:: Imaging ::
The Imaging Division of the Brain Research Institute facilitates, co-ordinates and assists in research in the neurosciences using imaging techniques. Understanding how the brain works is one of the final frontiers in understanding the human body. Only recently has the technology advanced to the point where real answers as to how the brain works are available. The integrated application of radiology, physics, neurology and other neurosciences provide powerful means to combat brain disease and to understand normal brain function. Knowledge about the brain will be increasingly gained from neuroimaging methods.
As a member of the Victorian Biomedical Imaging Capability (VBIC), BRI is also able to facilitate access to a broad range of imaging techniques outside BRI. VBIC provides access to biomedical imaging equipment and expertise across Victoria. For details of available equipment and access processes see the VBIC website - www.vbic.org.au
Photographs of both our 3 tesla MRI facility and mock scanner can be viewed here.
Diffusion MRI is an imaging technique that is unique in its ability to probe tissue microarchitecture at the cellular level non-invasively. It is increasingly used to investigate brain white matter and its disorders, providing a wealth of important information that cannot be obtained by any other method. White matter consists of myelinated axonal fibres that connect cortical regions, where the processing of information takes place. These connections are essential for normal brain function.
Perfusion MRI is a non-invasive imaging technique for measuring cerebral perfusion (blood delivery to brain tissue per unit time). Blood delivers oxygen and nutrients to the tissue, which are necessary for cellular metabolism. The survival of the brain is dependent on a continuous and adequate supply of blood, and failure of the cerebral circulation can result in cell death. Similarly, some clinical conditions are associated with a hyperperfusion status (such as epilepsy and tumours) due to their increased energy demand. For these reasons, the ability to measure perfusion accurately, non-invasively, and with good spatial resolution would offer the chance to identify and characterise abnormal tissue in many clinical conditions.
An indicator of the health of brain tissue, the measurement of T2 relaxation time (“T2 relaxometry”), has been established as a reliable tool for the quantitative measure of tissue abnormalities in temporal lobe epilepsy. At BRI the measurement of the T2 is achieved using an optimized pulse sequence that has been developed in our Institute. We have also developed a novel analysis method that we call voxel based relaxometry (VBR) which provides an automated objective description of areas of T2 abnormality in groups of patients with epilepsy compared to control patients. Results of volume and T2 abnormalities in a group of subjects with unilateral left hippocampal sclerosis (HS) are shown above.
At BRI we are now able to generate images based on sodium, the second most common nucleus in tissue. The physical properties of sodium result in the signal being very short-lived so to detect this small signal, a new pulse sequence called twisted-projectionimaging (TPI) is necessary. This pulse sequence allows the collection of images such as those shown above, such images have potential use in a number of diseases such as epilepsy and stroke.
We use functional connectivity to measure the laterality of language networks, without the need for active performance of a language task. Connectivity can detect language networks largely similar to those seen in an activation study and detect subtle changes in these networks in patients with epilepsy. Our approach promises assessment of language laterality in patients with severe epilepsy, as well as in infants and young children with language impairment, none of whom cannot be assessed with current approaches, which require the performance of an active language task.
Magnetic Resonance Spectroscopy
Magnetic resonance spectroscopy (MRS) gives information about metabolites containing a particular nucleus in regions of the brain. The technique provides a metabolite profile that can act as a disease ‘finger-print’ so we use MRS at the BRI to measure metabolites that contain either proton or phosphorus nuclei. The metabolite profiles have the potential to show a ‘metabolic phenotype’ associated with different forms of epilepsy – such as the effect of genetic changes that result in increased susceptibility to epilepsy. Metabolite information is also useful in cases that do not show abnormalities with standard imaging methods. This technique also provides information on the short-term and longterm changes associated with seizures.
Copyright© 2009 Brain Research Institute