Monte Carlo Values Research Articles

Experimental comparison of cylindrical and plane parallel ionization chambers for reference dosimetry in continuous and pulsed scanned proton beams

Objective. In this experimental work we compared the determination of absorbed dose to water using four ionization chambers (ICs), a PTW-34045 Advanced Markus, a PTW-34001 Roos, an IBA-PPC05 and a PTW-30012 Farmer, irradiated under the same conditions in one continuous- and in two pulsed-scanned proton beams. Approach. The ICs were positioned at 2 cm depth in a water phantom in four square-field single-energy scanned-proton beams with nominal energies between 80 and 220 MeV and in the middle of 10 × 10 × 10 cm3 dose cubes centered at 10 cm or 12.5 cm depth in water. The water-equivalent thickness (WET) of the entrance window and the effective point of measurement was considered when positioning the plane parallel (PP) ICs and the cylindrical ICs, respectively. To reduce uncertainties, all ICs were calibrated at the same primary standards laboratory. We used the beam quality (k Q ) correction factors for the ICs under investigation from IAEA TRS-398, the newly calculated Monte Carlo (MC) values and the anticipated IAEA TRS-398 updated recommendations. Main results. Dose differences among the four ICs ranged between 1.5% and 3.7% using both the TRS-398 and the newly recommended k Q values. The spread among the chambers is reduced with the newly k Q values. The largest differences were observed between the rest of the ICs and the IBA-PPC05 IC, obtaining lower dose with the IBA-PPC05. Significance. We provide experimental data comparing different types of chambers in different proton beam qualities. The observed dose differences between the ICs appear to be related to inconsistencies in the determination of the k Q values. For PP ICs, MC studies account for the physical thickness of the entrance window rather than the WET. The additional energy loss that the wall material invokes is not negligible for the IBA-PPC05 and might partially explain the low k Q values determined for this IC. To resolve this inconsistency and to benchmark MC values, k Q values measured using calorimetry are needed.

Statistical-mechanical liquid theories reproduce anomalous thermodynamic properties of explicit two-dimensional water models.

We have developed an analytical theory for a simple model of liquid water. We apply Wertheim's thermodynamic perturbation theory (TPT) and integral equation theory (IET) for associative liquids to the rose model, which is among the simplest models of water. The particles interact through rose potentials for orientation dependent pairwise interactions. Modifying both the shape and range of a three-petal rose function, we construct an efficient and dynamical mimic of the two-dimensional (2D) Mercedes-Benz (MB) water model. The particles in 2D MB are 2D Lennard-Jones disks with three hydrogen bonding arms arranged symmetrically, resembling the Mercedes-Benz logo. Both models qualitatively predict both the anomalous properties of pure water and the anomalous solvation thermodynamics of nonpolar molecules. The IET is based on the orientationally averaged version of the Ornstein-Zernike equation. This is one of the main approximations in the present work. IET correctly predicts the pair correlation functions at high temperatures. Both TPT and IET are in semi-quantitative agreement with the Monte Carlo values of the molar volume, isothermal compressibility, thermal expansion coefficient, and heat capacity. A major advantage of these theories is that they require orders of magnitude less computer time than the Monte Carlo simulations.

Analytical evaluation of geometry correction factor and effectiveness parameter for BSS irradiated by a voluminous neutron source

The deviation in reading due to inverse square law is an important issue in the calibration of neutron detection systems. The geometry correction factor of a neutron-measuring device is a unique property of this type of device, and may depend on the dimensions, shape of the source and the detector, the distance between them and the neutron source spectrum. This study deals with the geometric analysis of angular distribution for landing neutrons from a non-point source on a Bonner sphere spectrometer (BSS) and solid angles subtended by detectors from distributed source. Using mathematical relations, an analytical function was introduced to calculate the geometry correction factor and the effectiveness parameter. By comparing the analytical and Monte Carlo values of geometry factors, it was found that the effectiveness parameter (δ′) for BSS depends on the source radius, the BSS radius and the energy of the source (energy itself depends on the distance). The effectiveness parameter in this case was δ′≡δ′[RD,RS,E(l′)].

