Prostate intrafraction motion during the preparation and delivery of MR-guided radiotherapy sessions on a 1.5T MR-Linac
de Muinck Keizer, D. M.; Kerkmeijer, L. G.W.; Willigenburg, T.; van Lier, A. L.H.M.W.; Hartogh, M. D.den; 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) Radiotherapy and Oncology, volume 151, pp. 88 - 94
(Article)
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
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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.
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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
ISSN: 0167-8140
Publisher: Elsevier Ireland Ltd
Note: Funding Information: The department of radiotherapy has a research agreement with Elekta. This research received no funding or financial compensation from Elekta. This work received financial support by ZonMw IMDI/LSH-TKI foundation projectnr. 104006004. Funding Information: The department of radiotherapy has a research agreement with Elekta. This research received no funding or financial compensation from Elekta. This work received financial support by ZonMw IMDI/LSH-TKI foundation projectnr. 104006004. Publisher Copyright: © 2020 The Author(s)
(Peer reviewed)