Investigation of the effects on dose calculations of correction-based algorithms in different tissue medium

Abstract

The aim of this study is to determine the effects of correction-based algorithms on dose distributions in the inhomogeneous medium and dosimetric parameters depending on the algorithms preferred in breast and lung treatment plans. In the treatment planning system (TPS) in which the Pencil Beam Convolution (PBC) dose calculation algorithm is used, dose calculations were performed in different correction-based algorithms Modified Batho and Equivalent Tissue-Air Ratio (ETAR) for soft tissue, bone and air medium. Rectilinear virtual phantoms were created in TPS for soft tissue, bone and air materials, and deep dose values and dose distribution profiles at lateral depth were obtained. Intensity modulated radiotherapy (IMRT) treatment planning technique was applied to 20 patients with breast and lung cancer diagnosis on computed tomography (CT) sections, and dose calculations were performed. Different dosimetric parameters obtained within the target volume were calculated. Although the effects of correction-based algorithms on dose values depending on the depth and dose distribution profiles in lateral depth were calculated below 1% in dose calculations performed on soft tissue virtual phantom, dose profiles were obtained as approximately 20% in bone and air medium. It was concluded that correction-based algorithms in the different inhomogeneous mediums have a significant effect on the dose values calculated in TPS.

Keywords

• Radiotherapy
• inhomogeneous medium
• correction methods
• dose calculation
• pencil beam convolution

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