Assessment of the Monitor Unit Objective tool for VMAT in the Eclipse treatment planning system

Sánchez-Artuñedo, D.; Hermida-López, M.

doi:10.1016/j.rpor.2018.02.001

Cited by 7 publications

(6 citation statements)

References 8 publications

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“…In this respect, many strategies have been proposed to limit plan complexity, primarily reducing the delivered MU or directly simplifying the shape of the MLC during optimization. 9,11,[20][21][22][23][24] To limit VMAT complexity, a similar strategy has recently been introduced in v.15.5 of the Eclipse TPS (Varian Medical Systems, Palo Alto, CA). The aperture shape controller (ASC) is a new component in the leaf sequencer for VMAT in the photon optimizer (PO) algorithm that tends to increase the size and decrease the complexity of the MLC aperture.…”

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confidence: 99%

Limiting treatment plan complexity by applying a novel commercial tool

Scaggion

Fusella

Agnello

et al. 2020

J Applied Clin Med Phys

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Purpose: A recently introduced commercial tool is tested to assess whether it is able to reduce the complexity of a treatment plan and improve deliverability without compromising overall quality. Methods: Ten prostate and ten oropharynx plans of previously treated patients were reoptimized using the aperture shape controller (ASC) tool recently introduced in Eclipse TPS (Varian Medical Systems, Palo Alto, CA). The performance of ASC was assessed in terms of the overall plan quality using a plan quality metric, the reduction in plan complexity through the analysis of 14 of the most common plan complexity metrics, and the change in plan deliverability through 3D dosimetric measurements. Similarly, plans optimized limiting the total number of delivered monitor units was assessed and compared. The two strategies were also combined to assess their potential combination. Results: The plans optimized by exploiting the ASC generally show a reduced number of total Monitor Units, a more constant gantry rotation and a MLC modulation characterized by larger and less complicated shapes with leaves traveling shorter overall lengths. Conclusions: This first experience suggests that the ASC is an effective tool to reduce the unnecessary complexity of a plan. This turns into an increased plan deliverability with no loss of plan quality. K E Y W O R D S aperture shape controller, complexity metrics, MLC, plan complexity, plan quality metric, treatment planning 1 | INTRODUCTION Volumetric modulated arc therapy (VMAT) is nowadays the standard treatment technique in high-quality radiation therapy delivered with clinical LINACs. The rapid dose fall-off outside target boundaries grants highly conformed dose distributions and near-optimal sparing of surrounding critical structures. Volumetric modulated arc therapy has generally replaced intensity-modulated radiation therapy (IMRT) because of the shorter treatment time obtained through the simultaneous variation of gantry speed, dose rate and MLC position. 1,2 Moreover, VMAT tends to use fewer monitor units (MU) per fraction than IMRT and thus reduces the burden of second malignancies. 3-5

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confidence: 99%

Limiting treatment plan complexity by applying a novel commercial tool

Scaggion

Fusella

Agnello

et al. 2020

J Applied Clin Med Phys

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“…However, this is in accordance with other published results. 18 Regarding PTVs coverage, our results indicate that there is no significant variation in D 2% nor in D 98% , which means that a MU reduction may be achieved maintaining PTV coverage unaltered. For PTV45 Opt and PTV50 and considering only the cases with a higher MU reduction (30% and 60% of MU ref )…”

Section: Discussionmentioning

confidence: 65%

“…The average value of the Max MU parameter obtained in these two cases (maximum MU reduction) is 388 ± 49 (30% of MU ref ) and 389 ± 51 (60% of MU ref ) MU, which concurs with results obtained by other authors. 18 The 90% case offers a smaller reduction (3.4% average value), although this difference is not statistically significant (p > 0.5). A quite curious behavior appears when Max MU parameter is set to values which are higher than MU ref .…”

Section: Discussionmentioning

confidence: 79%

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Performance of the eclipse monitor unit objective tool utilizing volumetric modulated arc therapy for rectal cancer

