Rounded leaf end modeling in Pinnacle VMAT treatment planning for fixed jaw linacs

Young, L. D. G.; Yang, Fei; Cao, Ning; Meyer, Juergen

doi:10.1120/jacmp.v17i6.6343

Cited by 8 publications

(8 citation statements)

References 42 publications

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“…Additionally, each TPS manufacturer recommends different procedures to determine the configuration parameters for their MLC model. Some rely on matching beam profiles for a set of static MLC-defined fields (Williams and Metcalfe 2006, Mzenda et al 2014, Young et al 2016 while others propose a set of test beams for 2D gamma evaluation (Kinsella et al 2016, Snyder et al 2016. However, due to the limitations of the currently available procedures, a final empiric approach is typically needed.…”

Section: Introductionmentioning

confidence: 99%

A novel procedure for determining the optimal MLC configuration parameters in treatment planning systems based on measurements with a Farmer chamber

et al. 2020

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Modelling of the multi-leaf collimator (MLC) in treatment planning systems (TPS) is crucial for the dose calculation accuracy of intensity-modulated radiation therapy plans. However, no standardised methodology for their configuration exists to date. In this study we present a method that separates the effect of each dosimetric characteristic of the MLC, offering comprehensive equations for the determination of the configuration parameters used in the TPS model. The main advantage of the method is that it only requires prior knowledge of the nominal leaf width and is based on doses measured with a Farmer chamber, which is a very well established and robust methodology. Another significant advantage is the required time, since measuring the tests takes only about 30 minutes per energy. Firstly, we provide a theoretical general formalism in terms of the primary fluence constructed from the transmission map obtained from an MLC model for synchronous and asynchronous sweeping beams. Secondly, we apply the formalism to the RayStation TPS as a proof of concept and we derive analytical expressions that allow the determination of the configuration parameters (leaf tip width, tongue-and-groove width, x-position offset and MLC transmission) and describe how they intertwine. Finally, we apply the method to Varian’s Millennium120 and HD120 MLCs in a TrueBeam linear accelerator for different energies and determine the optimal configuration parameters. The proposed procedure is much faster and streamlined than the typical trial-and-error methods and increases the accuracy of dose calculation in clinical plans. Additionally, the procedure can be useful for standardising the MLC configuration process and it exposes the limitations of the implemented MLC model, providing guidance for further improvement of these models in TPSs.

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Section: Introductionmentioning

confidence: 99%

A novel procedure for determining the optimal MLC configuration parameters in treatment planning systems based on measurements with a Farmer chamber

et al. 2020

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“…As radiation delivery technology and TPS modeling has improved, the frequency of plans which fail IMRT QA has decreased [35]. Nevertheless, significant challenges in modeling photon fluence persist due to difficulties in accurately modeling beam penumbra near rounded multi-leaf collimator (MLC) leaf ends and tongue-and-groove edges [36,37]. Moreover, advancements in volumetric modulated arc therapy (VMAT) and high dose rate techniques (i.e.…”

Section: Discussionmentioning

confidence: 99%

Highly efficient and sensitive patient-specific quality assurance for spot-scanned proton therapy

et al. 2019

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The purpose of this work was to develop an end-to-end patient-specific quality assurance (QA) technique for spot-scanned proton therapy that is more sensitive and efficient than traditional approaches. The patient-specific methodology relies on independently verifying the accuracy of the delivered proton fluence and the dose calculation in the heterogeneous patient volume. A Monte Carlo dose calculation engine, which was developed in-house, recalculates a planned dose distribution on the patient CT data set to verify the dose distribution represented by the treatment planning system. The plan is then delivered in a pre-treatment setting and logs of spot position and dose monitors, which are integrated into the treatment nozzle, are recorded. A computational routine compares the delivery log to the DICOM spot map used by the Monte Carlo calculation to ensure that the delivered parameters at the machine match the calculated plan. Measurements of dose planes using independent detector arrays, which historically are the standard approach to patient-specific QA, are not performed for every patient. The nozzle-integrated detectors are rigorously validated using independent detectors in regular QA intervals. The measured data are compared to the expected delivery patterns. The dose monitor reading deviations are reported in a histogram, while the spot position discrepancies are plotted vs. spot number to facilitate independent analysis of both random and systematic deviations. Action thresholds are linked to accuracy of the commissioned delivery system. Even when plan delivery is acceptable, the Monte Carlo second check system has identified dose calculation issues which would not have been illuminated using traditional, phantom-based measurement techniques. The efficiency and sensitivity of our patient-specific QA program has been improved by implementing a procedure which independently verifies patient dose calculation accuracy and plan delivery fidelity. Such an approach to QA requires holistic integration and maintenance of patient-specific and patient-independent QA.

