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Effects of defining realistic compositions of the ocular melanoma on proton therapy.

Keshazare Sh, Masoudi SF, S Rasouli F - J Biomed Phys Eng (2014)

Bottom Line: The results show that the maximum delivered dose in ocular media is approximately 12-32% more than in water phantom.Also it is found that using the optimized weighted beams in water phantom leads to disturbance of uniformity of SOBP in ocular media.This effect is of special importance in creating SOBP, as well as in delivered dose in the tumor boundaries in proton pencil beam scanning method.

View Article: PubMed Central - PubMed

Affiliation: MSc Student in Applied Nuclear Physics, Department of Physics, KN Toosi University of Technology, Tehran, Iran.

ABSTRACT

Background: Recent studies in eye plaque brachytherapy have shown a considerable difference between the dosimetric results using water phantom and a model of human eye containing realistic materials. In spite of this fact, there is a lack of simulation studies based on such a model in proton therapy literatures. In the presented work, the effect of utilizing an eye model with ocular media on proton therapy is investigated using the MCNPX Monte Carlo Code.

Methods: Two different eye models are proposed to study the effect of defining realistic materials on dose deposition due to utilizing pencil beam scanning (PBS) method for proton therapy of ocular melanoma. The first model is filled with water, and the second one contains the realistic materials of tumor and vitreous. Spread out Bragg peaks (SOBP) are created to cover a typical tumor volume. Moreover, isodose curves are figured in order to evaluate planar variations of absorbed dose in two models.

Results: The results show that the maximum delivered dose in ocular media is approximately 12-32% more than in water phantom. Also it is found that using the optimized weighted beams in water phantom leads to disturbance of uniformity of SOBP in ocular media.

Conclusion: Similar to the results reported in eye brachytherapy published papers, considering the ocular media in simulation studies leads to a more realistic assessment of sufficiency of the designed proton beam in tissue. This effect is of special importance in creating SOBP, as well as in delivered dose in the tumor boundaries in proton pencil beam scanning method.

No MeSH data available.


Related in: MedlinePlus

A profile of depth-dose curves due to the irradiation of two typical proton pencil beams to the water phantom (solid lines) and ocular media (dashed lines) which are described in Materials and Methods. The 31 MeV and 23 MeV proton beams are corresponding to the peaks which are formed in the more and less depths, respectively.
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Figure 3: A profile of depth-dose curves due to the irradiation of two typical proton pencil beams to the water phantom (solid lines) and ocular media (dashed lines) which are described in Materials and Methods. The 31 MeV and 23 MeV proton beams are corresponding to the peaks which are formed in the more and less depths, respectively.

Mentions: As mentioned earlier, the more proton energy results in more penetration in tissue, and the beam designer should consider appropriate proton energies in order to cover the whole tumor volume. In the presented section, proton pencil beams with different energies are irradiated to two eye models described in previous section, and the resultant Bragg peaks and depth-dose curves are calculated. As an example of the performance of protons in depth of two models, Bragg curves corresponding to two typical energies are shown in figure 3.


Effects of defining realistic compositions of the ocular melanoma on proton therapy.

Keshazare Sh, Masoudi SF, S Rasouli F - J Biomed Phys Eng (2014)

A profile of depth-dose curves due to the irradiation of two typical proton pencil beams to the water phantom (solid lines) and ocular media (dashed lines) which are described in Materials and Methods. The 31 MeV and 23 MeV proton beams are corresponding to the peaks which are formed in the more and less depths, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4289521&req=5

Figure 3: A profile of depth-dose curves due to the irradiation of two typical proton pencil beams to the water phantom (solid lines) and ocular media (dashed lines) which are described in Materials and Methods. The 31 MeV and 23 MeV proton beams are corresponding to the peaks which are formed in the more and less depths, respectively.
Mentions: As mentioned earlier, the more proton energy results in more penetration in tissue, and the beam designer should consider appropriate proton energies in order to cover the whole tumor volume. In the presented section, proton pencil beams with different energies are irradiated to two eye models described in previous section, and the resultant Bragg peaks and depth-dose curves are calculated. As an example of the performance of protons in depth of two models, Bragg curves corresponding to two typical energies are shown in figure 3.

Bottom Line: The results show that the maximum delivered dose in ocular media is approximately 12-32% more than in water phantom.Also it is found that using the optimized weighted beams in water phantom leads to disturbance of uniformity of SOBP in ocular media.This effect is of special importance in creating SOBP, as well as in delivered dose in the tumor boundaries in proton pencil beam scanning method.

View Article: PubMed Central - PubMed

Affiliation: MSc Student in Applied Nuclear Physics, Department of Physics, KN Toosi University of Technology, Tehran, Iran.

ABSTRACT

Background: Recent studies in eye plaque brachytherapy have shown a considerable difference between the dosimetric results using water phantom and a model of human eye containing realistic materials. In spite of this fact, there is a lack of simulation studies based on such a model in proton therapy literatures. In the presented work, the effect of utilizing an eye model with ocular media on proton therapy is investigated using the MCNPX Monte Carlo Code.

Methods: Two different eye models are proposed to study the effect of defining realistic materials on dose deposition due to utilizing pencil beam scanning (PBS) method for proton therapy of ocular melanoma. The first model is filled with water, and the second one contains the realistic materials of tumor and vitreous. Spread out Bragg peaks (SOBP) are created to cover a typical tumor volume. Moreover, isodose curves are figured in order to evaluate planar variations of absorbed dose in two models.

Results: The results show that the maximum delivered dose in ocular media is approximately 12-32% more than in water phantom. Also it is found that using the optimized weighted beams in water phantom leads to disturbance of uniformity of SOBP in ocular media.

Conclusion: Similar to the results reported in eye brachytherapy published papers, considering the ocular media in simulation studies leads to a more realistic assessment of sufficiency of the designed proton beam in tissue. This effect is of special importance in creating SOBP, as well as in delivered dose in the tumor boundaries in proton pencil beam scanning method.

No MeSH data available.


Related in: MedlinePlus