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Microresolution Dosimetry System for Patient Specific Quality Assurance of Ocular Melanoma Eye Plaque Based Treatments

S Pokhrel1*, A Wiles1 , T Knewtson1 ,Y Feng 1,2, M Ballo1,2 , E W Izaguirre1,2 , (1) university Tennessee Health Science Center,Methodist university Hospital, Memphis, TN., (2)West Cancer Center, Germantown, TN.


(Wednesday, 8/1/2018) 7:30 AM - 9:30 AM

Room: Davidson Ballroom A

Purpose: To develop a phantom and companion software to determine the dose delivered by using non-COMS eye plaque constructs with sub-millimetric resolution for the measurement of patient specific quality assurance of ocular melanoma treatments.

Methods: We designed and constructed a water equivalent phantom to measure the dose delivered by a non-COMS eye plaque using calibrated radiochromic film. The phantom body was 3D printed using micrometric resolution layer deposition printing techniques. The phantom has a gelatin spheroid core mimicking the globe of the eye. Dose is measured on radiochromic films positioned at the three principle Cartesian planes within the globular phantom core. An in house developed program generates a 3D reconstruction of the dose in the eye globe volume region by interpolating the dose from the films irradiated at the three Cartesian planes. Film dosimetry was performed using calibrated XR-QA2 film and scanned with a sampling rate of 50 um or better.

Results: The phantom was tested using non-COMS plaques from 12 mm diameter to 22 mm diameter. Phantom dose measurements agree within 10% of point dose estimations predicted by a commercial treatment planning system. Dose was determined in each plane with 0.1 mm resolution with minimal noise in the isodose. The interpolation of the isodose in the globe volume shows the expected distribution at any plane orientation. Some abnormalities in the dose distribution symmetry were observed and we determined that they originate from variations in seed positioning and activity.

Conclusion: We validated the design, construction, and implementation of a dosimetric system consisting of a phantom and software for quality assurance of eye plaque constructs to determine the volumetric dose delivered to ocular melanomas. This is the first high-resolution 3D dosimetry study performed on eye plaques.


Brachytherapy, Eye Plaques


TH- Brachytherapy: Calibration & Quality Assurance

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