Fig. 2
Representative dose-volume histograms of spine stereotactic ablative radiotherapy (SABR) cases (patient #29 and #23) for thoracic (T) spine (a) and lumbar (L) spine (b), respectively, are shown. A progressive resolution optimizer (PRO), and photon optimizer (PO) are plotted with the solid and dashed lines, respectively, for planning target volume (PTV), spinal cord (SC), the corresponding planning organ-at-risk volume (SC PRV), cauda equine (CE), the corresponding PRV (CE PRV), and 1.5-cm ring structure surrounding PTV (Ring1.5 cm)