Delivering RapidArc®: A comprehensive study on accuracy and long term stability

Scaggion, A.; Negri, A.; Rossato, M.A.; Roggio, A.; Simonato, F.; Bacco, S.; Paiusco, M.

doi:10.1016/j.ejmp.2016.05.056

Cited by 15 publications

(16 citation statements)

References 32 publications

(74 reference statements)

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“…[2][3][4] VMAT's advantages can be realized if a comprehensive commissioning and quality assurance (QA) program are routinely implemented. 5 Previous studies 6,7 have proposed a set of tests that are specific to the implementation of Varian RapidArc (Varian Medical Systems, Palo Alto, CA, USA). However, due to difficulties related to film dosimetry and portal images, the delivery aspects of VMAT could not be assessed separately and with sufficient gantry-angle resolution.…”

Section: Introductionmentioning

confidence: 99%

Quality assurance of VMAT on flattened and flattening filter‐free accelerators using a high spatial resolution detector

Matar

Wilkinson

Davis

et al. 2020

J Applied Clin Med Phys

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Purpose: This study investigated the use of high spatial resolution solid-state detectors (DUO and Octa) combined with an inclinometer for machine-based quality assurance (QA) of Volumetric Modulated Arc Therapy (VMAT) with flattened and flattening filter-free beams. Method: The proposed system was inserted in the accessory tray of the gantry head of a Varian 21iX Clinac and a Truebeam linear accelerator. Mutual dependence of the dose rate (DR) and gantry speed (GS) was assessed using the standard Varian customer acceptance plan (CAP). The multi-leaf collimator (MLC) leaf speed was evaluated under static gantry conditions in directions parallel and orthogonal to gravity as well as under dynamic gantry conditions. Measurements were compared to machine log files. Results: DR and GS as a function of gantry angle were reconstructed using the DUO/inclinometer and in agreement to within 1% with the machine log files in the sectors of constant DR and GS. The MLC leaf speeds agreed with the nominal speeds and those extracted from the machine log files to within 0.03 cm s −1. The effect of gravity on the leaf motion was only observed when the leaves traveled faster than the nominal maximum velocity stated by the vendor. Under dynamic gantry conditions, MLC leaf speeds ranging between 0.33 and 1.42 cm s −1 were evaluated. Comparing the average MLC leaf speeds with the machine log files found differences between 0.9% and 5.7%, with the largest discrepancy occurring under conditions of fastest leaf velocity, lowest DR and lowest detector signal. Conclusions: The investigation on the use of solid-state detectors in combination with an inclinometer has demonstrated the capability to provide efficient and independent verification of DR, GS, and MLC leaf speed during dynamic VMAT delivery. Good agreement with machine log files suggests the detector/inclinometer system is a useful tool for machine-specific VMAT QA.

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Section: Introductionmentioning

confidence: 99%

Quality assurance of VMAT on flattened and flattening filter‐free accelerators using a high spatial resolution detector

Matar

Wilkinson

Davis

et al. 2020

J Applied Clin Med Phys

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“…Scaggion et al reported that the mean mechanical errors in clinical VMAT plans were less than 1 mm, 0.5°, and 0.1 MU for MLC position, gantry angle, and MU, respectively, during RapidArc treatments delivered with a 6 MV UNIQUE linac (Varian Medical Systems, Palo Alto, CA, USA) over 2 years [ 9 ]. José Olasolo-Alonso et al also reported that the average RMSE values of the MLC were 0.3 mm for Clinac linac (Varian Medical Systems) in intensity-modulated radiation therapy (IMRT) treatments, and 0.04 mm for TrueBeam linacs (Varian Medical Systems) in VMAT treatments, according to 3000 logfiles obtained from four institutions [ 10 ].…”

Section: Discussionmentioning

confidence: 99%

“…Even if the dosimetric QA testing results meet institutional criteria, there is no guarantee that treatment machines will continue to perform correctly throughout the course of treatment. Several studies have reported that daily machine errors were small throughout the course of VMAT treatment [ 9 , 10 ]; however, it is generally difficult to predict dosimetric impacts on patient anatomy due to mechanical errors. Thus far, no studies have reported monitoring of the dosimetric impact of mechanical errors throughout the course of treatment.…”

