Towards Full-body X-ray Images

Zusammenfassung

Digital tomosynthesis is a tomographic imaging technique whose upsurge is mainly caused by breast imaging. However, it might also be useful in orthopedics due to its high in-plane resolution as well as the fact that tomosynthetic slices do not suffer from magnification or distortion, making measurements possible, for example, even without the need of any calibration object. Since the reading time of such a reconstruction is higher compared to conventional 2-D radiographs, a simple parallel projection of the volume can be computed to get an overview of the volume. However, this leads to a rather blurred image impression since all artifacts and inhomogeneities in the reconstructed volume as well as certain anatomical structures which are not necessary for the diagnosis, will end up in the projection. We propose a method which selects the slices to be projected into a smart synthetic X-ray image in a way which is optimal w.r.t to the sharpness of predefined ROIs (e. g. knee, spine or hip). Therefore, two Laplacian-based auto-focus measures are combined with a thin-plate spline yielding a sharp and homogenous image impression within the smart radiograph. It was shown that the auto-focus method is able to select the same slice as have been selected during an expert annotation. Upon visual inspection, it could be determined that the proposed method achieves higher contrast and clearly better visibility of complex bone structures like spine or hip.