Conference Papers Copyright (c) 2013 Dublin Institute of Technology All rights reserved. http://arrow.dit.ie/biodevcon Recent documents in Conference Papers en-us Wed, 15 May 2013 09:59:37 PDT 3600 Development of 3D Bone Scaffold Using Hyroxyapatite or Alumina Powders and Rapid Prototyping http://arrow.dit.ie/biodevcon/10 http://arrow.dit.ie/biodevcon/10 Tue, 06 Nov 2012 02:04:39 PST Bioceramic scaffolds with fully controlled macroporosity are highly desired materials for bone substitutes. In order to incorporate interconnecting pore channels into bioceramics, novel rapid prototyping techniques such as fused deposition modelling (FDM) or high definition stereolithography (SLA) were used. Polymer rapid prototyping moulds, with a strut size varying between 300 μm and 1 mm, were produced for ceramics casting. The moulds were filled with low viscosity aqueous hydroxyapatite or alumina slips. After burning out of the polymer and sintering of the bioceramics 3D bioceramic scaffolds were obtained. The final samples were characterized for their microstructure, density, porosity and mechanical properties.

]]> Natalia Pawlak et al. Investigation of a New Material for Heart Valve Tissue Engineering http://arrow.dit.ie/biodevcon/9 http://arrow.dit.ie/biodevcon/9 Tue, 25 Sep 2012 04:20:12 PDT Claire Brougham et al. Investigation of a New Material for Heart Valve Tissue Engineering http://arrow.dit.ie/biodevcon/8 http://arrow.dit.ie/biodevcon/8 Tue, 31 Jan 2012 02:01:31 PST Claire Brougham et al. Surgical Cutting and Ablation by Energy Based Devices: Principles and Applications http://arrow.dit.ie/biodevcon/7 http://arrow.dit.ie/biodevcon/7 Wed, 18 Jan 2012 06:40:14 PST Advances in ultrasound, radiofrequency, and water jet systems are facilitating their increased use in new medical ablation or cutting applications in fields as diverse as cardiology, orthopaedics, ophthalmology, dermatology, oncology and neurosurgery. These methods involve controlled alteration or destruction of tissues via the application of thermal, electrical or kinetic energy. This market segment is characterised by advanced devices capable of heating or cooling tissue from -200°C to 400°C, or inducing vibrations of up to 60 kHz to cause tissue damage. The medical conditions targeted primarily pertain to chronic and age-related diseases, but elective and cosmetic procedures are also addressed. Medical ablation research has the potential for significant clinical and commercial gains. New capabilities in terms of tissue ablation technologies can enable new medical procedures, affording opportunities for design creativity and entrepreneurship and ultimately delivering a health dividend.

]]> Garrett McGuinness et al. Soft Tissue Cutting with Ultrasonic Mechanical Waveguides http://arrow.dit.ie/biodevcon/6 http://arrow.dit.ie/biodevcon/6 Wed, 18 Jan 2012 01:26:53 PST The use of ultrasonic vibrations transmitted via small diameter wire waveguides represents a technology that has potential for minimally invasive procedures in surgery. This form of energy delivery results in distal tip mechanical vibrations with amplitudes of vibration of up to 50 μm and at frequencies between 20-50 kHz commonly reported. This energy can then be used by micro-cutting surgical tools and end effectors for a range of applications such as bone cutting, cement removal in joint revision surgery and soft tissue cutting. One particular application which has gained regulatory approval in recent years is in the area of cardiovascular surgery in the removal of calcified atherosclerotic plaques and chronic total occlusions. This paper builds on previous work that was focused on the ultrasonic perforation of soft vascular tissue using ultrasonically activated mechanical waveguides and the applied force required to initiate failure in soft tissue when compared with non-ultrasonic waveguides. An ultrasonic device and experimental rig was developed that can deliver ultrasonic vibrations to the distal tip of 1.0 mm diameter nickel-titanium waveguides. The operation of the ultrasonic device has been characterized at 22.5 kHz with achievable amplitudes of vibration in the range of 16 – 40μm. The experimental rig allows the ultrasonically activated waveguide to be advanced through a tissue sample over a range of feedrates and the waveguide-tissue interaction force can be measured during perforation into the tissue. Preliminary studies into the effects of feedrate on porcine aortic arterial tissue perforation forces are presented as part of this work. A range of amplitudes of vibration at the wire waveguide distal tip were examined. The resulting temperature increase when perforating artery wall when using the energized wire waveguides is also examined. Results show a clear multistage failure of the tissue. The first stage involves a rise in force up to some critical force and tissue displacement whereby the cut is initiated. The results show that with increasing ultrasonic amplitude of vibration the perforation force decreases considerably. The current results show that for the range of feedrates investigated 19-95 mm/min at an amplitude of vibration of 34.3 μm there was no significant effect on the perforation initiation force. The ΔT in the tissue 3.0 mm from the point of entry is also presented for a range of amplitudes of vibration.

