A modified optical flow based method for registration of 4D CT data of hepatocellular carcinoma patients

This paper expanded two-dimensional optical flow registration method to three-dimensional optical flow method (3D-OFM) to deform the four-dimensional computed tomography (4D CT) images. 4D CT can investigate the effect of breathing motion to the liver tumors and track the “trajectory” of the tumors. This algorithm was applied to the fully automated registration of 4D CT data for hepatocellular carcinoma patients. According to the respiratory phase, 4D CT data was segmented into 10-series CT images which were named CT0, CT10...CT90, and CT0 is at end inspiration and CT50 is at end expiration. In particular, The iodipin was used to help define the gross target volume of HCC to improve the image contrast. In addition, The iodipin also used to improve the registration method and verify the performance of registration method as the markers. We chose the end-exhale CT as the reference image. To verify the registration performance of this method, we qualitatively compared the subtractions of floating images and reference image and the iodipin deposition regions before and after registered, and we quantificationally computed the multi-information between floating images and reference image of 8 patients. The improving proportion of multi-information between end-exhale CT and in-exhale CT is from 1.71% to 4.17%.