Influence of oxygen flow rate on signal and T₁ changes in oxygen-enhanced ventilation imaging

Purpose: To investigate the optimal oxygen flow rate for oxygen-enhanced MR ventilation imaging. Materials and Methods: Using a cardiac-triggered nonselective inversion recovery (IR) half Fourier single-shot fast spin echo sequence, series of images were acquired with the subject alternately inhaling room air and 100% oxygen. Oxygen flow rates of 5 L/min, 10 L/min, 15 L/min, 20 L/min, and 25 L/min were studied, and signal intensity from the oxygen-enhanced ventilation images and T₁ of the lung were measured. Results: The average signal intensity was 63.0 ± 21.0 for 5 L/min, 98.7 ± 26.8 for 10 L/min, 133.8 ± 20.0 for 15 L/min, 138.7 ± 19.7 for 20 L/min, and 139.2 ± 37.9 for 25 L/min. The average T₁'s of the lung were 1399 msec ± 130 msec for room air, 1314 msec ± 101 msec for 5 L/min, 1276 msec ± 105 msec for 10 L/min, 1207 msec ± 71 msec for 15 L/min, 1206 msec ± 90 msec for 20 L/min, and 1207 msec ± 42 msec for 25 L/min. Conclusion: The optimal flow rate is 15 L/min for oxygen- enhanced ventilation imaging.