Application of Cone Beam Computed Tomography to Conventional Radiotherapy: Limited Angle of Projections for Lymph Nodes Located above or below the Collarbone

Abstract

Various techniques are used in image-guided radiotherapy (IGRT). Cone beam computed tomography (CBCT) is widely used in IGRT on linear accelerators. The increased accuracy of IGRT enables reducing planning target volume margins and doses to normal tissues. However, for radiation therapies requiring fractionated irradiation, increased exposure dose attributed to CBCT becomes problematic. We investigated the smallest projection angle required to provide target accuracy for CBCT of lymph nodes located above or below the collarbone in breast cancer patients.