Ray-wise weighted helical cone beam filtered backprojection algorithm for image reconstruction under moderate cone angle

摘要

With an accelerated pace the CT technology has achieved the latest milestone — cone beam volumetric CT with 40mm detector coverage. To obtain an optimized image reconstruction solution for future cone beam VCT systems, the raywise weighted helical CB-FBP algorithm, which was proposed by us to reconstruct image under cone angles up to 4.25°, is optimized and evaluated in this study to verify its imaging performance for image reconstruction under larger cone angles up to 8.5°. The ray-wise weighted helical CB-FBP algorithm proposed by us possesses two important features: (a) tangential filtering that is naturally implemented via row-wise fan-to-parallel rebinning to maintain spatial resolution along patient's longitudinal direction; and (b) 3D weighting that is a ray-wise optimization process to obtain image quality controllability. By using computer-simulated phantoms, such as the helical body and humanoid head phantoms, it has been shown that the ray-wise weighted helical CB-FBP algorithm can provide a well balanced imaging performance over helical pitches while a large field of view (FOV) can be maintained. It is the optimized ray-wise weighting that enables the proposed CB-FBP algorithm performs well at larger cone angle. Based on the experimental evaluation, it is believed that the ray-wise weighted helical CB-FBP algorithm can be a candidate solution for image reconstruction in future cone beam VCT systems with detectors corresponding to larger cone angles up to 8.5° (～ 80 mm detector z-coverage).