Imaging Techniques in Stereotactic Radiosurgery

Stereotactic radiosurgery (SRS) involves the delivery of a very precise, focal dose of radiation to a target. Radiologic imaging is crucial for accurate delineation of the treatment volume in order to achieve maximal dose to the target and optimal sparing of the normal surrounding tissue. Conventional imaging refl ects only anatomic rather than functional properties of the tumor. In contrast, metabolic and physiologic imaging provides in vivo measures of tumor tissue properties. In this chapter, physiologic MR imaging techniques including proton spectroscopy, blood volume, blood fl ow, vascular permeability, diffusion, and diffusion tensor imaging, as well as metabolic PET imaging, will be described. Although SRS treatment has been established for many years, recent advances in modern imaging combined with improved radiotherapy techniques can provide better target defi nition, reduce normal tissue toxicity, and provide better assessment of treatment response. This chapter describes the role of novel MR and PET imaging in the treatment planning and posttreatment follow-up of both malignant and benign central nervous system (CNS) intracranial tumors. Imaging and Treatment Planning Considerations