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Description
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The aim of this work is to provide an alternative method to the
standard perfusion techniques for determining cerebral blood flow from
images obtained using dynamic susceptibility contrast-enhanced
magnetic resonance imaging (DSCE-MRI).
A bolus of the paramagnetic contrast agent Gd-DTPA through the brain
results in a drop in signal intensity, the log change is proportional
to contrast agent concentration. The area under the graph of the
contrast agent concentration over time is therefore proportional to
the volume of contrast agent which has passed through the voxel (CBV). The
mean transit time (MTT) of the contrast from the arterial to venous pools is
standardly computed using a deconvolution of the voxel residue
function (ie, the amount of contrast still remaining in the voxel at a
certain time) by the Arterial Input Function (AIF) (ie, the
contrast-time curve measured in an artery). Cerebral blood flow
(relative) is then calculated as CBV/MTT.
This technique suffers several drawbacks, most notably that the mean
transit time cannot be reliably calculated.
We have developed a novel technique to obtain a Net Mean Transit Time
and hence absolute Net Cerebral Blood Flow for every imaged
voxel. Instead of using deconvolution to obtain an MTT, we calculate
the average time of arrival of the contrast in each voxel and use
spatial differentiation of these times to calculate the Net mean
transit time of contrast across the voxel. CBV can be made absolute by
normalising to a voxel which is 100% blood (in an artery or
vein). Net cerebral blood flow is therefore CBV/NMTT scaled by a
factor to transform the value into the standard physiological units of
ml/100g/min.
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Contacts
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Funding
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This work was funded as part of a Wellcome Trust project on relating cross-sectional and longitudinal changes in brain function to cognitive function in normal old age.
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Software
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For a demonstration of the software associated with this project, please download Tina5 and build the NCBF example toolkit under tina5/tina-tools/toolkits/ncbf/.
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Documents
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Marietta's PhD thesis entitled ``Towards a Quantitative Methodology for the Assessment of Cerebral Blood Flow in Magnetic Resonance Imaging'', published Summer 2005 by the University of Manchester is available below as a pdf file and as text:
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| Thesis as a pdf |
Thesis as text |
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