TH-E-BRC-05: Dosimetric Effects of Tissue Heterogeneity and Small Field Size in Proton Therapy - a Monte Carlo Study

2011 ◽  
Vol 38 (6Part36) ◽  
pp. 3869-3870
Author(s):  
Y Liu ◽  
Y Zheng
Keyword(s):  
Monte Carlo ◽  
Proton Therapy ◽  
Monte Carlo Study ◽  
Field Size ◽  
Small Field ◽  
Tissue Heterogeneity

SU-F-T-157: Physics Considerations Regarding Dosimetric Accuracy of Analytical Dose Calculations for Small Field Proton Therapy: A Monte Carlo Study

2016 ◽  
Vol 43 (6Part15) ◽  
pp. 3498-3498
Author(s):  
C Geng ◽  
J Daartz ◽  
K Cheung ◽  
M Bussiere ◽  
H Shih ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Proton Therapy ◽  
Monte Carlo Study ◽  
Small Field ◽  
Dose Calculations ◽  
Dosimetric Accuracy

Monte Carlo study on mucosal dose in oral and naval cavity using photon beams with small field

2011 ◽  
Vol 10 (4) ◽  
pp. 261-271 ◽  
Author(s):  
James C.L. Chow ◽  
Amir M. Owrangi
Keyword(s):  
Monte Carlo ◽  
Beam Energy ◽  
Field Size ◽  
Small Field ◽  
Beam Angle ◽  
Photon Beams ◽  
Dose Ratio ◽  
Dose Enhancement ◽  
Bone Interface ◽  
Energy Beam

AbstractWe study how mucosal dose in the oral or nasal cavity depends on the irradiated small segmental photon fields varying with beam energy, beam angle and mucosa thickness. Dose ratio (mucosal dose with bone underneath to dose at the same point without bone) reflecting the dose enhancement due to the bone backscatter was determined by Monte Carlo simulation (EGSnrc-based code), validated by measurements. Phase space files based on the 6 and 18 MV photon beams with small field size of 1 × 1 cm2, produced by a Varian 21 EX linear accelerator, were generated using the BEAMnrc Monte Carlo code. Mucosa phantoms (mucosa thickness = 1, 2 and 3 mm) with and without a bone under the mucosa were irradiated by photon beams with gantry angles varying from 0 to 30°. Doses along the central beam axis in the mucosa and the dose ratio were calculated with different mucosa thicknesses. For the 6 MV photon beams, the dose at the mucosa-bone interface increased by 44.9–41.7%, when the mucosa thickness increased from 1 to 3 mm for the beam angle ranging from 0 to 30°. These values were lower than those (58.8–53.6%) for the 18 MV photon beams with the same beam angle range. For both the 6 and 18 MV photon beams, depth doses in the mucosa were found to increase with an increase of the beam angle. Moreover, the dose gradient in the mucosa was greater for the 18 MV photon beams compared to the 6 MV. For the dose ratio, it was found that the dose enhancement due to the bone backscatter increased with a decrease of mucosa thickness, and was more significant at both the air-mucosa and mucosa-bone interface. Mucosal dose with bone was investigated by Monte Carlo simulations with different experimental configurations, and was found vary with the beam energy, beam angle and mucosa thickness for a small segmental photon field. The dosimetric information in this study should be considered when searching for an optimized treatment strategy to minimize the mucosal complications in the head-and-neck intensity-modulated radiation therapy.

SU-GG-T-381: Monte Carlo Study of Neutron Dose Equivalent for a Compact Proton Therapy Unit

2010 ◽  
Vol 37 (6Part21) ◽  
pp. 3273-3273 ◽  
Author(s):  
Y Zheng ◽  
E Klein ◽  
K Chen ◽  
Y Liu
Keyword(s):  
Monte Carlo ◽  
Proton Therapy ◽  
Monte Carlo Study ◽  
Neutron Dose ◽  
Dose Equivalent ◽  
Neutron Dose Equivalent

scholarly journals The Influence of Brass Compensator Thickness and Field Size on Neutron Contamination Spectrum in 18MV Elekta SL 75/25 Medical Linear Accelerator with and without Flattening Filter: A Monte Carlo Study

2018 ◽  
Vol 8 (3Sep) ◽  
Author(s):  
A S Talebi ◽  
M Maleki ◽  
P Hejazi ◽  
M Jadidi ◽  
R Ghorbani
Keyword(s):  
Monte Carlo ◽  
Linear Accelerator ◽  
Monte Carlo Study ◽  
High Energy ◽  
Nonparametric Tests ◽  
Primary Electron ◽  
Field Size ◽  
Dose Ratio ◽  
Medical Linear Accelerator ◽  
Flattening Filter

