Shape-aided kidney extraction in MR urography

MR Urography (MRU) plays an important role in pediatric renal diagnoses. While accurate measurement of the kidney is essential for each imaging study, it is challenging to extract the kidney from its background. In this paper, we propose a co-focus elliptical kidney model (CEKM) to integrate the shape prior and build a novel extraction method with both regional and edge information. With a similarity metric defined between a binary mask and CEKM, a kidney template can be obtained using optimization technique. Then, a shape term derived from a distance and orientation description is designed to modify an active contour model. The distance map is used to control the contours in terms of CEKM and orientation map is designed to reduce the artifacts resulting from fake edges. The final kidney was determined with iterative solution. With the priori shape description in a parametric space, the new method can precisely extract the kidney without training, and supply promising results as the experiments demonstrated.