Calibration of thickness measurement errors of hip joint cartilage from MR images

In the hip joint, the femoral and acetabular cartilages are in proximity to each other, a conventional measurement technique based on the edge detection, can introduce large underestimation errors in measurement of cartilage thickness. In this study, we develop a model-based approach for accurate thickness measurement. We model the imaging process of two adjacent sheet structures, which simulate two articular cartilages in the hip joint. This model can be used to predict the shape of the intensity profile along the sheet normal orientation. Using an optimization technique, the model parameters are adjusted to minimize the difference between the predicted intensity profile and the actual intensity profiles observed in the MR data. The set of model parameters that minimize the difference between the model and the MR data yield the thickness estimation. Using three cadaveric human hip joints, we present results showing that the new model-based approach is more accurate than the edge detection method at estimating the hip cartilage thickness.