Gradient-Based Differential Approach for 3-D Motion Compensation in Interventional 2-D/3-D Image Fusion

In interventional radiology, preoperative 3-D volumes can be fused with intra-operative 2-D fluoroscopic images. Since the accuracy is crucial to the clinical usability of image fusion, patient motion resulting in misalignments has to be corrected during the procedure. In this paper, a novel gradient based differential approach is proposed to estimate the 3-D rigid motion from the 2-D tracking of contour points. The mathematical relationship between the 3-D differential motion and the 2-D motion is derived using the 3-D gradient, based on which a tracking-based motion compensation pipeline is introduced. Given the initial registration, the contour points are extracted and tracked along 2-D frames. The 3-D rigid motion is estimated using the iteratively re-weighted least square minimization to enhance the robustness. Our novel approach is evaluated on 10 datasets consisting of 1010 monoplane fluoroscopic images of a thorax phantom with 3-D rigid motion. Over all datasets, the maximum structure shift in the 2-D projection caused by the 3-D motion varies from 17.3 mm to 33.2 mm. Our approach reduces the 2-D structure shift to the range of 1.93 mm to 6.52 mm. For the most challenging longitudinal off-plane rotation, our approach achieves an average coverage of 79.9% regarding to the ground truth.