BackgroundOne of the most significant Intensity Modulated Radiation Therapy treatment benefits is a high target to normal tissue dose ratio. To improve this advantage, an additional accessory such as a compensator is used to delivering doses. Compensator-based IMRT treatment is usually operated with an energy higher than 10 MV. Photoneutrons, which have high linear energy transfer and radiobiological effectiveness, are produced by colliding high-energy photon beams with linear accelerator structures, then they deliver the unwanted doses to patients and staff. Therefore, the neutron energy spectra should be determined in order to calculate and reduce the photoneutron risk.Objective: We have conducted a comprehensive and precise study on the influence of brass compensator thickness and field size on neutron contamination spectrum in an Elekta SL 75/25 medical linear accelerator with and without the flattening filter by Monte Carlo method.Materials and Methods: MCNPX MC Code version 2.6.0 was utilized to simulate the detailed geometry of Elekta SL 75/25 head components based on Linac’s manual. This code includes an important feature to simulate the photo-neutron interactions. Photoneutrons spectrum was calculated after the Linac output benchmarking based on tuning the primary electron beam.Results and Conclusion: Based on the Friedman and Wilcoxon nonparametric tests results (P<0.05), photoneutron fluence directly depends on the field size and compensator thickness. Moreover, the unflattened beam provides lower photoneutron fluence than the flattened beam. Photoneutrons fluence is not negligible in compensator-based IMRT treatment. However, in order to optimize treatment plans, this additional and unwanted dose must be accounted for patients.

scholarly journals Estimation of Dosimetric Parameters based on KNR and KNCSF Correction Factors for Small Field Radiation Therapy at 6 and 18 MV Linac Energies using Monte Carlo Simulation Methods

2019 ◽  
Vol 9 (1Feb) ◽  
Author(s):  
S A Rahimi ◽  
B Hashemi ◽  
S R Mahdavi
Keyword(s):  
Monte Carlo ◽  
Correction Factor ◽  
Reference Conditions ◽  
Field Size ◽  
Monte Carlo Code ◽  
Small Field ◽  
Correction Factors ◽  
Photon Beams ◽  
Small Field Dosimetry ◽  
Circular Field

Background: Estimating dosimetric parameters for small fields under non-reference conditions leads to significant errors if done based on conventional protocols used for large fields in reference conditions. Hence, further correction factors have been introduced to take into account the influence of spectral quality changes when various detectors are used in non-reference conditions at different depths and field sizes.Objective: Determining correction factors (KNR and KNCSF) recommended recently for small field dosimetry formalism by American Association of Physicists in Medicine (AAPM) for different detectors at 6 and 18 MV photon beams.Methods: EGSnrc Monte Carlo code was used to calculate the doses measured with different detectors located in a slab phantom and the recommended KNR and KNCSF correction factors for various circular small field sizes ranging from 5-30 mm diameters. KNR and KNCSF correction factors were determined for different active detectors (a pinpoint chamber, EDP-20 and EDP-10 diodes) in a homogeneous phantom irradiated to 6 and 18 MV photon beams of a Varian linac (2100C/D).Results: KNR correction factor estimated for the highest small circular field size of 30 mm diameter for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.993, 1.020 and 1.054; and 0.992, 1.054 and 1.005 for the 6 and 18 MV beams, respectively. The KNCSF correction factor estimated for the lowest circular field size of 5 mm for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.994, 1.023, and 1.040; and 1.000, 1.014, and 1.022 for the 6 and 18 MV photon beams, respectively.Conclusion: Comparing the results obtained for the detectors used in this study reveals that the unshielded diodes (EDP-20 and EDP-10) can confidently be recommended for small field dosimetry as their correction factors (KNR and KNCSF) was close to 1.0 for all small field sizes investigated and are mainly independent from the electron beam spot size.

SU-GG-T-319: Monte Carlo Study of Distal Edge Degradation in Proton Therapy Due to Heterogeneities. Proof of Principle with a Case Study

2008 ◽  
Vol 35 (6Part14) ◽  
pp. 2798-2798
Author(s):  
U Titt ◽  
X Zhang ◽  
Y Li ◽  
D Mirkovic ◽  
G Sawakuchi ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Proton Therapy ◽  
Monte Carlo Study ◽  
Distal Edge ◽  
Proof Of Principle

SU-F-T-217: A Comprehensive Monte-Carlo Study of Out-Of-Field Secondary Neutron Spectra in a Scanned-Beam Proton Therapy Treatment Room

2016 ◽  
Vol 43 (6Part16) ◽  
pp. 3512-3512
Author(s):  
F Englbrecht ◽  
S Trinkl ◽  
V Mares ◽  
W Ruehm ◽  
M Wielunski ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Proton Therapy ◽  
Monte Carlo Study ◽  
Secondary Neutron ◽  
Neutron Spectra ◽  
Treatment Room ◽  
Beam Proton ◽  
Therapy Treatment
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