Tim M Mcgloughlin

• B.E., M.EngSc., PhD
• Chair at Khalifa University of Science Technology

Proceedings of the 12th Annual meeting of Bioengineering in Ireland, Galway

Stress urinary incontinence (SUI), the involuntary urine leakage due to failure of the urethral closure mechanism, is a global health challenge with substantial human suffering and socioeconomic costs. Approximately 167 million male and female patients are predicted to suffer from SUI in 2018, worldwide. A wide range of surgical interventions are a...

In this paper, we propose a statistical based method using a topology prior model, integrating both intensity and shape information, to segment abdominal aortic aneurysm (AAA) from computed tomography angiography (CTA) scans. The method was tested on a total of 48 slices taken from 6 different patients and has shown competitive performance compared...

There are several issues attributed with abdominal aortic aneurysm endovascular repair. The positioning of bifurcated stent-grafts (SG) may affect SG hemodynamics. The hemodynamics and geometrical parameters of crossing or non-crossing graft limbs have not being totally accessed. Eight patient-specific SG devices and four pre-operative cases were c...

A new multiple watermarking scheme for medical images which is based on spatial and discrete cosine transform domains is developed. In this scheme, the radiologist can specify the regions of interest to be avoided during embedding. Two watermarks are embedded where the first one is robust for ownership protection and the second one is fragile for s...

Objective: To investigate the repeatability of automatic decellularisation of porcine aortae using a non-enzymatic approach, addressing current limitations associated with other automatic decellularisation processes. Materials and methods: Individual porcine aortae (n = 3) were resected and every third segment (n = 4) was allocated to one of thr...

Purpose: The pre-conditioning of tissue-engineered vascular scaffolds with mechanical stimuli is being recognised as an essential step in producing a functional vascular construct. In this study we design and evaluate a novel bioreactor, which exerts a mechanical strain on developing vascular scaffolds via subatmospheric pressure. Methods: We de...

Introduction: Existing synthetic vascular grafts have unacceptably high failure rates when replacing below knee arteries. In vitro endothelisation is a technique, which has been shown to enhance the patency rates of below knee vascular grafts. Synthetic materials are however poor cellular substrates and must be combined with coatings to promote ce...

Current tissue engineered skin substitutes employ a cellular scaffold, typically a collagen biopolymer to support the transfer of cells to the wound bed. These scaffolds however, exhibit poor approximation of epidermal-dermal histogenesis and delayed vascularisation upon implantation in vivo. In this study we evaluate a novel decellularised extrace...

Disclosed herein is a nickel-titanium alloy comprising nickel, titanium, and at least one rare earth element. The nickel-titanium alloy comprises from about 34 at. % to about 60 at. % nickel, from about 34 at. % to about 60 at. % titanium, and from about 0.1 at. % to about 15 at. % at least one rare earth element. The nickel-titanium alloy may furt...

Varying degrees of calcification are present in most abdominal aortic aneurysms (AAAs). However, their impact on AAA failure properties and AAA rupture risk is unclear. The aim of this work is evaluate and compare the failure properties of partially calcified and predominantly fibrous AAA tissue and investigate the potential reasons for failure. Un...

Objective: To construct an automatic decellularization platform (ADP) for preparing xenogenic extracellular matrices (ECMs), and to demonstrate that automatic decellularization for preparing xenogenic ECMs reduces processing time, requires fewer attendee hours, and is as effective as the manual gold standard preparation protocols. Materials and m...

Rupture of the abdominal aortic aneurysm (AAA) occurs when the local wall stress exceeds the local wall strength. Knowledge of AAA wall mechanics plays a fundamental role in the development and advancement of AAA rupture risk assessment tools. Therefore, the aim of this study is to evaluate the biaxial mechanical properties of AAA tissue. Multiple...

Background: Preservation of the native artery׳s functionality can be important in both clinical and experimental applications. Although, simple cryopreservation techniques offer an attractive solution to this problem, the extent to which freezing affects the tissue׳s properties is widely debated. Earlier assessments of the mechanical properties po...

