Evaluation of the eclipse electron Monte Carlo dose calculation for small fields

Xu, Zhigang; Walsh, Sarah; Telivala, Tejas; Meek, Allen G.; Yang, Guozhen

doi:10.1120/jacmp.v10i3.2834

Cited by 35 publications

(29 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While these implementations of Monte Carlo are available for clinical treatment planning, previous publications have shown that they may be inaccurate for small field dose calculations. 14,15 Further, it is well know that the Monte Carlo method is advantageous in calculating accurate dose distributions at air-tissue interfaces when compared to pencil beam algorithms, 16 and an accurate Monte Carlo model of the True-Beam will thus be beneficial to all electron therapy techniques. Moreover, the current implementation in the Eclipse TPS does not allow planning of dynamic electron radiation therapy techniques including multiple mechanical axes motions such as gantry and couch.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

View full text Add to dashboard Cite

Purpose: To evaluate the latent variance (LV) of Varian TrueBeam photon phase-space files (PSF) for open 10x10 cm 2 and small stereotactic fields and estimate the number of phase spaces required to be summed up in order to maintain sub-percent latent variance in Monte Carlo (MC) dose calculations. Method: BEAMnrc/DOSXYZnrc software was used to transport particles from Varian phase-space files (PSFA) through the secondary collimators. Transported particles were scored into another phase-space located under the jaws (PSFB), or transported further through the cone collimators and scored straight below, forming PSFC. Phase-space files (PFSB) were scored for 6MV-FFF, 6MV, 10MV-FFF, 10MV and 15MV beams with 10x10 cm 2 field size, and PSFC were scored for 6MV beam under circular cones of 0.13, 0.25, 0.35, 1.0, 1.2, 1.5 and 4 cm diameter. Both PSFB and PSFC were transported into a water phantom with particle recycling number ranging from 10 to 1000. For 10x10 cm 2 fields 0.5x0.5x0.5cm 3 voxels were used to score the dose, whereas the dose was scored in 0.1x0.1x0.5cm 3 voxels for beams collimated with small cones. In addition, for small 0.25 cm diameter cone-collimated 6MV beam, phantom voxel size varied as 0.02x0.02x0.5cm 3 , 0.05x0.05x0.5cm 3 and 0.1x0.1x0.5cm 3. Dose variances were scored in all cases and latent variance evaluated as per Sempau et al. Results: For the 10x10 cm 2 fields calculated LVs were greatest at the phantom surface and decreased with depth until reached a plateau at 5 cm depth. LVs were found to be 0.54%, 0.96%, 0.35%, 0.69% and 0.57% for the 6MV-FFF, 6MV, 10MV-FFF, 10MV and 15MV energies, respectively at the depth of 10cm. For the 6 MV phase-space collimated with cones of 0.13, 0.25, 0.35, 1.0 cm diameter, the LVs calculated at 1.5 cm depth were 75.6%, 25.4%, 17.6% and 8.0% respectively. Calculated latent variances for the 0.25 cm cone-collimated 6MV beam were 61.2%, 40.7%, 22.5% in 0.02x0.02x0.5cm 3 , 0.05x0.05x0.5cm 3 and 0.1x0.1x0.5cm 3 voxels respectively. Conclusions: In order to achieve sub-percent latent variance in open 10x10 cm 2 field MC simulations single PSF can be used, whereas for small SRS fields more PSFs would have to be summed.

show abstract

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Known limitations for eMC calculation of electron beams with energies ≤6E include 16 differences in up to 5% between measured and calculated outputs for 6E electron beams and differences in up to 14% for circular inserts with a diameter of 3 cm at an extended SSD of 115 cm. 17 Approximations of the electron path in the direction distribution and dose deposition determine whether large sphere sizes for the electron transport are used in eMC. 18 However, several studies demonstrate that eMC can predict dose distributions for high-energy electron beams with high accuracy.…”

Section: Discussionmentioning

confidence: 99%

Convolution‐based modified Clarkson integration (CMCI) for electron cutout factor calculation

