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Study of the Reduction Technique for the Secondary Cancer Risk Due to Cone Beam CT in Image Guided Radiotherapy

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J Sung

J Sung1,2*, D Kim2, D Kim2, T Baek1, H Lee1, W Chung2, M Yoon1, (1) Korea University, Seoul, Korea, (2) Kyung Hee University Hospital at Gangdong, Seoul, Korea


SU-E-T-306 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: This study evaluated the effectiveness of a thin lead sheet based simple shielding method for imaging doses from cone beam computed tomography (CBCT) in image-guided radiotherapy (IGRT).

Methods: The entire body, except for the region scanned by CBCT, was shielded by wrapping in a 2 mm lead sheet. Reduction of secondary doses from CBCT was measured using a radio-photoluminescence glass dosimeter (RPLGD) placed inside an anthropomorphic phantom and changes in secondary cancer risk due to the shielding effect were estimated using BEIR VII model.

Results: Doses to out-of-field organs for head-and-neck, chest, and pelvis scans were decreased 15~100 %, 23~90 %, and 23~98 %, respectively, and the average reductions in lifetime secondary cancer risk due to the 2 mm lead shielding were 1.61, 10.4, and 12.8 persons per 100,000, respectively.

Conclusion: This study suggests that a simple thin lead sheet based shielding method results in a non-negligible reduction of secondary doses to out-of-field regions for CBCT.

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