Senior Principal Research Scientist
NHMRC Senior Research Fellow
Conjoint Professor, UNSW Medicine
+612 9399 1673
From a background in biomechanical engineering, the focus of my research is on how the soft tissues in the human body respond to mechanical loading – both those loads which cause injury and those which are part of normal function. I develop novel methods for measuring biomechanical properties and behaviour of soft tissues in humans, particularly using Magnetic Resonance Imaging and rheometry. I apply these techniques to study mechanisms of traumatic injury, disorders of cerebrospinal fluid flow in the brain and spinal cord, and obstructive sleep apnoea.
Obstructive sleep apnoea is a sleep disorder that affects more than 4% of the population and can lead to symptoms from daytime drowsiness to high blood pressure. People with sleep apnoea are often not breathing normally during sleep and may experience periods where the airway closes and they are unable to breathe. In severe sleep apnoea this can occur 50-60 times each hour. That is once each minute. The closure of the upper airway is thought to be due to a number of factors, one of which is that the neural drive to the airway muscles is insufficient in people with sleep apnoea. In our lab, we have made the first extensive recordings from the major muscle of the upper airway, genioglossus. We have shown that the neural drive to this muscle is very complex, more so than any limb muscle. At NeuRA, we have also pioneered new methods to image this muscle using fMRI and ultrasound. We are now planning to look at how changes in muscle architecture and mechanics relate to the neural drive to the muscle and whether that relationship is maintained in people with sleep apnoea.
Syringomyelia is an enigmatic condition in which high pressure fluid-filled cysts form in the spinal cord, often after spinal cord injury or in congenital conditions where there is obstruction to cerebrospinal fluid flow near the brainstem. In collaboration with neurosurgeon Prof Marcus Stoodley, we are using magnetic resonance imaging, computational modelling and experimental models to understand how cerebrospinal fluid flow in the central nervous system is altered, and the mechanisms by which this gives rise to build-up of fluid in the spinal cord. • Honours and PhD projects are available to study the biomechanical and basic biological mechanisms of syringomyelia, using magnetic resonance imaging, experimental and computational modelling.
We have developed novel imaging methods to measure the stiffness and movement of the upper airway muscles, and are using these together with measures of pharyngeal sensation, and electromyography to determine the patient-specific causes of obstructive sleep apnoea. We aim to use this information to tailor treatments for patients. One such treatment is a mandibular advancement splint, but currently it’s not possible to predict who will benefit from use a splint. We have a major project that aims to predict splint treatment outcome, based on our novel imaging methods.• Honours and PhD projects are available to study the neural, biomechanical and physiological aspects of obstructive sleep apnoea, including computational modelling
We have developed new MRI methods to measure the mechanical properties of soft tissues (Magnetic Resonance Elastography or MRE). So far, MRE has been used to measure the stiffness of the brain, muscles and other tissues. We continue to develop new approaches, such as combining elastography with Diffusion Tensor Imaging to measure the anisotropic properties of muscles and brain white matter tracts, and how this changes in muscle and neurological disorders. We have discovered that there are changes in tissue stiffness in hydrocephalus (a brain disorder), obstructive sleep apnoea, and degenerative muscle conditions (muscular dystrophy). We are currently working on new methods to measure tissue properties under loading. Honours and PhD projects are available both for developing new methods (to suit engineers and physicists) or in applying these techniques to study clinical disorders.
Hydrocephalus is a neurological disorder where the ventricles in the brain enlarge, often due to obstruction to cerebrospinal fluid flow pathways in the brain. However, the biological and biomechanical mechanisms are not well understood, and treatment is currently unsatisfactory, with patients undergoing multiple shunt surgeries. We are studying how brain stiffness and oedema are involved in the development of hydrocephalus, using magnetic resonance imaging, computational modelling and experimental models of hydrocephalus. Honours and PhD projects are available to study the biomechanical and basic biological mechanisms of hydrocephalus, using magnetic resonance imaging, experimental and computational modelling.