Accuracy of the doses computed by the Eclipse treatment planning system near and inside metal elements

Metal artefacts degrade clinical image quality which decreases the confidence of using computed tomography (CT) for the delineation of key structures for treatment planning and leads to dose errors in affected areas. In this work, we investigated accuracy of doses computed by the Eclipse treatment planning system near and inside metallic elements for two different computation algorithms. An impact of CT metal artefact reduction methods on the resulting calculated doses has also been assessed. A water phantom including Gafchromic film and metal inserts was irradiated (max dose 5 Gy) using a 6 MV photon beam. Three materials were tested: titanium, alloy 600, and tungsten. The phantom CT images were obtained with the pseudo-monoenergetic reconstruction (PMR) and the iterative metal artefact reduction (iMAR). Image sets were used for dose calculation using an Eclipse treatment planning station (TPS). Monte Carlo (MC) simulations were used to predict the true dose distribution in the phantom allowing for comparison with doses measured by film and calculated by TPS. Measured and simulated percentage depth doses (PDDs) were not statistically different (p > 0.618). Regional differences were observed at edges of metallic objects (max 8% difference). However, PDDs simulated with and without film were statistically different (p < 0.002). PDDs calculated by the Acuros XB algorithm based on the dose-to-medium approach best matched the MC reference regardless of the CT reconstruction methods and inserts used (p > 0.078). PDDs obtained using other algorithms significantly differ from the MC values (p < 0.011). The Acuros XB algorithm with a dose-to-medium approach provides reliable dose calculation in all metal regions when using the Varian system. The inability of the AAA algorithm to model backscatter dose significantly limits its clinical application in the presence of metal. No significant impact on the dose calculation was found for a range of metal artefact reduction strategies.

Monte Carlo simulations and phantom validation of low-dose radiotherapy to the lungs using an interventional radiology C-arm fluoroscope.

To use MC simulations and phantom measurements to investigate the dosimetry of a kilovoltage x-ray beam from an IR fluoroscope to deliver low-dose (0.3-1.0Gy) radiotherapy to the lungs. PENELOPE was used to model a 125kV, 5.94mm Al HVL x-ray beam produced by a fluoroscope. The model was validated through depth-dose, in-plane/cross-plane profiles and absorbed dose at 2.5-, 5.1-, 10.2- and 15.2-cm depths against the measured beam in an acrylic phantom. CT images of an anthropomorphic phantom thorax/lungs were used to simulate 0.5Gy dose distributions for PA, AP/PA, 3-field and 4-field treatments. DVHs were generated to assess the dose to the lungs and nearby organs. Gafchromic film was used to measure doses in the phantom exposed to PA and 4-field treatments, and compared to the MC simulations. Depth-dose and profile results were within 3.2% and 7.8% of the MC data uncertainty, respectively, while dose gamma analysis ranged from 0.7 to 1.0. Mean dose to the lungs were 1.1-, 0.8-, 0.9-, and 0.8- Gy for the PA, AP/PA, 3-field, and 4-field after isodose normalization to cover∼95% of each lung volume. Skin dose toxicity was highest for the PA and lowest for the 4-field, and both arrangements successfully delivered the treatment on the phantom. However, the dose distribution for the PA was highly non-uniform and produced skin doses up to 4Gy. The dose distribution for the 4-field produced a uniform 0.6Gy dose throughout the lungs, with a maximum dose of 0.73Gy. The average percent difference between experimental and Monte Carlo values were -0.1% (range -3% to +4%) for the PA treatment and 0.3% (range -10.3% to +15.2%) for the 4-field treatment. A 125kV x-ray beam from an IR fluoroscope delivered through two or more fields can deliver an effective low-dose radiotherapy treatment to the lungs. The 4-field arrangement not only provides an effective treatment, but also significant dose sparing to healthy organs, including skin, compared to the PA treatment. Use of fluoroscopy appears to be a viable alternative to megavoltage radiation therapy equipment for delivering low-dose radiotherapy to the lungs.

