J Neurol Surg A Cent Eur Neurosurg 2018; 79(04): 341-343
DOI: 10.1055/s-0037-1604285
Case Report
Georg Thieme Verlag KG Stuttgart · New York

Large In-mask Motion during Frameless Radiosurgery of a Brain Metastasis

Maciej Harat
1  Department of Radiotherapy, The Franciszek Lukaszczyk Oncology Center, Bydgoszcz, Poland
Jacek Furtak
2  Department of Neurosurgery, 10th Military Research Hospital, Bydgoszcz, Poland
› Author Affiliations
Further Information

Publication History

25 September 2016

27 December 2016

Publication Date:
23 March 2018 (online)


Frameless radiosurgery is now a common alternative to traditional in-frame treatment. Several dosimetric studies have reported small in-mask positioning inaccuracies during frameless radiosurgery. We present a case of an uncommonly large deviation in in-mask motion detected offline in a patient undergoing linear accelerator–based frameless radiosurgery. Our case illustrates how the use of a thermoplastic mask can lead to unacceptable setup errors for passive image-guided radiosurgery. The case underlines the need for correct patient preparation, adequate time between mask molding and computed tomography, and routine intrafraction imaging. Image-guided positioning is recommended to achieve clinically acceptable setup accuracy (< 1 mm) for stereotactic radiosurgery.