Section: Introductionmentioning

confidence: 99%

Monitoring of mechanical errors and their dosimetric impact throughout the course of non-coplanar continuous volumetric-modulated arc therapy

et al. 2018

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BackgroundVolumetric-modulated Dynamic WaveArc therapy (VMDWAT) is a non-coplanar continuous volumetric modulated radiation therapy (VMAT) delivery technique. Here, we monitored mechanical errors and their impact on dose distributions in VMDWAT using logfiles throughout the course of treatment.MethodsFifteen patients were enrolled (2 skull base tumor patients and 13 prostate cancer patients). VMDWAT plans were created for the enrolled patients. The prescribed dose for the skull base tumor was set as 54 Gy at 1.8 Gy per fraction, and that for the prostate cancer was set as 72 to 78 Gy at 2 Gy per fraction. We acquired logfiles to monitor mechanical errors and their impact on dose distribution in each fraction. The root mean square error (RMSE) in the multi-leaf collimator (MLC), gantry angle, O-ring angle and monitor unit (MU) were calculated using logfiles throughout the course of VMDWAT for each patient. The dosimetric impact of mechanical errors throughout the course of VMDWAT was verified using a logfile-based dose reconstruction method. Dosimetric errors between the reconstructed plans and the original plans were assessed.ResultsA total of 517 datasets, including 55 datasets for the 2 skull base tumor patients and 462 datasets for the 13 prostate cancer patients, were acquired. The RMSE values were less than 0.1 mm, 0.2°, 0.1°, and 0.4 MU for MLC position, gantry angle, O-ring angle, and MU, respectively. For the skull base tumors, the absolute mean dosimetric errors and two standard deviations throughout the course of treatment were less than 1.4% and 1.1%, respectively. For prostate cancer, these absolute values were less than 0.3% and 0.5%, respectively. The largest dosimetric error of 2.5% was observed in a skull base tumor patient. The resultant dosimetric error in the accumulated daily delivered dose distribution, in the patient with the largest error, was up to 1.6% for all dose-volumetric parameters relative to the planned dose distribution.ConclusionsMLC position, gantry rotation, O-ring rotation and MU were highly accurate and stable throughout the course of treatment. The daily dosimetric errors due to mechanical errors were small. VMDWAT provided high delivery accuracy and stability throughout the course of treatment.Trial registrationUMIN000023870. Registered: 1 October 2016.Electronic supplementary materialThe online version of this article (10.1186/s13014-018-0972-7) contains supplementary material, which is available to authorized users.

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“…In this work, we also tried to analyze MLC speed properties because it is an important VMAT plan parameter and it has direct relation to beam to the scale of beam modulation and deliverability [6,[14][15][16][17]28]. Thus, VMAT plans can be characterized by MLC speed.…”

Section: ) Mlc Speed Errormentioning

confidence: 99%

Plan-Class Specific Reference Quality Assurance for Volumetric Modulated Arc Therapy

Rahman

Kim

2019

J Radiat Prot Res

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Background: There have been much efforts to develop the proper and realistic machine Quality Assurance (QA) reflecting on real Volumetric Modulated Arc Therapy (VMAT) plan. In this work we propose and test a special VMAT plan of plan-class specific (pcsr) QA, as a machine QA so that it might be a good solution to supplement weak point of present machine QA to make it more realistic for VMAT treatment. Materials and Methods: We divided human body into 5 treatment sites: brain, head and neck, chest, abdomen, and pelvis. One plan for each treatment site was selected from real VMAT cases and contours were mapped into the computational human phantom where the same plan as real VMAT plan was created and called plan-class specific reference (pcsr) QA plan. We delivered this pcsr QA plan on a daily basis over the full research period and tracked how much MLC movement and dosimetric error occurred in regular delivery. Several real patients under treatments were also tracked to test the usefulness of pcsr QA through comparisons between them. We used dynalog file viewer (DFV) and Dynalog file to analyze position and speed of individual MLC leaf. The gamma pass rate from portal dosimetry for different gamma criteria was analyzed to evaluate analyze dosimetric accuracy. Results and Discussion: The maxRMS of MLC position error for all plans were all within the tolerance limit of < 0.35 cm and the positional variation of maxPEs for both pcsr and real plans were observed very stable over the research session. Daily variations of maxRMS of MLC speed error and gamma pass rate for real VMAT plans were observed very comparable to those in their pcsr plans in good acceptable fluctuation. Conclusion: We believe that the newly proposed pcsr QA would be useful and helpful to predict the mid-term quality of real VMAT treatment delivery.

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Delivering RapidArc®: A comprehensive study on accuracy and long term stability

Cited by 15 publications

References 32 publications

Quality assurance of VMAT on flattened and flattening filter‐free accelerators using a high spatial resolution detector

Quality assurance of VMAT on flattened and flattening filter‐free accelerators using a high spatial resolution detector

Monitoring of mechanical errors and their dosimetric impact throughout the course of non-coplanar continuous volumetric-modulated arc therapy

Plan-Class Specific Reference Quality Assurance for Volumetric Modulated Arc Therapy

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