The present invention provides a self-propelled image read module, which comprises a sensor, a guide rod, a motor, a gear set, and a belt. A plurality of patient-specific models of the mitral valve are generated, each from pre-operative image data obtained using a separate imaging modality. A number of configurations of gas absorption columns are described as being suitable for use in accordance with the teachings of this method. The keystone-correction unit is configured to correct keystone distortion in the document image. The second tier side and end rails have a different unique cross-section.