Investigation of field output factors using IAEA-AAPM TRS-483 code of practice recommendations and Monte Carlo simulation for 6 MV photon beams

Abstract Introduction: This study aims to experimentally determine field output factors using the methodologies suggested by the IAEA-AAPM TRS-483 for small field dosimetry and compare with the calculation from Monte Carlo (MC) simulation. Methods: The IBA-CC01, Sun Nuclear EDGE and IBA-SFD detectors were employed to determine the uncorrected and the corrected field output factors for 6 MV photon beams. Measurements were performed at 100 cm source to axis distance, 10 cm depth in water, and the field sizes ranged from 1 × 1 to 10 × 10 cm2. The use of field output correction factors proposed by the TRS-483 was utilised to determine field output factors. The measured field output factors were compared to that calculated using the egs_chamber user code. Results: The decrease in the percentage standard deviation of the measured three detectors was observed after applying the field output correction factors. Measured field output factors using CC01 and EDGE detectors agreed with MC values within 3% for field sizes down to 1 × 1 cm2, except the SFD detector. Conclusions: The corrected field output factors agree with the calculation from MC, except the SFD detector. CC01 and EDGE are suitable for determining field output factors, while the SFD may need more implementation of the intermediate field method.

Experimental validation of Fastcat kV and MV cone beam CT (CBCT) simulator.

To experimentally validate the Fastcat cone beam computed tomography (CBCT) simulator against kV and MV CBCT images acquired with a Varian Truebeamlinac. kV and MV CBCT images of a Catphan 504 phantom were acquired using a 100 kVp beam with the on-board imager (OBI) and a 6 MV treatment beam with the electronic portal imaging device (EPID), respectively. The kV Fastcat simulation was performed using detailed models of the x-ray source, bowtie filter, a high resolution voxelized virtual Catphan phantom, anti-scatter grid, and the CsI scintillating detector. Likewise, an MV Fastcat CBCT was simulated with detailed models for the beam energy spectrum, flattening filter, a high-resolution voxelized virtual Catphan phantom, and the gadolinium oxysulfide (GOS) scintillating detector. Experimental and simulated CBCT images of the phantom were compared with respect to HU values, contrast to noise ratio (CNR), and dose linearity. Detector modulation transfer function (MTF) for the two detectors were also experimentally validated. Fastcat's dose calculations were compared to Monte Carlo (MC) dose calculations performed with Topas. For the kV and MV simulations, respectively: Contrast agreed within 14 and 9 HUs and detector MTF agreed within 4.2% and 2.5%. Likewise, CNR had a root mean squared error (RMSE) of 2.6% and 1.4%. Dose agreed within 2.4% and 1.6% of MC values. The kV and MV CBCT images took 71 and 72 s to simulate in Fastcat with 887 and 493 projections, respectively. We present a multienergy experimental validation of a fast and accurate CBCT simulator against a commercial linac. The simulator is open source and all models found in this work can be downloaded from https://github.com/jerichooconnell/fastcat.git.

Calculation of Jaws-only IMRT (JO-IMRT) dose distributions based on the AAPM TG-119 test cases using Monte Carlo simulation and Prowess Panther treatment planning system

