Distributive quality assurance and delivery of stereotactic ablative radiotherapy treatments amongst beam matched linear accelerators: A feasibility study

Rijken, James; Schachenmayr, Hilmar; Crowe, Scott; Kairn, Tanya; Trapp, Jamie

doi:10.1002/acm2.12567

Cited by 9 publications

(30 citation statements)

References 27 publications

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“…For the three linacs, the maximum difference in the mean GPR and the median GPR was 0.72% and 0.80%, respectively. In terms of the GPR, this result indicates that the three linacs are well beam matched 29,30 . In the control chart, linac1 showed much noise in the PSQA data; linac2 initially showed significant noise before stabilizing; and linac3 initially showed some noise, stabilized, and finally became noisy again.…”

Section: Discussionmentioning

confidence: 80%

“…In terms of the GPR, this result indicates that the three linacs are well beam matched. 29,30 In the control chart, linac1 showed much noise in the PSQA data; linac2 initially showed significant noise before stabilizing; and linac3 initially showed some noise, stabilized, and finally became noisy again. Critically, the LCL of linac2 obtained from the three non-normal-based methods was about 2% lower than that of linac1 and 3% lower than that of linac3.…”

Section: Discussionmentioning

confidence: 99%

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Statistical process control and process capability analysis for non‐normal volumetric modulated arc therapy patient‐specific quality assurance processes

Xiao

Bai

et al. 2020

Medical Physics

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Applying statistical process control (SPC) to intensity-modulated radiotherapy (IMRT)/ volumetric modulated arc therapy (VMAT) patient-specific quality assurance (PSQA) program was recommended by the American Association of Physics in Medicine Task Group 218 report, but a comprehensive analysis of PSQA processes with non-normal distributions is lacking. This study investigates SPC and process capability analysis (PCA) methods for non-normal IMRT/VMAT PSQA processes. Methods: 1119 VMAT PSQAs were performed on three beam-matched linear accelerators (linacs), using gamma analysis. The Anderson-Darling statistic was used to test normality. The control charts for each PSQA process were obtained using three non-normal-based methods and compared with the conventional Shewhart method. The ability of each PSQA process to produce an output within the specification limit was measured using the C pk index; in this study, the C pk index was calculated using two transformation methods and compared with that calculated using the conventional method. The performances of the three linacs were assessed using SPC and PCA methods. Results: All three PSQA processes were non-normal (P < 0.005). Compared to the non-normalbased SPC and PCA methods, the false alarm rates of the conventional method for linac1, linac2, and linac3 were 0.83%, 3.77%, and 4.95% respectively; the minimum overestimated C pk values were 0.59, 0.87, and 1.49, respectively. The process capabilities of the three beam-matched linacs were at different levels. Conclusion: For non-normal VMAT PSQA processes, the conventional SPC and PCA methods increase the false alarm rates and overestimate process capabilities. Instead, non-normal-based SPC and PCA methods are more reliable and accurate in non-normal PSQA processes. Statistical process control and PCA are useful tools for assessing the performance of beam-matched linacs.

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Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Statistical process control and process capability analysis for non‐normal volumetric modulated arc therapy patient‐specific quality assurance processes

Xiao

Bai

et al. 2020

Medical Physics

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“…Additionally, parameters such as coincidence of kV‐MV isocenter, and of radiation–mechanical isocenter, were ensured to be ≤1 mm as per TG‐142 tolerances for linacs used for SRS, 26 and average deviation from the radiation isocenter to a ball‐bearing center for all acquired projections was ≤0.75 mm for Winston‐Lutz tests. These criteria, which are also stricter than those suggested by Hrbacek et al, 16 Sarkar et al, 27 and Xu et al 28 were shown to be sufficient for distributive QA and delivery of cases more complex than single‐target SRS, such as stereotactic body radiotherapy (SBRT) to vertebral lesions 24 …”

Section: Methodsmentioning

confidence: 96%

“…The four linacs (referred to as FS1, ST3, TC1, and TC2) were Elekta Versa HD® (Elekta, Crawley, UK), equipped with Agility™ MLC of leaf width 5 mm. Their 6 MV flattening filter free (FFF) beams were matched using criteria recommended by Rijken et al, 24 which add to those outlined by the vendor.…”

Section: Methodsmentioning

confidence: 99%

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Consistency of small‐field dosimetry, on and off axis, in beam‐matched linacs used for stereotactic radiosurgery

