriction, the estimates of the in vivo patient data were improved (r > 0.85). However, correlation of only the normal and low-level iron overload patients wa (open full item for complete abstract)

Committee: Pedro Diaz (Advisor) Subjects:

Master of Science in Engineering, University of Akron, 2008, Biomedical Engineering

This research study purpose is to design an optical transillumination based system and explore the potential of imaging enhancement, utilizing various contrast agents and polarimetry. This novel design can be used to study the polarimetric image characteristics of an optical phantom which replicates the nature of biological tissue, determining the morphological and metabolic information. Linearly polarized light was used to probe the phantom under test. Subsurface structure of the phantom was detected, with contrast agents like sugar solution, isopropyl alcohol and insulin solution. Co-polarized images provided results to affirm efficacy of the system design and principle adopted. A significant increase in the signal detected was observed with the increased contrast agent concentration, as an outcome of this study. Even under increased scattering conditions, the designed system was superior enough to provide enhanced detection. Polarization difference images have exhibited that the contrast, defined as signal to background ratio, can be augmented by multiple folds in comparison with just co-polarized images. Classification of the materials based on the results would be effective to learn about the embedded tissue structure and its optical characteristics. It would be interesting to apply advanced image processing algorithms that can reveal more information on this data. The whole study gives an additional dimension to optical imaging as significant platform with applications in the medical diagnostic arena.

Committee: George Giakos (Advisor) Subjects: