ABSTRACT
Stereotactic treatments are, by definition, high-precision treatments of challenging tumor geometries with very high doses per fraction. The high-stakes environment, created by high levels of potential damage associated with stereotactic hypofractionated treatment approaches along with immediate proximity
11.1.1 Evolution of stereotactic delivery modalities 234 11.1.2 Gamma Knife 234 11.1.3 Cone-based delivery 236 11.1.4 Intensity-modulated radiosurgery (IMRS) 237 11.1.5 CyberKnife 237 11.1.6 Conformal arc delivery 237 11.1.7 Intensity modulated arc therapy (IMAT) 239 11.1.8 Stereotactic body radiation therapy (SBRT) 240
11.2 Stereotactic treatment-planning concepts and subtleties 244 11.2.1 Treatment-planning considerations for sphere-based delivery approaches 244 11.2.2 Treatment-planning considerations for intensity-modulating delivery approaches 245 11.2.3 Treatment-planning considerations for CyberKnife delivery approaches 249 11.2.4 Treatment-planning considerations for arc-based delivery approaches 249 11.2.5 Treatment-planning considerations for SBRT treatment approaches 253
11.3 Differences between “conventional” and “stereotactic” treatment-planning systems 255 11.3.1 Structure and dose grid voxel size 256 11.3.2 Small-field dosimetry 259 11.3.3 Image registration and stereotactic frame of reference 259 11.3.4 Stereotactic body radiation therapy: Dose calculation accuracy 261 11.3.5 Margin definition 262
11.4 Conclusion 263 References 263
to sensitive healthy structures typically encountered in stereotactic treatments, make the “standard” treatment-planning problem even more challenging. For example, the percentage isodose line that can be tolerated to encroach on a nearby healthy structure is almost always less for a typical stereotactic treatment because the dose per fraction is so high, thus making a treatment plan design all the more difficult (Figure 11.1). The fact that the targeted lesion was designated for stereotactic treatment in the first place typically means that there are important and sensitive normal structures nearby. Simply put, treatment planning for stereotactic delivery environments faces all of the challenges of standard treatment planning with amplified levels of challenge and importance.
