Figure 1

Prescription isodose distribution in axial and coronal views of a skull base metastasis compressing the optic chiasm (contoured in yellow). The planning target volume (contoured in blue) was created by the geometric expansion of tumour plus 1 mm. The patient was treated with a linear accelerator (LINAC) multi-fraction stereotactic radiosurgery (5 x 5 Gy) with the use of 8 noncoplanar conformal beams. The dose was prescribed to the 87% isodose line normalized to the maximum dose, with a minimum PTV coverage of 98%. The isodose curves showing dose levels delivered to surrounding tissues and adjacent critical structures are represented.