Monte Carlo systems used for treatment planning and dose verification

BackgroundPRIMO is a graphical environment based on PENELOPE Monte Carlo (MC) simulation of radiotherapy beams able to compute dose distribution in patients, from plans with different techniques. The dosimetric characteristics of an HD-120 MLC (Varian), simulated using PRIMO, were here compared with measurements, and also with Acuros calculations (in the Eclipse treatment planning system, Varian).Materials and methodsA 10 MV FFF beam from a Varian EDGE linac equipped with the HD-120 MLC was used for this work. Initially, the linac head was simulated inside PRIMO, and validated against measurements in a water phantom. Then, a series of different MLC patterns were established to assess the MLC dosimetric characteristics. Those tests included: i) static fields: output factors from MLC shaped fields (2 × 2 to 10 × 10 cm2), alternate open and closed leaf pattern, MLC transmitted dose; ii) dynamic fields: dosimetric leaf gap (DLG) evaluated with sweeping gaps, tongue and groove (TG) effect assessed with profiles across alternate open and closed leaves moving across the field. The doses in the different tests were simulated in PRIMO and then compared with EBT3 film measurements in solid water phantom, as well as with Acuros calculations. Finally, MC in PRIMO and Acuros were compared in some clinical cases, summarizing the clinical complexity in view of a possible use of PRIMO as an independent dose calculation check.ResultsStatic output factor MLC tests showed an agreement between MC calculated and measured OF of 0.5%. The dynamic tests presented DLG values of 0.033 ± 0.003 cm and 0.032 ± 0.006 cm for MC and measurements, respectively. Regarding the TG tests, a general agreement between the dose distributions of 1–2% was achieved, except for the extreme patterns (very small gaps/field sizes and high TG effect) were the agreement was about 4–5%. The analysis of the clinical cases, the Gamma agreement between MC in PRIMO and Acuros dose calculation in Eclipse was of 99.5 ± 0.2% for 3%/2 mm criteria of dose difference/distance to agreement.ConclusionsMC simulations in the PRIMO environment were in agreement with measurements for the HD-120 MLC in a 10 MV FFF beam from a Varian EDGE linac. This result allowed to consistently compare clinical cases, showing the possible use of PRIMO as an independent dose calculation check tool.

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“…For this work, PRIMO [14] was used from version 0.1.3.137 to 1.0.0.1756-beta following the software development updates.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2019

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“…For example, version 3 beta of the ADAC Pinnacle treatment planning system was based on a C++ port of DPM. ADAC was subsequently acquired by Philips Medical Systems in 2000 but the Pinnacle version based on DPM was never released [4]. The code was also integrated into the University of Michigan’s in-house treatment planning system (UMPlan) [15].…”

Section: Methodsmentioning

confidence: 99%

“…PENELOPE implements an accurate physics model of the interaction cross sections and the radiation transport process but exhibits a relatively low computational performance compared with fast Monte Carlo codes specifically designed for radiotherapy problems [4]. One such code is the Dose Planning Method (DPM v1.1) [5] which simulates absorbed dose distributions deposited by electron-photon showers in external beam radiotherapy treatments.…”

