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Purpose To evaluate feasibility and accuracy of various fiducial markers when using a gimbaled linac of Vero SBRT system for real time tumor tracking(RTTT).Methods and Materials We used various fiducial markers consisting of titanium,stainless steel,iron,copper,silver,gold,and tantalum for their potential use as tracking markers in RTTT.All markers,1 mm in diameter and 5 mm in length,were located on a 2-dimensional moving phantom(Brainlab,Germany)producing sinusoidal motion with frequencies up to 30 breaths per minute(bpm).CT scans for the phantom were acquired and orthogonal kV images were taken for detection of fiducial markers.For measurement of accuracy of target centers,dose profiles were measured using GAFCHROMIC EBT2 films.The gantry and o-ring angles for this experiment were combined as 0° and 45° for synchronous motion of pan/tilt.Results Fiducial markers having atomic number less than 29 such as titanium,stainless steel,and iron were not detected on kV images for RTTT system.Other fiducial markers having atomic number higher than 29(copper,silver,gold,and tantalum)were precisely detected on orthogonal kV images.Regarding fiducial markers detected in the angles of gantry 0(!)(AE)/o-ring 0(!)(AE)(G0/R0),the deviation between static field and RTTT field was within 0.78 mm at pan/tilt motion.In the angles of gantry 0(!)(AE)/o-ring 45(!)(AE)(G0/R45),the maximal deviation was 0.89 mm.Conclusions The markers consisting of high atomic number material(>29)were feasible as fiducial markers for RTTT using a gimbaled linac of Vero system with high geometric accuracy.