Prado¹,

Gaitán²,

Leonor³

et al. 2019

Reports of Practical Oncology & Radiotherapy

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Aim: To assess the performance of the monitor unit (MU) Objective tool in Eclipse treatment planning system (TPS) utilizing volumetric modulated arc therapy (VMAT) for rectal cancer. Background: Eclipse VMAT planning module includes a tool to control the number of MUs delivered: the MU Objective tool. This tool could be utilized to reduce the total number of MUs in rectal cancer treatments. Materials and methods: 20 rectal cancer patients were retrospectively studied using VMAT and the MU Objective tool. The baseline plan for each patient was selected as the one with no usage of the MU Objective tool. The number of MUs of this plan was set to be the reference number of MUs (MU ref). Five plans were re-optimized for each patient only varying the Max MU parameter. The selected values were 30%, 60%, 90%, 120% and 150% of MU ref for each patient. Differences with respect to the baseline plan were evaluated regarding MU number and parameters for PTVs coverage evaluation, PTVs homogeneity and OARs doses assessment. A two-tailed, paired-samples t-test was used to quantify these differences. Results: Average relative differences in MU number obtained was 10% for Max MU values of 30% and 60% of MU ref , respectively (p < 0.03). PTVs coverage and homogeneity were not compromised and discrepancies obtained with respect to baseline plans were not significant. Furthermore, maximum OARs doses deviations were also not significant. Conclusions: A 10% reduction in the MU number could be obtained without an alteration of PTV coverage and OARs doses for rectal cancer.

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“…17 The MU objective has been available in the Eclipse treatment planning system for RapidArc optimization since version 8.5. Previous work established use of the MU objective results in reduction in the total MUs, and therefore in the beam-on time, while preserving adequate dosimetry by using the MU objective in prostate, 18,19 head and neck, 18,20 gynecological, 18 and lung SABR. 21 However, the impact on the aperture complexity by using the MU objective was not addressed in these previous studies.…”

Section: Introductionmentioning

confidence: 99%

On the reduction of aperture complexity in kidney SABR

Gaudreault

Offer

Kron

et al. 2021

J Applied Clin Med Phys

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Background: Stereotactic ablative body radiotherapy (SABR) of primary kidney cancers is confounded by motion. There is a risk of interplay effect if the dose is delivered using volumetric modulated arc therapy (VMAT) and flattening filter-free (FFF) dose rates due to target and linac motion. This study aims to provide an efficient way to generate plans with minimal aperture complexity. Methods: In this retrospective study, 62 patients who received kidney SABR were reviewed. For each patient, two plans were created using internal target volume based motion management, on the average intensity projection of a four-dimensional CT. In the first plan, optimization was performed using a knowledge-based planning model based on delivered clinical plans in our institution. In the second plan, the optimization was repeated, with a maximum monitor unit (MU) objective applied in the optimization. Dose-volume, conformity, and complexity metric (with the field edge metric and the modulation complexity score) were compared between the two plans. Results are shown in terms of median (first quartilethird quartile). Results: Similar dosimetry was obtained with and without the utilization of an objective on the MU. However, complexity was reduced by using the objective on the MUs (modulation complexity score = 0.55 (0.50-0.61) / 0.33 (0.29-0.36), Pvalue < 10 −10 , with/without the MU objective). Reduction of complexity was driven by a larger aperture area (area aperture variability = 0.68 (0.64-0.73) / 0.42 (0.37-0.45), P-value < 10 −10 , with/without the MU objective). Using the objective on the MUs resulted in a more spherical dose distribution (sphericity 50% isodose = 0.73 (0.69-0.75) / 0.64 (0.60-0.68), P-value < 10 −8 , with/without the MU objective) reducing dose to organs at risk given respiratory motion. Conclusions: Aperture complexity is reduced in kidney SABR by using an objective on the MU delivery with VMAT and FFF dose rate.

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Assessment of the Monitor Unit Objective tool for VMAT in the Eclipse treatment planning system

Abstract: For the three studied clinical sites, establishing = 400 led to the optimum MU reduction, maintaining the original dose distribution and dosimetric parameters practically unaltered.

Cited by 7 publications

References 8 publications

Limiting treatment plan complexity by applying a novel commercial tool

Limiting treatment plan complexity by applying a novel commercial tool

Performance of the eclipse monitor unit objective tool utilizing volumetric modulated arc therapy for rectal cancer

On the reduction of aperture complexity in kidney SABR

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