Respiratory motion management

During radiation therapy, the targets—particularly those located in the thoracic and abdominal regions—move during respiration. Conventionally, the internal target volume method is commonly adapted to perform radiation therapy for such targets, as it sufficiently covers the range of movement. However, using this approach, the surrounding normal tissue is also irradiated with a high dose, which may have adverse consequences. With recent advances in radiotherapy systems, four-dimensional radiotherapy can be performed in clinical practice. In this approach, breath-hold, respiratory gating, and real-time tumor tracking techniques can be adopted to manage respiratory motion. According to AAPM TG-76, respiratory motion management should be conducted if the range of target motion in any direction is greater than 5 mm. In this chapter, the conventional respiratory motion management method will first be introduced. Then, the basic methodologies and developments of real-time tumor tracking will be discussed.