MRI image acquisition on the MR-Linac for patients with locally advanced lung cancer (LALC)
Shiarli, A. M. Brown, Sean Cobben, David Wetscherek, A. Dubec, Michael Herbert, T. Smith, G. Lawes, R. Barnes, H. Faivre-Finn, Corinne
Shiarli, A. M.
Brown, Sean
Cobben, David
Wetscherek, A.
Dubec, Michael
Herbert, T.
Smith, G.
Lawes, R.
Barnes, H.
Faivre-Finn, Corinne
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Abstract
Introduction: MR-Linacs (hybrid MRI radiotherapy RT delivery
systems) are an attractive tool for implementation of real time
adaptation in lung cancer patients. MRI can offer better soft tissue
definition with potential improvement in RT delivery accuracy.
The air-tissue interface, respiratory motion and the low proton
density in the lung, all impact MRI image quality, leading to a need
for optimisation of MRI sequences for planning and verification purposes. We report our first experience in scanning patients with
LALC on a high-field MR-Linac (1.5T with 6MV linear accelerator).
Methods: Five patients with LALC, were scanned on the Elekta
Unity MR-Linac with 6 different MRI sequences with volumetric
excitation: T1w turbo spin echo (TSE), T2w TSE, respiratory-gated
nonfat-suppressed T2w TSE, respiratory-gated fat-suppressed T2w
TSE, T1w 2-point Dixon and T1w radial fast gradient echo (TFE). Five
clinical oncologists and 1 radiographer from 2 UK centres scored the
anonymised images using a four-point Visual Grading Analysis (VGA)
scale where 4 is ‘very clear’ and 1 is ‘not visible’. The scores for the
organs at risk (OAR) and gross tumour volume (GTV) are reported.
Results: The T1w Dixon and T1w radial TFE sequences scored the
highest overall, with 82% and 79% of observations scoring as
‘clear’/‘very clear’, respectively. For the primary tumour, the T1w
Dixon and the T2w respiratory-gated non-fat suppressed sequence
scored at 79% and 63% respectively. For lymph nodes, the T1w Dixon
and T1w radial TFE scored 67%. The overall best scoring OARs were
spinal cord and trachea. The brachial plexus scored best on the T1w
TSE sequence (83%) Conclusion: We assessed image quality for 6 MRI sequences for
patients with LALC on the MR-Linac. The T1w Dixon sequence
performed the best for both disease and OAR visualisation. Ongoing
multidisciplinary work will allow further optimisation of MRI
sequences.
Description
Date
2020
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Shiarli AM, Brown S, Cobben D, Wetscherek A, Dubec M, Herbert T, et al. MRI image acquisition on the MR-Linac for patients with locally advanced lung cancer (LALC). Lung Cancer. 2020;139:S35-S6