Drs. Tandon, Greil, and Hussain, with collaborators from King’s College London, published a paper looking at two different methods of performing image segmentation, to go from source MRI data to a 3D STL file. Their results showed that a semi-automated method is more reproducible for complex datasets.
View the paper, "Use of a semi-automated cardiac segmentation tool improves reproducibility and speed of segmentation of contaminated right heart magnetic resonance angiography," Int J Cardiovasc Imaging. 2016 May 12. [Epub ahead of print].