]]> Mark Wylie et al. Perforation of Arterial Tissue Using Kilohertz Frequency Ultrasound Delivered via Wire Waveguides http://arrow.dit.ie/biodevcon/5 http://arrow.dit.ie/biodevcon/5 Wed, 18 Jan 2012 01:19:45 PST An emerging technology proposes the use of low frequency-high power ultrasound transmitted via wire waveguides for the disruption and ablation of atherosclerotic lesions, more specifically advanced fibrous or calcified plaques such as chronic total occlusions (CTO). This energy delivery selectively ablates rigid diseased tissue by means of direct mechanical contact, cavitation and other forces generated by the intense dynamic pressure fields generated.

The first clinical device using this energy delivery was granted FDA approval in 2007 [1] for the ablation of CTOs and most research to date has focused on ablation and disruption of hard, fibrous or calcified tissues [2]. This work, however, investigates the affects this energy delivery has on the perforation of soft healthy tissue (porcine aorta).

Materials and methods

An ultrasonic apparatus has been developed with operational characteristics similar to clinical devices reported in the literature i.e. frequency of operation (22.5kHz) and distal-tip ultrasonic amplitudes of vibration (~15-50μm). This apparatus delivers ultrasound via 1mm nitinol wire waveguides (132mm in length) with flat distal tips.

An experimental test rig was developed to perform controlled tests (ultrasonic power delivery and feedrates) on tissue samples in a thermostatic tank (37oC). Perforation force measurement was achieved by means of a strain gauge arrangement on a cantilever tissue holder.

A miniature hydrophone was also incorporated for the detection of cavitation by analysing the acoustic spectrum while the device was activated. Sub, super and ultra harmonics of the fundamental are all considered indicative of stable cavitation, whereas an increase in the broadband noise, in regions absent of significant harmonics, are indicative of inertial cavitation [3].

Porcine aorta was exhumed, stored in saline and tested less then 24 hours after death. Connective tissue was removed and samples (10x20mm) were cut from the descending aorta. Wires were advanced towards the tissue at a constant feedrate of 38 mm/min until perforation.

Results

As shown in Figure 1, an increase in distal tip amplitudes of vibration reduced the perforation force. It was found that stable cavitation occurred at all power settings (> 15μm). At the high power displacement amplitude setting of 34.3μm the perforation force was 1.2N when compared with 5.5N with no ultrasonic activation. The inertial cavitation threshold was crossed at distal-tip amplitudes of vibration greater than 30μm. However, no significant decrease in perforation force was evident in the inertial cavitation region. At the macro level, the tissue appears to fail in a similar manner for all distal-tip amplitudes of vibration.

Discussion

Perforation force of soft arterial tissue does not appear to be significantly effected by the onset of inertial cavitation. Further histological examination may be required to determine residual tissue damage from cavitation. Additional studies are needed to determine to what extent tissue is ablated, cut or removed at various power levels. It is suggested, however, that tissue removal using this energy on soft tissue is minimal when compared to that of hard brittle tissue ablation.

