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Sean Brown
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P2.01 - Advanced NSCLC (Not CME Accredited Session) (ID 950)
- Event: WCLC 2018
- Type: Poster Viewing in the Exhibit Hall
- Track:
- Presentations: 2
- Moderators:
- Coordinates: 9/25/2018, 16:45 - 18:00, Exhibit Hall
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P2.01-15 - A Radiologist-Led Training Workshop for MR Based Normal Tissue and Tumour Delineation for Lung Cancer Radiotherapy. (ID 13857)
16:45 - 18:00 | Presenting Author(s): Sean Brown
- Abstract
Background
A potential benefit of MR-image guided radiotherapy (MRIgRT) in lung cancer is the reduction of treatment related uncertainties through improved soft tissue contrast. However, this benefit may be obscured by inter-observer variation in gross tumour volume (GTV) and organ at risk (OAR) contouring. A radiologist led workshop was organised to provide training in such contouring on MR.
a9ded1e5ce5d75814730bb4caaf49419 Method
Planning CT, PET-CT and MRI were acquired in four lung cancer patients. MR sequences included 3D radial gradient echo, T2 DIXON Turbo Spin Echo (TSE), and T2 TSE with and without fat-sat. Data sets were local rigidly registered and imported into the so-called “Big Brother” contouring software.
The radiologist led teaching on OAR and GTV contouring used an MR lung atlas (produced by this group). Seven radiation oncologists contoured the brachial plexus (BP), heart, proximal bronchial tree, oesophagus and GTV. This was followed by a multi-disciplinary group discussion (oncologists, radiologists and physicists) on the contouring challenges and subsequently contours were reviewed and the atlas adjusted.
4c3880bb027f159e801041b1021e88e8 Result
The BP and heart were the most difficult OARs to contour and showed the largest inter-observer variation. Following contour review and discussion between radiologist and oncologists updates to atlas and protocols were made. The GTV was found to be most challenging at the soft tissue interfaces and requires further work (Figure 1).
8eea62084ca7e541d918e823422bd82e Conclusion
This early work demonstrates the need for radiologist-led training in OAR and GTV contouring in lung cancer patients using MR images. This will be especially important for the integration of MR into treatment planning and an MRIgRT adaptive workflow. We have arranged future workshops in order to provide further training and to assess inter-observer variation in OAR and GTV contouring using MR on more cases.
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P2.01-27 - MR, CT and Cone-Beam CT for Lymph Node Visualisation in Locally-Advanced Lung Cancer (ID 11800)
16:45 - 18:00 | Presenting Author(s): Sean Brown
- Abstract
Background
The largest benefit of MR-guided radiotherapy in lung cancer may be on-board visualisation of malignant lymph nodes (LNs). In this study, we assessed whether MR images were suitable for LN visualisation for treatment adaptation. We hypothesised that MR would outperform CT and Cone-Beam-CT (CBCT).
a9ded1e5ce5d75814730bb4caaf49419 Method
CT, CBCT and MR images were acquired in four lung cancer patients with malignant LNs, confirmed using PET-CT and/or endobronchial ultrasound-guided biopsies. A total of 15 LNs from mediastinal and hilar nodal stations were assessed. Imaging datasets included: (1) CT planning scan with IV contrast; (2) MR1 (within 1 week of CT); (3) Mid-treatment CBCT (without contrast); and (4) MR2 (day of CBCT). MR sequences included: Turbo Spin Echo (TSE), TSE with fat-sat and 3D radial gradient echo. The images were randomised and independently scored by four thoracic radiation oncologists according to whether the malignant LN in each nodal station was visualised well enough to permit contouring. Scores were: not visible (1), unclear (2), clear (3) and very clear (4). Scores 3 and 4 were designated as ‘suitable for contouring’.
4c3880bb027f159e801041b1021e88e8 Result
As shown in figure 1, there was no significant difference in the number of LNs deemed suitable for contouring on CT (87%) compared to MR1 (82%). A significant difference was found between CBCT (10%) and MR2 (80%).
8eea62084ca7e541d918e823422bd82e Conclusion
MR did not out-perform CT with contrast for malignant LN visualisation, possibly due to greater observer familiarity with CT. MR was significantly better than CBCT, likely due to superior soft tissue contrast. These findings support the use of MR-guided radiotherapy in locally-advanced lung cancer for adaptive planning or treatment verification. The greater variation in MR scores between oncologists (especially between sequences) could be due to lack of experience with thoracic MR. Future research will optimise MR for this task and assess LN localisation on a larger dataset.
6f8b794f3246b0c1e1780bb4d4d5dc53