The aim of this study is to calculate the JO-IMRT dose distributions based on the AAPM TG-119 using Monte Carlo (MC) simulation and Prowess Panther treatment planning system (TPS) (Panther, Prowess Inc., Chico, CA). JO-IMRT dose distributions of AAPM TG-119 were calculated by the TPS and were recalculated by MC simulation. The DVHs and 3D gamma index using global methods implemented in the PTW-VeriSoft with 3%/3 mm were used for evaluation. JO-IMRT dose distributions calculated by TPS and MC were matched the TG-119 goals. The gamma index passing rates with 3%/3 mm were 98.7% for multi-target, 96.0% for mock prostate, 95.4% for mock head-and-neck, and 96.6% for C-shape. The dose in the planning target volumes (PTV) for TPS was larger than that for the MC. The relative dose differences in D99 between TPS and MC for multi-target are 1.52%, 0.17% and 1.40%, for the center, superior and inferior, respectively. The differences in D95 are 0.16% for C-shape; and 0.06% for mock prostate. Mock head-and-neck difference is 0.40% in D99. In contrast, the organ curve for TPS tended to be smaller than MC values. JO-IMRT dose distributions for the AAPM TG-119 calculated by the TPS agreed well with the MC.

Driven by fundamentals or exploded by emotions: Detecting bubbles in oil prices

Crude oil is the world's largest energy commodity, and its domestic and international supplies affect the short-term and long-term economic balances of many countries. It also has a strategic and political role in making important contributions related to the production of reserve assets. Given the increasing and often destabilizing role of the futures market on spot oil prices, this study tries to address the question of whether the oil market behaves efficiently and rationally, or do speculators lead it? Using monthly data from 2000M01–2020M12 for crude oil prices and a range of advanced econometric tools such as breakpoint unit root tests, probability-based bubble detection mechanism, right-tailed Supremum Augmented Dickey-Fuller (SADF), and Generalized SADF (GSADF) approaches based on Monte Carlo and bootstrap critical values, we detect multiple bubbles exhibited by the oil market in different periods. The exact identification of these bubbles is essential to analyze the underlying fundamentals that may have caused these bubbles. It can also help policymakers and regulators to assess the exposure oil prices have towards several economic and fundamental factors. Finally, detecting bubbles and exploring the factors causing them, may help improve the oil market's overall efficiency and thus improve investors' decision-making.

Thermodynamic perturbation theory for rotational degrees of freedom. Application to the Mercedes–Benz water model

We developed a fast theory for studying how the rotational temperature (and rotational degrees of freedom) affects the properties of a simple model of liquid water. Wertheim's Thermodynamic perturbation theory (TPT) for associative liquids was applied to the Mercedes-Benz (MB) model. 2D MB model is one of the simplest models of water. The MB particles are modelled as Lennard-Jones disks with three hydrogen bonding arms arranged symmetrically as in the MB logo. We previously applied TPT to this model. We found that the physical properties were well reproduced by the theory. Here, we propose an modified version of the thermodynamic perturbation theory in which it is possible to treat rotational degrees of freedom by using different averaging then used before. By holding translational or rotational temperature constant and varying the other one, we investigate their effect on the properties of the simple water model and how well TPT reproduces computer simulation results. The new results are in good agreement with the Monte Carlo values of the pressure and energy. We also investigated how rotational temperature affects thermodynamic properties of the critical point. A major advantage of these theories is that they require orders of magnitude less computer time than the Monte Carlo simulations.

Integral equation study of the effects of rotational degrees of freedom on properties of the Mercedes–Benz water model

We developed an analytical theory for studying of rotational degrees of freedom of a simple model of liquid water. Wertheim's integral equation theory (IET) for associative liquids was applied to the Mercedes-Benz (MB) model, which is among the simplest models of water. The MB water molecules are modeled as 2-dimensional Lennard-Jones disks with three hydrogen bonding arms arranged symmetrically, resembling the MB logo. IET is based on the orientationally averaged version of the Ornstein-Zernike equation. In varying of rotational degrees of freedom we use different averaging then used before. By holding one of the temperatures constant and varying the other one, we investigate the effect of faster motion in the corresponding degrees of freedom on the properties of the simple water model and how well IET reproduce computer simulation results. The pair correlation function of the model water at high rotational or translation temperatures is correctly predicted. IET results are in good agreement with the Monte Carlo values of the pressure, energy, heat capacity. A major advantage of these theories is that they require orders of magnitude less computer time than the Monte Carlo simulations.

