TH‐C‐141‐08: A Feasibility Study of the Utility of Dynamic Contrast‐Enhanced MRI for Treatment Planning and Monitoring Treatment Response in Lung Stereotactic Body Radiation Therapy

Abstract

Purpose: To investigate the feasibility of pulmonary DCE‐MRI in 1) identifying regions of functional lung for lung SBRT treatment planning; 2) assessing tumor response during and after SBRT; and 3) characterizing regions of radiation‐induced lung injury after SBRT. Methods: In this IRB‐approved feasibility study, participants being treated with 3–5 fractions of 12–18 Gy undergo pulmonary DCE‐MRI at baseline, during treatment (1–2 days after first fraction) and post‐treatment (1–2 weeks and then 3–4 months). DCE‐MRI is performed using a clinical 3D DCE‐MRI protocol, that includes T2‐weighted HASTE, T1‐weighted VIBE, and 3D turbo FLASH sequences. The parameters for the 3D turbo FLASH were: TR/TE=2.2/0.84msec, FOV=400mm, 256×208, slice thickness 3.6 mm, 1 excitation, BW=930kHz, FA=10, coronal orientation, temporal resolution=4sec, 42 frames, Gd‐DTPA iv. 0.1 mmol/kg. Time‐intensity curves are derived after motion‐correction, and fit to a two‐compartment plasma/extracellular extravascular space (EES) model to derive pharmacokinetic parameters for the tumor and surrounding treated lung, including kep, the characteristic rate of transfer of contrast tracer between plasma and the EES. The study aims to enroll 20 patients, with a preliminary assessment of feasibility after 7 patients. Results: The first patient was enrolled, and all the 4 MRI studies were successfully completed within the timeframe defined by the protocol, without complications. Images of the lung and tumor were obtained with satisfactory quality for pharmacokinetic analysis. Pharmacokinetic parameter maps based on DCE‐MRI were generated and registered to the corresponding planning 4DCT for each scan. In this first patient, kep in a tumor ROI was 1.09 before treatment, 0.20 after 2 fractions of 18 Gy, and 0.76 two weeks after the final fraction. Conclusion: The feasibility of acquiring and incorporating information from DCE‐MRI into lung stereotactic body radiation therapy has been demonstrated on an initial patient. Quantitative analysis will be performed after accrual of more participants. Kaye Scholar Grant and Siemens Research Partnership Grant