Isoluminance: a color technique for visualizing multivariable medical image data

We have developed a technique for visualizing medical image data sets that have multiple values at each physical location. These data sets are increasingly common as physicians attempt to correlate between modalities (for instance, CT and nuclear medicine, MR and PET, CT and MR) as well as within modalities (for instance, MR metabolic and anatomical scans). Our technique, termed 'isoluminance', is designed primarily for displaying sets that have two scalar values associated with each physical (x,y) location on a two dimensional scan. A perceptually uniform luminance scale is used to encode one dimension. At each step of the luminance scale a set of isoluminant hue steps are used to encode the other dimension. The hue scale is chosen to be perceptually uniform and as 'natural' as possible. The resulting data set can then be displayed as a single image on a color display. We have found observers using our technique are able to comprehend both of the data sets, to understand relationships between the data sets, and, when using interactive manipulation techniques, are able to select or label specific features of the data set.