Monte Carlo calculations of correction factors for plastic phantoms in clinical photon and electron beam dosimetry

Araki, Fujio; Hanyu, Yuji; Fukuoka, M.; Matsumoto, Kenji; Okumura, Masahiko; Oguchi, Hiroshi

doi:10.1118/1.3151809

Cited by 17 publications

(6 citation statements)

References 33 publications

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“…Burns (1994) derived a method for determining a conversion factor for graphite to water that accounts for absorbed dose due to collision kerma, mass-energy absorption and stopping power ratios [3]. Fluence scaling factors for various chambers were also investigated by Araki (2009) which found absorbed dose in PW were within 1% of dose measured in water [4]. Similarly, dose conversion factors for solid water and lucite/PMMA phantoms were determined by Seuntjens et al [5].…”

Section: Introductionmentioning

confidence: 99%

Determination of RW3-to-water mass-energy absorption coefficient ratio for absolute dosimetry

Seet

Hanlon

Charles

2011

Australas Phys Eng Sci Med

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The measurement of absorbed dose to water in a solid-phantom may require a conversion factor because it may not be radiologically equivalent to water. One phantom developed for the use of dosimetry is a solid water, RW3 white-polystyrene material by IBA. This has a lower mass-energy absorption coefficient than water due to high bremsstrahlung yield, which affects the accuracy of absolute dosimetry measurements. In this paper, we demonstrate the calculation of mass-energy absorption coefficient ratios, relative to water, from measurements in plastic water and RW3 with an Elekta Synergy linear accelerator (6 and 10 MV photon beams) as well as Monte Carlo modeling in BEAMnrc and DOSXYZnrc. From this, the solid-phantom-to-water correction factor was determined for plastic water and RW3.

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Section: Introductionmentioning

confidence: 99%

Determination of RW3-to-water mass-energy absorption coefficient ratio for absolute dosimetry

Seet

Hanlon

Charles

2011

Australas Phys Eng Sci Med

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“…In additional investigations, we measured the physical density and analyzed the elemental composition of PMMA in a portion of Delta4 with the thermal conductivity method for hydrogen and carbon, and the infrared absorption spectrophotometry for oxygen. Consequently, the physical density was 1.19 g/cm 3 , and the elemental composition closely matched the nominal elemental composition . The DSF are the lowest density scaling factor acquired theoretically.…”

Section: Discussionmentioning

confidence: 61%

“…TG‐21 calculated a relative electron density of 1.137 from the physical density of 1.17 g/cm 3 for PMMA. However, the physical density of PMMA was shown as 1.19 g/cm 3 . In additional investigations, we measured the physical density and analyzed the elemental composition of PMMA in a portion of Delta4 with the thermal conductivity method for hydrogen and carbon, and the infrared absorption spectrophotometry for oxygen.…”

Section: Discussionmentioning

confidence: 99%

“…For each phantom material, the appropriateness of DSF was verified through comparisons of the dose distributions measured with Delta4 and calculated with three different density scaling factors: the nominal physical density (PD), nominal relative electron density (ED), and DSF . The PDs of PMMA and PWDT are 1.190 and 1.039 g/cm 3 , and EDs of PMMA and PWDT are 1.159 and 1.003, respectively . The following dose calculation algorithms were used for the verification: AdC (Pinnacle 3 ver.…”

Section: Methodsmentioning

confidence: 99%

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Density scaling of phantom materials for a 3D dose verification system

