Room: Exhibit Hall | Forum 6
Purpose: Magnetic Resonance Imaging (MRI) using hyperpolarized-Â¹Â²â?¹Xe enables 3-Dimensional imaging of regional lung function. Using this novel technique, we investigate dose-dependent changes in regional lung function of patients receiving thoracic radiation therapy (RT).
Methods: Three IRB-approved human subjects receiving conventional RT for NSCLC underwent breath-hold MRI using hyperpolarized-Â¹Â²â?¹Xe gas both pre- and post-treatment. The solubility and chemical shift of Â¹Â²â?¹Xe permit 3D imaging of its distribution into the airspaces (ventilation), uptake in the interstitial barrier tissues, and its transfer to red blood cells (RBC). The signal ratios of barrier/ventilation (barrier uptake) and RBC/ventilation (RBC transfer) provide a quantitative measure of regional function. RT planning CT scans were deformably registered to the pre-treatment anatomical Â¹H MRI; post-treatment MRIs were rigidly registered to pre-treatment scans to calculate functional change. Analysis excluded high dose gradient regions (â‰¥200cGy/mm) and voxels receiving â‰¥95% of prescription. One-tailed t-tests were performed to examine observed trends for statistical significance in each patient.
Results: In the patient imaged 6 weeks post-RT, lung voxels receiving >30Gy on average experienced a decrease in ventilation, barrier uptake, and RBC transfer of -6%Â±8%, -10%Â±7%, and -27%Â±9%, which were significantly larger reductions than observed in voxels receiving 5-30Gy (P<0.01). The two remaining patients, imaged at 12 weeks post-RT, both presented with decreased RBC transfer (-2%Â±29% and -14%Â±39%) and increased barrier uptake (9%Â±15% and 9%Â±22%) in lung voxels receiving >20Gy; changes were again significantly greater than voxels receiving 5-20Gy (P<0.01). Trends in the ventilation changes were not consistent across the two 12-week patients.
Conclusion: Hyperpolarized-Â¹Â²â?¹Xe MRI acquired pre- and post-treatment revealed dose-dependent changes in ventilation, barrier uptake, and gas transfer for 3 RT patients. Although studies of larger cohorts are clearly needed to confirm these observations, this new modality shows promise as a new tool to evaluate, predict, and help minimize radiation-induced lung injury.
Funding Support, Disclosures, and Conflict of Interest: This work was supported in part by grants R01HL105643 and P41 EB015897. All human subjects in this work were enrolled on an approved IRB protocol #Pro00060259. Dr Driehuys is a founder of and shareholder in Polarean Imaging, has a patent US 9625550 B2, and receives loyalties paid by Polarean Imaging.