ABSTRACT
Objective To investigate the accuracy of three dimensional facial measurement system based on structured light projection, and explore the methods to reduce noise of the output images. Methods The known object for calibration was measured by the measurement system to correct the parameters of the system and enhance the measurement accuracy. The mechanism of noise was analysed, and the noise and sundry of the images were eliminated. Results The parameters of each assembly of system were obtained by calculation and calibrated, and the measurement accuracy (0.028 mm) of three dimensional facial measurement system based on structured light projection was increased. Application of image processing technology reduced the noise and sundry of output images. Conclusion The accuracy of three dimensional facial measurement system based on structured light projection is high. The image output is reliable, and can be clinically used in facial scanning and three dimensional reconstruction.
ABSTRACT
The main reason of invalidation of prosthetic hip joint is the prostheses flexibility and shift, dislocation and disjunction. Promoting the long time stability of the prostheses is the key of improving the long term hip joint replacement effect. Former research work was focused on the upper segment of femur, and assumed the acetabulum cup to be a spheric concave, and the external form of acetabulum prostheses was basically semi spheric. This paper presents a method of acquiring the point data on the surface of the hip bone using the reverse engineering technology. By analyzing the acetabulum surface fitting error we use rotating elliptical surface to fit the acetabulum surface, together with the optimal technique to build up the CAD model of acetabulum surface. We compare the fitting error between the sphere fitting and rotating elliptical surface fitting and get the result that the rotating elliptical surface fitting error is smaller than the sphere fitting error, and the rotating elliptical surface can describe the shape of the acetabulum better.
Subject(s)
Humans , Acetabulum , Anthropometry , Arthroplasty, Replacement, Hip , Computer Simulation , Computer-Aided Design , Hip Joint , Hip Prosthesis , Models, Anatomic , Prosthesis DesignABSTRACT
The research on the morphology features of the acetabulum bone joint surface area would be helpful to establishing the acetabulum 3D model for the purpose of the biomechanical analysis of hip joint, and therefore might have its important clinical significance. However, in former studies, the acetabulum was simply considered as a semi sphere. In this study, based on the acetabulum 3D-point data acquired by the 3D laser surface scanner and the reverse engineering technology together with the optimal fit algorithm, two kinds of best-fit model were achieved by a sphere surface and a rotating elliptical surface respectively approaching to the acetabulum bone joint surface. Both fitting errors were then compared and analyzed. The results showed that the fitting error of the rotating elliptical surface was significantly less than that of the sphere surface (P < 0.001). The average radius of fitting sphere was 24.37 +/- 2.22 mm and the average long axis of fitting rotating elliptical surface was 26.02 +/- 2.76 mm while its short axis was 24.17 +/- 2.16 mm. These findings would be helpful to our new recognition of the acetabulum since they were results of the first quantitative analyses for the acetabulum bone surface and also might serve as an important reference base in its further studies and application.