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A. V. Chappelow, A. D. Singh, D. A. Wilkinson, M. Kolar, P. Fleming; Comparison of Radiation Dosage to Ocular Structures With Ru-106 and I-125 Plaques for Choroidal Melanoma. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5235.
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To compare radiation dosage to the macula, optic nerve head, lens, and sclera with Ru-106 or I-125 radiation plaques for choroidal melanoma.
Using treatment planning software (Plaque Simulator; Bebig, Berlin, Germany), brachytherapy was simulated with each of two isotopes (Ru-106 and I-125) for 45 patients with choroidal melanoma 5mm or less in thickness. Plaque size and location varied based upon actual tumor size, but radiation dose to the tumor apex was held constant at 85 Gy. Radiation dosage to the optic nerve head, lens, macula and sclera was recorded for treatment simulations with both Ru-106 and I-125. Differences in radiation dosage between the two isotopes at each anatomic location were calculated and statistical significance evaluated with the paired two-sample t-test.
The mean dose to the optic nerve head, lens, and macula was 48% (p<0.0001), 82% (p<0.0001), and 14% (p=0.05) less with Ru-106 than with I-125, respectively. The inner and outer scleral doses were greater (17%, p<0.001; 29%, p<0.0001) for the beta-emitter Ru-106.
In selected cases of choroidal melanoma (not exceeding 5mm in thickness), brachytherapy with Ru-106 (vs. I-125) significantly reduces radiation dosage to the optic nerve head, lens, and macula. Brachytherapy with Ru-106 may be associated with reduced risk of visual morbidity.
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