Abstract: In a method and system for outlining a region of interest in a Positron Emission Tomography (PET) scan study, a processor may, based on application of Masked Volume Wise Principal Component Analysis (MVW-PCA) to a plurality of scan images, generate a PC2 image showing kinetic behavior of a particular part of a subject, in particular, the grey matter of the cerebellar cortex of the subject, and may outline, in the PC2 image, a region of the PC2 image having highest pixel intensity values of the PC2 image or of a portion thereof as a region of interest, and, in particular, as a reference region. The processor may generate a PC3 image showing kinetic behavior of a different part of the subject, in particular, blood vessels of the subject, import the outline into the PC3 image to determine the correctness of the outline, and modify the outline if it is incorrect.