The comparison of two deformable registration algorithms and analysis of morphology of normal liver and tumor by breathing motion

Abstract

Objective To study the morphology of normal liver and tumors by breathing motion of hepatocellular carcinoma patients,through comparing the modified demons algorithm and FFD algorithm based on B-spline,and combing four-dimensional computed tomography (4DCT).Methods The 4DCT images of 8 HCC patients were segmented into 10-series which were named CT0,CT10 … CT80,CT90 according to the respiratory phases,CT0 and CT50 are defined to be end-inhale and end-exhale respectively.CT50 was chosen as the reference image.We used the modified demons algorithm and FFD algorithm based on B-spline to deform the images.Linear interpolation was used in both mode 1 and mode 2.The normalized mutual information (NMI),Hausdorff distance (dH) and registration speed were used to verify the registration performance.Results The average NMI for the end-inhale and end-exhale images of 8 HCC patients after demons registration in mode 1 improved 4.75％ with FFD algorithm based on B-spline(P =0.002).And the difference of dH after demons reduced 15.2％ comparing with FFD model algorithm (P =0.02).In addition,demons algorithm has the absolute advantage in registration speed(P =0.036).Conclusions The breathing movement for deformation of normal liver and tumor targets is significant.These two algorithms can achieve the registration of 4DCT images and the modified demons registration can deform 4DCT images effectively. Key words: Liver neoplasm/radiotherapy; Tomography, X-ray computed, four-dimensional; Modified demons algorithm; Free form deformable model