Trial Information

Serial CT Scans for the Evaluation of Two Different Relocatable Fixation Systems in Fractionated Stereotactic Radiotherapy

Stereotactic conformal radiotherapy (SCRT) combines the precision of the stereotactically
guided tumor localisation and the radiobiological advantages of the fractionation. This
implies an highly accurate repositioning of the isocenter of the cerebral target at the
isocenter of the linac gantry and couch + 30 times. In the use of stereotactic conformal
radiotherapy (SCRT) accuracy is the mainstay for the treatment of brain tumours. The reason
are reduced safety margins around the tumour (or no margins) in order to reduce normal
tissue dose.

This study aims at providing a quantitative evaluation of the accuracy of two different
fixation systems, where one system is also evaluated with two different set-ups. The first
approach will be based on the BrainLAB thermoplastic masque (the masque with (= standard
fixation) and without a custom made bite-block), the second will use the BrianLAB
relocatable frame with the bite- block and a home made fixation system.

Repositioning accuracy will be evaluated in a randomized manner patient-dependent and
independent with the two fixation systems mentioned above.

The rationale is to determine the margins to define the planning target volume (PTV), it is
necessary to know the set-up accuracy of the immobilization system. An overestimation of the
PTV would lead to possible toxicity and an underestimation could lead to a geographical
miss.

The main endpoint of this trial will be the accurate reproducibility of the fixation system
evaluated by repeated CT scan.