A comprehensive review of image-guided techniques in adaptive radiotherapy

Radiotherapy (RT) is a treatment modality that utilizes various forms of radiation, such as electrons, photons, protons, and carbon ions, to eradicate tumor cells. Although RT demonstrates significant efficacy in tumor eradication, it concurrently causes harm to adjacent normal tissues and organs. The primary challenge in RT lies in achieving adequate dose delivery to the tumor target area while minimizing damage to surrounding normal tissues. Traditional RT is typically administered in fractions during which changes can occur in the patient’s body shape, tumor size and shape, filling and displacement of organs at risk (OARs) near the target area, and beam entry distance. Adaptive RT (ART) is a personalized RT approach that enhances tumor local control and reduces toxicity to OARs by correcting both systematic errors, including anatomical changes or tumor position shifts, through the optimization of prescription doses and margins, as well as modifying initial plans when necessary. ART encompasses three main modes: offline ART, online ART, and real-time ART. Image guidance methods employed in ART include computed tomography (CT), cone-beam CT, and magnetic resonance imaging. This review primarily discussed the advantages and disadvantages of these three image guidance methods.