Brachytherapy in primary ocular tumors

Freire, Jorge E.; Potter, Patrick De; Brady, Luther W.; Longton, Wallace A.

doi:10.1002/(sici)1098-2388(199705/06)13:3<167::aid-ssu3>3.0.co;2-5

Cited by 34 publications

(2 citation statements)

References 35 publications

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“…18,19,20 For average and small sizes tumors, beta-ray applicators ( 106 Ru or 90 Sr) are preferred. 2,9,21 The available treatment planning system for 106 Ru applicators is based on simplified physical models of radiation transport and on a very rough approximation of the anatomy of the eye, which is assumed to be a homogeneous water sphere. 22 The Monte Carlo method has been used widely in dosimetric research of the human eye with different radioisotopes (ophthalmic applicators), beta and gamma emitters.…”

Section: Introductionmentioning

confidence: 99%

Assessment of ocular beta radiation dose distribution due to 106Ru/106Rh brachytherapy applicators using MCNPX Monte Carlo code

Barbosa¹,

Rosa²,

Menezes³

et al. 2014

Int J Cancer Ther Oncol

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Purpose: Melanoma at the choroid region is the most common primary cancer that affects the eye in adult patients. Concave ophthalmic applicators with 106 Ru/ 106 Rh beta sources are the more used for treatment of these eye lesions, mainly lesions with small and medium dimensions. The available treatment planning system for 106 Ru applicators is based on dose distributions on a homogeneous water sphere eye model, resulting in a lack of data in the literature of dose distributions in the eye radiosensitive structures, information that may be crucial to improve the treatment planning process, aiming the maintenance of visual acuity. Methods: The Monte Carlo code MCNPX was used to calculate the dose distribution in a complete mathematical model of the human eye containing a choroid melanoma; considering the eye actual dimensions and its various component structures, due to an ophthalmic brachytherapy treatment, using 106 Ru/ 106 Rh beta-ray sources. Two possibilities were analyzed; a simple water eye and a heterogeneous eye considering all its structures. Two concave applicators, CCA and CCB manufactured by BEBIG and a complete mathematical model of the human eye were modeled using the MCNPX code. Results and Conclusion: For both eye models, namely water model and heterogeneous model, mean dose values simulated for the same eye regions are, in general, very similar, excepting for regions very distant from the applicator, where mean dose values are very low, uncertainties are higher and relative differences may reach 20.4%. For the tumor base and the eye structures closest to the applicator, such as sclera, choroid and retina, the maximum difference observed was 4%, presenting the heterogeneous model higher mean dose values. For the other eye regions, the higher doses were obtained when the homogeneous water eye model is taken into consideration. Mean dose distributions determined for the homogeneous water eye model are similar to those obtained for the heterogeneous eye model, indicating that the homogeneous water eye model is a reasonable one. The determined isodose curves give a good visualization of dose distributions inside the eye structures, pointing out their most exposed volume.

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Section: Introductionmentioning

confidence: 99%

Assessment of ocular beta radiation dose distribution due to 106Ru/106Rh brachytherapy applicators using MCNPX Monte Carlo code

Barbosa¹,

Rosa²,

Menezes³

et al. 2014

Int J Cancer Ther Oncol

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“…[1] Literature studies reveal globe preservation with nonsurgical treatment, using radiation therapy with possible preservation of vision. The dose of teleradiation with megavoltage therapy required to control the primary tumor like melanomas or metastasis can exceed the tolerance of retina, optic nerve, lens, eyelids and lashes.…”

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confidence: 99%

Dosimetry and treatment planning of Occu-Prosta I-125 seeds for intraocular lesions

et al. 2008

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Intraocular malignant lesions are frequently encountered in clinical practice. Plaque brachytherapy represents an effective means of treatment for intraocular lesions. Recently Radiopharmaceutical Division, BARC, Mumbai, has indigenously fabricated reasonable-cost I-125 sources. Here we are presenting the preliminary experience of dosimetry of sources, configuration of treatment planning system (TPS) and quality assurance (QA) for eye plaque therapy with Occu-Prosta I-125 seeds, treated in our hospital, for a patient with ocular lesions. I-125 seeds were calibrated using well-type chamber. BrachyVision TPS was configured with Monte Carlo computed radial dose functions and anisotropy functions for I-125 sources. Dose calculated by TPS at different points in central axis and off axis was compared with manually calculated dose. Eye plaque was fabricated of 17 karat pure gold, locally. The seeds were arranged in an outer ring near the edge of the plaque and in concentric rings throughout the plaque. The sources were manually digitized on the TPS, and dose distribution was calculated in three dimensions. Measured activity using cross-calibrated well-type chamber was within ±10% of the activity specified by the supplier. Difference in TPS-calculated dose and manually calculated dose was within 5%. Treatment time calculated by TPS was in concordance with published data for similar plaque arrangement.

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