Extracting parametric images from dynamic contrast-enhanced MRI studies of the brain using factor analysis

Factor analysis of dynamic studies (FADS) is a technique that allows structures with different temporal characteristics to be extracted from dynamic contrast enhanced studies without making any a priori assumptions about physiology. These dynamic structures may correspond to different tissue types or different organs or they may simply be a useful way of characterising the data. This paper describes a method of automatically extracting factor images and curves from contrast enhanced MRI studies of the brain. This method has been applied to 107 studies carried out on patients with acute stroke. The results show that FADS is able to extract factor curves correlated to arterial and venous signal intensity curves and that the corresponding factor images allow a distinction to be made between areas of the brain with normal and abnormal perfusion. The method is robust and can be applied routinely to dynamic studies of the brain. The constraints described are sufficiently general to be applicable to other dynamic MRI contrast enhanced studies where an increase in contrast concentration produces an increase in signal intensity.