摘要：A simple procedure to plan, verify and implement craniospinal irradiation（CSI） with patients supine is presented. Treatment is conducted with a single posterior spinal field abutting two lateral cranial fields. The opposed lateral fields are half-blocked and the inferior line is perpendicular. The posterior field uses some fixed field parameters so that the cephalad edge of the posterior field is coplanar with the caudal edges of the lateral fields and it is independent of the height of the couch. A steel-shot ball is used to measure the size of overlap or gap at the junction using portal images of an electron portal image device or portal films. The results of analyzing the portal images show that the errors of the junction are within ± 1 mm. The dose-volume histograms （DVHs）show that there are not unbearable hot or cold spots in the clinic target volumes （CTVs）. Supine craniospinal treatment is a reliable and convenient alternative to treatment in the prone position and avoids the technical difficulties of the latter. The use of fixed field geometry greatly facilitates treatment planning and effectively reduces the amount of time of setup, verification and treatment.