3D-Printing Offers Dry Replication and New Insight into Unique Museum Specimens

Students dissection classes again and again reveal unique anatomical variations and pathologies, which are usually preserved and stored in fluid. Due to their unique nature and hazardous conservation fluids, they neither ever leave their display case again nor are handed over to students at the dissection lab. Thus the present study aims at routinely generating solid, dry, and numerically unlimited 3D-replica of such unique specimens. We have selected a particularely severe case of Mönckebergs aortic valve sclerosis and a transcatheter aortic valve implantation (TAVI)-treated valve to develop a standard scanning, segmentation and multicolor 3D-printing protocol for soft and hard tissue specimens. Subsequent to anatomical dissection of the appropriate valve segment from the ventricular outlet and the ascending aorta, scanning was performed on a Skyscan 1173 micro-CT at a x-y-z resolution of 30µm. Soft tissue, calcified tissue, and the TAVI's wire cage were segmented separately using the software packages Slicer and Medtool. For 3D-printing, the Prusa MK3S filament printer and the Prusa SL 1 resin printer were used. The overall time expense for scanning (40 minutes), data processing and segmentation (about 16 hours) was around two to three working days per model. The 3D-printing took from 5 hours (single-color resin printing at a scale of 1:1) up to 4 days (triple-color filament printing at a scale of 3:1). The generated display models range from real size, opaque surface models to semi-vitreous visualizations of the calcification pattern and the implanted TAVI. Taken together, after a substantial time expenditure for initial data processing and modeling, with small time requirements not only hands on replica for teaching can be easily reproduced at different scales without limitation by specimen durability or chemical hazards. Additional impact is achieved by the ability to highlight and analyze internal structures in situ, making laborious, traditional whole mount staining and -clearing dispensable. In a next step, the adaption of colors and material characteristics will approximate the haptic experience to the real specimen.