Water calorimetry in MR-linac: Direct measurement of absorbed dose and determination of chamber .

To use a portable 4°C cooled MR-compatible water calorimeter to measure absorbed dose in a magnetic resonance-guided radiation therapy (MRgRT) system. Furthermore, to use the calorimetric dose results and direct cross-calibration to experimentally measure the combined beam quality and magnetic field correction factor ( ) of a clinically used reference-class ionization chamber placed under the same radiation field. An Elekta Unity MR-linac (7MV FFF, B=1.5T) was used in this study. Measurements were taken using the in-house designed and built water calorimeter. Following preparation and cooling of the system, the MR-compatible calorimeter was positioned using a combination of MR and EPID imaging and the dose to water was measured by monitoring the radiation-induced temperature change. Immediately after the calorimetric measurements, an A1SL ionization chamber was placed inside the calorimeter for direct cross-calibration. The results allowed for a direct and absolute experimental measurement of for this chamber and comparison against existing Monte Carlo values. The calorimeter was successfully positioned using imaging in under an hour. The 1-hour setup time is from the time the calorimeter leaves storage to the first calorimetric measurement. Absorbed dose was successfully measured with a relative combined standard uncertainty of 0.71 % (k=1). Through a cross-calibration, the for an Exradin A1SL ionization chamber, set up perpendicular to the incident photon beam and opposite to the direction of the Lorentz force, was directly determined in water in absolute terms to be 0.977±0.010. The currently published results, obtained via Monte Carlo calculations, agree with experimental measurements in this work within combined uncertainties. A novel design of an MR-compatible water calorimeter was successfully used to measure absorbed dose in an MR-linac and determine an experimental value of for a clinically used ionization chamber.

Evaluation of dosimetric parameters of small fields of 6 MV flattening filter free photon beam measured using various detectors against Monte Carlo simulation

AbstractPurpose:This study aims to evaluate dosimetric parameters like percentage depth dose, dosimetric field size, depth of maximum dose surface dose, penumbra and output factors measured using IBA CC01 pinpoint chamber, IBA stereotactic field diode (SFD), PTW microDiamond against Monte Carlo (MC) simulation for 6 MV flattening filter-free small fields.Materials and Methods:The linear accelerator used in the study was a Varian TrueBeam® STx. All field sizes were defined by jaws. The required shift to effective point of measurement was given for CC01, SFD and microdiamond for depth dose measurements. The output factor of a given field size was taken as the ratio of meter readings normalised to 10 × 10 cm2 reference field size without applying any correction to account for changes in detector response. MC simulation was performed using PRIMO (PENELOPE-based program). The phase space files for MC simulation were adopted from the MyVarian Website.Results and Discussion:Variations were seen between the detectors and MC, especially for fields smaller than 2 × 2 cm2 where the lateral charge particle equilibrium was not satisfied. Diamond detector was seen as most suitable for all measurements above 1 × 1 cm2. SFD was seen very close to MC results except for under-response in output factor measurements. CC01 was observed to be suitable for field sizes above 2 × 2 cm2. Volume averaging effect for penumbra measurements in CC01 was observed. No detector was found suitable for surface dose measurement as surface ionisation was different from surface dose due to the effect of perturbation of fluence. Some discrepancies in measurements and MC values were observed which may suggest effects of source occlusion, shift in focal point or mismatch between real accelerator geometry and simulation geometry.Conclusion:For output factor measurement, TRS483 suggested correction factor needs to be applied to account for the difference in detector response. CC01 can be used for field sizes above 2 × 2 cm2 and microdiamond detector is suitable for above 1 × 1 cm2. Below these field sizes, perturbation corrections and volume averaging corrections need to be applied.

