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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.
SIOP Ependymoma II –
PTV2 boost target
volume
Intracranial ependymoma