All patients were simulated in a head-first, supine position, immobilised with five-clamp thermoplastic covering the brain to chest level. If the patient was non-cooperative and no sedition was used, an additional two-clamp thermoplastic was used to immobilise the abdomen pelvis region7 (link). Anesthesia was used if needed. All patients were simulated in a Brilliance Big Bore CT scanner (Philips, Eindhoven, The Netherlands) with 3-mm uniform slice thickness from brain to mid-thigh, with the first marker in the brain and second marker at the abdomen level to keep the patient straight during the simulation. CT Images were transferred to the SomaVision (Varian Medical Systems, Palo Alto, CA) contouring station and co-registered with three-dimensional (3D) T1-contrast, T2-flair magnetic resonance images (MRI).
The gross tumour volumes (GTV) of the brain and the spine were delineated as follows: the cranial contouring included the whole brain and up to the junction of the cervical vertebrae C5 and C6. The superior end of the spinal cord starts from the end of brain GTV and goes up to the inferior end of the thecal sac, as seen on the sagittal view of the MRI. The planning target volume (PTV) for the brain was generated by applying a 3 mm margin on the GTV. For the spinal cord, the PTV was generated using a 7 mm margin over GTV7 (link). The brain and spinal PTVs were summed to generate a single PTV for the plan optimisation. To standardise the contouring of organs at risk for all patients, a predefined structure template consisting of bladder, bowel, brain stem, chiasm, cochlea (bilateral), duodenum, esophagus, eyes (bilateral), thyroid gland, heart, humerus head (bilateral), kidneys (bilateral), lacrimal gland (bilateral), larynx, lens (bilateral), lung (bilateral), mandible, optic nerve (bilateral), oral cavity, ovary (bilateral for female patients), parotid (bilateral), pituitary gland, rectum, stomach, and submandibular glands (bilateral) was used.
The gross tumour volumes (GTV) of the brain and the spine were delineated as follows: the cranial contouring included the whole brain and up to the junction of the cervical vertebrae C5 and C6. The superior end of the spinal cord starts from the end of brain GTV and goes up to the inferior end of the thecal sac, as seen on the sagittal view of the MRI. The planning target volume (PTV) for the brain was generated by applying a 3 mm margin on the GTV. For the spinal cord, the PTV was generated using a 7 mm margin over GTV7 (link). The brain and spinal PTVs were summed to generate a single PTV for the plan optimisation. To standardise the contouring of organs at risk for all patients, a predefined structure template consisting of bladder, bowel, brain stem, chiasm, cochlea (bilateral), duodenum, esophagus, eyes (bilateral), thyroid gland, heart, humerus head (bilateral), kidneys (bilateral), lacrimal gland (bilateral), larynx, lens (bilateral), lung (bilateral), mandible, optic nerve (bilateral), oral cavity, ovary (bilateral for female patients), parotid (bilateral), pituitary gland, rectum, stomach, and submandibular glands (bilateral) was used.
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