Human balance strategies during standing have been studied extensively. Most of these studies rely on perturbations to the feet, for example by moving platforms or treadmills, and focus on the sagittal plane. Less research has been done on reactions to perturbations to the upper body, and the direction dependence of stabilizing strategies is still...

Tubularized porcine extracellular matrices (ECMs) are under investigation as adjuvant scaffolds for endovascular aneurismal repair (EVAR). Limitations with tubularized ECMs in this setting include difficulties in achieving a confluent endothelium on the scaffold's luminal surface prior to in vivo implantation. In this in vitro study a rotational "c...

Intraluminal Thrombus (ILT) is present in 75% of clinically-relevant abdominal aortic aneurysms (AAAs) yet, despite much research effort, its role in AAA biomechanics remains unclear. The aim of this work is to further evaluate the biomechanics of ILT and determine if different ILT morphologies have varying mechanical properties. Biaxial mechanical...

Deployment of stent-grafts, derived from synthetic biomaterials, is an established minimally invasive approach for effectively treating abdominal aortic aneurysms (AAAs). However, a notable disadvantage associated with this surgical technique is migration of the deployed stent-graft due to poor biocompatibility and inadequate integration in vivo. R...

Tissue engineered acellular vascular grafts are an emerging concept in the development of vascular prostheses for the minimally invasive treatment of cardiovascular diseases. Extracellular matrix (ECM) scaffolds, such as small intestinal submucosa (SIS) and urinary bladder matrix (UBM), offer many advantages over currently available synthetic devic...

Endovascular aneurysm repair is developing as the standard of care in treating abdominal aortic aneurysms. Long term complications and late rupture risks remain a primary concern of this new therapeutic approach, mandating life time surveillance. Post endovascular aneurysm repair (EVAR) follow up and management of reintervention utilizes a number o...

A strong correlation between the localization of atherosclerotic lesions with abnormal wall shear stress (WSS) has long been recognized at the distal anastomosis of a peripheral bypass where disturbed flow occurs. Identification of a WSS variable that significantly contributes to disease formation at this site has been elusive to date, as endotheli...

Predicting the wall stress in abdominal aortic aneurysm (AAA) using computational modeling may be a useful adjunct to traditional clinical parameters that indicate the risk of rupture. Maximum diameter has been shown to have many limitations, and using current technology it is possible to provide a patient-specific computational risk assessment usi...

Computational hemodynamic studies of abdominal aortic aneurysm (AAA) can help elucidate the mechanisms responsible for growth and development. The aim of this work is to determine if AAAs expand and develop intraluminal thrombus (ILT) in regions of low wall shear stress (WSS) predicted with computational fluid dynamics (CFD). Computed tomography (C...

Ligand-capped nanoparticles are dispersed in an organic solvent. There is then phase transfer of the nanoparticles introducing into the organic solvent an aqueous solution of polymer surfactant dissolved in water. The organic solvent and the aqueous solution are then mixed until the polymer forms micelles which encapsulate the nanoparticles in asse...

Tissue-engineered biomaterials have shown recent promise as adjuvant scaffolds for treating stress urinary incontinence (SUI). The objective of the present study was to compare their mechanical and regenerative properties with synthetic biomaterials in this urogynaecological setting. The biomechanical properties of polypropylene (Serasis®; n = 12),...

Abdominal Aortic Aneurysm (AAA) is the gradual and irreversible local widening of the distal region of the aorta. If undetected or untreated the intramural stress can exceed the strength of the aneurysm wall causing the structure to rupture. Upon rupture, AAA has a 90% mortality rate. It has been hypothesized, and shown in some studies, that region...

Abdominal aortic aneurysm (AAA) represents an asymptomatic cardiovascular type of disease, that is diagnosed in elder people over 60 years old. It is characterised by a ballooning of the abdominal aorta, which grows, at different rates in different patients. If left untreated, it will rupture causing severe internal bleeding, which can lead to shoc...

Measuring the physical dimensions of soft tissue is difficult due to its deformable nature. Such measurements are used to evaluate the tissue's mechanical properties. Imprecise measurements of the tissue's thickness can alter the assessment of tensile stress which may have significant clinical relevance when used as a diagnostic tool. The performan...

