Investigating the impact of treatment delivery uncertainties on treatment effectiveness for lung SABR

Blake, S; Arumugam, Sankar; Holloway, Lois; Vinod, Shalini; Ochoa, Cesar E.; Phan, Penny; Hansen, Christian Rønn; Thwaites, David

doi:10.1007/s13246-017-0591-x

Cited by 10 publications

(15 citation statements)

References 16 publications

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“…Sen et al 21 reported that when the magnitude of MLC random error in nasopharyngeal carcinoma reaches 2 mm, it has few effects on target and OARs. Blake et al 22 reported that there was less patient‐to‐patient variation occurred from MLC delivery uncertainties in VMAT than step‐and‐shoot IMRT. The abovementioned studies on MLC position error were all based on the manual planning.…”

Section: Discussionmentioning

confidence: 99%

Effect of MU‐weighted multi‐leaf collimator position error on dose distribution of SBRT radiotherapy in peripheral non‐small cell lung cancer

Feng

Chen

Wang

et al. 2020

J Applied Clin Med Phys

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Purpose: Position accuracy of the multi-leaf collimator (MLC) is essential in stereotactic body radiotherapy (SBRT). This study is aimed to investigate the dosimetric impacts of the MU-weighted MLC positioning uncertainties of SBRT for patients with early stage peripheral non-small cell lung cancer (NSCLC). Methods: Three types of MLC position error were simulated: Type 1, random error; Type 2, system shift, in which both MLC banks shifted to the left or right direction; and Type 3, in which both MLC banks moved with same magnitudes in the opposite directions. Two baseline plans were generated: an automatic plan (AP) and a manually optimized plan (MP). Multi-leaf collimator position errors were introduced to generate simulated plans with the preset MLC leaf position errors, which were then reimported into the Pinnacle system to generate simulated plans, respectively. The dosimetric parameters (CI, nCI, GI, etc.) and gEUD values of PTV and OARs were calculated. Linear regression between MU-weighted/unweighted MLC position error and gEUD was performed to obtain dose sensitivity. Results: The dose sensitivities of the PTVs were −4.93, −38.94, −41.70, −55.55, and 30.33 Gy/mm for random, left shift, right shift, system close, and system open MLC errors, respectively. There were significant differences between the MU-weighted and the unweighted dose sensitivity, which was −38.94 Gy/mm vs −3.42 Gy/mm (left shift), −41.70 Gy/mm vs −3.56 Gy/mm (right shift), −55.55 Gy/mm vs −4.84 Gy/mm (system close), and 30.33 vs 2.64 Gy/mm (system open). For the system open/close MLC errors, as the PTV volume became larger, the dose sensitivity decreased. APs provided smaller dose sensitivity for the system shift and system close MLC errors compared to the conventional MPs. Conclusions: There was significant difference in dose sensitivity between MUweighted and unweighted MLC position error of SBRT radiotherapy in peripheral NSCLC. MU is suggested to be included in the dosimetric evaluation of the MLC misalignments, since it is much closer to clinical radiotherapy.

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Section: Discussionmentioning

confidence: 99%

Effect of MU‐weighted multi‐leaf collimator position error on dose distribution of SBRT radiotherapy in peripheral non‐small cell lung cancer

Feng

Chen

Wang

et al. 2020

J Applied Clin Med Phys

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“…15 baseline lung SBRT VMAT plans (15 patients) and 88 generated plans with different delivery variations across these patients were selected from a previous planning study, 19 based on the clinical significance of the differences. The plans were generated in the Pinnacle (Phillips Healthcare, Fitchburg, WI, USA), v9.8 treatment planning system (TPS), using a 6 MV photon beam from an Elekta Versa HD linear accelerator with a 40 leaf pairs Agility MLC (Elekta, Crawley, UK).…”

Section: Methodsmentioning

confidence: 99%

“…Any of these variations which caused any one or more of a range of DVH metrics to deviate by more than ±2% were defined as clinically significant. The following DVH metrics were considered; PTV (D mean , D max , V95%, V100%), spinal cord (D mean , D0.1 cc), and healthy lung (lung‐PTV) (D mean , V20 Gy) 19 . Only brief details were provided here of the planning study, to indicate the source of the selected plans, but full details can be seen in that reference 19 .…”

