Prostate intrafraction motion during the preparation and delivery of MR-guided radiotherapy sessions on a 1.5T MR-Linac
Publication date
2020-10
Authors
De, D. M. Muinck Keizer
Kerkmeijer, Linda G.W.
Willigenburg, Thomas
van Lier, Astrid L H M W
den Hartogh, M. D.
van der Voort van Zyp, J. R N
de Groot-van Breugel, E. N.
Raaymakers, Bas W
Lagendijk, Jan J.W.
de Boer, J C J
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Document Type
Article
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Abstract
Purpose: To evaluate prostate intrafraction motion using MRI during the full course of online adaptive MR-Linac radiotherapy (RT) fractions, in preparation of MR-guided extremely hypofractionated RT. Material and methods: Five low and intermediate risk prostate cancer patients were treated with 20 × 3.1 Gy fractions on a 1.5T MR-Linac. Each fraction, initial MRI (Pre) scans were obtained at the start of every treatment session. Pre-treatment planning MRI contours were propagated and adapted to this Pre scan after which plan re-optimization was started in the treatment planning system followed by dose delivery. 3D Cine-MR imaging was started simultaneously with beam-on and acquired over the full beam-on period. Prostate intrafraction motion in this cine-MR was determined with a previously validated soft-tissue contrast based tracking algorithm. In addition, absolute accuracy of the method was determined using a 4D phantom. Results: Prostate motion was completely automatically determined over the full on-couch period (approx. 45 min) with no identified mis-registrations. The translation 95% confidence intervals are within clinically applied margins of 5 mm, and plan adaption for intrafraction motion was required in only 4 out of 100 fractions. Conclusion: This is the first study to investigate prostate intrafraction motions during entire MR-guided RT sessions on an MR-Linac. We have shown that high quality 3D cine-MR imaging and prostate tracking during RT is feasible with beam-on. The clinically applied margins of 5 mm have proven to be sufficient for these treatments and may potentially be further reduced using intrafraction plan adaptation guided by cine-MR imaging.
Keywords
Cine-MR, Intrafraction motion, MR-guided radiotherapy, MR-Linac, Prostate cancer, Tracking, Movement, Humans, Male, Prostatic Neoplasms/diagnostic imaging, Magnetic Resonance Imaging, Radiotherapy Planning, Computer-Assisted, Particle Accelerators, Hematology, Oncology, Radiology Nuclear Medicine and imaging, Journal Article, Research Support, Non-U.S. Gov't
Citation
de Muinck Keizer, D M, Kerkmeijer, L G W, Willigenburg, T, van Lier, A L H M W, Hartogh, M D D, van der Voort van Zyp, J R N, de Groot-van Breugel, E N, Raaymakers, B W, Lagendijk, J J W & de Boer, J C J 2020, 'Prostate intrafraction motion during the preparation and delivery of MR-guided radiotherapy sessions on a 1.5T MR-Linac', Radiotherapy and Oncology, vol. 151, pp. 88-94. https://doi.org/10.1016/j.radonc.2020.06.044