Image Guidance During Head-and-Neck Cancer Radiation Therapy: Analysis of Alignment Trends With In-Room Cone-Beam Computed Tomography Scans

Using the first five CBCT shift measurements as an estimation of the systematic setup error improves daily setup accuracy for a subset of patients with head-and-neck cancer receiving intensity-modulated radiation therapy and primarily benefited those with large 3D correction vectors (>5 mm). Daily CBCT is still necessary until methods are developed that more accurately determine which patients may benefit from alternative imaging strategies.