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In BT a PTV margin into the lateral and antero-posterior direction and a renormalisation of
dose according to the PTV will result in a general dose escalation. Application of PTV
margins is strongly discouraged
WHY TO USE D90 INSTEAD OF D98 OR D100: MARGINS
In EBRT a PTV margin will result in an increase of the volume irradiated to a high dose.
The dose plateau becomes larger in size, but the CTV dose remains unchanged.
Tanderup K. PTV margins should not be used to compensate for uncertainties in 3D image guided intracavitary BT. Radiother
Oncol 2010; 97:495-500