Background The dynamic hip screw (DHS) has been widely adopted as the implant of choice in the treatment of intertrochanteric fractures. There have been attempts over the years to improve on the DHS lag screw design in order to reduce failure in the form of “cut out”. The purpose of this study was to investigate how two new design variations of the...

Despite the fact that binary NiTi alloy is one of the most important biomaterials currently used in minimally invasive procedures and indwelling devices, its visibility under and X-ray is poor. The addition of a third, radiopaque element can significantly enhance radiopacity. In the past, noble metals such as platinum or gold have been added to NiT...

Objective: Abnormal haemodynamics is commonly agreed to be a major contributor to the development of distal anastomotic intimal hyperplasia. A new vascular graft design proposed by computational studies was used to demonstrate its surgical feasibility and to compare it with the conventional graft in a porcine model. Method: The device was used i...

Purpose: Autogenous ileal tissue remains the gold-standard biomaterial for bladder replacement purposes; however, cell-seeded extracellular matrix (ECM) scaffolds have shown promise. Although the biological advantages of cell-seeded ECMs in urological settings are well documented, there is a paucity of data available on their biomechanical propert...

Fresh morselized impacted bone graft usually fails due to shear forces. The presence of fat, water, and marrow particles act as interparticle lubricants, reducing the interlocking of particles and allowing the graft to move more freely. Furthermore, the presence of this incompressible fluid damps and resists compressive forces during impaction, pre...

Endovascular repair is now a recognised procedure for treating abdominal aortic aneurysms. However, post-operative complications such as stent graft migration and thrombus may still occur. To assess these complications numerically, the correct input boundary conditions, which include the full human aorta with associated branching, should be include...

The long-term success of the endovascular procedure for the treatment of Abdominal Aortic Aneurysms (AAAs ) depends on the secure fixation of the proximal end and the geometry of the stent-graft (SG) device. Variations in SG types can affect proximal fixation and SG hemodynamics. Such hemodynamic variations can have a catastrophic effect on the vas...

Localized delivery of temperature-sensitive biologically active materials (enzymes, cells, biotheraputics, phages) on the surfaces of devices are technologically challenging. Many of the limitations associated with realizing the full potential of localized delivery at are process related. We present summary of existing to date industry related chal...

Multilayered biological scaffolds derived from mammalian extracellular matrix (ECM) have shown promising long-term clinical results when reconstructing damaged tissues and organs. Despite their established clinical applicability, experimental studies that describe the effects of alternate manufacturing protocols on an ECM's mechanical properties ar...

Abdominal Aortic Aneurysms (AAA) is one of the major cardiovascular diseases that can lead to death if left untreated. An AAA is defined as a permanent and irreversible localised dilation of the infrarenal aorta. Aneurysms can result from accidents, arteriosclerosis, and high blood pressure or as a congenital disease. There are currently two surgic...

The objective of this study was to determine if a synthetic bone substitute would provide results similar to bone from osteoporotic femoral heads during in vitro testing with orthopaedic implants. If the synthetic material could produce results similar to those of the osteoporotic bone, it could reduce or eliminate the need for testing of implants...

Purpose To investigate the use of regional variations in the mechanical properties of abdominal aortic aneurysms (AAA) in finite element (FE) modeling of AAA rupture risk, which has heretofore assumed homogeneous mechanical tissue properties. Methods Electrocardiogram-gated computed tomography scans from 3 male patients with known infrarenal AAA w...

To design and construct a urinary bladder bioreactor for urologic tissue-engineering purposes and to compare the viability and proliferative activity of cell-seeded extracellular matrix scaffolds cultured in the bioreactor with conventional static growth conditions. A urinary bladder bioreactor was designed and constructed to replicate physiologic...

Numerous scaffold materials have been developed for tissue engineering and regenerative medicine applications to replace or repair damaged tissues and organs. Naturally occurring scaffold materials derived from acellular xenogeneic and autologous extracellular matrix (ECM) are currently in clinical use. These biological scaffold materials possess i...

Abdominal aortic aneurysms (AAAs) remain a significant cause of death in the Western world with over 15,000 deaths per year in the US linked to AAA rupture. Recent research [1] has questioned the use of maximum diameter as a definitive risk parameter as it is now believed that alternative factors may be important in rupture-prediction. Wall stress...

