Oxygen-enhanced magnetic resonance imaging: influence of different gas delivery methods on the T1-changes of the lungs.

Objective: The clinical feasibility of oxygen-enhanced magnetic resonance imaging (MRI) of the lung may benefit from the use of a simple gas delivery method. In this study, the oxygen-induced T1 change of the lung obtained using a closed O(2) delivery system was compared with that obtained by a conventional nontight face mask.

Material And Methods: Twenty-three healthy subjects (15 men, 8 women, mean age = 25 years, age range = 20-35 years) underwent oxygen-enhanced MRI of the lung using a closed O(2) delivery system composed by a tightly fitting face mask and a 60-L reservoir bag (equipment type A: n = 13, 9 men, 4 women, mean age = 24.4 years, age range = 20-32 years), or a clinically available nontight face mask (equipment type B: n = 10; 6 men, 4 women, mean age = 25.8 years, age range = 20-35 years). The effect of 100%-oxygen inhalation was assessed using a Snapshot FLASH T1-mapping technique (repetition time/echo time = 1.5-1.6/0.56 milliseconds; matrix = 128 x 90; acquisition time = 3.3-3.7 seconds; slice thickness = 15-20 mm; number of images = 40). By nonlinear curve fitting, the mean T1 values of the left and right lung at room air and 100%-oxygen ventilation were calculated (T1(room air, right); T1(oxygen, right); T1(room air, left); T1(oxygen, left)). The average T1 differences (DeltaT1 = T1(room air) - T1(oxygen)) of the 2 volunteer groups were compared (Wilcoxon signed rank test, Mann-Whitney U test).

Results: The mean T1 values obtained using the 2 respiratory equipments at room air or oxygen ventilation were not significantly different (A vs. B at room air ventilation: P = 0.85 for the right lung, P = 0.27 for the left lung; A vs. B at oxygen ventilation: P = 0.55 for the left lung, P = 0.29 for the right lung). With both systems, the mean T1 values decreased significantly after oxygen inhalation (P = 0.03-0.0002). For both lungs, the DeltaT1 obtained using the equipment type A was statistically equivalent to that obtained using the equipment type B: DeltaT1A, right = 96 +/- 19 milliseconds versus DeltaT1B, right = 97 +/- 34 milliseconds (P = 0.82); DeltaT1A, left = 74 +/- 47 milliseconds versus DeltaT1B, left = 68 +/- 63 milliseconds (P = 0.85).

Conclusion: Gas delivery in oxygen-enhanced MRI of the lung can be performed with a clinically available standard face mask, without the need for closed sophisticated equipments.