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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

Relative isodose curves due to irradiation of a 32 MeV proton pencil beam to the water phantom (red curves) and ocular media (black curves). For better resolution, the horizontal axis is limited between 0.4 to 1.1 cm.
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Figure 6: Relative isodose curves due to irradiation of a 32 MeV proton pencil beam to the water phantom (red curves) and ocular media (black curves). For better resolution, the horizontal axis is limited between 0.4 to 1.1 cm.

Mentions: The depth-dose curves reported in previous section show comparisons between the proton beam performances in realistic ocular media and water in the direction parallel to the beam axis. In order to evaluate the performance of the beams in two models, the results are figured in the form of isodose curves, which provide a demonstration of lines passing through points of equal dose. Figure 6 is an example of these curves corresponding to irradiation of 32 MeV proton beam to both models. These planar variations of deposited energy in two models not only agree with the results of depth-dose curves shown in figure 3, but also confirm with this known fact that proton therapy is a convenient method to protect surrounding healthy tissue as much as possible. In other words, the proton beam effect corresponds solely to the depths which are located in the direction of beam.


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

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

Relative isodose curves due to irradiation of a 32 MeV proton pencil beam to the water phantom (red curves) and ocular media (black curves). For better resolution, the horizontal axis is limited between 0.4 to 1.1 cm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Relative isodose curves due to irradiation of a 32 MeV proton pencil beam to the water phantom (red curves) and ocular media (black curves). For better resolution, the horizontal axis is limited between 0.4 to 1.1 cm.
Mentions: The depth-dose curves reported in previous section show comparisons between the proton beam performances in realistic ocular media and water in the direction parallel to the beam axis. In order to evaluate the performance of the beams in two models, the results are figured in the form of isodose curves, which provide a demonstration of lines passing through points of equal dose. Figure 6 is an example of these curves corresponding to irradiation of 32 MeV proton beam to both models. These planar variations of deposited energy in two models not only agree with the results of depth-dose curves shown in figure 3, but also confirm with this known fact that proton therapy is a convenient method to protect surrounding healthy tissue as much as possible. In other words, the proton beam effect corresponds solely to the depths which are located in the direction of beam.

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