]]> Mark Wylie et al. Direct Least-Squares Ellipse Fitting http://arrow.dit.ie/biodevcon/4 http://arrow.dit.ie/biodevcon/4 Thu, 15 Sep 2011 02:54:17 PDT Many biological and astronomical forms can be best represented by ellipses. While some more complex curves might represent the shape more accurately, ellipses have the advantage that they are easily parameterised and define the location, orientation and dimensions of the data more clearly. In this paper, we present a method of direct least-squares ellipse fitting by solving a generalised eigensystem. This is more efficient and more accurate than many alternative approaches to the ellipse-fitting problem such as fuzzy c-shells clustering and Hough transforms. This method was developed for human body modelling as part of a larger project to design a marker-free gait analysis system which is being undertaken at the National Rehabilitation Hospital, Dublin.

]]> Jane Courtney et al. Mechano-Biological Interactions of Endothelial Cells http://arrow.dit.ie/biodevcon/3 http://arrow.dit.ie/biodevcon/3 Wed, 23 Mar 2011 03:02:24 PDT Atherosclerosis is an ever-increasing cause of morbidity in the western world. Current surgical treatments include bypass grafts and coronary artery stents. However, there is still a need for alternative approaches especially for those who cannot receive conventional therapy. Tissue engineering is one such approach that may hold the key to the repair and regeneration. Tissue engineering is one such approach that may hold the key to the repair and regeneration of coronary arteries. Nevertheless, many questions need to be answered before a vialbe vascular tissie with the inherent properties of native tissue becomes a real contender with the surgical therapies in use today.

]]> Claire Brougham et al. Characterising 3D Soft Tissue Features on Joint Surfaces http://arrow.dit.ie/biodevcon/2 http://arrow.dit.ie/biodevcon/2 Mon, 14 Feb 2011 08:00:35 PST A crucial aspect of orthopaedic implant design is the prediction of surgical outcomes when the shape of a bone is necessarily altered by the addition of the implant. Matching native kinematics as closely as possible is generally considered a core aim of joint replacement surgery. The overall hypothesis behind this research is that soft tissue geometry, including cartilage thickness distribution and ligament attachment sites, influences kinematics in the knee joint. In order to enable investigation of possible links between geometry and kinematics, the ability to characterise the shape variation of the soft tissue relative to the underlying bony geometry must first be developed. This is the aspect which has been addressed in this work.

]]> Colm O'Kane Estimation of 3D shape in the Patellofemoral Joint using Statistical Shape Models and 2D Data http://arrow.dit.ie/biodevcon/1 http://arrow.dit.ie/biodevcon/1 Mon, 14 Feb 2011 07:48:41 PST Disorders of the patellofemoral joint (PFJ) including PF osteoarthritis and PF pain disorder have been estimated to represent 25% of all patients presenting for knee joint treatment. The diagnosis and treatment of these disorders is curtailed by lack of understanding of the mechanical operation of the joint. A crucial aspect to be considered in understanding contact patterns and kinematics of the PFJ is the alignment of the patella in the trochlear groove. Investigation of patellar alignment necessitates accurate knowledge of the 3D articular surfaces of both patella and femur, along with underlying bone geometry. These 3D data are generally obtained for bones and cartilage plates through reconstruction of images from computed tomography (CT) and/or magnetic resonance imaging (MRI) respectively. This research proposes to develop a parametric model to enable the accurate estimation of the patient-specific 3D shape of a patella and distal femur from several 2D images. There are several drivers for this work: the labour and cost (and radiation exposure in the case of CT) entailed in 3D scanning mean that it would be greatly advantageous to have the ability to characterise 3D joint geometry using 2D images obtained through the economical, timely and traditionally widely used x-ray / fluoroscopy method. Statistical shape modelling (SSM) and principal component analysis (PCA) has previously been applied to analysis of the distal femur with the aim of developing more sophisticated sizing and shaping rationales for replacement components. This level of shape analysis has not previously been applied to the patellofemoral joint.

]]> Colm O'Kane