Section: Methodsmentioning

confidence: 99%

“…The following DVH metrics were considered; PTV (D mean , D max , V95%, V100%), spinal cord (D mean , D0.1 cc), and healthy lung (lung‐PTV) (D mean , V20 Gy) 19 . Only brief details were provided here of the planning study, to indicate the source of the selected plans, but full details can be seen in that reference 19 . A total of 103 plans with different variations in delivery were selected for this study, where 15 were the baseline plans (no variations, or no errors, NE).…”

Section: Methodsmentioning

confidence: 99%

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Intrinsic detector sensitivity analysis as a tool to characterize ArcCHECK and EPID sensitivity to variations in delivery for lung SBRT VMAT plans

Alharthi

Vial

Holloway

et al. 2021

J Applied Clin Med Phys

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Purpose To investigate intrinsic sensitivity of an electronic portal imaging device (EPID) and the ArcCHECK detector and to use this in assessing their performance in detecting delivery variations for lung SBRT VMAT. The effect of detector spatial resolution and dose matrix interpolation on the gamma pass rate was also considered. Materials and methods Fifteen patients’ lung SBRT VMAT plans were used. Delivery variations (errors) were introduced by modifying collimator angles, multi‐leaf collimator (MLC) field sizes and MLC field shifts by ±5, ±2, and ±1 degrees or mm (investigating 103 plans in total). EPID and ArcCHECK measured signals with introduced variations were compared to measured signals without variations (baseline), using OmniPro‐I'mRT software and gamma criteria of 3%/3 mm, 2%/2 mm, 2%/1 mm, and 1%/1 mm, to test each system's basic performance. The measurement sampling resolution for each was also changed to 1 mm and results compared to those with the default detector system resolution. Results Intrinsic detector sensitivity analysis, that is, comparing measurement to baseline measurement, rather than measurement to plan, demonstrated the intrinsic constraints of each detector and indicated the limiting performance that users might expect. Changes in the gamma pass rates for ArcCHECK, for a given introduced error, were affected only by dose difference (DD %) criteria. However, the EPID showed only slight changes when changing DD%, but greater effects when changing distance‐to‐agreement criteria. This is pertinent for lung SBRT where the minimum dose to the target will drop dramatically with geometric errors. Detector resolution and dose matrix interpolation have an impact on the gamma results for these SBRT plans and can lead to false positives or negatives in error detection if not understood. Conclusion The intrinsic sensitivity approach may help in the selection of more meaningful gamma criteria and the choice of optimal QA device for site‐specific dose verification.

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“…The aim of this work was to investigate any variations in the ability of three dosimetry systems (ArcCHECK (3D), EPID (2D) and MatriXX Evolution (2D)) to detect systematic delivery errors in step-and-shoot IMRT. This work is part of a larger investigation by the local research group of the impact of uncertainties on advanced radiotherapy treatment techniques [18,[37][38][39][40][41][42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the ability of three commercially available dosimeters to detect systematic delivery errors in Step-and-Shoot IMRT plans

Gray

Bawazeer

Arumugam

et al. 2021

Rep Pract Oncol Radiother.

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Investigating the impact of treatment delivery uncertainties on treatment effectiveness for lung SABR

Cited by 10 publications

References 16 publications

Effect of MU‐weighted multi‐leaf collimator position error on dose distribution of SBRT radiotherapy in peripheral non‐small cell lung cancer

Effect of MU‐weighted multi‐leaf collimator position error on dose distribution of SBRT radiotherapy in peripheral non‐small cell lung cancer

Intrinsic detector sensitivity analysis as a tool to characterize ArcCHECK and EPID sensitivity to variations in delivery for lung SBRT VMAT plans

Evaluation of the ability of three commercially available dosimeters to detect systematic delivery errors in Step-and-Shoot IMRT plans

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