A Monte Carlo simulation framework for electron beam dose calculations using Varian phase space files for TrueBeam Linacs

Rodrigues, Anna; Sawkey, D; Yin, Fang‐Fang; Wu, Qiuwen

doi:10.1118/1.4916896

Cited by 25 publications

(39 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For version‐2, the phase‐space files are stored in a

6.5 \times 6.5 {cm}^{2}

two‐dimensional plane located 26.7 cm from the source. Recent studies by Belosi et al (17) and Rodrigues et al (18) validated these version‐2 phase‐space files with measurement data for photon and electron beams, respectively. In this study, we report a comparison of the Monte Carlo simulations with measurements by small field detectors of output factors for Varian SRS system with conical collimators for energy of 6 MV flattening filter‐free (6 MV) and 10 MV flattening filter‐free (10 MV) on the Varian TrueBeam accelerator.…”

Section: Introductionmentioning

confidence: 87%

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter‐free stereotactic radiosurgery system

Cheng

Ning

Arora

et al. 2016

J Applied Clin Med Phys

View full text Add to dashboard Cite

The dose measurements of the small field sizes, such as conical collimators used in stereotactic radiosurgery (SRS), are a significant challenge due to many factors including source occlusion, detector size limitation, and lack of lateral electronic equilibrium. One useful tool in dealing with the small field effect is Monte Carlo (MC) simulation. In this study, we report a comparison of Monte Carlo simulations and measurements of output factors for the Varian SRS system with conical collimators for energies of 6 MV flattening filter‐free (6 MV) and 10 MV flattening filter‐free (10 MV) on the TrueBeam accelerator. Monte Carlo simulations of Varian's SRS system for 6 MV and 10 MV photon energies with cones sizes of 17.5 mm, 15.0 mm, 12.5 mm, 10.0 mm, 7.5 mm, 5.0 mm, and 4.0 mm were performed using EGSnrc (release V4 2.4.0) codes. Varian's version‐2 phase‐space files for 6 MV and 10 MV of TrueBeam accelerator were utilized in the Monte Carlo simulations. Two small diode detectors Edge (Sun Nuclear) and Small Field Detector (SFD) (IBA Dosimetry) were applied to measure the output factors. Significant errors may result if detector correction factors are not applied to small field dosimetric measurements. Although it lacked the machine‐specific kQitalicclin,Qitalicmsrfitalicclin,fitalicmsr correction factors for diode detectors in this study, correction factors were applied utilizing published studies conducted under similar conditions. For cone diameters greater than or equal to 12.5 mm, the differences between output factors for the Edge detector, SFD detector, and MC simulations are within 3.0% for both energies. For cone diameters below 12.5 mm, output factors differences exhibit greater variations.PACS number(s): 87.55.k, 87.55.Qr

show abstract

“…For version‐2, the phase‐space files are stored in a

6.5 \times 6.5 {cm}^{2}

Section: Introductionmentioning

confidence: 87%

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter‐free stereotactic radiosurgery system

Cheng

Ning

Arora

et al. 2016

J Applied Clin Med Phys

View full text Add to dashboard Cite

show abstract

“…The experimental validation study focuses on electron beams, which tests the limits of the code performance due to higher overall sensitivity to beam quality, depth, and angle than for photon beams . Our clinical machine is a Varian TrueBeam, whose BEAMnrc model data and parameters were provided by the vendor (Varian Medical Systems, Inc., Palo Alto, CA) . Eight electron beams were simulated with nominal energies of 6–20 and 22 MeV at 10 × 10‐cm

^{2}

and 20 × 20‐cm

^{2}

field size, respectively, and 100‐cm SSD …”

