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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

The created spread out Bragg peaks (SOBP) inside instance depths in water phantom and ocular media based on the optimized weighting factors reported in table 2.
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Figure 4: The created spread out Bragg peaks (SOBP) inside instance depths in water phantom and ocular media based on the optimized weighting factors reported in table 2.

Mentions: It is well known that a strictly monoenergetic proton beam is unsuitable for cancer treatment due to the longitudinally narrow peak. Rather, it is necessary to ‘spread out’ the Bragg peak to deliver uniform dose within the target volume, by providing a suitably weighted energy distribution of the incident beam [24]. This section aims to investigate the effect of defining realistic media on uniformity of delivered dose to tumor. The method is based on multiplying appropriate optimized weighting factors in pristine Bragg curves to cover the extended tumor target volume in each depth with the required dose in both designed models (See eq. 1). The optimized weights for all utilized pencil beams irradiated in water phantom are presented in table 2, as well as the ocular media. The created SOBPs based on these weights are shown in figure 4. The effect of more penetration of pristine Bragg peaks in water phantom in comparison to ocular media can be seen in two SOBPs, too. 


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

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

The created spread out Bragg peaks (SOBP) inside instance depths in water phantom and ocular media based on the optimized weighting factors reported in table 2.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 4: The created spread out Bragg peaks (SOBP) inside instance depths in water phantom and ocular media based on the optimized weighting factors reported in table 2.
Mentions: It is well known that a strictly monoenergetic proton beam is unsuitable for cancer treatment due to the longitudinally narrow peak. Rather, it is necessary to ‘spread out’ the Bragg peak to deliver uniform dose within the target volume, by providing a suitably weighted energy distribution of the incident beam [24]. This section aims to investigate the effect of defining realistic media on uniformity of delivered dose to tumor. The method is based on multiplying appropriate optimized weighting factors in pristine Bragg curves to cover the extended tumor target volume in each depth with the required dose in both designed models (See eq. 1). The optimized weights for all utilized pencil beams irradiated in water phantom are presented in table 2, as well as the ocular media. The created SOBPs based on these weights are shown in figure 4. The effect of more penetration of pristine Bragg peaks in water phantom in comparison to ocular media can be seen in two SOBPs, too. 

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