Content Validity of Temporal Bone Models Printed Via Inexpensive Methods and Materials.

Hypothesis: Computed tomographic (CT) scans of the 3-D printed temporal bone models will be within 15% accuracy of the CT scans of the cadaveric temporal bones. Background: Previous studies have evaluated the face validity of 3-D-printed temporal bone models designed to train otolaryngology residents. The purpose of the study was to determine the content validity of temporal bone models printed using inexpensive printers and materials. Methods: Four cadaveric temporal bones were randomly selected and clinical temporal bone CT scans were obtained. Models were generated using previously described methods in acrylonitrile butadiene styrene (ABS) plastic using the Makerbot Replicator 2x and Hyrel printers. Models were radiographically scanned using the same protocol as the cadaveric bones. Four images from each cadaveric CT series and four corresponding images from the model CT series were selected, and voxel values were normalized to black or white. Scan slices were compared using PixelDiff software. Gross anatomic structures were evaluated in the model scans by four board certified otolaryngologists on a 4-point scale. Results: Mean pixel difference between the cadaver and model scans was 14.25 +/- 2.30% at the four selected CT slices. Mean cortical bone width difference and mean external auditory canal width difference were 0.58 +/- 0.66 mm and 0.55 +/- 0.46 mm, respectively. Expert raters felt the mastoid air cells were well represented (2.5 +/- 0.5), while middle ear and otic capsule structures were not accurately rendered (all averaged

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