Our group is studying how injuries occur in children when they are involved in crashes, and how changes to the types and design of restraints used by children can reduce serious injuries and death. Key problems include whether children use restraints correctly and whether they use restraints that are appropriate for their size. Recent findings include that rates of misuse of child restraints are high, and much of this misuse is serious enough to compromise the effectiveness of the restraints in crashes. Building on our recent work that led to major changes in child restraint design and usage laws in Australia, Dr Julie Brown and I are currently studying how restraint ergonomics and comfort affect how children use restraints, and whether we can improve how restraints are labelled to help parents to use them correctly.
KATIE PELLAND Visiting PhD student
ROB LLOYD PhD student
DR ELIZABETH CLARKE Visiting postdoctoral fellow
DR ELIZABETH BROWN Postdoctoral fellow
ALICE HATT Research assistant
ALICE PONG PhD student
FIONA KNAPMAN Research assistant
DR PETER BURKE Postdoctoral fellow
Rear seat occupants are now at a higher risk of injury relative to front seat occupants and there is a need for enhanced protection. This study aimed to examine the pattern of injury, injury mechanisms and injury sources to restrained motor vehicle rear seat occupants involved in a frontal impact. The seat belt is the most common source of injury to rear seat passengers in frontal impact with variations in injury with age. There is a need to provide appropriate belt fit and better control seat belt loads for rear seat passengers. This could be achieved, at least in part, with existing technologies currently used in front seat positions, although novel technologies may also be useful.
The mechanisms leading to upper airway (UA) collapse during sleep are complex and poorly understood. We previously developed an anesthetized rabbit model for studying UA physiology. On the basis of this body of physiological data, we aimed to develop and validate a two-dimensional (2D) computational finite element model (FEM) of the passive rabbit UA and peripharyngeal tissues. Model geometry was reconstructed from a midsagittal computed tomographic image of a representative New Zealand White rabbit, which included major soft (tongue, soft palate, constrictor muscles), cartilaginous (epiglottis, thyroid cartilage), and bony pharyngeal tissues (mandible, hard palate, hyoid bone). Other UA muscles were modeled as linear elastic connections. Initial boundary and contact definitions were defined from anatomy and material properties derived from the literature. Model parameters were optimized to physiological data sets associated with mandibular advancement (MA) and caudal tracheal displacement (TD), including hyoid displacement, which featured with both applied loads. The model was then validated against independent data sets involving combined MA and TD. Model outputs included UA lumen geometry, peripharyngeal tissue displacement, and stress and strain distributions. Simulated MA and TD resulted in UA enlargement and nonuniform increases in tissue displacement, and stress and strain. Model predictions closely agreed with experimental data for individually applied MA, TD, and their combination. We have developed and validated an FEM of the rabbit UA that predicts UA geometry and peripharyngeal tissue mechanical changes associated with interventions known to improve UA patency. The model has the potential to advance our understanding of UA physiology and peripharyngeal tissue mechanics.
Head and jaw position influence upper airway patency and electromyographic (EMG) activity of the main upper airway dilator muscle, the genioglossus. However, it is not known whether changes in genioglossus EMG activity translate into altered muscle movement during respiration. The aim of this study was to determine the influence of head and jaw position on dilatory motion of the genioglossus in healthy adult men during quiet breathing by measuring the displacement of the posterior tongue in six positions-neutral, head extension, head rotation, head flexion, mouth opening, and mandibular advancement. Respiratory-related motion of the genioglossus was imaged with spatial modulation of magnetization (SPAMM) in 12 awake male participants. Tissue displacement was quantified with harmonic phase (HARP) analysis. The genioglossus moved anteriorly beginning immediately before or during inspiration, and there was greater movement in the oropharynx than in the velopharynx in all positions. Anterior displacements of the oropharyngeal tongue varied between neutral head position (0.81 ± 0.41 mm), head flexion (0.62 ± 0.45 mm), extension (0.39 ± 0.19 mm), axial rotation (0.39 ± 0.2 mm), mouth open (1.24 ± 0.72 mm), and mandibular advancement (1.08 ± 0.65 mm). Anteroposterior displacement increased in the mouth-open position and decreased in the rotated position relative to cross-sectional area (CSA) (P= 0.002 and 0.02, respectively), but CSA did not independently predict anteroposterior movement overall (P= 0.057). The findings of this study suggest that head position influences airway dilation during inspiration and may contribute to variation in airway patency in different head positions.