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.
Sleep apnoea results in cognitive dysfunction, excessive sleepiness, doubling of workplace accidents and more than 2-fold increased motor vehicle crash risk presenting a huge health care burden in Australia and internationally. The disorder is also associated with increased risk of stroke, heart disease and possibly dementia. It is a complex disorder with multiple impacts including hypoxia, sleep deprivation, metabolic syndrome and cardiovascular risk factors.
This project aims to unravel the impact of OSA on the brain and to determine whether deleterious effects can be reversed or slowed by treatment options.
Main collaborators: Andrew Vakulin, Flinders; Ron Grunstein, Woolcock Institute, Angela D’Rozario, Woolcock Institute, Delwyn Bartlett, Woolcock Institute; Lynne Bilston, NeuRA, Michael Green, NeuRA
Miller, C.B., Rae, C.D. Green, M., Yee, B.J., Kyle, S.D., Gordon, C.J., Marshall, N.S., Espie, C.A., Grunstein, R.R. & Bartlett, D.J. (2017) An objective short-sleep insomnia disorder subtype is associated with reduced brain metabolites in vivo: a preliminary magnetic resonance spectroscopy assessment. Sleep 40, zsx148
D’Rosario, A., Bartlet, D., Wong, K.H., Sach, T, Yang, Q., Grunstein, R.R. & Rae, C.D. (2018) Brain bioenergetics during resting wakefulness are related to neurobehavioural deficits in severe obstructive sleep apnea. Sleep 41(8) zsy117.
Obstructive sleep apnoea (OSA) is characterised by the recurrent collapse or narrowing of the upper airway during sleep. OSA is also associated with adverse cardiovascular, metabolic, neurocognitive, quality of life and safety consequences. The first line treatment continuous positive airway pressure (CPAP) which is highly efficacious but poorly tolerated. Oral mandibular advancement splint (MAS) therapy is the leading alternative to CPAP to treat obstructive sleep apnoea, although it is difficult to predict treatment success.
Therefore, this study aims to determine the efficacy of targeted therapeutic approaches to treat OSA whilst using novel techniques to advance knowledge of upper airway function and the mechanisms of a MAS device. We aim to develop accurate tools to predict treatment outcome with a MAS device, develop novel approaches to monitor and diagnose OSA. This study is a part of the government Cooperative Research Centre Program linking researchers and industry.
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
DR PETER BURKE Postdoctoral fellow
Purpose To determine if healthy hepatic mechanical properties differ between pediatric and adult subjects at magnetic resonance (MR) elastography. Materials and Methods Liver shear moduli in 24 healthy pediatric participants (13 children aged 5-14 years [seven boys, six girls] and 11 adolescents aged 15-18 years [six boys, five girls]) and 10 healthy adults (aged 22-36 years [five men, five women]) were obtained with 3-T MR elastography at 28, 56, and 84 Hz. Relationships between shear moduli and age were assessed with Spearman correlations. Differences between age groups were determined with one-way analysis of variance and Tukey multiple comparisons tests. Results Liver stiffness values (means ± standard deviations) were significantly lower in children and adolescents than in adults at 56 Hz (children, 2.2 kPa ± 0.3; adolescents, 2.2 kPa ± 0.2; adults, 2.6 kPa ± 0.3; analysis of variance, P = .009) and 84 Hz (children, 5.6 kPa ± 0.8; adolescents, 6.5 kPa ± 1.2; adults, 7.8 kPa ± 1.2; analysis of variance, P = .0003) but not at 28 Hz (children, 1.2 kPa ± 0.2; adolescents, 1.3 kPa ± 0.3; adults, 1.2 kPa ± 0.2; analysis of variance, P = .40). At 56 and 84 Hz, liver stiffness increased with age (Spearman correlation, r = 0.38 [P = .03] and r = 0.54 [P = .001], respectively). Stiffness varied less with frequency in children and adolescents than in adults (analysis of variance, P = .0009). No significant differences were found in shear moduli at 28, 56, or 84 Hz or frequency dependence between children and adolescents (P = .38, P = .99, P = .14, and P = .30, respectively, according to Tukey tests). Conclusion Liver stiffness values are lower and vary less with frequency in children and adolescents than in adults. Stiffness increases with age during normal development and approaches adult values during adolescence. Comparing pediatric liver stiffness to adult baseline values to detect pediatric liver mechanical abnormalities may not allow detection of mild disease and may lead to underestimation of severity. (©) RSNA, 2016 Online supplemental material is available for this article.
This study showed that although brain tissue in the adult hydrocephalic rats was severely compressed, their brain tissue stiffness did not change significantly. These results are in contrast with our previous findings in juvenile hydrocephalic rats which had significantly less brain compression (as the brain circumference was able to stretch with the cranium due to the open skull sutures) and had a significant increase in caudate putamen stiffness. These results suggest that change in brain mechanical properties in hydrocephalus is complex and is not solely dependent on brain tissue deformation. Further studies on the interactions between brain tissue stiffness, deformation, tissue oedema and neural damage are necessary before MRE can be used as a tool to track changes in brain biomechanics in hydrocephalus.
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.