ABSTRACT
Intrafraction organ motion, predominantly caused by patient breathing, can compromise the treatment outcome of radiation therapy for tumors in the thorax and abdomen, either by reducing the tumor-control probability with insufficient safety margins or by increasing the normal tissue toxicity by setting excessively large margins. Respiratory motion affects all tumor sites in the thorax and in the abdominal region, resulting in temporal anatomic changes. Such motion may distort the tumor volume and position (Chen, Kung, and Beaudette 2004; Shimizu et al. 2000). It has been shown in the literature that tumor motion due to respiration can be as large as 3 cm, especially in the superior/inferior direction, and heavily depends on the location of the tumor and the individual patient (Table 9.1).
