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Comparative Effectiveness and Safety of Radiotherapy Treatments for Head and Neck Cancer

Slide: 11 of 36

Two-Dimensional Radiation Therapy and Three-Dimensional Conformal Radiation Therapy

Modern advances in computers have led to parallel advances in imaging technologies, allowing for higher levels of complexity in radiation therapy (RT) treatment-planning systems. Over the last 20 years, RT designs have evolved from being based on two-dimensional (2D) images to being based on three-dimensional (3D) images. During this evolution, increasingly complex computer algorithms have been incorporated. 2DRT consists of one to four beams with the radiation fields designed on 2D fluoroscopic simulation images; whereas, 3D conformal RT (CRT) employs computed tomography simulation, which permits more precise tumor definition. 3DCRT represented a major advance over 2DRT, because it permitted more accurate dose calculations by taking into account axial anatomy and complex tissue contours. 3DCRT also permits the use of a greater number of beams than are typically used in 2DRT.