Doctor of Philosophy

dissertationMilitary personnel with amputations face unique challenges due to their short residual limbs and high incidences of multiple limb loss sustained after blast injuries. However, transcutaneous osseointegrated implant (TOI) technology may provide an alternative for individuals with poor socket tolerance by allowing a structural and functional connection between living bone and the surface of a load bearing implant. While TOI has improved activity levels in European patients with limb loss, a lengthy rehabilitation period has limited the expansion of this technology, and may be accelerated with electrical stimulation. The unique advantage of electrically induced TOI is that the exposed exoprosthetic attachment may function as a cathode for regulating electrical current while also serving as the means of prosthetic limb attachment to the host bone. Using this design principle, the goal of this dissertation was to investigate the potential of electrical stimulation for enhancing the rate and magnitude of skeletal fixation at the periprosthetic interface using the implant as a cathode. Although previous studies have examined electrical stimulation for healing atrophic nonunions, inconsistent results have required new predictive measures. Therefore, finite element analysis (FEA) was used as a prerequisite for estimating electric field and current density magnitudes prior to in vivo experimentation. Retrospective computed tomography scans from 11 service members (28.3 ± 5.0 years) demonstrated the feasibility of electrically induced TOI, but variability in residual limb anatomy and the presence of heterotopic ossification confirmed the necessity for patient-specific modeling. Electrically induced osseointegration was also evaluated in vivo in skeletally mature rabbits after establishing design principles based on in vitro cell culturing and FEA. Data from the animal experiment indicated that there were no statistical differences for the appositional bone index (ABI), mineral apposition rate and porosity between the electrically stimulated implants and the unstimulated control implants (UCI). Higher mechanical push-out forces were observed for the UCI group at 6 weeks (p=0.034). In some cases, qualitative backscattered electron images and ABI did indicate that direct current may hold promise for improving suboptimal implant "fit and fill," as bone ongrowth around the cathode was observed despite not having direct contact with the endosteum

Doctor of Philosophy

dissertationInjury from explosive blast is a growing public health threat worldwide with complex mechanisms and limited treatment and prevention pathways. Blast-related traumatic brain injury (bTBI) is a multimodal injury event in which cerebral blood vessels play a central role in both the mechanical and physiological response to blast loading. This dissertation seeks to define the nature of vessel injury from primary blast loading by measuring injury thresholds for vasculature in bTBI by assessing blood-brain barrier (BBB) integrity and disruption, examining which types of vessels are affected, and mapping the distribution of injury in the brain. To assess the consequences of vascular injury, we measured inflammatory changes in glial cell activity with immunohistological techniques, and evaluated changes in behavior in a rodent model of bTBI. The importance of overpressure duration and impulse are examined by performing matched assays with two distinct blast tube devices capable of producing a wide range of blast wave characteristics. Exploration in measuring changes in cerebral blood flow, blood oxygen levels, and cerebral hemorrhage is described. Our primary findings include the presence of focal deposits of IgG in the parenchymal brain tissue indicating an elevated permeability of the blood-brain barrier, a heterogeneous distribution of these lesions among various brain structures, changes in astrocyte glial fibrillary acidic protein (GFAP) expression at lesion locations, and decrease in nociception and pedal withdrawal reflex following primary blast exposure. Changes in macrophage and neural cell populations were observed using markers for IBA1, CD68, and NeuN. Injury levels between devices were broadly similar; however, some differences in both histology and behavior were seen following high-impulse blast testing. Blast injury research remains an important topic with many unanswered questions, and further effort will provide help to those afflicted and preventative protection for those at risk

Absorb Bioresorbable Vascular Scaffold (BVS) for the treatment of coronary artery disease in clinical practice

Drug-eluting stents (DES) are widely used as first choice devices in percutaneous coronary interventions (PCI). However, certain concerns are associated with the use of DES, i.e. neo-atherosclerosis, late stent thrombosis and hypersensitivity reactions to the DES polymer. Bioresorbable scaffolds (BRS) such as the Absorb Bioresorbable Vascular Scaffold (BVS) are the next development within the field of PCI, introducing the concept of supporting the natural healing process following initial intervention without leaving any foreign body materials resulting in late adverse events. The first-generation devices have shown encouraging results in multiple studies of selected patients with non-complex lesions up to the point of full bioresorption. It supported the introduction in regular patient care. During its introduction in daily clinical practice outside the previous selected patient groups, a careful approach should be followed in which outcome is continuously monitored. The aim of this thesis was to investigate the safety and efficacy of the Absorb BVS in more complex lesions and higher-risk patients, when treated in a diverse clinical practice

