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A Method for Objective Evaluation of Functional Images

National Institutes of Health, Bethesda, Maryland
Institute of Nuclear Medicine, Utrecht, The Netherlands

Correspondence: For reprints contact: Stephen L. Bacharach, National Institutes of Health, Building 10, Room 1B38, Bethesda, MD 20205.

ABSTRACT

A method is described for characterizing functional maps by means of a frequency distribution function (DF) of pixels. The method makes use of a map of the standard deviation of the functional parameter. By use of this map the method (a) becomes less sensitive to imprecise definition of the organ borders, (b) compensates for random fluctuations in the functional map, and (most importantly) (c) permits spatial information to be included in the DF. This spatial information is included by performing spatial cluster weighting—a procedure that emphasizes regional dysfunction over global dysfunction. The method is illustrated by applying it to phase maps of the left ventricle. In this example, it is shown that analysis of the DF permits detection of regional abnormalities of LV wall motion and that an improvement in detectability is obtained with cluster weighting.