Room: Exhibit Hall | Forum 2
Purpose: To investigate early feasibility of dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI)for semi-quantitative tissue perfusion analysis on a 0.35 T MR system using a free-breathing golden angle radial stack of stars k-space sampling scheme.
Methods: An initial pilot study was conducted using a 3.8 liter water phantom outfitted with tubing to mimic the aorta and arterial vasculature. Subsequently, two female radiotherapy patients consented to the pilot research scan at a single institution. Images were acquired using a 0.35 T MRI system (ViewRay Technologies Inc., Mountain View, CA) with a 3-dimensional T1-weighted golden angle radial stack of stars sequence. 512 radial spokes were acquired continuously over 3 minutes with FOV = 349 x 349 x 120 mm, image matrix = 208 x 208 x 80, spatial resolution = 1.68 x 1.68 x 1.5 mm, TR = 4.44 ms, TE = 2 ms, flip angle = 12 degrees, BW = 601 Hz/voxel. Intravenous injection of 0.025 mmol/kg Gd-EOB-DTPA (Eovist, Bayer Healthcare, Whippany, NJ) was begun 10 seconds after the start of the sequence at a rate of 2 mL/s.
Results: Reconstruction grouping 16 spokes per dynamic frame produced a temporal resolution of 5.6 seconds. Dynamic signal intensity of regions of interest located in the phantom center and central liver on patient scans demonstrate characteristic contrast wash-in and plateau, allowing for estimation of baseline signal intensity, peak signal intensity and onset time. Further protocol optimization to improve SNR will be necessary to quantify wash-in slope or initial area under the curve (IAUC) at 2 mL/s bolus injection.
Conclusion: These results indicate early feasibility of DCE MRI for semi-quantitative perfusion analysis on low-field MRI systems with further protocol optimization. Perfusion imaging on low-field MR-guided radiotherapy systems has the potential to be used as a measure of dynamic treatment response.
Funding Support, Disclosures, and Conflict of Interest: The authors acknowledge funding support from the National Institutes of Health, the Ronald Reagan UCLA medical center, and ViewRay Technologies Inc. Dr. Yang has served as an honorary speaker and in a short-term consulting role with ViewRay Technologies Inc.