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
DR ELIZABETH CLARKE Visiting postdoctoral fellow
ALICE HATT Research assistant
ALICE PONG PhD student
FIONA KNAPMAN Research assistant
DR PETER BURKE Postdoctoral fellow
Characterising soft biological tissues outside the linear viscoelastic regime is challenging due to their complex behaviour. In addition, the viscoelastic properties of tissues have been shown to be sensitive to sample preparation and loading regime resulting in inconsistent data varying by orders magnitude in the literature. This paper presents a novel technique to characterise the non-linear behaviour of tissues which uses Fourier Transformation to decompose the stress output waveform under large amplitude oscillatory shear (LAOS) into harmonic contributions. The effect of varying preload, the compressive strain exerted on a liver tissue specimen prior to shear testing to minimise slip, was also investigated. Results showed that in the linear regime, preload affects the viscoelastic response of liver. Histological analysis indicated that there were structural changes as a result of the preload that may be linked to the differences in observed behaviour. Fourier analysis was used to extract the first and third harmonic components of the shear moduli at large strain. At 50% shear strain, a change in the third harmonic component of the shear moduli was accompanied by a marked change in the micro-structural arrangement of the sinusoids. This paper demonstrates a method of efficiently characterising soft biological tissues under large amplitude oscillatory shear under combined loading.
Background and Objectives. To determine the most appropriate technique for tumour followup in experimental therapeutics, we compared ultrasound (US) and magnetic resonance imaging (MRI) to characterize ectopic and orthotopic colon carcinoma models. Methods. CT26 tumours were implanted subcutaneously (s.c.) in Balb/c mice for the ectopic model or into the caecum for the orthotopic model. Tumours were evaluated by histology, spectrofluorescence, MRI, and US. Results. Histology of CT26 tumour showed homogeneously dispersed cancer cells and blood vessels. The visualization of the vascular network using labelled albumin showed that CT26 tumours were highly vascularized and disorganized. MRI allowed high-resolution and accurate 3D tumour measurements and provided additional anatomical and functional information. Noninvasive US imaging allowed good delineation of tumours despite an hypoechogenic signal. Monitoring of tumour growth with US could be accomplished as early as 5 days after implantation with a shorter acquisition time (<5 min) compared to MRI. Conclusion. MRI and US afforded excellent noninvasive imaging techniques to accurately follow tumour growth of ectopic and orthotopic CT26 tumours. These two techniques can be appropriately used for tumour treatment followup, with a preference for US imaging, due to its short acquisition time and simplicity of use.
The mechanical anisotropic ratio of the shear storage moduli measured by an anisotropic MR elastographic technique can distinguish between healthy muscle and dystrophic muscle.