Radiotherapy of the head without the need of a thermoplastic mask, a clinical feasibility study.

During radiation of the brain, a thermoplastic mask is used to fixate the head,
preventing movements during the treatment. However, many patients complain
about the tightness and experience discomfort. Therefore, a treatment method
without the necessity of a head mask is of advantage for patients. An optical
surface scanner can be used as a movement monitoring tool during radiation
therapy of the head. We will evaluate whether stabilization of the back of the
head is sufficient, such that movement is minimized, which is needed for whole
brain radiotherapy.
Based on literature we expect patients to be able to lie still during the
treatment. With sufficient support of the head and by using an optical surface
scanner, we expect a mask is not necessary.

To prove the clinical feasibility of palliative whole brain radiotherapy
without using a thermoplastic mask. Clinical feasibility in this study is
defined when more than 70% of the patients can complete the radiation treatment
without a mask. We suppose a failure of less than 30% to be acceptable for both
patients and clinicians. A complete treatment consists of five fractions. The
treatment is considered to be successful when three or more fractions of one
patient have been successful. A fraction is defined to be successful if no more
than two times a session, repositioning is needed.

The study is a clinical feasibility study. All subjects participating in the
study receive whole brain radiotherapy without using a thermoplastic mask.

The intervention in this study concerns the treatment method of whole brain
radiotherapy; the treatment itself is the same whether patients participate in
the study or not. Patients are instructed to lie as still as possible on the
treatment table and not to move their head during the radiotherapy treatment.
As is common with radiotherapy of the head, online imaging is used for a
reproducible inter-fractional position of the head. For movement detection
during the treatment an optical surface scanner is used. The surface scanner
used for this study is the Catalyst* (C-RAD AB, Sweden), which constructs a
3D-reconstruction of a subject. The actual position of the patient is compared
to a daily made reference image and the deviation is presented on a screen. If
it becomes clear a patient is not able to lie still, the treatment can be
continued by using a mask.

If the movement of the head exceeds the threshold, the radiation is temporary
stopped. The technologist repositions the patient and the radiation continues.
The treatment can in any case be continued using a mask during the next
fraction. Therefore, an unsuccessful treatment method has no consequences for
the effectiveness of the radiotherapy for the patient.