Fig. 2
From: Methods for verification of 3D printed anatomic model accuracy using cardiac models as an example
Digital photographic measurement technique. a-d Four discrete 3D model features (a Feature 1, b Feature 2, c Feature 3, and d Feature 4) were chosen for measurement, based on their accessibility on an exterior surface and the fact that they had distinguishing features that would allow for repeat measurements. All digital photographs were calibrated before measurement. This was achieved by placing a marker of known length at the same height and angle as the feature of interest before photographing the model. Once the photograph was imported into an image analysis software (in this case, ImageJ), the length of the known marker was measured in pixels, and a conversion factor was calculated for pixels to millimeters. Of note, insufficient illumination for feature 3 (panel c) caused blending of edges, most pronounced along the inferior aspect of the photograph. This affected accuracy of measurements for this feature (see Table 2)