Section: Methodsmentioning

confidence: 99%

“…The modified code is tested with monoenergetic parallel electrons on a thin water slab. Detector configurations are examined for broad [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] MeV electron beams from a BEAMnrc TrueBeam model, with a focus on h AE dh ¼ 90 AE 90 (4p detection), 90 AE 5 , and 42 AE 5 (h ¼ 42 is the CE angle of relativistic electrons in water). We perform a relative experimental validation at 90 with electron beams, using a simple detector design with spherical optics and geometrical optics approximation of the sensitive volume, which spans the water tank.…”

mentioning

confidence: 99%

Cherenkov emission‐based external radiotherapy dosimetry: I. Formalism and feasibility

et al. 2019

View full text Add to dashboard Cite

Purpose Cherenkov emission (CE)‐based external beam dosimetry is envisioned to involve the detection of CE directly in water with placement of a high‐resolution detector out of the field, avoiding perturbations encountered with traditional dosimeters. In this work, we lay out the groundwork for its implementation in the clinic and motivate CE‐based dosimeter design efforts. To that end, we examine a formalism for broad‐beam in‐water CE‐based dosimetry of external radiotherapy beams, design and test a Monte Carlo (MC) simulation framework for the calculation of CE‐to‐dose conversion factors used by the formalism, and demonstrate the experimental feasibility of this method. Methods The formalism is conceptually analogous to ionization‐based dosimetry and employs CE‐to‐dose conversion factors, knormalCθ0.166667em±0.166667emnormalδθ, including only and all CE generated within polar angles θ ± δθ on beam axis. The EGSnrc user code SPRRZnrc is modified to calculate knormalCθ0.166667em±0.166667emnormalδθ, as well as CE spectral and angular distributions. The modified code is tested with monoenergetic parallel electrons on a thin water slab. Detector configurations are examined for broad 6–22 MeV electron beams from a BEAMnrc TrueBeam model, with a focus on θ±δθ=90∘±90∘ (4π detection), 90∘±5∘, and 42∘±5∘ (θ=42∘ is the CE angle of relativistic electrons in water). We perform a relative experimental validation at 90∘ with electron beams, using a simple detector design with spherical optics and geometrical optics approximation of the sensitive volume, which spans the water tank. Due to transient charged particle equilibrium, broad photon beams are generally less sensitive to beam quality, depth, and angle. Results For 0.1–50 MeV electrons on a thin water slab, the code outputs CE photon spectral density per unit mass (calculated from dose and knormalCθ0.166667em±0.166667emnormalδθ) and angle in agreement with theory within ±0.03% and ±0.01∘, respectively, corresponding to the output precision. The 42∘ configuration was found impractical due to detection considerations. Detection at 90∘±δθ for small δθ exhibited beam quality dependence of the same order as well as strong superficial depth dependence. A 4π configuration ameliorates these effects. A more practical approach may employ a large numerical aperture. In comparing with literature, we find that these effects are less pronounced for broad photon beams in water, as expected. Measured relative knormalC90∘0.166667em±0.166667emnormalδθ at small δθ were within 1% of simulated factors (relative to their local average) for percent‐depth CE (PDC) >50%. At other depths, deviations were in accordance with signal‐to‐noise, known detector limitations, and approximations. It was found that the CE spectrum is beam quality and depth invariant, while for electron beams the CE angular distribution is strongly dependent on beam quality and depth. However, the uncertainty of CE and PDC measurement at 90∘±δθ detection for small δθ due to ±0.1∘ deviations around δθ was shown to be ≤1% and ...

show abstract

“…A clinically representative library of electron beams was simulated with the BEAMnrc code of the particle transport simulation package EGSnrc . BEAMnrc models include a Varian Clinac 2100C/D at Karolinska University Hospital in Sweden (downloaded from the IAEA phase‐space database), Varian Clinac 21EX at the Montreal General Hospital, Varian TrueBeam data provided by the vendor (Varian Medical Systems, Inc., Palo Alto, CA), and Elekta Precise at the National Research Council of Canada . Twenty electron beams were simulated with nominal energies of 4–20 and 22 MeV at 10 × 10‐cm