Chang

Lin

et al. 2018

J Applied Clin Med Phys

View full text Add to dashboard Cite

Electron therapy is widely used to treat shallow tumors because of its characteristic sharp dose fall‐off beyond a certain range. A customized cutout is typically applied to block radiation to normal tissues. Determining the final monitor unit (MU) for electron treatment requires an output factor for the cutout, which is usually generated by measurement, especially for highly irregular cutouts. However, manual measurement requires a lengthy quality assurance process with possible errors. This work presents an accurate and efficient cutout output factor prediction model, convolution‐based modified Clarkson integration (CMCI), to replace patient‐specific output factor measurement. Like the Clarkson method, we decompose the field into basic sectors. Unlike the Clarkson integration method, we use annular sectors for output factor estimation. This decomposition method allows calculation via convolution. A 2D distribution of fluence is generated, and the output factor at any given point can be obtained. We applied our method to 10 irregularly shaped cutouts for breast patients for 6E, 9E, and 15E beams and compared the results with measurements and the electron Monte Carlo (eMC) calculation using the Eclipse planning system. While both the CMCI and eMC methods showed good agreement with chamber measurements and film measurements in relative distributions at the nominal source to surface distance (SSD) of 100 cm, eMC generated larger errors than the CMCI method at extended SSDs, with up to −9.28% deviations from the measurement for 6E beam. At extended SSD, the mean absolute errors of our method relative to measurements were 0.92 and 1.14, while the errors of eMC were 1.42 and 1.79 for SSD 105 cm and 110 cm, respectively. These results indicate that our method is more accurate than eMC, especially for low‐energy beams, and can be used for MU calculation and as a QA tool for electron therapy.

show abstract

“…(3) The accuracy of the Eclipse eMC algorithm has been evaluated in terms of optimal calculation parameters, (4) accuracy in heterogeneous and homogeneous phantoms, (5) radiochromic film verification, (6) and small field dose calculation. (7) Currently, radiochromic film is used to perform eMC verification measurements and has been shown to agree within 2%/1 mm with measurements taken using an ionization chamber, and 2%/2 mm with an eMC algorithm. (8) However, using radiochromic film can require significant time to prepare the film for use and to read out the resulting exposure.…”

Section: Introductionmentioning

confidence: 98%

Verification measurements of an eMC algorithm using a 2D ion chamber array

Wanklyn

Kidane

Crees

2016

J Applied Clin Med Phys

View full text Add to dashboard Cite

The aim of this study was to assess the suitability of the Im'RT MatriXX 2D ion chamber array for performing verification measurements on the Varian Eclipse electron Monte Carlo (eMC) algorithm for a range of clinical energies (6, 12, and 20 MeV) on a Varian 2100iX linear accelerator. Firstly, the suitability of the MatriXX for measuring percentage depth doses (PDD) in water was assessed, including characterization of the inherent buildup found in the MatriXX. Secondly the suitability of the MatriXX for measuring dose distributions in homogeneous and heterogeneous phantoms was assessed using gamma analysis at 3%/3 mm. It was found that after adjusting the PDD curves for the inherent buildup, that the position of R50,normalD measured using the MatriXX agreed to within 1 mm to the PDDs generated using the eMC algorithm for all energies used in this study. Gamma analysis at 3%/3 mm showed very good agreement (>95%) for all cases in both homogeneous and heterogeneous phantoms. It was concluded that the Im'RT MatriXX is a suitable device for performing eMC verification and could potentially be used for routine energy checks of electron beams.PACS number(s): 87.55.km, 87.55.Qr

show abstract

Evaluation of the eclipse electron Monte Carlo dose calculation for small fields

Cited by 35 publications

References 12 publications

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

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

Convolution‐based modified Clarkson integration (CMCI) for electron cutout factor calculation

Verification measurements of an eMC algorithm using a 2D ion chamber array

Contact Info

Product

Resources

About