RESUMO
Objective To analyze the factors influencing fiducial number used for tracking abdominal tumor with stereotactic body radiation therapy (SBRT),which was implemented by CyberKnife.Methods 254 abdominal tumor patients chosen which adopted fiducial tracking and classified the fiducials.We gathered data of the patients with ＜ 3 fiducials used for tracking and patients with ≥ 3 fiducials respectively,and analyzed the reason why ＜ 3 fiducials were left for tracking.Results Among 254 patients,22 patients were showed that the number of fiducial implantation were equal to play number of fiducial;232 patients with no equation which 49 patients (21.1％) used ＜ 3 fiducials for tracking,183 patients (78.9％) used ≥3 fiducials for tracking.Among the 49 patients with ＜3 fiducials for tracking,9 patients had fiducials migrated,1 patient had an unrecognizable fiducial,23 patients had the implantation not qualified for tracking,and 16 patients had the rigid error surpassing the threshold.Conclusions 78.9％ patients were implanted ≥ 3 fiducials and thus qualified for fiducial tracking.Major reasons of disqualification include insufficient implanted fiducials,unqualified implantation and rigid error surpassing the threshold.