MRI and CBCT for lymph node identification and registration in patients with NSCLC undergoing radical radiotherapy

• Published in: Radiotherapy and oncology 2021-06, Vol.159, p.112-118
• Main Authors: Dubec, Michael, Brown, Sean, Chuter, Robert, Hales, Rosie, Whiteside, Lee, Rodgers, John, Parker, Jacqui, Eccles, Cynthia L., van Herk, Marcel, Faivre-Finn, Corinne, Cobben, David
• Format: Article
• Language: English
• Subjects: Cone beam CT; Cone-Beam Computed Tomography; Humans; Image registration; Lung cancer; Lung Neoplasms - diagnostic imaging; Lung Neoplasms - radiotherapy; Lymph nodes; Lymph Nodes - diagnostic imaging; Magnetic Resonance Imaging; MR guided-radiotherapy; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Image-Guided; Spiral Cone-Beam Computed Tomography
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2021.03.015

•MRI compared to cone-beam CT for thoracic lymph node identification and registration.•MRI is suitable for lymph node registration in locally advanced NSCLC.•MR-Linac systems could permit thoracic lymph node targeting and treatment adaptation. This study compared MRI to CBCT for the identification and registration of lymph nodes (LN) in patients with locally advanced (LA)-NSCLC, to assess the suitability of targeting LNs in future MR-image guided radiotherapy (MRgRT) workflows. Radiotherapy radiographers carried out Visual Grading Analysis (VGA) assessment of image quality, LN registration and graded their confidence in registration for each of the 24 LNs on CBCT and two MR sequences, MR1 (T2w Turbo Spin Echo) and MR2 (T1w DIXON water only image). Pre-registration image quality assessment revealed MR1 and MR2 as significantly superior to CBCT in terms of image quality (p ≤ 0.01). No significant differences were noted in interobserver variability for LN registration between CBCT, MR1 and MR2. Observers were more confident in their MR registrations compared to their CBCT based LN registrations (p ≤ 0.02). Interobserver setup correction variability was not found to be significantly different between CBCT and MR. Image quality and registration confidence were found to be superior for MRI sequences. This is a promising step towards MR-guided radiotherapy for the treatment of LA-NSCLC.