Using 3D dosimetry to quantify the Electron Return Effect (ERE) for MR-image-guided radiation therapy (MR-IGRT) applications

9th International Conference on 3D Radiation Dosimetry

Lee, Hannah J.^1,2 ; Won Choi, Gye^1,2 ; Alqathami, Mamdooh^1 ; Kadbi, Mo^3 ; Ibbott, Geoffrey^1

Department of Radiation Physics, UT MD Anderson Cancer Center, Houston

TX, United States^1

UT at Houston Graduate School of Biomedical Sciences, Houston

TX, United States^2

MR Therapy, Philips HealthTech, Cleveland

OH, United States^3

关键词: Different densities;    Electron return effects;    Image-guided radiation therapy;    Patient positioning;    Secondary electrons;    Strong magnetic fields;    Threedimensional (3-d);    Treatment planning;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/847/1/012057/pdf
DOI  :  10.1088/1742-6596/847/1/012057

来源: IOP

【 摘 要 】

Image-guided radiation therapy (IGRT) using computed tomography (CT), cone-beam CT, MV on-board imager (OBI), and kV OBI systems have allowed for more accurate patient positioning prior to each treatment fraction. While these imaging modalities provide excellent bony anatomy image quality, MRI surpasses them in soft tissue image contrast for better visualization and tracking of soft tissue tumors with no additional radiation dose to the patient. A pre-clinical integrated 1.5 T magnetic resonance imaging and 7 MV linear accelerator system (MR-linac) allows for real-time tracking of soft tissues and adaptive treatment planning prior to each treatment fraction. However, due to the presence of a strong magnetic field from the MR component, there is a three dimensional (3D) change in dose deposited by the secondary electrons. Especially at nonhomogeneous anatomical sites with tissues of very different densities, dose enhancements and reductions can occur due to the Lorentz force influencing the trajectories of secondary electrons. These dose changes at tissue interfaces are called the electron return effect or ERE. This study investigated the ERE using 3D dosimeters.