QUANTIFICATION OF INTENSITY VARIATIONS IN FUNCTIONAL MR-IMAGES USING ROTATED PRINCIPAL COMPONENTS

In functional MRI (fMRI), the changes in cerebral haemodynamics relate d to stimulated neural brain activity are measured using standard clin ical MR equipment. Small intensity variations in fMRI data have to be detected and distinguished from non-neural effects by careful image an alysis. Based on multivariate statistics we describe an algorithm invo lving oblique rotation of the most significant principal components fo r an estimation of the temporal and spatial distribution of the stimul ated neural activity over the whole image matrix. This algorithm takes advantage of strong local signal variations. A mathematical phantom w as designed to generate simulated data for the evaluation of the metho d. In simulation experiments, the potential of the method to quantify small intensity changes, especially when processing data sets containi ng multiple sources of signal variations, was demonstrated. In vivo fM RI data collected in both visual and motor stimulation experiments wer e analysed, showing a proper location of the activated cortical region s within well known neural centres and an accurate extraction of the a ctivation time profile. The suggested method yields accurate absolute quantification of in vivo brain activity without the need of extensive prior knowledge and user interaction.