+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Analysis of the track- and dose-averaged LET and LET spectra in proton therapy using the geant4 Monte Carlo code



Analysis of the track- and dose-averaged LET and LET spectra in proton therapy using the geant4 Monte Carlo code



Medical Physics 42(11): 6234-6247



The motivation of this study was to find and eliminate the cause of errors in dose-averaged linear energy transfer (LET) calculations from therapeutic protons in small targets, such as biological cell layers, calculated using the geant 4 Monte Carlo code. Furthermore, the purpose was also to provide a recommendation to select an appropriate LET quantity from geant 4 simulations to correlate with biological effectiveness of therapeutic protons. The authors developed a particle tracking step based strategy to calculate the average LET quantities (track-averaged LET, LETt and dose-averaged LET, LETd) using geant 4 for different tracking step size limits. A step size limit refers to the maximally allowable tracking step length. The authors investigated how the tracking step size limit influenced the calculated LETt and LETd of protons with six different step limits ranging from 1 to 500 μm in a water phantom irradiated by a 79.7-MeV clinical proton beam. In addition, the authors analyzed the detailed stochastic energy deposition information including fluence spectra and dose spectra of the energy-deposition-per-step of protons. As a reference, the authors also calculated the averaged LET and analyzed the LET spectra combining the Monte Carlo method and the deterministic method. Relative biological effectiveness (RBE) calculations were performed to illustrate the impact of different LET calculation methods on the RBE-weighted dose. Simulation results showed that the step limit effect was small for LETt but significant for LETd. This resulted from differences in the energy-deposition-per-step between the fluence spectra and dose spectra at different depths in the phantom. Using the Monte Carlo particle tracking method in geant 4 can result in incorrect LETd calculation results in the dose plateau region for small step limits. The erroneous LETd results can be attributed to the algorithm to determine fluctuations in energy deposition along the tracking step in geant 4. The incorrect LETd values lead to substantial differences in the calculated RBE. When the geant 4 particle tracking method is used to calculate the average LET values within targets with a small step limit, such as smaller than 500 μm, the authors recommend the use of LETt in the dose plateau region and LETd around the Bragg peak. For a large step limit, i.e., 500 μm, LETd is recommended along the whole Bragg curve. The transition point depends on beam parameters and can be found by determining the location where the gradient of the ratio of LETd and LETt becomes positive.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 057194349

Download citation: RISBibTeXText

PMID: 26520716

DOI: 10.1118/1.4932217


Related references

Erratum: "Analysis of the track- and dose-averaged LET and LET spectra in proton therapy using the geant4 Monte Carlo code" [Med. Phys. 42 (11), page range 6234-6247(2015). Medical Physics 45(3): 1302-1302, 2018

Ambient Dose Equivalent Per Therapeutic Dose for 250 Mev Proton Interactions in Tissues using GEANT4 Monte Carlo Code. International Journal of Radiation Oncology*biology*physics 75(3): S704-S705, 2009

Track a Monte Carlo computer code to assist design of scattering and collimating systems for proton therapy beams. Reports of Practical Oncology & RadioTherapy 9(6): 235-241, 2004

Dose conversion coefficients for ICRP110 voxel phantom in the Geant4 Monte Carlo code. Radiation Physics and Chemistry 95: 309-312, 2014

Track structure modeling in liquid water: A review of the Geant4-DNA very low energy extension of the Geant4 Monte Carlo simulation toolkit. Physica Medica 31(8): 861-874, 2015

Radiation transport calculations for 50 MV photon therapy beam using the Monte Carlo code GEANT4. Radiation Protection Dosimetry 115(1-4): 503-507, 2005

Clinical CT-based calculations of dose and positron emitter distributions in proton therapy using the FLUKA Monte Carlo code. Physics in Medicine and Biology 52(12): 3369-3387, 2007

The Monte Carlo code MCPTV--Monte Carlo dose calculation in radiation therapy with carbon ions. Physics in Medicine and Biology 55(13): 3917-3936, 2010

Characterization and validation of a Monte Carlo code for independent dose calculation in proton therapy treatments with pencil beam scanning. Physics in Medicine and Biology 60(21): 8601-8619, 2015

Radiobiological quantities in proton-therapy: Estimation and validation using Geant4-based Monte Carlo simulations. Physica Medica 58: 72-80, 2019

Analysis of the physical interactions of therapeutic proton beams in water with the use of Geant4 Monte Carlo calculations. Zeitschrift für Medizinische Physik 19(3): 174-181, 2009

Distributions of secondary particles in proton and carbon-ion therapy: a comparison between GATE/Geant4 and FLUKA Monte Carlo codes. Physics in Medicine and Biology 58(9): 2879-2899, 2013

SU-E-T-500: Pencil-Beam versus Monte Carlo Based Dose Calculation for Proton Therapy Patients with Complex Geometries. Clinical Use of the TOPAS Monte Carlo System. Medical Physics 39(6part18): 3820, 2012

Benchmarking and validation of a Geant4-SHADOW Monte Carlo simulation for dose calculations in microbeam radiation therapy. Journal of Synchrotron Radiation 21(Pt 3): 518-528, 2014

Optimization of the Monte Carlo simulation model of NaI(Tl) detector by Geant4 code. Applied Radiation and Isotopes 130: 75-79, 2017