Ultrasonic mirror image from ruthenium plaque facilitates calculation of uveal melanoma treatment dose

Background/aimsTo present a new method to determine dose depth and the distance from the concave side of the plaque to the tumour base in patients with uveal melanoma treated with ruthenium-106 based on ultrasonic mirror image.MethodsWe used the mirror image associated with ultrasound during plaque brachytherapy to determine intraobserver reproducibility and interobserver agreement between two surgeons. 230 eyes with primary uveal melanoma were included in a retrospective analysis to determine the distance from the plaque to the tumour base using ultrasound. A phantom study was used to illustrate the effects on radiation dose to apex of the tumour when the dose depth was incorrectly determined. Doses to apex of the tumour were determined using Plaque Simulator.ResultsThe intraobserver variation in dose depth measurement with plaque was significantly lower than for measures without plaque (p