paediatrics Brussels 17

Intracranial ependymoma

SIOP Ependymoma II – PTV2 boost target volume

Target Volumes Gross Tumour Volume ( GTV ): the GTV includes all the measurable pathological tissue with or without contrast enhancement after surgery/ies as documented by MRI at the end of conformal treatment to tumour bed. Clinical target Volume ( CTV ): CTV=GTV i.e. no additional margin to be applied to GTV for CTV. This is to restrict the boost volume as far as possible, in view of the likely adjacency of the brainstem for most patients, the hypofractionated schedule and the resulting cumulative biological effective dose. Planning Target Volume ( PTV ): the PTV is a geometric expansion of the GTV/CTV to take in to account for uncertainty in immobilisation, daily patient positioning and image registration. The PTV margin is 0.2-0.3 cm in all directions according to local policies.