Fatemeh Sadat Rasouli
Abstract
Among the approaches commonly used to extend the sharp peak of the deposited dose in proton therapy, passive scattering is widely used and also is of concern because of the potential for generating secondary particles, especially neutrons, which can damage the non-target healthy tissues. The present ...
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Among the approaches commonly used to extend the sharp peak of the deposited dose in proton therapy, passive scattering is widely used and also is of concern because of the potential for generating secondary particles, especially neutrons, which can damage the non-target healthy tissues. The present simulation-based study investigates the effect of using the passive method for different primary proton energies on the dose delivered to the tissue compared with those of the pencil beam scanning method. The results show that the generation of secondary neutrons strongly depends on the material used in the beam design. Also, it was found that the passive method would lead to the physical neutron dose higher than that of the beam scanning method for various primary proton energies.
S. Farhad Masoudi; Fatemeh Sadat Rasouli
Abstract
Due to the selectively treating tumors and largely sparing normal neighboring cells, Boron Neutron Capture Therapy (BNCT) continues to be of special significance and interest for wide groups of researchers. One of the most important challenges in this context is to design an optimized ...
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Due to the selectively treating tumors and largely sparing normal neighboring cells, Boron Neutron Capture Therapy (BNCT) continues to be of special significance and interest for wide groups of researchers. One of the most important challenges in this context is to design an optimized beam based on an appropriate neutron source. The recent studies, focused on investigating neutron sources as alternatives for nuclear reactors, revealed the high potential of electron linac-based photoneutron sources to improve the efficiency of this treatment method. Inquiring about the efficiency of a layered model of beam shaping assembly (BSA) for photoneutron sources to be used in BNCT of deep tumors is the main subject of this simulation study. This model, unlike the traditional BSA in which the reflector surrounds the whole moderator, includes many concentric cylinders of reflectors and moderators. The MCNPX simulations for various primary energies show that the layered model results in more appropriate beam characteristics compared with that of the common geometry. Moreover, the parameters governing the beam properties such as the thickness of the layers, moderator/reflector and collimator lengths, and the thickness of the surrounding reflector have been investigated. The results are encouraging and offer new ways to accomplish more researches in studies on the BNCT technique.
Fatemeh Sadat Rasouli
Abstract
As one of the most clinically relevant parameters in proton radiotherapy, the range of incident particles can be measured either by counting the number of protons or through depth-dose evaluation in the target. In the latter, the range is defined as the depth in the ...
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As one of the most clinically relevant parameters in proton radiotherapy, the range of incident particles can be measured either by counting the number of protons or through depth-dose evaluation in the target. In the latter, the range is defined as the depth in the target at the distal 80% point of the Bragg peak. In this work, a highly accurate analytical model was employed to predict depth-dose distribution, and hence the range, in a desired target. Aiming to study the effect of energy spread on the range, proton beams with initial Gaussian distributions have been considered. For our arbitrary tested energies, the results show that the more the width of energy distribution increases, the more the Bragg peaks shift in depth, by about -0.25% to -25%, compared with those of monoenergetic beams. Furthermore, it was found that for different widths of initial energy spectrum, keeping the mean energy the same, the range remains unchanged. It was also shown that the results corresponding to utilizing analytical range determination for proton beams of different incident energies in stack of materials deviate from those of Monte Carlo simulations by less than 1.7%. The results are encouraging, although accurate modeling of analytical proton dose distribution in the presence of tissue inhomogeneities is still an unsolved problem.