Immobilization, target delineation and contouring of organs at risk

Patient immobilization, target delineation and contouring of organs at risk (OARs) are essential to the successful clinical implementation of spinal stereotactic radiosurgery or stereotactic body radiation therapy. The target is in very close proximity to OARs, especially the spinal cord. The treatment planning aims to generate a very steep dose fall-off to allow delivery of high-dose radiation to the target volume while keeping the OARs below radiation tolerance. This chapter will provide an overview of tumor/organ/ patient motion and the clinical use of immobilization during spinal stereotactic radiosurgery/stereotactic body radiation therapy. The International Commission on Radiation Units and Measurements concept of gross tumor volume, clinical target volume and planning treatment volume as well as contouring of OARs will be addressed. Consensus guidelines of target delineation in spinal lesions involving different parts of the vertebra will be discussed.