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Development and Application of a High Precision Optical Guidance System for Customizable I-125 Eye Plaque Production

K Nealon*, A Ayan , N Gupta , J Woollard , Ohio State Univ, Columbus, OH


(Tuesday, 7/31/2018) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 6

Purpose: Development of an optical guidance system to be clinically implemented to increase the precision of seed placement, and thus limit the dosimetric uncertainty, for customizable I-125 eye plaques.

Methods: Following a study which demonstrated the substantial impact a slight deviation in seed placement can have on the total dose delivered by an eye plaque, a high precision optical guidance system was developed as an alternative to the caliper-based technique which is currently in place at our institution. In this system, the plaque is secured in a fixed location to ensure that both of the physicist’s hands are free to assist with placement. A camera, located above the stand, overlays the planned seed position on a live video feed of the plaque. This provides real-time feedback with sub-millimeter resolution, to limit the intrinsic uncertainty of this process.

Results: A proof-of-concept design has been developed which verifies the feasibility of our system. A MATLAB code performs a spatial calibration of an image by relating the number of pixels to the dimensions of a known object. This code has been used to analyze plaques created without optical system guidance. By projecting the planned locations on these plaques, it was possible to determine the deviation between intended and actual seed position. Analyzing this data for several plaques, an average positional deviation of .602mm ± .687mm was found. By modelling the plaques according to the actual position of the seeds, an average deviation from prescribed dose of 5.1% was determined.

Conclusion: A preliminary model has been developed, validated and shown to be useful in improving the accuracy of eye plaque seed positioning. Upon implementation, it will be possible to place seeds in a more predictable and consistent method, ensuring accurate dose delivery. A higher resolution system is currently in development for full clinical use.


Eye Plaques, Optical Imaging, Brachytherapy


TH- Brachytherapy: Development (new technology and techniques)

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