Physics of SBRT

Stereotactic body radiotherapy (SBRT) has become a widely accepted technique that is available on all modern linear accelerators and specialized systems such as CyberKnife, Tomotherapy, and more recently Halcyon and integrated magnetic resonance imaging (MRI)-guided linacs. This chapter discusses some of the physics issues that require attention for SBRT including: how the sources of uncertainty factor into the selection of planning target volume (PTV) margin; treatment planning considerations; adaptive planning; and small-field dosimetry. The chapter includes selected literature that highlights key concepts, including recent international guidelines for safe practice.