Tumor-site specific geometric distortions in high field integrated magnetic resonance linear accelerator radiotherapy

Signe Winther Hasler; Uffe Bernchou; Anders Bertelsen; Elisabeth van Veldhuizen; Tine Schytte; Vibeke Nordmark Hansen; Carsten Brink; Faisal Mahmood

doi:10.1016/j.phro.2020.07.007

Tumor-site specific geometric distortions in high field integrated magnetic resonance linear accelerator radiotherapy

Phys Imaging Radiat Oncol. 2020 Aug 19:15:100-104. doi: 10.1016/j.phro.2020.07.007. eCollection 2020 Jul.

Authors

Signe Winther Hasler^{1

2

3}, Uffe Bernchou^{1

2

3}, Anders Bertelsen^{1

2}, Elisabeth van Veldhuizen^{1

2}, Tine Schytte^{2

3}, Vibeke Nordmark Hansen^{1

2}, Carsten Brink^{1

2

3}, Faisal Mahmood^{1

2

3}

Affiliations

¹ Laboratory of Radiation Physics, Odense University Hospital, Kløvervænget 19, 5000 Odense C, Denmark.
² Department of Oncology, Odense University Hospital, Kløvervænget 19, 5000 Odense C, Denmark.
³ Department of Clinical Research, University of Southern Denmark, J. B. Winsløws Vej 19.3, 5000 Odense C, Denmark.

Abstract

Magnetic resonance imaging (MRI) has exquisite soft-tissue contrast and is the foundation for image guided radiotherapy (IGRT) with integrated magnetic resonance linacs. However, MRI suffers from geometrical distortions. In this study the MRI system- and patient-induced geometric distortion at four different tumor-sites was investigated: adrenal gland (7 patients), liver (4 patients), pancreas (6 patients), prostate (20 patients). Maximum level of total distortion within the gross-tumor-volume (GTV) was 0.96 mm with no significant difference between abdominal patients (adrenal gland, liver, pancreas) and pelvic patients (prostate). Total tumor-site specific distortion depended on location in the field-of-view and increased with the distance to MRI iso-center.

Keywords: Adaptive radiotherapy; Geometric distortion; MR guided radiotherapy; MR-linac; MRI; QA.