Determination of effective doses in image-guided radiation therapy system

13th South-East Asian Congress of Medical Physics 2015

物理学;医药卫生

Pyone, Y.Y.^1 ; Suriyapee, S.^1 ; Sanghangthum, T.^1,2 ; Oonsiri, S.^2 ; Tawonwong, T.^2

Medical Imaging, Department of Radiology, Faculty of Medicine, Chulalongkom University, Bangkok, Thailand^1

Division of Therapeutic Radiology and Oncology, Department of Radiology, King Chulalongkorn Memorial Hospital, Bangkok, Thailand^2

关键词: Anteroposterior;    Cone-beam CT;    Conversion coefficients;    Effective dose;    Entrance surface air kerma (ESAK);    Image guided radiotherapy;    Image-guided radiation therapy;    Pencil ionization chambers;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/694/1/012007/pdf
DOI  :  10.1088/1742-6596/694/1/012007

学科分类：卫生学

来源: IOP

【 摘 要 】

The organ and effective doses in image-guided radiotherapy system are determined in this study. For 2D imaging, incident air kerma (Ki) was measured by 6cc ionization chamber with Accu-Pro dosimeter. The entrance surface air kerma (ESAK) was calculated by multiplying Kiwith backscatter factor. The effective dose was calculated by multiplying ESAK with conversion coefficient. For 3D imaging, computed tomography/cone-beam dose index (CTDI/CBDI) measurements were performed by using 100mm pencil ionization chamber with Accu-Pro dosimeter. The dose index in air and in CTDI phantom from planning CT and cone- beam CT were measured. Then, effective dose was calculated by ImPACT software. The effective doses from 2D conventional simulator for anteroposterior and lateral projections were 01 and 0.02mSv for head, 0.15 and 0.16mSv for thorax, 0.22 and 0.21mSv for pelvis, respectively. The effective doses from 3D, planning CT and CBCT, were 3.3 and 0.1mSv for head, 13 and 2.4mSv for thorax and 7.2 and 4.9mSv for pelvis, respectively. Based on 30 fractions of treatment course, total effective dose (3D CT, 2D setup verification and 6 times CBCT) of head, thorax and pelvis were 3.93, 27.71 and 37.03mSv, respectively. Therefore, IGRT should be administered with significant parameters to reduce the dose.