The invention provides a system for virtually designing a medical device conformed for use with a specific patient. Using the system, a three-dimensional geometric model of a patient-specific body cavity or lumen is reconstructed from scanned volume images such as obtained x-rays, magnetic resonance imaging (MRI), computer tomography (CT), ultrasound (US), angiography or other imaging modalities. Knowledge of the physical properties of the cavity/lumen is obtained by determining the relationship between image density and the stiffness or elasticity of tissues in the body cavity or lumen and is used to model interactions between a simulated device and a simulated body cavity or lumen.