%0 Journal Article
%A Balaggan, Kamaljit S
%A Hamiliton, Russell J.
%A Drew, Mary E.
%A Patel, Praveen J
%A Hanumunthadu, Daren
%A Schindler, Reid
%A Restori, Marie
%A Ilgins, Tomas
%A McGovern, Meghan
%A Marsteller, Laurence
%T A comparison of expected dwell times and dose variations for neovascular age-related macular degeneration (n-AMD) patients treated with an episcleral brachytherapy device.
%B Investigative Ophthalmology & Visual Science
%D 2016
%J Investigative Ophthalmology & Visual Science
%V 57
%N 12
%P 4426-4426
%@ 1552-5783
%X To evaluate variations in dwell times and doses expected when using an episcleral brachytherapy device for treatment of n-AMD based on Optical Coherence Tomography and Ocular Ultrasound imaging modalities. To determine if a mean target depth is appropriate for all patients receiving episcleral brachytherapy. Data from 40 eyes from 40 subjects with known n-AMD was acquired through the Distance of Choroid Study (DOCS) conducted at Moorfields Eye Hospital. The purpose of DOCS was to determine the repeatability and limits of agreement of existing imaging modalities for the determination of retinal, choroidal and scleral thickness at the fovea and choroidal neovascularization (CNV) lesion in vivo. Each subject underwent EDI SD-OCT, SS-OCT and Ocular Ultrasound (O-US). Using the percentage depth dose for a Sr-90 episcleral brachytherapy device, dwell times and doses delivered are computed to determine the expected variations of each subject. The mean distance to target depth and the 95% confidence interval (CI) determined by combining O-US with SD-OCT were 1326 (956,1696)mm and with SS-OCT were 1332 (970,1693)mm. The calculated corresponding mean dwell times and 95% (CI) were 334 (223, 445)s and 335 (226, 445)s for SD-OCT and SS-OCT determined depths, respectively. The patient population average target depth for treatment planning results in dose variations of +/-33% over the 95% CI. The mean dwell times showed no significant difference between SD-OCT and SS-OCT. Each patient should have individualized imaging studies to determine the target depth. This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016. The apex dose for each patient found using the dwell time calculated based on the population average depth. The solid line is the intended prescription dose of 24Gy and the dotted lines are ±15% variations above and below this. The apex dose differs by more than 15% for 40% (16/40) of the patients if the population average depth is used for the dwell time calculation. Depth dose curve along a line through the center of the applicator and perpendicular to it. The dose changes rapidly with depth. When the prescription dose (24Gy) is delivered at a depth equal to the mean apex depth of the patients in our study (1.326mm), the doses at the apex depths within the 95% confidence interval of our patients, 0.956mm to 1.696mm, range from 33.6Gy to 17.1Gy.
%[ 3/31/2020