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“…Computed tomography was simulated with a 5-mm-layer thickness enhancement scan. The treatment was planned using Pinnacle [14]. The gross tumor volume (GTV) was defined as primary lesion and regional lymph nodes (The single lymph node with a short diameter of ≥ 1.0 cm or at least three lymph nodes with a diameter of ≥ 0.5 cm).…”

Section: Radiotherapy Protocolmentioning

confidence: 99%

“…The clinical target volume (CTV) was defined as a three-dimensional expansion of the GTV edge by 0.6 cm and combined with anatomical barriers, and the planning target volume (PTV) was defined as a three-dimensional expansion of the CTV edge by 0.5 to 1 cm. The Pinnacle system [14] was used to complete the radiotherapy plan design. The IMRT of the primary tumor employed four to eight coplanar or non-coplanar fields, and VMAT required two to four arcs.…”

Section: Radiotherapy Protocolmentioning

confidence: 99%

“…Studies have shown that improving the primary tumor control rate can prolong survival. In order to improve the primary tumor control rate, this study compared IMRT with Volumetric Modulated Arc Therapy (VMAT), which has more optimized conformation, composite lung V20 and dose monitor unit (MU), and better radiophysical quality assurance [12][13][14]. The clinical value of VMAT technology was evaluated in the treatment of primary tumors of A-NSCLC by propensity score matching.…”

Section: Introductionmentioning

confidence: 99%

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Volumetric-modulated arc therapy as an alternative to intensity-modulated radiotherapy for primary tumors of advanced non–small-cell lung cancer: A multicenter retrospective analysis based on propensity score matching

Liu¹,

Li²,

Wang³

et al. 2022

Trop. J. Pharm Res

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Purpose: To investigate the effect of volumetric-modulated arc therapy (VMAT) versus intensity-modulated radiotherapy (IMRT) for advanced non–small-cell lung cancer (NSCLC). Methods: Cases in which the primary tumors were treated with IMRT or VMAT as initial intervention in stages III and IV NSCLC patients from September 2008 to March 2020 were retrospectively analyzed. Propensity Score Matching (PSM) was used to assess the efficacy and toxicity of the two radiotherapy techniques. Results: A total of 637 patients were included, out of which 483 cases were treated with IMRT, while 154 received VMAT. A total of 308 patients were selected after PSM. Patients who were having acute radiation esophagitis and pneumonia treated with VMAT had a lower percentage than those treated with IMRT (p < 0.05) before PSM. However, there was no significant difference in grades 3 - 4 toxicity (χ2 = 2.77, p = 0.096). There were also no significant differences in the primary endpoints between the two groups after PSM (p > 0.05), while for secondary endpoints, all lung V5, and V20, mean lung dose and heart V30, heart V40, mean heart dose in all patients and stage N2 patients in VMAT after PSM were significantly lower than those of IMRT (p < 0.05). Conclusion: Radiation therapy of A-NSCLC primary tumors using VMAT and IMRT seem to produce similar efficacy. The volume parameters of normal tissues and organs is significantly lower in VMAT, especially in patients with stage N2. Therefore, VMAT may be more beneficial for reducing radiation damage in normal tissues and organs.

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Rounded leaf end modeling in Pinnacle VMAT treatment planning for fixed jaw linacs

Cited by 8 publications

References 42 publications

A novel procedure for determining the optimal MLC configuration parameters in treatment planning systems based on measurements with a Farmer chamber

A novel procedure for determining the optimal MLC configuration parameters in treatment planning systems based on measurements with a Farmer chamber

Highly efficient and sensitive patient-specific quality assurance for spot-scanned proton therapy

Volumetric-modulated arc therapy as an alternative to intensity-modulated radiotherapy for primary tumors of advanced non–small-cell lung cancer: A multicenter retrospective analysis based on propensity score matching

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