2. different steps to create a 3D personalized breast model 2.1. 3D reconstruction of MRI data The 3D reconstruction requires the segmentation of the anatomical elements within the 2D images. Segmentation is done using a computer software called Medical Image Segmentation Tool (MIST) which allows semi-automatic and manual segmentation of the following elements: tumor, mammary gland, sternum, skin, pectoralis major and minor muscles. The 3D reconstruction is then performed by an indirect volume rendering method, the marching cubes. Instant Mesh software is then used for post-processing.