MLC parameters from static fields to VMAT plans: an evaluation in a RT-dedicated MC environment (PRIMO)

Paganini, L.; Reggiori, G.; Stravato, A.; Palumbo, V.; Mancosu, P.; Lobefalo, F.; Gaudino, A.; Fogliata, A.; Scorsetti, Marta; Tomatis, S.

doi:10.1186/s13014-019-1421-y

Cited by 12 publications

(17 citation statements)

References 34 publications

(49 reference statements)

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“…a larger FWHM consistent with the reported values (6.7 ± 0.2 mm) in this study. A similar issue with lower resolution was also reported for 2D planar and cylindrical diode arrays [33], while other studies presented discrepancies of 20-40% between Monte Carlo simulations, TPS and measurements [34,35]. When we integrated a sequence of 10 images (resulting in a 200 ms integrated image), the signal-to-noise ratio improved and the difference observed in the valleys were 2-3%, with FHWM = 5.5 ± 0.2 mm.…”

Section: Discussionsupporting

confidence: 77%

Two-dimensional real-time quality assurance dosimetry system using μ-Al2O3:C,Mg radioluminescence films

Nascimento

Verellen

Goossens

et al. 2020

Physics and Imaging in Radiation Oncology

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Background and purpose: There is a continual need for more accurate and effective dosimetric systems for quality assurance (QA) as radiotherapy evolves in complexity. The purpose of this project was to introduce a new system that minimally perturbs the main beam, while assessing its real time 2D dose-rate and field shapes. The system combined reusability, linear dose-rate response, and high spatial and time resolution in a single radiation detection technology that can be applied to surface dose estimation and QA. Materials and methods: We developed a 2D prototype system consisting of a camera, focusing lenses and short pass filter, placed on the head of a linear accelerator, facing an Al 2 O 3 :C,Mg radioluminescent film. To check the appropriateness of multi-leaf collimator, stability/reproducibility QA tests were prepared using the treatment planning system: including the routinely used alternating leaves, chair and pyramid checks. Results: The Al 2 O 3 :C,Mg film did not perturb the dose vs. depth dose curves determined with a point detector (-0.5% difference). Our results showed a dose-rate linear film response (R 2 = 0.999), from 5 to 600 MU/min. Measured output factors agreed with reference data within ~1%, indicating a potential for small field dosimetry. Both chair and pyramid measured profiles were comparable with those obtained with the treatment planning system within 1%. The alternating leaves test showed an average discrepancy in the valleys of 14%. Conclusions: The prototype demonstrated promising results. It obviated the need for corrections regarding the relative position of the camera, confirming accurate dose-rate delivery and detection of radiation fields.

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Section: Discussionsupporting

confidence: 77%

Two-dimensional real-time quality assurance dosimetry system using μ-Al2O3:C,Mg radioluminescence films

Nascimento

Verellen

Goossens

et al. 2020

Physics and Imaging in Radiation Oncology

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“…The geometrical description of the Millennium 120 MLC is done according to the blueprints of the collimator. By following this approach and conducting an accurate transport of radiation through all the collimating and beam-modifying elements of the gantry, it is possible to reproduce the dose distributions conformed by the linac without resorting to non-physical parameters such as the dynamic leaf gap ( 26 , 30 , 31 ). The geometrical description of the MLC is a faithful model of the actual collimator.…”

Section: Methodsmentioning

confidence: 99%

Experimental Validation of an Analytical Program and a Monte Carlo Simulation for the Computation of the Far Out-of-Field Dose in External Beam Photon Therapy Applied to Pediatric Patients

et al. 2022

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BackgroundThe out-of-the-field absorbed dose affects the probability of primary second radiation-induced cancers. This is particularly relevant in the case of pediatric treatments. There are currently no methods employed in the clinical routine for the computation of dose distributions from stray radiation in radiotherapy. To overcome this limitation in the framework of conventional teletherapy with photon beams, two computational tools have been developed—one based on an analytical approach and another depending on a fast Monte Carlo algorithm. The purpose of this work is to evaluate the accuracy of these approaches by comparison with experimental data obtained from anthropomorphic phantom irradiations.Materials and MethodsAn anthropomorphic phantom representing a 5-year-old child (ATOM, CIRS) was irradiated considering a brain tumor using a Varian TrueBeam linac. Two treatments for the same planned target volume (PTV) were considered, namely, intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). In all cases, the irradiation was conducted with a 6-MV energy beam using the flattening filter for a prescribed dose of 3.6 Gy to the PTV. The phantom had natLiF : Mg, Cu, P (MCP-N) thermoluminescent dosimeters (TLDs) in its 180 holes. The uncertainty of the experimental data was around 20%, which was mostly attributed to the MCP-N energy dependence. To calculate the out-of-field dose, an analytical algorithm was implemented to be run from a Varian Eclipse TPS. This algorithm considers that all anatomical structures are filled with water, with the exception of the lungs which are made of air. The fast Monte Carlo code dose planning method was also used for computing the out-of-field dose. It was executed from the dose verification system PRIMO using a phase-space file containing 3x109 histories, reaching an average standard statistical uncertainty of less than 0.2% (coverage factor k = 1 ) on all voxels scoring more than 50% of the maximum dose. The standard statistical uncertainty of out-of-field voxels in the Monte Carlo simulation did not exceed 5%. For the Monte Carlo simulation the actual chemical composition of the materials used in ATOM, as provided by the manufacturer, was employed.ResultsIn the out-of-the-field region, the absorbed dose was on average four orders of magnitude lower than the dose at the PTV. For the two modalities employed, the discrepancy between the central values of the TLDs located in the out-of-the-field region and the corresponding positions in the analytic model were in general less than 40%. The discrepancy in the lung doses was more pronounced for IMRT. The same comparison between the experimental and the Monte Carlo data yielded differences which are, in general, smaller than 20%. It was observed that the VMAT irradiation produces the smallest out-of-the-field dose when compared to IMRT.ConclusionsThe proposed computational methods for the routine calculation of the out-of-the-field dose produce results that are similar, in most cases, with the experimental data. It has been experimentally found that the VMAT irradiation produces the smallest out-of-the-field dose when compared to IMRT for a given PTV.

