Radiation and Cancer Physics
SS 37 - Physics 11 - Online Imaging and Motion Management
269 - Early Experience of Magnetic Resonance Sequence Evaluation Using an MR-Linac System
Wednesday, October 24
11:50 AM - 12:00 PM
Location: Room 302
Cynthia Eccles, PhD
Royal Marsden NHS Foundation Trust: research radiographer: Employee; The Institute of Cancer Research: Research Radiographer: Honorary Appointment
Early Experience of Magnetic Resonance Sequence Evaluation Using an MR-Linac System
C. L. Eccles1, A. Hunt2, H. McNair2, T. Herbert1, A. Tree1, A. Kirby1, S. Bhide1, S. Lalondrelle1, A. Pathmanathan2, I. White2, K. Newbold1, K. Aitken1, F. McDonald1, H. C. Mandeville1, N. Lavan2, S. Nill3, S. Hafeez2, K. Harrington2, U. Oelfke3, and R. A. Huddart2; 1The Royal Marsden NHS Foundation Trust, London, United Kingdom, 2The Institute of Cancer Research/The Royal Marsden NHS Foundation Trust, London, United Kingdom, 3Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom
Purpose/Objective(s): To report on the selection of ‘optimal’ MR sequences following volunteer imaging on a 1.5 Tesla (T) MR-Linac imaging platform.
Materials/Methods: Non-patient volunteers were recruited to an Ethics Review Board-approved prospective MR-only imaging study on a 1.5 T MR-Linac system. The study was advertised on an internal institutional electronic notice board. Volunteers attended 1-3 imaging sessions that included an mDixon, and a combination of 2D, 3D, T1w and T2w sequences. Each sequence was acquired over 2-7 minutes. The images from each session were independently reviewed by a panel of 3 observers (a clinical oncologist, a therapy radiographer and one other MR-Linac-based researcher). Visibility of pertinent organs-at-risk was used to determine image quality on a 4-point Likert scale of very clear, clear, unclear and not visible. Sequences were acquired iteratively until deemed unfit for purpose (online image matching or re-planning), or until 3 observers agreed they were suitable in 3 volunteers. A combination of sequences was then selected for image acquisition in patient volunteers.
Results: Eighteen volunteers underwent 21 imaging sessions to one of four general anatomical regions: male pelvis (n=7), female pelvis (n=3), thorax-chest wall/breast (n=5), abdomen (n=3). Each session was reviewed with the view to being used within a particular patient population and, therefore, possibly reviewed by multiple panels. For example, volunteers undergoing imaging to the male pelvis were reviewed by clinical oncologists and fellows specialising in prostate, bladder, and rectal cancers; the abdominal images were reviewed by hepatobiliary-pancreatic (HBP) and paediatric oncologists; and the female pelvis by doctors treating cervix, bladder and rectal cancers. On average, volunteers underwent 10 sequences (range 5-20), with a maximum scan time of approximately one hour. Table 1 details the preferred sequences and acquisition times for each of the tumour sites evaluated. The majority of observers preferred T2-weighted 3D sequences. The breast team was the only group to prefer T1-weighted imaging; and only the abdominal group preferred triggered image acquisitions.
| Anatomical Region || Tumour Site || Preferred Sequence 1 || Acquisition time (mins) || Preferred Sequence 2 || Acquisition Time (mins) |
| Pelvis || Bladder/ Prostate || T2 TSE 3D (isotropic) || 6:05 || T2 TSE MV || 5:26 |
| Rectum || T2 MS TSE || 3:00 || T2 3D TSE || 6:05 |
| Cervix || T2 TSE MV || 5:26 || T2 3D TSE || 6:05 |
| Thorax || Breast || T1 Dixon TFE || 5:00 || T2 TSE MV || 5:26 |
| Abdomen || Adult HBP/ Paediatric intra-abdominal || T2 TSE (Triggered) || 3:03 || T2 TSE MV || 5:26 |
TSE turbo spin echo, MV multi-vein, MS multi-slice, TFE Turbo field echo
Conclusion: By the end of this process, all treatment sites had agreed suitable sequences to be evaluated in patient volunteers. To date, 4 patient volunteers have undergone imaging on the system including bladder (n=1), prostate (n=1), pancreas (n=1) and cervix (n=1). Work in head and neck and lung volunteers is on-going.
Author Disclosure: C.L. Eccles: Honorary Appointment; The Institute of Cancer Research. A. Hunt: Research Grant; Cancer Research UK. H. McNair: Honorary Appointment; The Institute of Cancer Research. T. Herbert: None. A. Tree: Research Grant; Accuray Inc. Research Grants, travel awards, Honoraria; Elekata. A. Kirby: Employee; The Royal Surrey County Hospital, The University of Surrey. Independent Contractor; Cancer Centre London. Honorary Contract; The Institute of Cancer Research. Partnership; Cancer Centre London. S. Bhide: Honorary Appointment; The Institute of Cancer Research. S. Lalondrelle: Research Grant; Roche, MSD. Honoraria and Travel Expenses; Elekta. I. White: None. K. Newbold: Honorary Appointment; The Institute of Cancer Research. Honoraria; Sanofi-Genzyme, Eisai. K. Aitken: Honoraria; Brainlab, Elekta Inc. F. McDonald: Employee; East Surrey Hospital. Honorary Contract; The Institute of Cancer Research. Honoraria; MSD, Boehringer Ingelheim. Travel Expenses; MSD, Boehringer Ingelheim. H.C. Mandeville: Honorary Appointment; The Institute of Cancer Research. Chair of Radiotherapy Committee; European Paediatric Soft Tissue Sarcoma Group. S. Nill: Research Grant; Elekta Inc. S. Hafeez: None. K. Harrington: Honoraria, research grants, travel expenses; Pfizer, MSD, Merck, BMS, Amgen, AZ. Executive Board member; CTRad. Trustee; Oracle Cancer Trust. U. Oelfke: Honorary Contract; The Royal Marsden NHS Foundation Trust. Member of Atlantic Consortium Committee; Elekta. Member of Cyberknife Clinical Advisory board; Accuray Incorporated. R.A. Huddart: Independent Contractor; Cancer Centre London. Research Grant; Elekta Inc, Cancer Research UK. Partnership; Cancer Centre London. Education secretary and Trustee; British Uro Oncology Group. Work Stream Co-Chair; CT RAD.