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 (T_1f) and nonselective (T₁) inversion. The average T₁ was 1360 ms ± 116 ms, and the average T_1f was 1012 ms ± 112 ms, yielding a difference that isstatistically 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.