Figure 8.

Digitization and alignment of a 3D printed model. The original STL model is printed as a 3D object, which is subsequently digitized—by using CT in this example. After the original and digitized STL models are aligned, the distances between the vertices of one STL model—in this example, the digitized version—and the surface of the other model—in this example, the original STL version—can be calculated. The reference-standard STL model can be an arbitrary model to test printer accuracy or a digitized (eg, laser-scanned) model of a cadaveric specimen to establish the accuracy of the entire process, including the technique used to image the specimen and the segmentation technique used to create the model.