Characterization of alar ligament on 3.0T MRI: a cross-sectional study in IIUM Medical Centre, Kuantan

INTRODUCTION: The main purpose of the study is to compare the normal anatomy of alar ligament on MRI between male and female. The specific objectives are to assess the prevalence of alar ligament visualized on MRI, to describe its characteristics in term of its course, shape and signal homogeneity and to find differences in alar ligament signal intensity between male and female. This study also aims to determine the association between the heights of respondents with alar ligament signal intensity and dimensions. MATERIALS & METHODS: 50 healthy volunteers were studied on 3.0T MR scanner Siemens Magnetom Spectra using 2-mm proton density, T2 and fat-suppression sequences. Alar ligament is depicted in 3 planes and the visualization and variability of the ligament courses, shapes and signal intensity characteristics were determined. The alar ligament dimensions were also measured. RESULTS: Alar ligament was best depicted in coronal plane, followed by sagittal and axial planes. The orientations were laterally ascending in most of the subjects (60%), predominantly oval in shaped (54%) and 67% showed inhomogenous signal. No significant difference of alar ligament signal intensity between male and female respondents. No significant association was found between the heights of the respondents with alar ligament signal intensity and dimensions. CONCLUSION: Employing a 3.0T MR scanner, the alar ligament is best portrayed on coronal plane, followed by sagittal and axial planes. However, tremendous variability of alar ligament as depicted in our data shows that caution needs to be exercised when evaluating alar ligament, especially during circumstances of injury

Case series of breast fillers and how things may go wrong: radiology point of view

INTRODUCTION: Breast augmentation is a procedure opted by women to overcome sagging breast due to breastfeeding or aging as well as small breast size. Recent years have shown the emergence of a variety of injectable materials on market as breast fillers. These injectable breast fillers have swiftly gained popularity among women, considering the minimal invasiveness of the procedure, nullifying the need for terrifying surgery. Little do they know that the procedure may pose detrimental complications, while visualization of breast parenchyma infiltrated by these fillers is also deemed substandard; posing diagnostic challenges. We present a case series of three patients with prior history of hyaluronic acid and collagen breast injections. REPORT: The first patient is a 37-year-old lady who presented to casualty with worsening shortness of breath, non-productive cough, central chest pain; associated with fever and chills for 2-weeks duration. The second patient is a 34-year-old lady who complained of cough, fever and haemoptysis; associated with shortness of breath for 1-week duration. CT in these cases revealed non thrombotic wedge-shaped peripheral air-space densities. The third patient is a 37‐year‐old female with right breast pain, swelling and redness for 2- weeks duration. Previous collagen breast injection performed 1 year ago had impeded sonographic visualization of the breast parenchyma. MRI breasts showed multiple non- enhancing round and oval shaped lesions exhibiting fat intensity. CONCLUSION: Radiologists should be familiar with the potential risks and hazards as well as limitations of imaging posed by breast fillers such that MRI is required as problem-solving tool

Brain and Human Body Modeling

This open access book describes modern applications of computational human modeling with specific emphasis in the areas of neurology and neuroelectromagnetics, depression and cancer treatments, radio-frequency studies and wireless communications. Special consideration is also given to the use of human modeling to the computational assessment of relevant regulatory and safety requirements. Readers working on applications that may expose human subjects to electromagnetic radiation will benefit from this book’s coverage of the latest developments in computational modelling and human phantom development to assess a given technology’s safety and efficacy in a timely manner. Describes construction and application of computational human models including anatomically detailed and subject specific models; Explains new practices in computational human modeling for neuroelectromagnetics, electromagnetic safety, and exposure evaluations; Includes a survey of modern applications for which computational human models are critical; Describes cellular-level interactions between the human body and electromagnetic fields

Advances in Ophthalmology

This book focuses on the different aspects of ophthalmology - the medical science of diagnosis and treatment of eye disorders. Ophthalmology is divided into various clinical subspecialties, such as cornea, cataract, glaucoma, uveitis, retina, neuro-ophthalmology, pediatric ophthalmology, oncology, pathology, and oculoplastics. This book incorporates new developments as well as future perspectives in ophthalmology and is a balanced product between covering a wide range of diseases and expedited publication. It is intended to be the appetizer for other books to follow. Ophthalmologists, researchers, specialists, trainees, and general practitioners with an interest in ophthalmology will find this book interesting and useful