Assessment of monitor unit limiting strategy using volumetric modulated arc therapy for cancer of hypopharynx

Ahamed, Shabbir; Singh, Navneet; Gudipudi, Deleep Kumar; Mulinti, Suneetha; Talluri, Anil Kumar; Soubhagya, Bhudevi; Sresty, Madhusudhana

doi:10.1016/j.ejmp.2017.01.016

Cited by 7 publications

(9 citation statements)

References 25 publications

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“…Concerning the MU limitation, the results presented here match those already reported in the literature for prostate and hypopharynx, despite the different optimizers. 20,22 No clinically significant differences in the plan quality was measured for any of the optimization strategies. Not even low dose highly complicated shapes which can be largely simplified by the ASC.…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, it is also well known that limiting the delivered MU is an indirect way to limit MLC movement and modulation. 22,26 For this reason, three different strategies to limit MLC modulation were tested and compared: three plans were optimized by the same expert planner for each of the selected patients. For each patient the optimization was started with a set of constraints that was maintained practically unaltered for all the relative plans.…”

Section: B | Vmat Plansmentioning

confidence: 99%

“…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%

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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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Section: Discussionmentioning

confidence: 99%

Section: B | Vmat Plansmentioning

confidence: 99%

mentioning

confidence: 99%

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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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“…Several authors have studied the performance of the MU Objective tool for distinct pathologies. Ahamed et al 20 investigated hypopharynx plans using 50%, 60% and 80% of the baseline plan MU. They reported variations in MU from 8.6% to 34.7% for different combinations of Min MU, Max MU and S parameters.…”

Section: Discussionmentioning

confidence: 99%

“…16 In this context, it is imperative to assess the task of limiting MU for several pathologies. For this purpose, some authors have investigated the use of the MU Objective tool for the prostate, [17][18][19] head and neck, 18,20 gynecological locations, 17 lung SBRT 21 or breast. 22…”

Section: Introductionmentioning

confidence: 99%

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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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 monitor unit limiting strategy using volumetric modulated arc therapy for cancer of hypopharynx

Cited by 7 publications

References 25 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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