Segmentation accuracy of long bones

The use of three-dimensional imaging methodologies in new applications in the orthopaedic field has introduced a need for high accuracy, in addition to a correct diagnosis. The aim of this study was to quantify the absolute dimensional errors between models reconstructed from computed tomography and magnetic resonance images compared to a ground truth for various regions of the bone. Clinical CT and MRI scans were acquired from nine lower leg cadavers and the bones were subsequently cleaned from soft tissues. 3D models of the tibia were created from the segmented CT and MRI images and compared to optical scans of the cleaned bones (considered as ground truth). The 3D reconstruction using CT images resulted in an RMS error of 0.55 mm, corresponding to an overestimated CT bone model compared to the cleaned bone. MR imaging resulted in an RMS error of 0.56 mm; however, the MRI bone model was on average a small underestimation of the cleaned bone. Different regions of the bones were analysed, indicating a difference in accuracy between diaphysis and epiphysis. This study demonstrates a high accuracy for both CT and MRI imaging, supporting the feasibility of using MRI technology for the 3D reconstruction of bones in medical applications.