Oxygen-Enhanced Magnetic Resonance Imaging: Influence of Different Gas Delivery Methods on the T1-changes of the Lungs

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Abstract

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 O2 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 O2 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 × 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 (T1room air, right; T1oxygen, right; T1room air, left; T1oxygen, left). The average T1 differences (ΔT1 = T1room air − T1oxygen) 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 ΔT1 obtained using the equipment type A was statistically equivalent to that obtained using the equipment type B: ΔT1A, right = 96 ± 19 milliseconds versus ΔT1B, right = 97 ± 34 milliseconds (P = 0.82); ΔT1A, left = 74 ± 47 milliseconds versus ΔT1B, 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.

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