TH-C-AUD-08: Comparison of Tomotherapy Dose Distributions for 6MV X-Rays and Different Cobalt-60 Source Designs Using Monte Carlo Methods

Radiation dose distributions in various parts of the body are of importance in radiotherapy. Also, the percent depth dose at different body depths is an important parameter in radiation therapy applications. Monte Carlo simulation techniques are the most accurate methods for such purposes. Monte Carlo computer calculations of photon spectra and the dose ratios at surfaces and in some internal organs of a human equivalent phantom were performed. In the present paper, dose distributions in different organs during bladder radiotherapy by 6 MeV X-rays were measured using thermoluminescence dosimetry placed at different points in the human-phantom. The phantom was irradiated in exactly the same manner as in actual bladder radiotherapy. Four treatment fields were considered to maximize the dose at the center of the target and minimize it at non-target healthy organs. All experimental setup information was fed to the MCNP-4b code to calculate dose distributions at selected points inside the proposed phantom. Percent depth dose distribution was performed. Also, the absorbed dose as ratios relative to the original beam in the surrounding organs was calculated by MCNP-4b and measured by thermoluminescence dosimetry. Both measured and calculated data were compared. Results indicate good agreement between calculated and measured data inside the phantom. Comparison between MCNP-4b calculations and measurements of depth dose distribution indicated good agreement between both.

Download Full-text

Validation of a Monte Carlo simulation for Microbeam Radiation Therapy on the Imaging and Medical Beamline at the Australian Synchrotron

Scientific Reports ◽

10.1038/s41598-019-53991-9 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Andrew Dipuglia ◽

Matthew Cameron ◽

Jeremy A. Davis ◽

Iwan M. Cornelius ◽

Andrew W. Stevenson ◽

...

Keyword(s):

Magnetic Field ◽

Monte Carlo ◽

Radiation Therapy ◽

Planning System ◽

Treatment Planning System ◽

Photon Flux ◽

X Rays ◽

Dose Distributions ◽

Microbeam Radiation Therapy ◽

Independent Verification

AbstractMicrobeam Radiation Therapy (MRT) is an emerging cancer treatment modality characterised by the use of high-intensity synchrotron-generated x-rays, spatially fractionated by a multi-slit collimator (MSC), to ablate target tumours. The implementation of an accurate treatment planning system, coupled with simulation tools that allow for independent verification of calculated dose distributions are required to ensure optimal treatment outcomes via reliable dose delivery. In this article we present data from the first Geant4 Monte Carlo radiation transport model of the Imaging and Medical Beamline at the Australian Synchrotron. We have developed the model for use as an independent verification tool for experiments in one of three MRT delivery rooms and therefore compare simulation results with equivalent experimental data. The normalised x-ray spectra produced by the Geant4 model and a previously validated analytical model, SPEC, showed very good agreement using wiggler magnetic field strengths of 2 and 3 T. However, the validity of absolute photon flux at the plane of the Phase Space File (PSF) for a fixed number of simulated electrons was unable to be established. This work shows a possible limitation of the G4SynchrotronRadiation process to model synchrotron radiation when using a variable magnetic field. To account for this limitation, experimentally derived normalisation factors for each wiggler field strength determined under reference conditions were implemented. Experimentally measured broadbeam and microbeam dose distributions within a Gammex RMI457 Solid Water® phantom were compared to simulated distributions generated by the Geant4 model. Simulated and measured broadbeam dose distributions agreed within 3% for all investigated configurations and measured depths. Agreement between the simulated and measured microbeam dose distributions agreed within 5% for all investigated configurations and measured depths.

Download Full-text

Study of Tissue Inhomogeneity Effects on Central Axis Radiation Beam Parameters using Monte Carlo Methods

International Journal of Medical Research and Review ◽

10.17511/ijmrr.2020.i05.03 ◽

2020 ◽

Vol 8 (5) ◽

pp. 352-362

Author(s):

Dr. Santhosh VS ◽

◽

Dr. Anand RK ◽

Keyword(s):

Monte Carlo ◽

Monte Carlo Methods ◽

Homogeneous Medium ◽

Central Axis ◽

Beam Parameter ◽

Monte Carlo Code ◽

X Rays ◽

Radiation Beam ◽

Beam Parameters ◽

Tissue Inhomogeneity

Introduction: The central axis radiation beam parameters are used for the dose calculations inradiotherapy and usually measured in a homogeneous medium. Human body is not homogeneous innature and the incident beam has to travel through different medium such as bone tissue air etc toreach the tumor. Objective: The objective of the present work is to study the effects of tissueInhomogeneity on central axis beam parameter such as percentage Depth Dose using Monte CarloMethods Materials and Methods: The Monte Carlo simulation is a virtual experiment and can beconducted with the Monte Carlo software tool installed in a PC. Input files are written as per thespecification of the Monte Carlo code. Two radiation beams beans commonly used for radiationtreatment such as Cobalt 60 and 6MV X ray were used for the simulation. Results: Depth Dosecharacteristics in homogeneous tissue medium for Cobalt60 and 6MV X rays beams were studied andis consistent with the published experimental values.In the second case, at the interface betweentissue and bone the PDD pattern changed as reported by the previous works. And the absorbed doseat bone layer is higher than the dose value predicated in a homogeneous condition. In the nextsimulation we conducted the simulation for a tissue air tissue medium. Conclusion: The presentstudy clearly demonstrate that Monte Carlo methods simulation can be used as a tool for estimationof dose in tissue Inhomogeneity where measurements are seldom possible.

Download Full-text