Parameterising microdosimetric distributions of mono-energetic proton beams for fast estimates of yD and y*

We present analytical models of the dose-mean lineal energy () and the saturation-corrected dose-mean lineal energy () for fast and accurate radiobiological calculations in proton therapy. These models are based on the modelling of microdosimetric distributions f(εs) obtained from Monte Carlo (MC) simulations of the energy deposited per interaction event, εs, for mono-energetic proton beams in water with an energy range from 0.6 MeV to 95 MeV. We also performed calculations of Relative Biological Effectiveness (RBE) based on both, MC and the analytical models of y*, using the Microdosimetric Kinetic Model (MKM) for Human Salivary Gland (HSG) cells. Both RBE calculations were then compared to demonstrate the consistency of the agreement between the microdosimetric distributions themselves as well as of any other distributions based on them. Maximum, mininum and average relative differences between MC and analytical values were reported as well as paired Student t-tests to display the goodness of our tool to model y* and RBE distributions. For values the maximum, minimum and average relative discrepancies were 0.99%, −1.67% and −0.06% respectively. In the case of values these differences were 0.98%, −1.55% and −0.07%, while for RBE values they were 0.37%, −0.75% and −0.04% respectively. The Student t-tests showed that no statistically significant differences were observed between MC and analytical values. Our analytical tool has provided instantaneous calculations of the magnitudes of interest, in contrast with the computation times required with MC simulations. We have developed an algorithm which provides fast calculations of and y*, maintaining a clinically relevant accuracy level.

Dependence of the multipole moments, static polarizabilities, and static hyperpolarizabilities of the hydrogen molecule on the H-H separation in the ground singlet state.

In this work, we provide values for the quadrupole moment Θ, the hexadecapole moment Φ, the dipole polarizability α, the quadrupole polarizability C, the dipole-octopole polarizability E, the second dipole hyperpolarizability γ, and the dipole-dipole-quadrupole hyperpolarizability B for the hydrogen molecule in the ground singlet state, evaluated by finite-field configuration interaction singles and doubles (CISD) and coupled-cluster singles and doubles (CCSD) methods for 26 different H-H separations r, ranging from 0.567 a.u. to 10.0 a.u. Results obtained with various large correlation-consistent basis sets are compared at the vibrationally averaged bond length r0 in the ground state. Results over the full range of r values are presented at the CISD/d-aug-cc-pV6Z level for all of the independent components of the property tensors. In general, our values agree well with previous ab initio results of high accuracy for the ranges of H-H distances that have been treated in common. To our knowledge, for H2 in the ground state, our results are the first to be reported in the literature for Φ for r > 7.0 a.u., γ and B for r > 6.0 a.u., and C and E for any H-H separation outside a narrow range around the potential minimum. Quantum Monte Carlo values of Θ have been given previously for H-H distances out to 10.0 a.u., but the statistical error is relatively large for r > 7.0 a.u. At the larger r values in this work, αxx and αzz show the expected functional forms, to leading order in r-1. As r increases further, Θ and Φ vanish, while α, γ, and the components of B converge to twice the isolated-atom values. Components of C and E diverge as r increases. Vibrationally averaged values of the properties are reported for all of the bound states (vibrational quantum numbers υ = 0-14) with rotational quantum numbers J = 0-3.

14 Determination of small MLC-fields output correction factors for four commercial detectors used in clinical dosimetry using GATE/Geant4 Monte Carlo simulations