Abdominal aortic aneurysms are irreversible dilations of the infrarenal aorta. If left untreated the aneurysm may continue to grow until eventually rupturing. Endovascular aneurysm repair (EVAR) is an established method for the treatment of abdominal aortic aneurysms (AAAs). Complications arising from this treatment include endoleaks and graft migr...

Rupture prediction of abdominal aortic aneurysms (AAAs) remains a clinical challenge. Finite element analysis (FEA) may allow for improved identification for intervention timing, but the method needs further substantiation. In this study, experimental photoelastic method and finite element techniques were compared using an idealised AAA geometry. T...

Augmentation cystoplasty (AC) with autogenous ileum remains the current gold standard surgical treatment for many patients with end-stage bladder disease. However, the presence of mucus-secreting epithelium within the bladder is associated with debilitating long-term complications. Currently, decellularised biological materials derived from porcine...

We biomechanically investigated whether the standard dynamic hip screw (DHS) or the DHS blade achieves better fixation in bone with regard to resistance to pushout, pullout and torsional stability. The experiments were undertaken in an artificial bone substrate in the form of polyurethane foam blocks with predefined mechanical properties. Pushout t...

This chapter describes experimental investigations of parameters which are likely to reduce the ability of an implanted stent-graft for the treatment of Abdominal Aortic Aneurysm (AAA) to resist migration. Idealised AAA analogues were manufactured with realistic wall properties. Both proximal stents and complete stent-graft devices were deployed in...

The drag forces acting on rigid abdominal aortic aneurysm stent-graft models have been previously determined by numerical, analytical, and experimental means. It is not clear what effect the assumption of rigidity has on the axial component of proximal migration (ACPM) force acting on the proximal end of a non-rigid stent-graft model. In this study...

To evaluate the viability and proliferative activity of human urothelial cells (HUCs) cultured on tissue-engineered extracellular matrix scaffolds and to assess the potential of extracellular matrixes to support the growth of HUCs in their expected in vivo urine environment. HUCs were obtained by bladder biopsy and cultured onto the luminal and abl...

Functional reconstruction of the human urinary bladder has been attempted by replacing defective bladder tissue with tissue-engineered xenogenic extracellular matrix (ECM) scaffolds. However, experimental studies that demonstrate the effects of implanted ECMs on important biomechanical properties such as total bladder capacity (TBC) and compliance...

An abdominal aortic aneurysm (AAA) is defined as a permanent and irreversible localized dilatation of the abdominal aorta. A reliable, non-invasive method to assess the wall mechanics of an aneurysm may provide additional information regarding their susceptibility to rupture. Acoustic radiation force impulse (ARFI) imaging is a phenomenon associate...

Maintaining vascular access (VA) patency continues to be the greatest challenge for dialysis patients. VA dysfunction, primarily due to venous neointimal hyperplasia development and stenotic lesion formation, is mainly attributed to complex hemodynamics within the arteriovenous fistula (AVF). The effect of VA creation and the subsequent geometrical...

Atherosclerosis is an arterial disease resulting in thickening of the arterial wall and occlusion of the vessels in advanced stages. In addition to hereditary and environmental factors, the effect of fluid-induced stresses on the arterial wall has also been implicated on the etiology of the disease due to the fact that the lesions are found in arte...

Migration of stent-grafts (SGs) after endovascular aneurysm repair of abdominal aortic aneurysms is a serious complication that may require secondary intervention. Experimental, analytical, and computational studies have been carried out in the past to understand the factors responsible for migration. In an experimental setting, it can be very chal...

Migration is a serious failure mechanism associated with endovascular abdominal aortic aneurysm (AAA) repair (EVAR). The effect of vessel material properties and pulsatile wall motion on stent fixation has not been previously investigated. A proximal stent from a commercially available stent graft was implanted into the proximal neck of silicone ru...

The field of tissue engineering focuses on developing strategies for reconstructing injured, diseased, and congenitally absent tissues and organs. During the last decade urologists have benefited from remodeling and regenerative properties of bioscaffolds derived from xenogenic extracellular matrices. We comprehensively reviewed the current literat...

