ABSTRACT
In recent years, it has become increasingly practical to irradiate tumors while they move under the inuence of respiration. In this process, the CyberKnife® system (Adler et al 1998) has won a rm spot in clinical treatment of moving tumors without using respiratory coaching, gating, or xation. However, as has been discussed in Chapter 1, it is usually necessary to use surrogate signals to infer the tumor’s changing position. To achieve this using the CyberKnife, the excursion of the patient’s chest is recorded and correlated to articial landmarks in the tumor observed during stereoscopic x-ray imaging (Schweikard et al 2000; Urschel et al 2007). (It has been demonstrated that this correlation process is actually feasible (Ahn et al 2004; Hoisak et al 2006).) is surrogate correlation model is subsequently used to guide the robotic arm carrying a linear accelerator to reduce or eliminate the eects of respiratory motion (see Chapter 4). Because the correlation between internal organ motion and the chest excursion may change, the model must be updated periodically.
