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Purpose: to investigate the influence of megavolt (MV) pulse artifacts and pulsing artifact suppression techniques on fiducial marker and marker-less detection success for verification of real-time tumor tracking (RTTT) on a gimbaled linac system using fast MV fluoroscopy. Methods: Because frame rates on current clinical available EPIDs is limited to 7.5 Hz, a new generation EPID (XRD-1642 AP19) with a maximum frame rate of 30 Hz was evaluated for RTTT verification. Both 0.5 mm and 0.75 mm Visicoil™ markers were used for MV marker tracking with a frame rate of respectively 7.5 Hz, 15 Hz and 30 Hz. Additionally, marker-less tumor tracking was conducted and compared with the ground-truth fiducial marker motion. Static markers under influence of increasing phantom thickness and dynamic (sine and human irregular) motion was used to investigate performance of MV target detection.For each MV sequence, the free running (FR-nF) (ignoring MV pulsing during readout) acquisition mode was compared with two acquisition modes aiming to reduce MV pulsing artifacts, i.e. combined wavelet-FFT filtering (FR-wF) and a hardware synchronized (S-nF) readout with respect to the MV pulses. Results: For a 0.75 mm visicoil, deviations of sine wave motion were sub-millimeter (RMSE 3 mm, while for MV fluoroscopy in S-mode RMSE |
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