Developing rapid response MRI-guided palliative radiotherapy for metastatic spinal cord compression
Benson, Rebecca Sideris, A. McDaid, Lisa Chuter, Robert Portner, Robin Freear, Linnea Clough, Abigael Nelder, Claire L Pitt, Eleanor Daly, Mairead
Benson, Rebecca
Sideris, A.
McDaid, Lisa
Chuter, Robert
Portner, Robin
Freear, Linnea
Clough, Abigael
Nelder, Claire L
Pitt, Eleanor
Daly, Mairead
Citations
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Abstract
Purpose or Objective
Implementation of a rapid response metastatic spinal cord compression (MSCC) pathway using diagnostic (dCT) imaging and
adaptive MR Linac treatment has the potential to reduce waiting times, align healthcare processes, and improve the patient
experience during a global pandemic. This work presents the preliminary feasibility testing of a rapid response, single
appointment MSCC pathway on the Elekta Unity MR Linac (MRL) using dCT imaging, as the diagnostic MR field of view is too
small.
Materials and Methods
Retrospective radiotherapy plan data were collected from ten patients who had received urgent/emergency palliative
spinal radiotherapy on conventional linear accelerators at our institution. The most recent dCT images prior to the
treatment planning scans were imported from the picture archiving communication system (PACS) to the MRL treatment
planning system (Monaco V5.40, Elekta). New treatment plans were then created on these dCT images to prepare for
delivery on the MRL (figure 1). In order to facilitate this target contours were required and generated by the treatment
planner with support from a clinical oncologist. Departmental policy for single dose radiotherapy was used in the creation
of these plans (8Gy treated in a single post field). To test implementation on the MRL, MR scans were acquired and
treatment delivered to a 3D abdominal phantom (CIRS) using MR-CT registration and the adapt to shape (ATS) workflow.
ATS ensures that if anatomical changes have occurred since dCT the contours can be adapted on the day to reflect these
changes, allowing for online plan adaptation
Results
Ten plans were created on imported dCT. Treatment site ranged from upper thoracic spine to sacrum. Target volumes
ranged from 156- 508 cm3, D95% ranged from 767-874cGy (figure 2). Acceptable coverage was achieved on all plans but
proved more challenging on those with larger treatment volumes. Approved plans were exported to Mosaiq (V2.83, Elekta)
to test delivery on a phantom on the MRL.
Conclusion
For MSCC we were able to import and transfer data, produce acceptable treatment plans on dCT images and preliminary
testing on the MRL. Attempted delivery of these plans highlighted technical issues that need to be overcome prior to clinical
implementation. These included the lack of origin and landmarking information on dCT can make patient positioning
challenging due to limitations of online shifts. Additionally, bulk density overrides are required for Hounsfield unit to
electron density conversion as dCT images may come from different diagnostic CT scanners for which commissioning data
is not available. Further work is on-going to confirm dosimetry.
Affiliation
Description
Date
2022
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Benson R, Sideris A, McDaid L, Chuter R, Portner R, Freear L, et al. Developing rapid response MRI-guided palliative radiotherapy for metastatic spinal cord compression. Radiotherapy and Oncology. 2022 May;170:S62-S. PubMed PMID: WOS:000806759200062.