Monte Carlo simulation of β–γ coincidence system using plastic scintillators in 4π geometry

2007 ◽  
Vol 580 (1) ◽  
pp. 380-383 ◽  
Author(s):  
M.S. Dias ◽  
H. Piuvezam-Filho ◽  
A.M. Baccarelli ◽  
M.N. Takeda ◽  
M.F. Koskinas
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Coincidence System ◽  
Plastic Scintillators

scholarly journals Quantifying Radiobiological Variation in Cancer Radiotherapy Using Monte Carlo Simulation and Doped Plastic Scintillators

2021 ◽  
Author(s):  
Humza Nusrat
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Organs At Risk ◽  
Treatment Plan ◽  
Effective Atomic Number ◽  
Major Step ◽  
Potential Applications ◽  
Plastic Scintillators ◽  
Optimized Treatment ◽  
The Impact

This dissertation examines the extent to which radiobiological variations occur in photon radiotherapy, and then presents a novel methodology and detector prototype to measure this variation. In the first section, I examine the change in maximum RBE (RBEM) outside the primary field in open and composite 6 MV x-ray beams. This is done using Monte Carlo simulation and microdosimetric techniques. It was found that when comparing an open 10 10 cm2 6 MV beam to a composite 10 10 cm2 beam comprising one hundred 1x 1 cm2 beamlets, the out-of-field increase in RBE occurs much closer to the field edge in the composite case. This finding may have consequences for IMRT cases in which large amount of scattered radiation may be causing a higher than expected effective dose to organs at risk. In the second section, the maximum RBE variation is examined in the context of brachytherapy. The sources examined include 192Ir, 125I, and 169Yb. It was determined that maximum RBE of 125I relative to the source position did not vary significantly as distance from the source was increased, however, 192Ir and 169Yb were found to exhibit RBEM increases of 3.0% and 6.6% at a distance of 8 cm, respectively. Also, the impact of this variation on an HDR 192Ir prostate treatment plan was examined; it was found that RBEM hotspots of +3.6% occur at the treatment plan’s periphery. In the third part, the impact of lead doping on plastic scintillator response is quantified, a major step required for the development of the LET detector prototype. In this stage, 4 differently doped plastic scintillators were obtained, and measurements were conducted in low and medium LET beams. Using Geant4 Monte Carlo and the measured scintillator responses, the scintillator parameters: kB and L0 were determined as a function of dopant concentration and effective atomic number. Finally, the uniquely energy dependent scintillators were combined into a detector prototype used to measure the LET spectra produced by five low energy photon beams. These beams included four orthovoltage energies (100, 180, 250, and 300 kVp) along with an 192Ir HDR source. In this proof-of-principle work, the detector prototype and technique was found to accurately determine the LET spectra and the mean LET for all beams with the exception of the 100 kVp orthovoltage beam. Potential applications for the real-time LET detector prototype and technique described in this dissertation include LET measurement in radiotherapy, allowing for biologically optimized treatment plans improving patient care. This technique and prototype also has numerous applications in non-medical fields such as health physics, space travel dosimetry, and nuclear safety.

Monte Carlo simulation to positron emitter standardized by means of 4πβ-γ coincidence system—Application to 22Na

2010 ◽  
Vol 68 (7-8) ◽  
pp. 1362-1366 ◽  
Author(s):  
Mauro S. Dias ◽  
Margareth L.O. Tongu ◽  
Mauro N. Takeda ◽  
Marina F. Koskinas
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
System Application ◽  
Coincidence System ◽  
Positron Emitter

scholarly journals Quantifying Radiobiological Variation in Cancer Radiotherapy Using Monte Carlo Simulation and Doped Plastic Scintillators

2021 ◽  
Author(s):  
Humza Nusrat
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Organs At Risk ◽  
Treatment Plan ◽  
Effective Atomic Number ◽  
Major Step ◽  
Potential Applications ◽  
Plastic Scintillators ◽  
Optimized Treatment ◽  
The Impact