Tani

Fujita

Wakita³

et al. 2018

J Applied Clin Med Phys

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In this study, the optimum density scaling factors of phantom materials for a commercially available three‐dimensional (3D) dose verification system (Delta4) were investigated in order to improve the accuracy of the calculated dose distributions in the phantom materials. At field sizes of 10 × 10 and 5 × 5 cm2 with the same geometry, tissue‐phantom ratios (TPRs) in water, polymethyl methacrylate (PMMA), and Plastic Water Diagnostic Therapy (PWDT) were measured, and TPRs in various density scaling factors of water were calculated by Monte Carlo simulation, Adaptive Convolve (AdC, Pinnacle3), Collapsed Cone Convolution (CCC, RayStation), and AcurosXB (AXB, Eclipse). Effective linear attenuation coefficients (μ eff) were obtained from the TPRs. The ratios of μ eff in phantom and water ((μ eff)pl,water) were compared between the measurements and calculations. For each phantom material, the density scaling factor proposed in this study (DSF) was set to be the value providing a match between the calculated and measured (μ eff)pl,water. The optimum density scaling factor was verified through the comparison of the dose distributions measured by Delta4 and calculated with three different density scaling factors: the nominal physical density (PD), nominal relative electron density (ED), and DSF. Three plans were used for the verifications: a static field of 10 × 10 cm2 and two intensity modulated radiation therapy (IMRT) treatment plans. DSF were determined to be 1.13 for PMMA and 0.98 for PWDT. DSF for PMMA showed good agreement for AdC and CCC with 6 MV x ray, and AdC for 10 MV x ray. DSF for PWDT showed good agreement regardless of the dose calculation algorithms and x‐ray energy. DSF can be considered one of the references for the density scaling factor of Delta4 phantom materials and may help improve the accuracy of the IMRT dose verification using Delta4.

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“…In this study, the EGSnrc‐based SPRRZnrc user code ( 20 ) is employed to compute the SPR for phantoms B and C. No SPR corrections are applied to the measurements in lung material since the stopping powers are equivalent to those in water within 1%. ( 21 ) …”

Section: Methodsmentioning

confidence: 99%

Validation of an electron Monte Carlo dose calculation algorithm in the presence of heterogeneities using EGSnrc and radiochromic film measurements

Aubry

Bouchard

Bessiéres

et al. 2011

J Applied Clin Med Phys

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The purpose of this study is to validate Eclipse's electron Monte Carlo algorithm (eMC) in heterogeneous phantoms using radiochromic films and EGSnrc as a reference Monte Carlo algorithm. Four heterogeneous phantoms are used in this study. Radiochromic films are inserted in these phantoms, including in heterogeneous media, and the measured relative dose distributions are compared to eMC calculations. Phantoms A, B, and C contain 1D heterogeneities, built with layers of lung‐ (phantom A) and bone‐ (phantoms B and C) equivalent materials sandwiched in Plastic Water. Phantom D is a thorax‐anthropomorphic phantom with 2D lung heterogeneities. Electron beams of 6, 9, 12 and 18 MeV from a Varian Clinac 2100 are delivered to these phantoms with a 10×10 cm2 applicator. Monte Carlo simulations with an independent algorithm (EGSnrc) are also used as a reference tool for two purposes: (1) as a second validation of the eMC dose calculations, and (2) to calculate the stopping power ratio between radiochromic films and bone medium, when dose is measured inside the heterogeneity. Percent depth dose (PDD) film measurements and eMC calculations agree within 2% or 3 mm for phantom A, and within 3% or 3 mm for phantoms B and C for almost all beam energies. One exception is observed with phantom B and the 6 MeV, where measured PDDs and those calculated with eMC differ by up to 4 mm. Gamma analysis of the measured and calculated 2D dose distributions in phantom D agree with criteria of 3%, 3 mm for 9, 12, and 18 MeV beams, and criteria of 5%, 3 mm for the 6 MeV beam. Dose calculations in heterogeneous media with eMC agree within 3% or 3 mm with radiochromic film measurements. Six (6) MeV beams are not modeled as accurately as other beam energies. The eMC algorithm is suitable for clinical dose calculations involving lung and bone.PACS numbers: 87.10.Rt, 87.55.km

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Monte Carlo calculations of correction factors for plastic phantoms in clinical photon and electron beam dosimetry

Cited by 17 publications

References 33 publications

Determination of RW3-to-water mass-energy absorption coefficient ratio for absolute dosimetry

Determination of RW3-to-water mass-energy absorption coefficient ratio for absolute dosimetry

Density scaling of phantom materials for a 3D dose verification system

Validation of an electron Monte Carlo dose calculation algorithm in the presence of heterogeneities using EGSnrc and radiochromic film measurements

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