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“…Some of the previous studies adopted the phase space files (PSF) from MyVarian website to model the linac head [ 25 , 29 , 35 , 39 ]. Some researchers simulated linacs using the default beam parameters given by PRIMO [ 31 , 34 ], while other studies modified the beam parameters based on the default recommendations in PRIMO [ 27 , 28 , 30 , 32 , 33 , 36 ]. As two critical parameters of linac head model, percentage depth dose (PDD) and off-axis ratio (OAR) were evaluated in many studies.…”

Section: Introductionmentioning

confidence: 99%

“…Since the deviation of MLC model in Eclipse™ TPS (transmission factor and DLG) could produce large dosimetric discrepancies, the MLC model should be evaluated comprehensively in beam configuration [40] . Paganini et al [ 34 ] established a series of different MLC patterns to evaluate the MLC model. The difference of DLG values obtained with PRIMO, Acuros, and EBT3 Gafchromic film measurements were within 0.008 cm [ 34 ].…”

Section: Introductionmentioning

confidence: 99%

“…Paganini et al [ 34 ] established a series of different MLC patterns to evaluate the MLC model. The difference of DLG values obtained with PRIMO, Acuros, and EBT3 Gafchromic film measurements were within 0.008 cm [ 34 ]. Although the film has high spatial resolution, it has the issues of regional non-uniformity and positioning error, which may cause the measurement uncertainty [ 41 ].…”

Section: Introductionmentioning

confidence: 99%

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Monte Carlo simulation of linac using PRIMO

Sun

Liang

et al. 2022

Radiat Oncol

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Background Monte Carlo simulation is considered as the most accurate method for dose calculation in radiotherapy. PRIMO is a Monte-Carlo program with a user-friendly graphical interface. Material and method A VitalBeam with 6MV and 6MV flattening filter free (FFF), equipped with the 120 Millennium multileaf collimator was simulated by PRIMO. We adjusted initial energy, energy full width at half maximum (FWHM), focal spot FWHM, and beam divergence to match the measurements. The water tank and ion-chamber were used in the measurement. Percentage depth dose (PDD) and off axis ratio (OAR) were evaluated with gamma passing rates (GPRs) implemented in PRIMO. PDDs were matched at different widths of standard square fields. OARs were matched at five depths. Transmission factor and dose leaf gap (DLG) were simulated. DLG was measured by electronic portal imaging device using a sweeping gap method. Result For the criterion of 2%/2 mm, 1%/2 mm and 1%/1 mm, the GPRs of 6MV PDD were 99.33–100%, 99–100%, and 99–100%, respectively; the GPRs of 6MV FFF PDD were 99.33–100%, 98.99–99.66%, and 97.64–98.99%, respectively; the GPRs of 6MV OAR were 96.4–100%, 90.99–100%, and 85.12–98.62%, respectively; the GPRs of 6MV FFF OAR were 95.15–100%, 89.32–100%, and 87.02–99.74%, respectively. The calculated DLG matched well with the measurement (6MV: 1.36 mm vs. 1.41 mm; 6MV FFF: 1.07 mm vs. 1.03 mm, simulation vs measurement). The transmission factors were similar (6MV: 1.25% vs. 1.32%; 6MV FFF: 0.8% vs. 1.12%, simulation vs measurement). Conclusion The calculated PDD, OAR, DLG and transmission factor were all in good agreement with measurements. PRIMO is an independent (with respect to analytical dose calculation algorithm) and accurate Monte Carlo tool.

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MLC parameters from static fields to VMAT plans: an evaluation in a RT-dedicated MC environment (PRIMO)

Cited by 12 publications

References 34 publications

Two-dimensional real-time quality assurance dosimetry system using μ-Al2O3:C,Mg radioluminescence films

Two-dimensional real-time quality assurance dosimetry system using μ-Al2O3:C,Mg radioluminescence films

Experimental Validation of an Analytical Program and a Monte Carlo Simulation for the Computation of the Far Out-of-Field Dose in External Beam Photon Therapy Applied to Pediatric Patients

Monte Carlo simulation of linac using PRIMO

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