(Monday, 7/30/2018) 1:15 PM - 1:45 PM
Room: Exhibit Hall | Forum 6
Purpose: Magnetic Resonance Imaging (MRI) using hyperpolarized-¹²�Xe 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-¹²�Xe gas both pre- and post-treatment. The solubility and chemical shift of ¹²�Xe 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 ¹H MRI; post-treatment MRIs were rigidly registered to pre-treatment scans to calculate functional change. Analysis excluded high dose gradient regions (≥200cGy/mm) and voxels receiving ≥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%±8%, -10%±7%, and -27%±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%±29% and -14%±39%) and increased barrier uptake (9%±15% and 9%±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-¹²�Xe 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.
Keywords
Taxonomy
IM/TH- MRI in Radiation Therapy: Development (new technology and techniques)
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