Section: Introductionmentioning

confidence: 99%

DPM as a radiation transport engine for PRIMO

et al. 2018

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BackgroundPRIMO is a dose verification system based on the general-purpose Monte Carlo radiation transport code penelope, which implements an accurate physics model of the interaction cross sections and the radiation transport process but with low computational efficiency as compared with fast Monte Carlo codes. One of these fast Monte Carlo codes is the Dose Planning Method (DPM). The purpose of this work is to describe the adaptation of DPM as an alternative PRIMO computation engine, to validate its performance against penelope and to validate it for some specific cases.MethodsDPM was parallelized and modified to perform radiation transport in quadric geometries, which are used to describe linacs, thus allowing the simulation of dynamic treatments. To benchmark the new code versus penelope, both in terms of accuracy of results and simulation time, several tests were performed, namely, irradiation of a multi-layer phantom, irradiation of a water phantom using a collimating pattern defined by the multileaf collimator (MLC), and four clinical cases. The gamma index, with passing criteria of 1 mm/1%, was used to compare the absorbed dose distributions. Clinical cases were compared using a 3-D gamma analysis.ResultsThe percentage of voxels passing the gamma criteria always exceeded 99% for the phantom cases, with the exception of the transport through air, for which dose differences between DPM and penelope were as large as 24%. The corresponding percentage for the clinical cases was larger than 99%. The speedup factor between DPM and penelope ranged from 2.5 ×, for the simulation of the radiation transport through a MLC and the subsequent dose estimation in a water phantom, up to 11.8 × for a lung treatment. A further increase of the computational speed, up to 25 ×, can be obtained in the clinical cases when a voxel size of (2.5 mm)3 is used.ConclusionsDPM has been incorporated as an efficient and accurate Monte Carlo engine for dose estimation in PRIMO. It allows the concatenated simulation of the patient-dependent part of the linac and the patient geometry in static and dynamic treatments. The discrepancy observed between DPM and penelope, which is due to an artifact of the cross section interpolation algorithm for low energy electrons in air, does not affect the results in other materials.

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“…However, these detectors attenuate the beam and change its energy spectrum. Modeling a transmission device in the treatment planning system is complex whilst modeling with Monte Carlo is difficult, with long computing times [8]. The current devices on the market, ScandiDos Delta4 discover [9], a solid-state detector, and the Dolphin [10], an ionization chamber system, have beam attenuations of 1.71% ± 0.02% and ∼ 10% at 6 MV, respectively.…”

Section: Introductionmentioning

confidence: 99%

A Novel Approach to Contamination Suppression in Transmission Detectors for Radiotherapy

Beck

Velthuis

Page

et al. 2020

IEEE Trans. Radiat. Plasma Med. Sci.

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The current trend in X-ray radiotherapy is to treat cancers that are in difficult locations in the body using beams with a complex intensity profile. Intensity-modulated radiotherapy (IMRT) is a treatment which improves the dose distribution to the tumor whilst reducing the dose to healthy tissue. Such treatments administer a larger dose per treatment fraction and hence require more complex methods to verify the accuracy of the treatment delivery. Measuring beam intensity fluctuations is difficult as the beam is heavily distorted after leaving the patient and transmission detectors will attenuate the beam and change the energy spectrum of the beam. Monolithic active pixel sensors (MAPSs) are ideal solid-state detectors to measure the 2-D beam profile of a radiotherapy beam upstream of the patient. MAPS sensors can be made very thin (∼30 µm) with still very good signal-to-noise performance. This means that the beam would pass through the sensor virtually undisturbed (<1% attenuation). Pixel pitches of between 2 µm to 100 µm are commercially available. Large area devices (∼15×15 cm 2) have been produced. MAPS can be made radiation hard enough to be fully functional after a large number of fractions. All this makes MAPS a very realistic transmission detector candidate for beam monitoring upstream of the patient. A remaining challenge for thin, upstream sensors is that the detectors are sensitive to the signal of both therapeutic photons and electron contamination. Here, a method is presented to distinguish between the signal due to electrons and photons and thus provide real-time dosimetric information in very thin sensors that does not require Monte Carlo simulation of each linear accelerator treatment head. Index Terms-Clinical/preclinical evaluation/application studies, dosimetry for radiation-based medical applications, monolithic active pixel sensors (MAPSs), Monte Carlo simulations for imaging and therapy, radiation detectors for medical applications, radiotherapy verification.

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Monte Carlo systems used for treatment planning and dose verification

Cited by 44 publications

References 96 publications

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

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

DPM as a radiation transport engine for PRIMO

A Novel Approach to Contamination Suppression in Transmission Detectors for Radiotherapy

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