Program Information

Free-Breathing Proton MRI Functional Lung Avoidance Maps to Guide Radiation Therapy

D Capaldi^1,2*, K Sheikh^1,2 , D Hoover^2,3 , B Yaremko^2,3 , D Palma^2,3 , G Parraga^1,2 , (1) Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada, (2) Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada, (3) Department of Oncology, The University of Western Ontario, London, Ontario, Canada

Presentations

TH-CD-202-9 (Thursday, August 4, 2016) 10:00 AM - 12:00 PM Room: 202

Purpose: Pulmonary functional MRI using inhaled gas contrast agents was previously investigated as a way to identify well-functioning lung in patients with NSCLC who are clinical candidates for radiotherapy. Hyperpolarized noble-gas (³He and ¹²⁹Xe) MRI has also been optimized to measure functional lung information, but for a number of reasons, the clinical translation of this approach to guide radiotherapy planning has been limited. As an alternative, free-breathing pulmonary ¹H MRI using clinically available MRI systems and pulse sequences provides a non-contrast-enhanced method to generate both ventilation and perfusion maps. Free-breathing ¹H MRI exploits non-rigid registration and Fourier decomposition of MRI signal intensity differences (Bauman et al., MRM, 2009) that may be generated during normal tidal breathing. Here, our objective was to generate free-breathing ¹H MRI ventilation and lung function avoidance maps in patients with NSCLC as a way to guide radiation therapy planning.

Methods: Stage IIIA/IIIB NSCLC patients (n=8, 68±9yr) provided written informed consent to a randomized controlled clinical trial (https://clinicaltrials.gov/ct2/show/NCT02002052) that aimed to compare outcomes related to image-guided versus conventional radiation therapy planning. Hyperpolarized ³He/¹²⁹Xe and dynamic free tidal-breathing ¹H MRI were acquired as previously described (Capaldi et al., Acad Radiol, 2015). Non-rigid registration was performed using the modality-independent-neighbourhood-descriptor (MIND) deformable approach (Heinrich et al., Med Image Anal, 2012). Ventilation-defect-percent (³He:VDP_He, ¹²⁹Xe:VDP_Xe, Free-breathing-¹H:VDP_FB) and the corresponding ventilation maps were compared using Pearson correlation coefficients (r) and the Dice similarity coefficient (DSC).

Results: VDP_FB was significantly related to VDP_He (r=.71; p=.04) and VDP_Xe (r=.80; p=.01) and there were also strong spatial relationships (DSC_He/DSC_Xe=89±3%/77±11%).

Conclusion: In this proof of concept study in NSCLC patients, free-breathing ¹H MRI ventilation defects were quantitatively and spatially related to inhaled-noble-gas MRI ventilation defects. Free-breathing ¹H MRI measures lung function/ventilation that can be used to optimize radiotherapy planning in NSCLC patients.

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