Monte Carlo simulation of conical collimators for stereotactic radiosurgery with a 6 MV flattening‐filter‐free photon beam

Hermida-López, M.; Sánchez-Artuñedo, D.; Rodríguez, Miguel; Brualla, L.

doi:10.1002/mp.14837

Cited by 4 publications

(6 citation statements)

References 43 publications

(105 reference statements)

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“…The associated mean relative standard deviation associated is 1.2%. A comparison with Monte Carlo field output factors calculated by Hermida‐Lopez et al 21 . reveals a maximum deviation of 3.2% which is similar to the deviations reported by these authors in their literature review.…”

Section: Resultssupporting

confidence: 86%

Defining field output factors in small fields based on dose area product measurements: A feasibility study

Jurczak,

Rapp,

Bordy

et al. 2024

Medical Physics

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BackgroundDose area product in water (DAPw) in small fields relies on the use of detectors with a sensitive area larger than the irradiation field. This quantity has recently been used to establish primary standards down to 5 mm field size, with an uncertainty smaller than 0.7%. It has the potential to decrease the uncertainty related to field output factors, but is not currently integrated into treatment planning systems.PurposeThis study aimed to explore the feasibility of converting DAPw into a point dose in small fields by determining the volume averaging correction factor. By determining the field output factors, a comparison between the so‐called “DAPw to point dose” approach and the IAEA TRS483 methodology was performed.MethodDiodes, microdiamonds, and a micro ionization chamber were used to measure field output factors following the IAEA TRS483 methodology on two similar linacs equipped with circular cones down to 6 mm diameter. For the “DAPw to point dose” approach, measurements were performed with a dedicated and built‐in‐house 3 cm diameter plane‐parallel ionization chamber calibrated in terms of DAPw in the French Primary Dosimetry Standards Laboratory LNE‐LNHB. Beam profile measurements were performed to generate volume averaging correction factors enabling the conversion of an integral DAPw measurement into a point dose and the determination of the field output factors. Both sets of field output factors were compared.ResultsAccording to the IAEA TRS483 methodology, field output factors were within ±3% for all detectors on both linacs. Large variations were observed for the volume averaging correction factors with a maximum spread between the detectors of 26% for the smallest field size. Consequently, deviations of up to 15% between the “IAEA TRS483” and the “DAPw to point dose” methodologies were found for the field output factor of the smallest field size. This was attributed to the difficulty in accurately determining beam profiles in small fields.ConclusionAlthough primary standards associated with small uncertainties can be established in terms of DAPw in a primary laboratory, the “DAPw to point dose” methodology requires volume averaging correction to derive a field output factor from DAPw measurements. None of the point detectors studied provided satisfactory results, and additional work using other detectors, such as film, is still required to allow the transfer of a DAP primary standard to users in terms of absorbed point dose.

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Section: Resultssupporting

confidence: 86%

Defining field output factors in small fields based on dose area product measurements: A feasibility study

Jurczak,

Rapp,

Bordy

et al. 2024

Medical Physics

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“…The circular small field sizes are mainly used for the treatment of very small tumors such as those seen in the SRS technique to treat brain metastases [ 24 ]. In the treatment of small tumors, the small fields made with cone collimators have more benefits than those formed using multi-leaf collimators due to lower penumbra and transmission [ 24 ]. In addition, the cone collimators have high mechanical stability because these collimators do not have moving parts.…”

Section: Discussionmentioning

confidence: 99%

Dosimetry of small photon fields in the presence of bone heterogeneity using MAGIC polymer gel, Gafchromic film, and Monte Carlo simulation

Parwaie

Geraily

Mehri-Kakavand

et al. 2022

Rep Pract Oncol Radiother.

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“… 40 validated the HD120 MLC for VMAT plans. Other applications of PRIMO included the use of PRIMO as an independent tool for the beam commissioning of a 6 MV Varian Truebeam STx, 41 simulation of out‐of‐field dose, 42 simulation of conical collimators for stereotactic radiosurgery, 43 and the use of PRIMO as an independent dose verification system for radiosurgery HyperArc plans. 44 …”

Section: Methodsmentioning

confidence: 99%

“…Esposito et al 39 validated the Millennium 120 MLC for the simulation of IMRT plans and Paganini et al 40 validated the HD120 MLC for VMAT plans. Other applications of PRIMO included the use of PRIMO as an independent tool for the beam commissioning of a 6 MV Varian Truebeam STx, 41 simulation of out-of -field dose, 42 simulation of conical collimators for stereotactic radiosurgery, 43 and the use of PRIMO as an independent dose verification system for radiosurgery HyperArc plans. 44 Table 1 summarizes the simulations details following the scheme proposed by the AAPM Task Group 268 report RECORDS.…”

Section: Primo Monte Carlo Simulationsmentioning

confidence: 99%

Validation of an in vivo transit dosimetry algorithm using Monte Carlo simulations and ionization chamber measurements

Sánchez‐Artuñedo,

Pié‐Padró,

Hermida‐López

et al. 2023

J Applied Clin Med Phys

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PurposeTransit dosimetry is a safety tool based on the transit images acquired during treatment. Forward‐projection transit dosimetry software, as PerFRACTION, compares the transit images acquired with an expected image calculated from the DICOM plan, the CT, and the structure set. This work aims to validate PerFRACTION expected transit dose using PRIMO Monte Carlo simulations and ionization chamber measurements, and propose a methodology based on MPPG5a report.MethodsThe validation process was divided into three groups of tests according to MPPG5a: basic dose validation, IMRT dose validation, and heterogeneity correction validation. For the basic dose validation, the fields used were the nine fields needed to calibrate PerFRACTION and three jaws‐defined. For the IMRT dose validation, seven sweeping gaps fields, the MLC transmission and 29 IMRT fields from 10 breast treatment plans were measured. For the heterogeneity validation, the transit dose of these fields was studied using three phantoms: 10 , 30 , and a 3 cm cork slab placed between 10 cm of solid water. The PerFRACTION expected doses were compared with PRIMO Monte Carlo simulation results and ionization chamber measurements.ResultsUsing the 10 cm solid water phantom, for the basic validation fields, the root mean square (RMS) of the difference between PerFRACTION and PRIMO simulations was 0.6%. In the IMRT fields, the RMS of the difference was 1.2%. When comparing respect ionization chamber measurements, the RMS of the difference was 1.0% both for the basic and the IMRT validation. The average passing rate with a γ(2%/2 mm, TH = 20%) criterion between PRIMO dose distribution and PerFRACTION expected dose was 96.0% ± 5.8%.ConclusionWe validated PerFRACTION calculated transit dose with PRIMO Monte Carlo and ionization chamber measurements adapting the methodology of the MMPG5a report. The methodology presented can be applied to validate other forward‐projection transit dosimetry software.

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Monte Carlo simulation of conical collimators for stereotactic radiosurgery with a 6 MV flattening‐filter‐free photon beam

Cited by 4 publications

References 43 publications

Defining field output factors in small fields based on dose area product measurements: A feasibility study

Defining field output factors in small fields based on dose area product measurements: A feasibility study

Dosimetry of small photon fields in the presence of bone heterogeneity using MAGIC polymer gel, Gafchromic film, and Monte Carlo simulation

Validation of an in vivo transit dosimetry algorithm using Monte Carlo simulations and ionization chamber measurements

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