A phantom based laser marking workflow to visually assess geometric image distortion in magnetic resonance guided radiotherapy

• Published in: Physics and imaging in radiation oncology Vol. 17; pp. 95 - 99
• Main Authors: Drobnitzky, Matthias, vom Endt, Axel, Dewdney, Andrew
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2021; Elsevier
• Subjects: External laser bridge; Gradient nonlinearity; Lightweight plastic skeleton; MR distortion correction; Patient marking workflow; Silicone-based spherical fiducials; Technical Note; MR distortion correction; External laser bridge; Patient marking workflow; Silicone-based spherical fiducials; Gradient nonlinearity; Lightweight plastic skeleton
• ISSN: 2405-6316; 2405-6316
• DOI: 10.1016/j.phro.2021.01.012

Magnetic resonance (MR)-only workflows require quality assurance due to potential dosimetric impacts of using geometry distorted MR images in radiotherapy planning. MR-visible silicone-based fiducials were arranged in regular 3D structures to cover extended imaging volumes. The scanner’s patient marking workflow with a 2-axes movable laser bridge allowed to visually check geometric distortions of each MR reconstructed fiducial against its true position in 3D space. A measurement resolution and uncertainty of the order of 0.5 mm in sagittal and coronal, and 1 mm in transversal direction was found. The proposed workflow required 1 min of evaluation time per fiducial position, and a 9 min 3D MR volume acquisition.