Patient-specific Respiratory Motion Estimation Using Sparse Motion Field Presentation

Respiratory motion estimation plays a significant role in radiation therapy. Previous motion estimation approaches usually depended on 4DCT, which introduced extra radio dose for patients, and the local motion details were ignored in the statistical model. In this paper, we propose a novel estimation framework, which employs the Sparse Motion Field Presentation (SMFP) method to obtain a coarse motion estimation which preserves patient-specific respiratory motion details and an Adaptive Variable Coefficient (AVC) motion prior registration approach is applied for the accurate estimation. The experimental results show that the proposed framework effectively preserved the local motion details and achieved more accurate motion estimations compared to the Mean Motion Model (MMM) and the Principal Component Analysis (PCA) model. We achieved motion estimations for diaphragmatic breathing type, thoracic breathing type and mixed type, respectively. The accuracy measured in the average symmetric surface distance (standard deviation) were 1.9(0.9) mm, 2.4(1.1) mm and 2.2(1.0) mm, when the sum of squared intensity difference (SSD) were 5.0, 6.1 and 5.6, respectively.