Introduction: During radiation therapy (RT) treatment, a real-time monitoring of the delivery could increase patients' safety. An independent monitor system was tested to prove the feasibility of real-time monitoring of calibration errors, malfunctions in multi-leaf collimator (MLC) or inappropriate setup parameter during VMAT plan. Material and Methods: 6 months of measures were carried out mounting the iQM® system below the gantry of an Elekta Synergy accelerator. The repeatability of the detector was tested in >70 quality assurance (QA) sessions. A dummy plan (17 segments 4 × 4 cm2 and 1 segment 10 × 10 cm2 with constant 50 MU per segments) and a complex Head and Neck (H&N) VMAT plan (1 arc with 140 control points, low gantry speed, high MU and low dose rate) were used. Sensitivity was tested by introducing specific dosimetric errors of MU (1÷20%) in the H&N plan. Correlation with gantry and collimator angles was evaluated. Results: Delivering the dummy plan in standard condition (gantry and collimator angles = 0°), a counts mean variability of 0.7 ± 1.0% was detected in comparison with the commissioning day. No statistical difference (ANOVA sign. ~1) was detected for all segments in rotational conditions (gantry angle: 0°–90°–180°–270° and collimator angle: 0°–45°–135°–225°–315°). Contrariwise, unexpected counts were observed in the H&N plan with low angle gantry (120° ÷ 240°), showing a mean dose discrepancy of 2.8 ± 1.0% from the original plan. The ad hoc MU introduced errors were detected within a range of [0.1–0.4%] with a linear trend (R2 = 0.99). Conclusion: The repeatability of measures highlights the robustness of the system. Uncorrected rotation of the gantry or increased MU delivered in comparison with the treatment plan was detected. Following the output for each beam segment with the differential and cumulative approach, the detector enables a real-time check during VMAT treatment finalized to patients' safety and to evaluate the daily condition of the machine during QA.
New era for QA and VMAT: Real-time monitor system in clinical practice
GUIDI, GABRIELEMembro del Collaboration Group
;CIARMATORI, ALBERTOMembro del Collaboration Group
;BALDAZZI, GIUSEPPESupervision
;COSTI, TIZIANA
2016
Abstract
Introduction: During radiation therapy (RT) treatment, a real-time monitoring of the delivery could increase patients' safety. An independent monitor system was tested to prove the feasibility of real-time monitoring of calibration errors, malfunctions in multi-leaf collimator (MLC) or inappropriate setup parameter during VMAT plan. Material and Methods: 6 months of measures were carried out mounting the iQM® system below the gantry of an Elekta Synergy accelerator. The repeatability of the detector was tested in >70 quality assurance (QA) sessions. A dummy plan (17 segments 4 × 4 cm2 and 1 segment 10 × 10 cm2 with constant 50 MU per segments) and a complex Head and Neck (H&N) VMAT plan (1 arc with 140 control points, low gantry speed, high MU and low dose rate) were used. Sensitivity was tested by introducing specific dosimetric errors of MU (1÷20%) in the H&N plan. Correlation with gantry and collimator angles was evaluated. Results: Delivering the dummy plan in standard condition (gantry and collimator angles = 0°), a counts mean variability of 0.7 ± 1.0% was detected in comparison with the commissioning day. No statistical difference (ANOVA sign. ~1) was detected for all segments in rotational conditions (gantry angle: 0°–90°–180°–270° and collimator angle: 0°–45°–135°–225°–315°). Contrariwise, unexpected counts were observed in the H&N plan with low angle gantry (120° ÷ 240°), showing a mean dose discrepancy of 2.8 ± 1.0% from the original plan. The ad hoc MU introduced errors were detected within a range of [0.1–0.4%] with a linear trend (R2 = 0.99). Conclusion: The repeatability of measures highlights the robustness of the system. Uncorrected rotation of the gantry or increased MU delivered in comparison with the treatment plan was detected. Following the output for each beam segment with the differential and cumulative approach, the detector enables a real-time check during VMAT treatment finalized to patients' safety and to evaluate the daily condition of the machine during QA.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
