Visual search in medical images : a new methodology to quantify saliency

The quantification of object saliency in 2D greyscale images is of primary importance in medical imaging. Saliency, in this paper, refers to the detectability of objects of unknown location, an object being a feature of interest in an image. Object saliency is commonly measured by the speed of an observer at performing a detection task. The more salient an object is, the more quickly it can be detected. The questions raised in this paper are 1 . whether the degree of saliency of an object can be solely predicted from its detectability as measured in a location known-exactly task, or whether factors such as geometry and context contribute to saliency in a more complex fashion; 2. whether the contribution of geometry and background complexity to saliency can be quantified. This paper focuses on the problem of detection of stenoses in simulated angiograms. Results from a first such study are presented. From those results, a new general methodology to measure saliency in 2D greyscale images was inferred and is presented.