Introduction The aim of this work is to calculate detector-specific output correction factors using Monte Carlo (MC) simulation for small nominal multi-leaf collimator (MLC) photon beams, according to the recent TRS-483 protocol [1] , [2] . is determined for four commercially available PTW active detectors (T31016 and T31022 PinPoint 3D ion chambers, T60019 microDiamond and T60017 Ediode) used for small photon fields measurements. This study considers the 6WFF, 6FFF and 10FFF nominal beams of a Varian Truebeam STx linear accelerator. Methods The precise geometries and material compositions of the detectors are modeled in detail in the Geant4 applications for emission tomography (GATE) code using blueprints and data provided by PTW-Freiburg. The accelerator head was formerly modeled in GATE for nominal small MLC photon fields ranging from 0.5 x 0.5 cm2 to 3 x 3 cm2, providing phase-space files as input to this study. Absorbed dose scored over the active volumes of the detectors in water are compared to absorbed dose scored in a small reference water volume in the simulations. obtained by MC simulations are compared to those obtained by EBT3 Gafchromic films and the T60003 PTW diamond detector measurements, considered as benchmarks. Combination of simulated and experimental output ratios are also used to report for. Obtained MC values are then compared to data provided in the TRS-483. Results For the 6WFF, the absorbed dose scored in the detectors (T31016, T31022 and T60017) are in good agreement ( 2%) with the absorbed dose calculated in a small volume of water for the 1 x 1 cm2and 2 x 2 cm2 MLC openings. The resulting uncertainties for the simulations are estimated to be within 0.5% at all field sizes. A good agreement was also found with the EBT3 and diamond measurements, with a relative difference of 1% for field sizes greater than 0.5 x 0.5 cm2. In the worst case, for the 6WFF beam and 0.5 x 0.5 cm2 field size, the Ediode response differs from that of EBT3 by around 4%. The output ratio for field sizes smaller than 2 x 2 cm2 are overestimated by the T60017 diode and underestimated by the T31016 and T31022 ion chambers. This work shows an overall good agreement, within 1.5% relative difference with stated values in the TRS-483. Conclusions Simulations in GATE for the determination of demonstrate comparable results with values obtained with EBT3 film and T60003 diamond detector measurements. Results for the 6FFF and 10FFF and for the T60019 are ongoing.

Monte Carlo dose verification of VMAT treatment plans using Elekta Agility 160-leaf MLC

In this study, we verified volumetric modulated arc therapy (VMAT) plans in an Elekta Synergy system with an integrated Agility 160-leaf multileaf collimator (MLC) by comparing them with Monte Carlo (MC)-calculated dose distributions using the AAPM TG-119 structure sets. The head configuration of the linear accelerator with the integrated MLC was simulated with the EGSnrc/BEAMnrc code. Firstly, the dosimetric properties of the MLC were evaluated with the MC technique and film measurements. Next, VMAT plans were created with the Pinnacle3 treatment planning system (TPS) for four regions in the AAPM TG-119 structures. They were then verified by comparing them with MC-calculated dose distributions using dose volume histograms (DVHs) and three-dimensional (3D) gamma analysis. The MC simulations for the Agility MLC dosimetric properties were in acceptable agreement with measurements. TPS-VMAT plans using TG-119 structure sets agreed with MC dose distributions within 2% in the comparison of D95 in planning target volumes (PTVs) evaluated from DVHs. In contrast, higher dose regions such as D20, D10, and D5 in PTVs for TPS tended to be smaller than MC values. This tendency was particularly noticeable for mock head and neck with complicated structures. In 3D gamma analysis, the passing rates with 3%/3mm criteria in PTVs were ≥99%, except for mock head and neck (89.5%). All passing rates for organs at risk (OARs) were in acceptable agreement of >96%. It is useful to verify dose distributions of PTVs and OARs in TPS-VMAT plans by using MC dose calculations and 3D gamma analysis.

