Using grey-level models to improve active shape model search

We describe methods for using flexible models to locate structures in images. We have previously described statistical models of shape and shape variability which can be used for this purpose (active shape models). In this paper we show how statistical models of grey-level appearance can be incorporated, leading to improved reliability and accuracy. We describe experiments designed to: 1) test how well an active shape model can locate an object in a new image; 2) to assess the effects on performance of varying the model parameters; and 3) to compare the results using grey-level models with those using a search for strongest edges. The results demonstrate that the addition of grey-level models leads to considerable improvement over earlier schemes.