Interventions to reduce organ motion effects in radiation delivery

Because organ motion during a radiation treatment fraction can be substantial, with resultant alterations in organ volume definition and dosimetry, interventions to reduce the impact of intratreatment organ motion are required for many patients if dose escalation and reduction of dose to normal tissue are treatment goals. Before radiation delivery, fluoroscopy, cine computed tomography scans and magnetic resonance imaging can be used to measure the magnitude of organ motion for an individual patient. Strategies to minimize organ motion caused by breathing during radiation include altering breathing patterns, treating during voluntary or controlled breath holds, gating the radiation beam or tracking it with organ motion. Here the first 2 interventions will be primarily discussed. Approaches to minimize nonrespiratory organ motion include maintaining the same preparative regimen before each treatment and ensuring comfortable immobilization and short overall treatment time.