Intrafractional Head Movement During Radiosurgery

Intrafractional 6D Head Movement With Mask Fixation During Stereotactic Intracranial RT-sessions

This study investigates the intrafractional accuracy of a frameless thermoplastic mask used for head immobilization during stereotactic radiotherapy. Non-invasive masks cannot completely prohibit head movements. Previous studies attempted to estimate the magnitude of intrafractional inaccuracy by means of pre- and postfractional measurements only. However, this might not be sufficient to accurately map also intrafractional head movements.

Intrafractional deviation of mask-fixed head positions is measured in five patients during a total of 94 fractions by means of close-meshed repeated ExacTrac measurements conducted during the entire treatment session. From the obtained data the investigators evaluate the need to adjust safety margins around the gross tumor volume (GTV) whenever the investigated thermoplastic mask is used instead of invasive ring fixation.

Inclusion Criteria:

• single intracranial tumour or metastasis
• stereotactic radiation therapy planned
• immobilization with thermoplastic mask