TY - JOUR
T1 - Dynamic Multileaf Collimator Tracking of Respiratory Target Motion Based on a Single Kilovoltage Imager During Arc Radiotherapy
AU - Poulsen, Per Rugaard
AU - Cho, Byungchul
AU - Ruan, Dan
AU - Sawant, Amit
AU - Keall, Paul J.
PY - 2010/6/1
Y1 - 2010/6/1
N2 - Purpose: To demonstrate and characterize dynamic multileaf collimator (DMLC) tracking of respiratory moving targets that are spatially localized with a single kV X-ray imager during arc radiotherapy. Methods and Materials: During delivery of an arc field (358° gantry rotation, 72-sec duration, circular field shape), the three-dimensional (3D) position of a fiducial marker in a phantom was estimated in real time from fluoroscopic kV X-ray images acquired orthogonally to the treatment beam axis. A prediction algorithm was applied to account for system latency (570 ms) before the estimated marker position was used for DMLC aperture adaptation. Experiments were performed with 12 patient-measured tumor trajectories that were selected from 160 trajectories (46 patients) and reproduced by a programmable phantom. Offline, the 3D deviation of the estimated phantom position from the actual position was quantified. The two-dimensional (2D) beam-target deviation was quantified as the positional difference between the MLC aperture center and the marker in portal images acquired continuously during experiments. Simulations of imaging and treatment delivery extended the study to all 160 tumor trajectories and to arc treatments of 3-min and 5-min duration. Results: In the experiments, the mean root-mean-square deviation was 1.8 mm for the 3D target position and 1.5 mm for the 2D aperture position. Simulations agreed with this to within 0.1 mm and resulted in mean 2D root-mean-square beam-target deviations of 1.1 mm for all 160 trajectories for all treatment durations. The deviations were mainly caused by system latency (570 ms). Conclusions: Single-imager DMLC tracking of respiratory target motion during arc radiotherapy was implemented, providing less than 2-mm geometric uncertainty for most trajectories.
AB - Purpose: To demonstrate and characterize dynamic multileaf collimator (DMLC) tracking of respiratory moving targets that are spatially localized with a single kV X-ray imager during arc radiotherapy. Methods and Materials: During delivery of an arc field (358° gantry rotation, 72-sec duration, circular field shape), the three-dimensional (3D) position of a fiducial marker in a phantom was estimated in real time from fluoroscopic kV X-ray images acquired orthogonally to the treatment beam axis. A prediction algorithm was applied to account for system latency (570 ms) before the estimated marker position was used for DMLC aperture adaptation. Experiments were performed with 12 patient-measured tumor trajectories that were selected from 160 trajectories (46 patients) and reproduced by a programmable phantom. Offline, the 3D deviation of the estimated phantom position from the actual position was quantified. The two-dimensional (2D) beam-target deviation was quantified as the positional difference between the MLC aperture center and the marker in portal images acquired continuously during experiments. Simulations of imaging and treatment delivery extended the study to all 160 tumor trajectories and to arc treatments of 3-min and 5-min duration. Results: In the experiments, the mean root-mean-square deviation was 1.8 mm for the 3D target position and 1.5 mm for the 2D aperture position. Simulations agreed with this to within 0.1 mm and resulted in mean 2D root-mean-square beam-target deviations of 1.1 mm for all 160 trajectories for all treatment durations. The deviations were mainly caused by system latency (570 ms). Conclusions: Single-imager DMLC tracking of respiratory target motion during arc radiotherapy was implemented, providing less than 2-mm geometric uncertainty for most trajectories.
KW - Arc radiotherapy
KW - Image-guided radiotherapy
KW - Intrafraction motion
KW - Tumor tracking
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U2 - 10.1016/j.ijrobp.2009.08.030
DO - 10.1016/j.ijrobp.2009.08.030
M3 - Article
C2 - 20133066
AN - SCOPUS:77951877433
SN - 0360-3016
VL - 77
SP - 600
EP - 607
JO - International Journal of Radiation Oncology Biology Physics
JF - International Journal of Radiation Oncology Biology Physics
IS - 2
ER -