Ventilation-perfusion ratio of signal intensity in human lung using oxygen-enhanced and arterial spin labeling techniques

This study investigates the distribution of ventilation‐perfusion (V/Q) signal intensity (SI) ratios using oxygen‐enhanced and arterial spin labeling (ASL) techniques in the lungs of 10 healthy volunteers. Ventilation and perfusion images were simultaneously acquired using the flow‐sensitive alternating inversion recovery (FAIR) method as volunteers alternately inhaled room air and 100% oxygen. Images of the T1 distribution were calculated for five volunteers for both selective (T1f) and nonselective (T1) inversion. The average T1 was 1360 ms ± 116 ms, and the average T1f was 1012 ms ± 112 ms, yielding a difference that is statistically significant (P < 0.002). Excluding large pulmonary vessels, the average V/Q SI ratios were 0.355 ± 0.073 for the left lung and 0.371 ± 0.093 for the right lung, which are in agreement with the theoretical V/Q SI ratio. Plots of the V/Q SI ratio are similar to the logarithmic normal distribution obtained by multiple inert gas elimination techniques, with a range of ratios matching ventilation and perfusion. This MRI V/Q technique is completely noninvasive and does not involve ionized radiation. A limitation of this method is the nonsimultaneous acquisition of perfusion and ventilation data, with oxygen administered only for the ventilation data. Magn Reson Med 48:341–350, 2002. © 2002 Wiley‐Liss, Inc.