Assessment of female breast dose for thoracic cone-beam CT using MOSFET dosimeters
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Wenzhao Sun1,*, Bin Wang1,*, Bo Qiu1, Jian Liang1, Weihao Xie1, Xiaowu Deng1, Zhenyu Qi1
1Department of Radiation Oncology, Sun Yat-Sen University Cancer Center, Collaborative Innovation Center for Cancer Medicine, State Key Laboratory of Oncology in South China, Guangzhou 510060, China
*These authors have contributed equally to this work
Zhenyu Qi, email: [email protected]
Keywords: radiotherapy, cone beam computed tomography (CBCT), metal oxide semiconductor field-effect transistor (MOSFET), breast dose, image registration
Received: July 26, 2016 Accepted: January 23, 2017 Published: February 21, 2017
Objective: To assess the breast dose during a routine thoracic cone-beam CT (CBCT) check with the efforts to explore the possible dose reduction strategy.
Materials and Methods: Metal oxide semiconductor field-effect transistor (MOSFET) dosimeters were used to measure breast surface doses during a thorax kV CBCT scan in an anthropomorphic phantom. Breast doses for different scanning protocols and breast sizes were compared. Dose reduction was attempted by using partial arc CBCT scan with bowtie filter. The impact of this dose reduction strategy on image registration accuracy was investigated.
Results: The average breast surface doses were 20.02 mGy and 11.65 mGy for thoracic CBCT without filtration and with filtration, respectively. This indicates a dose reduction of 41.8% by use of bowtie filter. It was found 220° partial arc scanning significantly reduced the dose to contralateral breast (44.4% lower than ipsilateral breast), while the image registration accuracy was not compromised.
Conclusions: Breast dose reduction can be achieved by using ipsilateral 220° partial arc scan with bowtie filter. This strategy also provides sufficient image quality for thorax image registration in daily patient positioning verification.
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