A comparison between computerized tomography, magnetic resonance imaging, and laser scanning for capturing 3-dimensional data from a natural ear to aid rehabilitation

PURPOSE: To compare dimensional measurements on computer images generated from data captured digitally by 3 different methods to those obtained directly from natural ears and ear casts, so as to determine the optimal method of creating a computer-generated ear image. MATERIALS AND METHODS: Magnetic resonance imaging (MRI) was used to obtain 3-dimensional (3D) data images of the normal ears of 14 subjects. Computerized tomography (CT) and laser scanning (LS) were used to obtain 3D data images from stone casts of the same ears. Dimensional measurements were recorded on 2 occasions between anthropometric landmarks on the subjects' natural ears, casts of the ears, and reconstructed ear images obtained by CT, MRI, and LS. The intraclass correlation coefficients and coefficients of repeatability were calculated. The means of the 2 measurements for each of the dimensions were analyzed using 2-way analysis of variance to determine whether there were differences between the methods of data collection. RESULTS: The intraclass correlation coefficients indicated that dimensions could be reliably measured on the natural ears, casts, and CT, MRI, and LS images. The coefficients of repeatability were all of a small magnitude in relation to the overall dimensions studied. No statistical differences existed between the various sources of data (P = .866) (i.e., direct, cast, CT, MRI, and LS). CONCLUSION: The 3 methods of imaging have generally resulted in dimensional measurements on the reconstructed images that are similar to those of the original source. These are considered appropriate for manufacturing 3D models that can be used to fabricate a prosthesis. However, other factors may also be important, such as shape, contour, and internal form, and these require further investigation.