Simulation of dose distribution and secondary particle production in proton therapy of brain tumor

AimThe aim of this study is simulation of the proton depth-dose distribution and dose evaluation of secondary particles in proton therapy of brain tumor using the GEANT4 and FLUKA Monte Carlo codes.BackgroundProton therapy is a treatment method for variety of tumors such as brain tumor. The most important feature of high energy proton beams is the energy deposition as a Bragg curve and the possibility of creating the spread out Bragg peak (SOBP) for full coverage of the tumor.Materials and methodsA spherical tumor with the radius of 1 cm in the brain is considered. A SNYDER head phantom has been irradiated with 30−130 MeV proton beam energy. A PMMA modulator wheel is used for covering the tumor. The simulations are performed using the GEANT4 and FLUKA codes.ResultsUsing a modulator wheel, the Spread Out Bragg Peak longitudinally and laterally covers the tumor. Flux and absorbed dose of secondary particles produced by nuclear interactions of protons with elements in the head are considerably small compared to protons.ConclusionsUsing 76.85 MeV proton beam and a modulator wheel, the tumor can be treated accurately in the 3-D, so that the distribution of proton dose in the surrounding tissues is very low. The results show that more than 99% of the total dose of secondary particles and protons is absorbed in the tumor

A case study of energy absorption buildup factors in some human bones for gamma energies 30 keV to 1.5 MeV

Human body consists of some tissues among which bone is one of the important living and growing tissue. In this research, energy absorption buildup factor (EABF) values of 27 types of bone have been computed for photon energy 0.03 to 1.5 MeV up to 40 mean free path (40mfp) penetration depths. The Inner bone tissue, Spongiosa and Male sternum had the largest values of EABF in low photon energies, and great differences below 150 keV photon energy were noted relative to the other bones. This study would be of utmost  importance for estimation of the effective dose to the human bones, radiation therapy and various medical applications.

Investigation of the Effect of Proton Energy on the Depth-dose Distribution in the Proton Therapy of the Eye Tumor Using MCNPX Code

Introduction: Depth-dose distribution curve of protons in the matter has a maximum is called Bragg peak. Bragg peak of a monoenergetic proton beam is too narrow. The spread out Bragg peak should be created for full coverage of the tumor. The spread out Bragg peak is obtained in the depth of the tumor with superposition of the several Bragg peaks. The aim of this study was coverage of an eye tumor in the proton therapy while healthy eye tissue absorbs less radiation. Methods: In this analytical study, the simulations were performed using MCNPX code. A tumor in the eye phantom was considered. The eye phantom has been irradiated with different proton beam energy. A Polystyrene modulator wheel was used for creating the spread out Bragg peak in the tumor region. Results: Bragg peaks were created in different depths of the tumor, by varying the proton beam energies from 20 MeV to 38 MeV. Bragg peak of the 32.85 MeV proton beam energy was precisely placed at the end of the tumor. Different pristine Bragg peaks were produced using a Polystyrene modulator wheel with different thicknesses and 32.85 MeV proton beam energy. The spread out Bragg peak was created in the tumor region by modulation of the pristine Bragg peaks. Neutrons and photons are produced by the inelastic nuclear interactions of protons with the nuclei of different tissues of eyes. The flux and absorbed dose of secondary neutrons and photons were considerably small compared to the depth-dose distribution of protons and the total absorbed dose in the tumor was more than other tissues of eyes. Conclusion: Using a modulator wheel the tumor can be treated, so that the minimal damage reaches the surrounding tissues. The results show that more than 92% of the total dose of secondary particles and protons is absorbed in the tumor

Measurement of cross sections and isomeric yield ratios for

The flux weighted average cross sections and the isomeric yield ratios of 110m, gIn, 111m, gIn and 112m, gIn in the natIn($\gamma$,xn) 112-110In reactions with the bremsstrahlung end-point energies of 65, 70 and 75 MeV have been determined by activation and off-line $\gamma$-ray spectrometric technique using the 100 MeV electron linac at Pohang accelerator laboratory, Korea. It was found that the natIn($\gamma$,xn) 112-110In reaction cross sections increase very fast from the threshold energy to a certain value of the bremsstrahlung energy, where the other reaction channel opens. After a certain energy, it remains constant because the cross section of the other reaction channel starts to increase. This indicates the partition of the excitation energy in different reaction channles. The isomeric yield ratios of 110m, gIn, 111m, gIn and 112m, gIn in the natIn($\gamma$,xn) reactions decrease very fast with the bemsstrahlung end-point energy from the threshold value to 15-30 MeV due to the giant dipole resonance (GDR) effect. Above that, the isomeric yield ratios increase slowly with the bremsstrahlung energy due to the increase of excitation energy

Comparing learning styles among students of Para medicine and Health faculties in Golestan University of medical sciences

Background and Objectives: The validity of an educational system is dependent on students' learning. Learning is a complex variable which is affected by multiple factors. One of the most important factors is learning styles. Knowledge of learning styles of students to educational programs is very important. Therefore, this study aimed to determine students' learning styles among students of Para medicine and Health faculties in Golestan University of medical sciences. Methods: In this cross-sectional study, 401 students of the faculty of Para medicine and Health in Golestan University of Medical Sciences since 1391 till 1392 were selected and filled out the Standard Kolb Learning Style Inventory (LSI) which was previously tested for reliability (8.0). Data was analyzed with SPSS version 18.0 using Chi-square and Fisher's exact test. Results: The mean age of students was 20.57 and 71.8 percent of them were female students. Learning styles of students included a convergent (63.4 %), absorber (25.4 %), accommodating (7.5%) and divergent (3.7 %). Learning style of study had no statistically significant difference in comparison to sex, school, age, GPA, credits, semester and education levels (P>0.05). Conclusion: Converging and absorbing learning styles were more dominant among students. Therefore, it is recommended to use training methods which fit this style such as showing hand-writings and presentations with self-study materials, simulations, laboratory assignments and problem-based learning

Measurement of photo-neutron cross sections and isomeric yield ratios in the Y-89(gamma,xn)Y89-x reactions at the bremsstrahlung end-point energies of 65, 70 and 75 MeV

The flux-weighted average cross sections of the Y-89(gamma,xn; x = 1- 4)Y-89 x reactions and the isomeric yield ratios of the Y-87m,Y-g, Y-86m,Y-g, and (85m,)gY radionuclides produced in these reactions with the bremsstrahlung end-point energies of 65, 70 and 75 MeV have been determined by an activation and off-line gamma-ray spectrometric technique using the 100 MeV electron linac in Pohang Accelerator Laboratory, Korea. The theoretical Y-89(gamma, xn; x = 1-4)Y89-x reactioncross sections for mono- energetic photonshave been calculated using the computer code TALYS 1.6. Then the flux- weighted theoretical values were obtaind to compare with the present data. The flux- weighted experimental and theoretical (89Y)(gamma,xn; x =1-4)Y89-x reaction cross sections increase very fast from the threshold values to a certain bremsstrahlung energy, wherethe other reaction channels open up. Thereafter it remains constant a while and then slowly decreases with the increase of cross sections for other reactions. Similarly, the isomeric yield ratios of Y-87m,Y-g, Y-86m,Y-g and Y-85m,Y- in the Y-89(gamma,xn; x =2-4)Y89-x reactions from the present work and literature data show an increasing trend from their respective threshold values to a certain bremsstrahlung energy. After a certain point ofenergy, the isomeric yield ratios increase slowly with the bremsstrahlung energy. These observations indicate therole of excitation energy and its partitioning in different reaction channels.111sciescopu