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SU‐E‐T‐307: A Dummy Eye Shield for Electron Treatment Planning
Author(s) -
Kang SK,
Park S,
Hwang T,
Cheong K,
Lee M,
Kim K,
Oh D,
Bae H
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3612258
Subject(s) - shield , materials science , dosimetry , pinnacle , tungsten , nuclear medicine , optics , radiation treatment planning , physics , medicine , geology , radiation therapy , metallurgy , surgery , petrology
Purpose: An electron treatment for the eyelid is routinely executed with the radiation shield accessory. However, the incorporation of the shield into the dose calculation is not satisfactory, mainly because of the metal artifacts from the shield. Here, we present the use of an acrylic dummy eye shield for tungsten shield and evaluate the procedure and accuracy. Methods: Both the 2 mm thickness tungsten eye shield and the acrylic eye shield machined with the same size were used for the CT scan and beam delivery. Considering the tungsten, steel knob and thin aluminum cover, Monte Carlo simulation and the Pinnacle (version, 8.0m; Phillips Medical Systems, Madison, WI, USA) plan were made for the electron 6 MeV deliveries. The results were confirmed with the metal oxide semiconductor field effect transistor (MOSFET) detectors and Gafchromic EBT2 film measurements. Results: From the MC and EBT2 film measurements, both the maximum dose below the tungsten shield and the eyelid dose above the shield agreed respectively to each other within 1.7%. The Pinnacle plan based on the CT number modified images of the acrylic shield showed the maximum dose agreed with the MC within 0.3%; however, the eyelid dose were under calculated by 19.3%. Conclusions: Using the dummy eye shield for the electron treatment plan on the Pinnacle, contouring of the tungsten shield body and steel knob only, and the following density adjustment was sufficient for the evaluation of the dose distribution below the eye shield. The eyelid dose, however, was underestimated by 19.3%.