This dissertation examines the extent to which radiobiological variations occur in photon radiotherapy, and then presents a novel methodology and detector prototype to measure this variation. In the first section, I examine the change in maximum RBE (RBEM) outside the primary field in open and composite 6 MV x-ray beams. This is done using Monte Carlo simulation and microdosimetric techniques. It was found that when comparing an open 10 10 cm2 6 MV beam to a composite 10 10 cm2 beam comprising one hundred 1x 1 cm2 beamlets, the out-of-field increase in RBE occurs much closer to the field edge in the composite case. This finding may have consequences for IMRT cases in which large amount of scattered radiation may be causing a higher than expected effective dose to organs at risk. In the second section, the maximum RBE variation is examined in the context of brachytherapy. The sources examined include 192Ir, 125I, and 169Yb. It was determined that maximum RBE of 125I relative to the source position did not vary significantly as distance from the source was increased, however, 192Ir and 169Yb were found to exhibit RBEM increases of 3.0% and 6.6% at a distance of 8 cm, respectively. Also, the impact of this variation on an HDR 192Ir prostate treatment plan was examined; it was found that RBEM hotspots of +3.6% occur at the treatment plan’s periphery. In the third part, the impact of lead doping on plastic scintillator response is quantified, a major step required for the development of the LET detector prototype. In this stage, 4 differently doped plastic scintillators were obtained, and measurements were conducted in low and medium LET beams. Using Geant4 Monte Carlo and the measured scintillator responses, the scintillator parameters: kB and L0 were determined as a function of dopant concentration and effective atomic number. Finally, the uniquely energy dependent scintillators were combined into a detector prototype used to measure the LET spectra produced by five low energy photon beams. These beams included four orthovoltage energies (100, 180, 250, and 300 kVp) along with an 192Ir HDR source. In this proof-of-principle work, the detector prototype and technique was found to accurately determine the LET spectra and the mean LET for all beams with the exception of the 100 kVp orthovoltage beam. Potential applications for the real-time LET detector prototype and technique described in this dissertation include LET measurement in radiotherapy, allowing for biologically optimized treatment plans improving patient care. This technique and prototype also has numerous applications in non-medical fields such as health physics, space travel dosimetry, and nuclear safety.

scholarly journals Monte Carlo simulation of activity measurements by means of 4pb-g coincidence system

2004 ◽  
Vol 34 (3a) ◽  
pp. 852-854 ◽  
Author(s):  
Mauro N. Takeda ◽  
Mauro S. Dias ◽  
Marina F. Koskinas
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Coincidence System ◽  
Activity Measurements

Electron Scattering in Solids

1990 ◽  
Vol 48 (2) ◽  
pp. 4-5
Author(s):  
Ryuichi Shimizu ◽  
Ze-Jun Ding
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Angular Distribution ◽  
Elastic Scattering ◽  
Electron Scattering ◽  
Cross Sections ◽  
Expansion Method ◽  
Electron Excitation ◽  
Partial Wave Expansion ◽  
Backscattered Electrons

Monte Carlo simulation has been becoming most powerful tool to describe the electron scattering in solids, leading to more comprehensive understanding of the complicated mechanism of generation of various types of signals for microbeam analysis.The present paper proposes a practical model for the Monte Carlo simulation of scattering processes of a penetrating electron and the generation of the slow secondaries in solids. The model is based on the combined use of Gryzinski’s inner-shell electron excitation function and the dielectric function for taking into account the valence electron contribution in inelastic scattering processes, while the cross-sections derived by partial wave expansion method are used for describing elastic scattering processes. An improvement of the use of this elastic scattering cross-section can be seen in the success to describe the anisotropy of angular distribution of elastically backscattered electrons from Au in low energy region, shown in Fig.l. Fig.l(a) shows the elastic cross-sections of 600 eV electron for single Au-atom, clearly indicating that the angular distribution is no more smooth as expected from Rutherford scattering formula, but has the socalled lobes appearing at the large scattering angle.

Determination of Stoichiometry of GaAs Component in (Gaas)Ge Epitaxially Grown Thin Films by Electron Microprobe X-Ray Analysis

1990 ◽  
Vol 48 (2) ◽  
pp. 264-265
Author(s):  
D. R. Liu ◽  
S. S. Shinozaki ◽  
R. J. Baird
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Compound Semiconductors ◽  
Energy Dispersive Analysis ◽  
X Ray ◽  
Metastable Alloys ◽  
Lower Voltage

The epitaxially grown (GaAs)Ge thin film has been arousing much interest because it is one of metastable alloys of III-V compound semiconductors with germanium and a possible candidate in optoelectronic applications. It is important to be able to accurately determine the composition of the film, particularly whether or not the GaAs component is in stoichiometry, but x-ray energy dispersive analysis (EDS) cannot meet this need. The thickness of the film is usually about 0.5-1.5 μm. If Kα peaks are used for quantification, the accelerating voltage must be more than 10 kV in order for these peaks to be excited. Under this voltage, the generation depth of x-ray photons approaches 1 μm, as evidenced by a Monte Carlo simulation and actual x-ray intensity measurement as discussed below. If a lower voltage is used to reduce the generation depth, their L peaks have to be used. But these L peaks actually are merged as one big hump simply because the atomic numbers of these three elements are relatively small and close together, and the EDS energy resolution is limited.

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