^{2}

and 20 × 20‐cm

^{2}

field size, respectively, and at SSD of 100 cm .…”

Section: Methodsmentioning

confidence: 99%

Cherenkov emission‐based external radiotherapy dosimetry: II. Electron beam quality specification and uncertainties

et al. 2019

View full text Add to dashboard Cite

Purpose Cherenkov emission (CE) is ubiquitous in external radiotherapy. It is also unique in that it carries the promise of 3D, micrometer‐resolution, perturbation‐free, in‐water dosimetry with a beam quality‐independent detector response calibration. Our aim is to bring CE‐based dosimetry into the clinic and we motivate this here with electron beams. We Monte Carlo (MC) calculate and characterize broad‐beam CE‐to‐dose conversion factors in water for a clinically representative library of electron beam qualities, address beam quality specification and reference depth selection, and develop a preliminary uncertainty budget based on our MC results and relative experimental work of a companion study (Paper I). Methods Broad electron beam CE‐to‐dose conversion factors knormalCθ0.166667em±0.166667emnormalδθ include CE generated at polar angles θ ± δθ on beam axis in water. With modifications to the EGSnrc code SPRRZnrc, knormalCθ0.166667em±0.166667emnormalδθ factors are calculated for a total of 20 electron beam qualities from four BEAMnrc models (Varian Clinac 2100C/D, Clinac 21EX, TrueBeam, and Elekta Precise). We examine beam quality, depth, and detection angle dependence for θ±δθ=90∘±90∘ (4π detection), 90∘±5∘, 45∘±45∘, and 90∘±45∘. As discussed in Paper I, 4π detection offers the strongest CE‐dose correlation and θ=90∘ with small δθ is most practical. The two additional configurations are considered as a compromise between these two extremes. We address beam quality specification and reference depth selection in terms of the electron beam quality specifier R50, obtained from the depth of 50% CE C50, and derive a best‐case uncertainty budget for the CE‐based dosimetry formalism proposed in Paper I at each detection configuration. Results The knormalCθ0.166667em±0.166667emnormalδθ factor was demonstrated to capture variations in the beam spectrum, angle, photon contamination, and electron fluence below the CE threshold (∼260 keV in the visible) in accordance with theory. The root‐mean‐square deviation and maximum deviation of a second‐order polynomial fit of simulated R50 values in terms of C50 were 0.05 and 0.11 mm at 4π and 0.20 and 0.33 mm at 90∘±5∘ detection, respectively. The fit performance on experimental data in Paper I was in agreement with these values within experimental uncertainties (±1.5 mm, 95% CI). A two‐term power function fit of knormalCθ0.166667em±0.166667emnormalδθ in terms of R50 at a reference depth dnormalref=aR50+b resulted in total dref‐dependent dose uncertainty contribution estimate of 0.8% and 1.1% and preliminary best‐case estimate of the combined standard dose uncertainty of 1.1% and 1.3% at 4π and 90∘±5∘ detection, respectively. The results and corresponding uncertainties with the two intermediate apertures were generally of the same order as the 4π case. In addition, a theoretically consistent downstream shift of the percent‐depth CE (PDC) by the difference between R50 and C50 improved the depth dependence of the 4π conversion by an order of magnitude (±2.8%). Therefore, a large aper...

show abstract

A Monte Carlo simulation framework for electron beam dose calculations using Varian phase space files for TrueBeam Linacs

Cited by 25 publications

References 65 publications

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter‐free stereotactic radiosurgery system

Output factor comparison of Monte Carlo and measurement for Varian TrueBeam 6 MV and 10 MV flattening filter‐free stereotactic radiosurgery system

Cherenkov emission‐based external radiotherapy dosimetry: I. Formalism and feasibility

Cherenkov emission‐based external radiotherapy dosimetry: II. Electron beam quality specification and uncertainties

Contact Info

Product

Resources

About