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Mapping cerebral haematocrit using MRI

The percentage blood volume occupied by red blood cells is known as haematocrit. Whereas it is straightforward to measure haematocrit in large arteries, it is very challenging to do it in the tissue (cerebral haematocrit). Currently, this can be done using invasive methods (such as PET, SPECT, or even ex vivo methods such as autoradiography), and their use is therefore very limited. Local variations in cerebral haematocrit have been reported in various brain abnormalities (such as in stroke and tumours). We have recently developed the only non-invasive method to map haematocrit, which is based on using MRI data. The method relies on combining data from two MRI measurements: one that provides haematocrit-weighted and other one haematocrit-independent values of the same parameter, thus providing an easily obtainable measurement of this important physiological parameter. Four different implementations were described, with one illustrated as proof-of-concept using data from healthy subjects (see figure). Cerebral haematocrit measurements were found to be in general agreement with literature values from invasive techniques and showed good test-retest reproducibility. The method was also able to detect statistically significant haematocrit gender differences in cortical regions. The proposed MRI technique should have important applications in various neurological diseases, such as in stroke and brain tumours. Our Lab will continue to develop, optimise and validate this MRI-based method, as well as to assess its role in various neurological disorders.

Reference:
Calamante F, Ahlgren A, van Osch MJ, Knutsson L. A novel approach to measure local cerebral haematocrit using MRI. J Cereb Blood Flow Metab 2016; 36:768-780. doi: 10.1177/0271678X15606143.
 

Population average results for the cerebral haematocrit, in axial (top), coronal (middle), and sagittal (bottom) projections. The maps are shown at 2 mm isotropic resolution.

MRI Blood Flow and Brain Connectivity Laboratory

Recent advances in MRI have revolutionised the way we investigate brain structure, brain function, and brain network connectivity. Our lab's main research interests include the development and application of MRI methods to measure cerebral blood flow (Perfusion MRI), super-resolution MRI methods based on diffusion MRI fibre-tracking (Super-Resolution Track-Weighted Imaging), as well as the role of these methods to study brain structural and functional connectivity. 

In particular, we specialise in the development of the two main Perfusion MRI techniques: Dynamic Susceptibility Contrast MRI (DSC-MRI) and Arterial Spin Labelling (ASL). The former is playing a key role in many clinical applications (e.g. stroke, tumours), while the latter provides a powerful quantitative tool to characterise functional connectivity.  

Super-Resolution Track-Weighted Imaging provides a means to exploit the information from whole-brain diffusion MRI fibre-tracking to achieve image resolution not previously possible in the human brain in vivo. This method not only can generate images with exquisite image detail, but also provides a unique framework to combine structural and functional connectivity information, and therefore investigate the structural-function relationships in brain networks. Given that the pathophysiological basis of many brain disorders is related to abnormalities in the structural and/or functional connections, this method is expected to have a major role in clinical neuroscience.

All Projects by this Lab

Perfusion MRI: novel methods to image cerebral blood flow and brain functionSuper-resolution MRI methods for the Human Brain ConnectomeMapping myeloarchitecture using diffusion MRIMRI brain parcellation based on data-driven methodsMapping cerebral haematocrit using MRINovel MRI methods to study dynamic brain connectivity

Imaging

The Florey is a world-leader in neuroimaging development and applied research. Both the Imaging and Epilepsy divisions specialise in advanced magnetic resonance imaging (MRI) methods development, especially related to diffusion MRI, perfusion MRI, and methods to study brain functional and structural connectivity. Functional MRI (fMRI) and simultaneous fMRI and electroencephalography (fMRI-EEG) methods development and application are also a major priority. Neuroimaging is also a crucial component of several studies undertaken in the Stroke division.

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All Labs that operate in this Division

Advanced MRI Development GroupImaging and EpilepsyMRI Blood Flow and Brain Connectivity Laboratory