Constraint problems in factor analysis of dynamic structures in nuclear medicine

It is shown that a principal components analysis yields images and curves which contain negative elements and, as such, does not describe the underlying physiology. It does, however, contain the information necessary for distinguishing among dynamic structures. The application of an oblique transformation, based on the non-negativity criterion, to the results of this analysis provides a possible solution. It is clear, however, that the use of this criterion alone will not provide a unique solution