Homogeneous and inhomogeneous material effect in gamma index evaluation of IMRT technique based on fan beam and Cone Beam CT patient images

10th International Seminar on Medical Physics; 1st AMDI International Oncology Symposium

物理学;医药卫生

Wibowo, W.E.^1,2 ; Waliyyulhaq, M.^2 ; Pawiro, S.A.^2

Department of Radiotherapy, National General Hospital Dr. Cipto Mangunkusumo, DKI Jakarta

10430, Indonesia^1

Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Kampus UI, Depok

16424, Indonesia^2

关键词: Dose calculation;    Grid resolution;    Homogeneous materials;    Inhomogeneous materials;    Intensity-modulated radiation therapy;    Patient images;    Patient specific;    Treatment planning systems;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/851/1/012021/pdf
DOI  :  10.1088/1742-6596/851/1/012021

学科分类：卫生学

来源: IOP

【 摘 要 】

Patient-specific Quality Assurance (QA) technique in lung case Intensity-Modulated Radiation Therapy (IMRT) is traditionally limited to homogeneous material, although the fact that the planning is carried out with inhomogeneous material present. Moreover, the chest area has many of inhomogeneous material, such as lung, soft tissue, and bone, which inhomogeneous material requires special attention to avoid inaccuracies in dose calculation in the Treatment Planning System (TPS). Recent preliminary studies shown that the role of Cone Beam CT (CBCT) can be used not only to position the patient at the time prior to irradiation but also to serve as planning modality. Our study presented the influence of a homogeneous and inhomogeneous materials using Fan Beam CT and Cone Beam CT modalities in IMRT technique on the Gamma Index (GI) value. We used a variation of the segment and Calculation Grid Resolution (CGR). The results showed the deviation of averaged GI value to be between CGR 0.2 cm and 0.4 cm with homogeneous material ranging from -0.44% to 1.46%. For inhomogeneous material, the value was range from -1.74% to 0.98%. In performing patient-specific IMRT QA techniques for lung cancer, homogeneous material can be implemented in evaluating the gamma index.