Application of a dummy eye shield for electron treatment planning.
Metallic eye shields have been widely used for near-eye treatments to protect critical regions, but have never been incorporated into treatment plans because of the unwanted appearance of the metal artifacts on CT images. The purpose of this work was to test the use of an acrylic dummy eye shield as a substitute for a metallic eye shield during CT scans. An acrylic dummy shield of the same size as the tungsten eye shield was machined and CT scanned. The BEAMnrc and the DOSXYZnrc were used for the Monte Carlo (MC) simulation, with the appropriate material information and density for the aluminum cover, steel knob and tungsten body of the eye shield. The Pinnacle adopting the Hogstrom electron pencil-beam algorithm was used for the one-port 6-MeV beam plan after delineation and density override of the metallic parts. The results were confirmed with the metal oxide semiconductor field effect transistor (MOSFET) detectors and the Gafchromic EBT2 film measurements. For both the maximum eyelid dose over the shield and the maximum dose under the shield, the MC results agreed with the EBT2 measurements within 1.7%. For the Pinnacle plan, the maximum dose under the shield agreed with the MC within 0.3%; however, the eyelid dose differed by -19.3%. The adoption of the acrylic dummy eye shield was successful for the treatment plan. However, the Pinnacle pencil-beam algorithm was not sufficient to predict the eyelid dose on the tungsten shield, and more accurate algorithms like MC should be considered for a treatment plan.
Department of Radiation Oncology, KangDong Sacred Heart Hospital, Hallym University College of Medicine, 445 Gil-Dong KangDong-Gu, Seoul 134-701, Korea. seikang@hallym.or.kr
Sei-Kwon
SK
Kang
Soah
S
Park
Taejin
T
Hwang
Kwang-Ho
KH
Cheong
Taejin
T
Han
Haeyoung
H
Kim
Me-Yeon
MY
Lee
Kyoung Ju
KJ
Kim
Do Hoon
DH
Oh
Hoonsik
H
Bae
D004583:Electrons / Q000627:therapeutic use; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005131:Eye Injuries / Q000209:etiology / Q000517:prevention & control*; D005135:Eye Protective Devices; D005142:Eyelid Neoplasms / Q000150:complications / Q000532:radiotherapy*; D006801:Humans; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control*; D011835:Radiation Protection / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D016896:Treatment Outcome