Aberdeen Biomedical Imaging Centre
Research Area: Cardiac Imaging
The clinical focus of the group is ischaemic heart disease. We have an interest in developing new techniques, including blood oxygen level dependent (BOLD) methods for imaging perfusion, and in developing new algorithms for cardiac image analysis. Correlation of MR imaging with ultrasound and positron emission tomographic (PET) data is an important part of our work.
First pass gadolinium myocardial perfusion
Following an intravenous injection of contrast agent a series of images are taken every 2 seconds. Signal increase denotes arrival of the agent.
The principal barrier to the routine clinical application of this technique is time. In order to analyse the temporal change in myocardial MR signal, regions of interest have to be hand drawn on up to 160 images. Automated methods are available but are not sufficiently robust to handle the sometimes poor quality images obtained from patients.
Temporal polar maps may be used to conveniently display the results of measuring myocardial signal change (Figure 2).
Figure 2
The signal uptake is colour coded from blue through green to yellow. Time is measured radially out from the centre. Therefore to extract a time activity curve (TAC) for any region you designate the angle of the region with respect to the centre of the short axis image and plot the uptake from the centre of the polar map to its edge. The shape of this TAC may be analysed using various models to obtain regional blood flow characteristics.
The total heart perfusion characteristics may be displayed in turn in polar map form where the different short axis results are overlayed in to map with apical slice information at the centre and basal values at the periphery.
The temporal polar map is the coloured diagram shown above
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| patlak anlysis 1 | fermi analysis 1 |
Cardiac BOLD MRI
With the availability of high field MR imagers, it is now possible to image small changes in the magnetic character of the heart as oxygenated blood from the lungs arrives in the coronary arteries. Blockage of these arteries can be detected by a change in the MR signal following injection of a stressing agent. This technique is called blood oxygen level dependent (BOLD) MRI. Should cardiac BOLD MRI prove as diagnostically accurate as the tracer based techniques, it would provide a simple non-invasive test of cardiac blood supply.
Contact: Professor T W Redpath
See also http://www.abdn.ac.uk/cardiology