Muñoz

Kron

Petasecca

et al. 2021

J Applied Clin Med Phys

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Purpose Stereotactic radiosurgery (SRS) can be delivered with a standard linear accelerator (linac). At institutions having more than one linac, beam matching is common practice. In the literature, there are indications that machine central axis (CAX) matching for broad fields does not guarantee matching of small fields with side ≤2 cm. There is no indication on how matching for broad fields on axis translates to matching small fields off axis. These are of interest to multitarget single‐isocenter (MTSI) SRS planning and the present work addresses that gap in the literature. Methods We used 6 MV flattening filter free (FFF) beams from four Elekta VersaHD® linacs equipped with an Agility™ multileaf collimator (MLC). The linacs were strictly matched for broad fields on CAX. We compared output factors (OPFs) and effective field size, measured concurrently using a novel 2D solid‐state dosimeter “Duo” with a spatial resolution of 0.2 mm, in square and rectangular static fields with sides from 0.5 to 2 cm, either on axis or away from it by 5 to 15 cm. Results Among the four linacs, OPF for fields ≥1 × 1 cm2 ranged 1.3% on CAX, whereas off axis a maximum range of 1.9% was observed at 15 cm. A larger variability in OPF was noted for the 0.5 × 0.5 cm2 field, with a range of 5.9% on CAX, which improved to a maximum of 2.3% moving off axis. Two linacs showed greater consistency with a range of 1.4% on CAX and 2.2% at 15 cm off axis. Between linacs, the effective field size varied by <0.04 cm in most cases, both on and off axis. Tighter matching was observed for linacs with a similar focal spot position. Conclusions Verification of small‐field consistency for matched linacs used for SRS is an important task for dosimetric validation. A significant benefit of concurrent measurement of field size and OPF allowed for a comprehensive assessment using a novel diode array. Our study showed the four linacs, strictly matched for broad fields on CAX, were still matched down to a field size of 1 x 1 cm2 on and off axis.

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Matched linac stereotactic radiotherapy: An assessment of delivery similarity and distributive patient‐specific quality assurance feasibility

Goodall

Dunn

Dunning

et al. 2022

J Applied Clin Med Phys

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Matching multiple linacs to common baseline data allows patients to be treated, and patient‐specific quality assurance (PSQA) to be completed on any linac. Stereotactic body radiotherapy (SBRT) requires higher levels of accuracy and quality assurance than routine radiotherapy. The achieved linac matching must therefore be evaluated before distributive treatment or PSQA models can be implemented safely. This investigation aimed to propose metrics for defining linacs to be matched for SBRT deliveries, assess 12 linacs against these criteria, and determine if a distributive PSQA model could be implemented by reviewing the rates of false PSQA results. Ten SBRT spine plans were delivered by 12 matched Elekta linacs and measured using one of seven SRS MapCHECK devices. For gamma criteria of (3%, 2 mm), 96.9% of equivalent location detectors, showed a range of gamma ≤ 1.0 and 99.9% showed a standard deviation of ≤ 0.5. For criteria of (3%,1 mm) and (2%,1 mm), these ranges decreased to 92.1% and 80.2% while the standard deviations decreased to 99.3% and 95.7%, respectively. The dose differences showed that 43.6%, 82.7%, and 91.4% of detectors had a dose range of ≤ 3.0%, ≤ 5.0%, and ≤ 6.0%, respectively. Standard deviations of dose differences were 1.5%, 2.5%, and 3.0% for 94.1%, 98.3%, and 99.5% of detectors, respectively. For the fleet of linacs, distributive PSQA yielded false results for 0.0%, 17.7%, and 33.0% of plans, equivalent to 1.2%, 3.5%, and 9.4% of detectors when using gamma criteria of (3%,2 mm), (3%,1 mm), or (2%,1 mm), respectively. These linacs could be considered matched for SBRT treatments and implement a distributive PSQA model when gamma analysis was completed with a criterion of (3%, 2 mm). For stricter criterion of (3%,1 mm) or (2%,1 mm), they did not meet the proposed metrics.

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Distributive quality assurance and delivery of stereotactic ablative radiotherapy treatments amongst beam matched linear accelerators: A feasibility study

Cited by 9 publications

References 27 publications

Statistical process control and process capability analysis for non‐normal volumetric modulated arc therapy patient‐specific quality assurance processes

Statistical process control and process capability analysis for non‐normal volumetric modulated arc therapy patient‐specific quality assurance processes

Consistency of small‐field dosimetry, on and off axis, in beam‐matched linacs used for stereotactic radiosurgery

Matched linac stereotactic radiotherapy: An assessment of delivery similarity and distributive patient‐specific quality assurance feasibility

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