Abdominal aortic aneurysm (AAA) rupture remains a significant cause of death in the developed world. Current treatment approaches rely heavily on the size of the aneurysm to decide on the most appropriate time for clinical intervention and treatment. However, in recent years, several alternative rupture risk indicators have been proposed. This brie...

Endovascular aneurysm repair for abdominal aortic aneurysm (AAA) is now a widely adopted treatment. Several complications remain to be fully resolved and perhaps the most significant of these is graft migration. Haemodynamic drag forces are believed to be partly responsible for migration of the device. The objective of this work was to investigate...

The finite volume solver Fluent (Lebanon, NH, USA) is a computational fluid dynamics software employed to analyse biological mass-transport in the vasculature. A principal consideration for computational modelling of blood-side mass-transport is convection-diffusion discretisation scheme selection. Due to numerous discretisation schemes available w...

Abdominal aortic aneurysm (AAA) is a permanent dilation of the infrarenal aorta and is defined as having a diameter 50% greater than the original diameter. If left untreated, an AAA will continue to expand until rupture. The maximum diameter is currently the primary indicator of rupture-risk with AAAs > 5.5 cm deemed a likely to rupture. There have...

Endovascular AAA repair has evolved since its inception in the late 1980s to become an accepted alternative to open surgery. This minimally invasive approach involves inserting a collapsed stent-graft through the vasculature to the AAA location and allowing it to expand to form a new conduit for blood flow [1]. EVAR carries lower operative risk tha...

Cardiovascular disease concerns any disease which affects the heart or blood vessels. Aneurysms account for a significant portion of these cardiovascular diseases. The most common type of aneurysm is abdominal aortic aneurysm (AAA) which affects up to 5% of the population over the age of 55. AAA is a focal balloon like dilation of the terminal aort...

A method for reliable, noninvasive estimation of abdominal aortic aneurysms (AAA) wall mechanics may be a useful clinical tool for rupture prediction. An in vitro AAA model was developed from an excised porcine aorta with elastase treatment. The AAA model behaviour was analysed using acoustic radiation force impulse (ARFI) imaging techniques to gen...

Coronary artery disease can be treated by implanting a stent into the blocked region of an artery, thus enabling blood perfusion to distal vessels. Minimally invasive procedures of this nature often result in damage to the arterial tissue culminating in the re-blocking of the vessel. In an effort to alleviate this phenomenon, known as restenosis, d...

The structural evolution of a Ni-rich NiTiPt alloy (Ni50Ti42.5Pt7.5) is studied here as a function of homogenisation temperature. The biphasic microstructure of the as-cast Ni50Ti42.5Pt7.5 alloy consisted of a high-Pt lath type structure that was dispersed in a martensitic NiTiPt matrix. Homogenisation of the as-cast structure at intermediate tempe...

In the event of abdominal aortic aneurysm (AAA) rupture, the outcome is often death. This paper aims to experimentally identify the rupture locations of in vitro AAA models and validate these rupture sites using finite element analysis (FEA). Silicone rubber AAA models were manufactured using two different materials (Sylgard 160 and Sylgard 170, Do...

Purpose To develop an improved methodology for investigating the parameters influencing stent-graft migration, with particular focus on the limitations of existing methods. Methods A physiological silicone rubber abdominal aortic aneurysm (AAA) model for fixation studies was manufactured based on an idealized AAA geometry: the model had a 24-mm ne...

Migration of endovascular stent grafts for abdominal aortic aneurysm (AAA) is a serious complication that can result in aneurysm sac repressurisation and rupture. Secure fixation of stent-grafts in the proximal neck and the iliac legs is crucial to prevent this complication. We outline an in vitro method of investigating the resistance to migration...

Clinicians routinely use the maximum transverse diameter of an abdominal aortic aneurysm (AAA) to help gauge the severity of the condition, with AAAs that reach or exceed 5.5 cm deemed a rupture-risk. The effectiveness of the maximum diameter criterion has been questioned and novel techniques to predict the rupture threat of AAAs have recently emer...