Modeling of hip prostheses for use in radiotherapy planning: Validation of a photogrammetry technique

Treatment planning for external beams radiotherapy for patients with metallic hip prosthesis is often difficult, in particular with regards to the contouring process, in case of poor CT imaging. This may result in inaccurate dosimetry for the femoral bone and regions next to it. In this work an alternative method to obtain more accurate prosthetic contourings, based on photogrammetry, was developed. More precisely, the process of 3D modeling of a femoral prosthetic component and the conversion to DICOM was developed, plus the effective employment in a treatment planning system was evaluated. Validation of the obtained model was performed by comparing several cross sections against experimental measurements. Comparison resulted in very low deviations, showing good accuracy of the photogrammetry technique, despite the high asymmetry of the object. The tests conducted in a research TPS indicate that models obtained with the proposed method are able to provide additional information in order to better characterize such prosthetic implants.