On the need for tuning the dosimetric leaf gap for stereotactic treatment plans in the Eclipse treatment planning system

Vieillevigne, L.; Khamphan, C.; Saez, Jordi; Hernández, Víctor

doi:10.1002/acm2.12656

Cited by 24 publications

(37 citation statements)

References 35 publications

(52 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Such complexities affect the uncertainties in dose calculations due to limitations in the calculation algorithm or in the beam model, e.g. in the MLC configuration [81]. They also influence the sensitivity of the delivered dose to small deviations in machine parameters during treatment delivery (even within their tolerances) and to variations in patient geometry, e.g.…”

Section: Plan Complexitymentioning

confidence: 99%

What is plan quality in radiotherapy? The importance of evaluating dose metrics, complexity, and robustness of treatment plans

Hernández

Hansen

Widesott³

et al. 2020

Radiotherapy and Oncology

Self Cite

101

114

View full text Add to dashboard Cite

Plan evaluation is a key step in the radiotherapy treatment workflow. Central to this step is the assessment of treatment plan quality. Hence, it is important to agree on what we mean by plan quality and to be fully aware of which parameters it depends on. We understand plan quality in radiotherapy as the clinical suitability of the delivered dose distribution that can be realistically expected from a treatment plan. Plan quality is commonly assessed by evaluating the dose distribution calculated by the treatment planning system (TPS). Evaluating the 3D dose distribution is not easy, however; it is hard to fully evaluate its spatial characteristics and we still lack the knowledge for personalising the prediction of the clinical outcome based on individual patient characteristics. This advocates for standardisation and systematic collection of clinical data and outcomes after radiotherapy. Additionally, the calculated dose distribution is not exactly the dose delivered to the patient due to uncertainties in the dose calculation and the treatment delivery, including variations in the patient set-up and anatomy. Consequently, plan quality also depends on the robustness and complexity of the treatment plan. We believe that future work and consensus on the best metrics for quality indices are required. Better tools are needed in TPSs for the evaluation of dose distributions, for the robust evaluation and optimisation of treatment plans, and for controlling and reporting plan complexity. Implementation of such tools and a better understanding of these concepts will facilitate the handling of these characteristics in clinical practice and be helpful to increase the overall quality of treatment plans in radiotherapy.

show abstract

Section: Plan Complexitymentioning

confidence: 99%

What is plan quality in radiotherapy? The importance of evaluating dose metrics, complexity, and robustness of treatment plans

Hernández

Hansen

Widesott³

et al. 2020

Radiotherapy and Oncology

Self Cite

101

114

View full text Add to dashboard Cite

show abstract

“…The optimal DLG was determined over 15 aOSG tests associated with different gaps and TG fractions in order to encompass a maximum of clinical situation and have a beam model adjusted for all treatments. However, selecting specific gaps or TG fractions can modify the optimized DLG as shown by Hernandez et al 19 and such selection could be necessary if a beam model was to be used for a specific treatment like SRS brain for example as was performed by Gardner et al 3 Viellevigne et al 6 for example decided to select aOSG tests for TGi values representative of their clinical plans (0.2–0.5). Several studies adjusted the DLG parameter by optimizing patient quality controls and concluded that the DLG measured with the sweeping gap tests had to be increased between 0.4 and 1.7 mm for a 120 HD MLC 6–9 .…”

Section: Discussionmentioning

confidence: 99%

“…All four parameters are associated with recommendations provided by the manufacturer 4 : measurement conditions for the transmission are provided, values for the effective target spot size are given depending on the algorithm and it is suggested to adjust the DLG based on the sweeping gap method. These recommendations have widely been discussed in the literature 3,5–9 . For example, Gardner et al 3 showed that for intracranial SRS VMAT planning on an Edge accelerator, the 0.5 mm effective target spot size yielded highest passing rates compared to the vendor recommended 1.0 mm effective target spot size.…”

Section: Introductionmentioning

confidence: 99%

Optimizing the effective spot size and the dosimetric leaf gap of the AcurosXB algorithm for VMAT treatment planning

Passal

Barreau

Tiplica

et al. 2021

J Applied Clin Med Phys

View full text Add to dashboard Cite

Purpose The aim of this study is to provide and test a new methodology to adjust the AcurosXB beam model for VMAT treatment plans. Method The effective target spot size of the AcurosXB v15 algorithm was adjusted in order to minimize the difference between calculated and measured penumbras. The dosimetric leaf gap (DLG) was adjusted using the asynchronous oscillating sweeping gap tests defined in the literature and the MLC transmission was measured. The impact of the four parameters on the small field output factors was assessed using a design of experiment methodology. Patient quality controls were performed for the three beam models investigated including two energies and two MLC models. Results Effective target spot sizes differed from the manufacturer recommendations and strongly depended on the MLC model considered. DLG values ranged from 0.7 to 2.3 mm and were found to be larger than the ones based on the sweeping gap tests. All parameters were found to significantly influence the calculated output factors, especially for the 0.5 cm × 0.5 cm field size. Interactions were also identified for fields smaller than 2 cm × 2 cm, suggesting that adjusting the parameters on the small field output factors should be done with caution. All patient quality controls passed the universal action limit of 90%. Conclusion The methodology provided is simple to implement in clinical practice. It was validated for three beam models covering a large variety of treatment types and localizations.

show abstract

“…This is beyond the scope of this study. Studies of tongue and groove index (TGi) and mean leaf gaps [7], might be useful.…”

Section: Discussionmentioning

confidence: 99%

Negative correlation of patient-specific quality assurance failure rates with Monitor Units for Volumetric-Modulated Arc Therapy

Hossain¹,

Papalia²

2020

Int J Radiol Radiat Oncol

View full text Add to dashboard Cite

There were inquiries into the dependencies of Gamma pass rate and some plan parameters like the degree of modulation, dose conformity, plan-complexity etc [6]. But to our knowledge MU has not been reported to correlate with GI. A consensus Abstract Purpose: Failure rates of patient-specifi c Quality Assurance tests in intensity modulated external beam radiation therapy are known to be correlated with both the degree of modulation and Monitor Units (MU). Our goal is to examine if this remains true for Volumetric-Modulated Arc Therapy (VMAT). Methods:We have analyzed the pass rates for 118 VMAT patient-plans for prostate cancer by examining the Gamma Index (GI) of two-dimensional portal dose distributions. Results:We found that the failure rates based on GI is negatively correlated with MU with correlation coeffi cients of -0.28 and -0.35 at 2%-2mm and 3%-3mm levels respectively. Lower MU plans have generally lower pass rates for the VMAT. This contrasts with the traditional results that the failure rates increase with the degree of intensity modulation. This difference is due to the manner of VMAT delivery. Conclusions:Lower MU VMAT plans generally have lower pass rates.

show abstract

On the need for tuning the dosimetric leaf gap for stereotactic treatment plans in the Eclipse treatment planning system

Cited by 24 publications

References 35 publications

What is plan quality in radiotherapy? The importance of evaluating dose metrics, complexity, and robustness of treatment plans

What is plan quality in radiotherapy? The importance of evaluating dose metrics, complexity, and robustness of treatment plans

Optimizing the effective spot size and the dosimetric leaf gap of the AcurosXB algorithm for VMAT treatment planning

Negative correlation of patient-specific quality assurance failure rates with Monitor Units for Volumetric-Modulated Arc Therapy

Contact Info

Product

Resources

About