Dose distribution assessment in human eye proton therapy by Monte

Carlo method

1 Department of Physics, Faculty of Science, University of Isfahan, Isfahan, Iran.

2 *Department of Biomedical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, Iran

Karimian@eng.ui.ac.ir

M. Tavakol1, A. Karimian 2* , S.M. Mostajab Aldaavati1

04/19/23 1

www.amazingeye.com04/19/23 2

Eye and its anatomic structure

Eye TumorsEye Tumors

Tumors in the eye usually are secondary tumors caused by cancers that have spread from other parts of the body, especially the breast, lung, bowel or prostate.

Two types of primary tumors arise within the eye itself and are known as retinoblastoma in children and melanoma in adults

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http://www.hopkinsmedicine.org/wilmer/conditions/tumors.html3

RetinoblastomaRetinoblastoma

Retinoblastoma is a cancer of the retina. This most common childhood

eye cancer usually strikes children under age five, affecting 500 to 600

in the United States each year. In nearly a third of the cases,

retinoblastoma occurs in both eyes.

04/19/23http://www.hopkinsmedicine.org/wilmer/conditions/

tumors.html4

melanomamelanoma

Malignant melanoma occurs most frequently in adults 60 to

65 years of age, arising from uncontrolled growth of cells

called melanocytes. From 1,500 to 2,000 new cases are

diagnosed annually in the United States

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Eye tumors Eye tumors affectsaffects

In addition to damaging vision, eye tumors can spread to the optic nerve, the

brain and the rest of the body.Melanoma tends to spread via blood

vessels to distant organs Therefore, early diagnosis and

treatment are extremely important.

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Eye tumor treatment methodsEye tumor treatment methods

There are various ways to treat eye tumors, depending on the size and aggressiveness of the

tumor, and other factors.

Surgery, Radiation Therapy, laser and cryosurgery may use for eye tumor treatment

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Radiation therapy

Internal radiation therapy

Proton therapy

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Tele-therapy (LINAC, …)

plaque therapy

Brachytherapy

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Advantags of proton particles

Noninvasive

Small dimensions

Focal Proton Particles

Energetic but

controlled

Rather short-range

Suitable Bragg Peak

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Individual mask

Block-Bite

[http://www.triumf.info/public/tech_transfer/treatment.php.]

Nozzle

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In spite of the advantages of proton therapy, during treatment, the tumor and also other components of vision like optic nerve, cornea, lens, anterior chamber are subjected to the radiation.

Malignant melanomas appear most commonly in the choroid

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In this research, one proton therapy system belonging to the Laboratori Nazionali del Sud- INFN as well as the human eye and its components were simulated by Monte Carlo method.Maximum proton energy beam = 250 MeVProton beam radius = 0.5 cm Modifier thickness = 1.5 cmNumber of particles per second = 1.25 E+10

In this research:Energy for eye = ( 50 – 65 ) MeVProton beam radius = ( 0.6 - 0.8 ) cmModifier thickness = ( 1 - 1.9 ) cm

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To assess the absorbed dose in different parts of eye, the proton therapy system, the nuzzle aperture, modifier, different parts of eye such as choroid and sclera, retina and etc, also vision sense parts such as optic nerve, cornea, lens and anterior chamber were simulated by Monte Carlo method.

The eye was simulated by considering real materials and densities of eye components such as lens, cornea, retina, anterior chamber .

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Optic nerve

Vitreous

Lens

Anterior chamber

Cornea

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Optic Nerve

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Treatment view of choroid and sclera cancer

The study was done in the following two stages, by changing the thickness of modifier in the range of 1.0 – 1.9 cm :

I. A tumor with the radius of 0.28 cm in choroid region (cell 23)

II. A tumor with the radius of 0.26 cm in choroid region and close to optic nerve (cell 27)

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Radius tumor = 0.28 cmVolume tumor = 0.0914 cm3

30

39

20

29

23

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23

cell No.23Radius tumor = 0.28 cm

Volume tumor = 0.0914 cm3

proton energy beam = 53.5 MeV

Modifier thickness = 1.5 cm

proton beam radius = 0.8 cm

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Dos

e (G

y)

Cell No

19

Cells The calculated total dose (Gy) in this study for the tumor in the choroid and sclera regions (cell No.23)

10 6.6411 2.5612 0.3913 7.9214 1.2820 43.1221 45.1222 47.5223 49.6824 47.1225 29.7626 8.2427 0.1228 029 030 0.007831 0.0003532 033 034 035 036 037 038 039 004/19/23 20

Radius tumor = 0.26 cmVolume tumor = 0.076 cm3

30

39

20

29

27

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27

cell No.27

Radius tumor = 0.26 cmVolume tumor = 0.076 cm3

proton energy beam = 65 MeV

modifier thickness = 1.5 cm

proton beam radius = 0.5 cm

Dos

e (G

y)

Cell No

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Cells The calculated total dose (Gy) in this study for the tumor in the choroid and sclera regions (cell No.27)

10 2.3211 0.3412 0.3313 20.0414 6.6420 43.221 42.5622 40.1623 3824 37.6825 40.426 47.627 49.3628 23.6829 6.2430 0.04631 0.03732 0.03833 0.01834 0.02135 0.02836 0.02437 0.005238 039 004/19/23 23

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This research showed in spite of the benefits of proton therapy in eye cancer treatment, the absorbed dose of healthy parts of eye specially the closed parts to the tumor are considerable and needs to reduce as much as possible.The absorbed dose depends on the energy of proton beam, modifier thickness, size and location of tumor, radiation angle , etc, Which can modify and improve by Monte Carlo method.

Position tumor

Radius tumor proton beam radius

modifier thickness

proton energy beam

Cell No.27 cm 0.26 cm 0.5 cm 1.5 MeV 65

Cell No.23 cm 0.28 cm 0.8 cm 1.5 MeV 53.5

Conclusion

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Thank you