Stopping power and dose calculations with analytical and Monte Carlo methods for protons and prompt gamma range verification

In this study, we have performed the calculations stopping power, depth dose, and range verification for proton beams using dielectric and Bethe–Bloch theories and FLUKA, Geant4 and MCNPX Monte Carlo codes. In the framework, as analytical studies, Drude model was applied for dielectric theory and effective charge approach with Roothaan–Hartree–Fock charge densities was used in Bethe theory. In the simulations different setup parameters were selected to evaluate the performance of three distinct Monte Carlo codes. The lung and breast tissues were investigated are considered to be related to the most common types of cancer throughout the world. The results were compared with each other and the available data in literature. In addition, the obtained results were verified with prompt gamma range data. In both stopping power values and depth-dose distributions, it was found that the Monte Carlo values give better results compared with the analytical ones while the results that agree best with ICRU data in terms of stopping power are those of the effective charge approach between the analytical methods and of the FLUKA code among the MC packages. In the depth dose distributions of the examined tissues, although the Bragg curves for Monte Carlo almost overlap, the analytical ones show significant deviations that become more pronounce with increasing energy. Verifications with the results of prompt gamma photons were attempted for 100–200 MeV protons which are regarded important for proton therapy. The analytical results are within 2%–5% and the Monte Carlo values are within 0%–2% as compared with those of the prompt gammas.

Theoretical and experimental determination of scaling factors in electron dosimetry for 3D-printed polylactic acid.

Plastic phantoms are commonly used in daily routine for dosimetric tasks in radiation therapy. Although water is the reference medium according to the dosimetric protocols, measurements with nonwater phantoms are easier to be performed. To succeed absorbed dose determination, certain scaling factors have to be applied to the acquired measurements. Taking into account the increased availability of three-dimensional (3D) printing, we attempted to obtain scaling factors for polylactic acid (PLA), a commonly used thermoplastic material for 3D printing. Measurements were performed with a custom-made phantom from PLA material, which was designed and constructed using 3D printing technology. Depth and fluence scaling factors were obtained within the range of 6 to 20 MeV. Moreover, Monte Carlo simulations were performed to verify the measured results. Experimental and Monte Carlo (MC) values showed a good agreement, especially in lower energies. Mean value of depth scaling factor (cpl ) over the whole range of energies was 0.946, while mean fluence scaling factor (hpl ) was found to be 1.050. For energies below 10 MeV, the corresponding mean values for cpl and hpl were 0.946 and 1.054, respectively. PLA phantoms could be constructed and used for electron beam nonreference measurements, reproducing even more complex geometries, from simple quality assurance devices to geometrically complicated anthropomorphic phantoms.

Validation Study of the Reactor Physics Lattice Transport Code DRAGON5 Based on DRAGLIB Libraries by TRX and BAPL Critical Experiments of Light Water Reactors for Neutronic Analysis of TRIGA MARK-II Research Reactor

The objective of this analysis is to present the validation study of the latest release of the reactor physics lattice transport code DRAGON5 by TRX and BAPL critical experiments of light water reactors for neutrons calculations of Moroccan 2 MW TRIGA MARK-II research reactor. This study is accomplished through the analysis of integral parameters of five light water reactor critical experiments TRX-1, TRX-2, BAPL-UO2-1, BAPL-UO2-2, and BAPL-UO2-3 based on the open-source Draglibs nuclear data libraries ENDF/B-VII.1 and JEFF-3.1.2. These experiments are being considered as standard benchmarks lattices for testing and validating the reactor physics lattice transport code DRAGON5 as well as nuclear data libraries. The integral parameters—keffρ28, δ25, δ28 and C* —of the said lattices are calculated using the reactor physics lattice transport code DRAGON5 at a room temperature and compared to measured values as well as the Monte Carlo values based on the Chinese evaluated nuclear data library CENDL-3.0. It was found that the results calculated show good agreement with the experiment and the MCNP results. Therefore, this study reflects the validation, the adequacy, and the accuracy of the reactor physics lattice transport code DRAGON5 based on the open-source Draglibs nuclear data libraries ENDF/B-VII.0.1 and JEFF 3.1.2 evaluation with SHEM-295 group-structure and can also be important to execute neutronic analysis of thermal reactor such as the Moroccan 2 MW TRIGA MARK-II research reactor at CENM, achieved initial criticality on May 2, 2007.