Oxygen-Enhanced MRI of the Lungs: Intraindividual Comparison Between 1.5 and 3 Tesla

Zusammenfassung

Ziel: Die Machbarkeit der sauerstoffverstärkten MRT der Lunge bei 3 Tesla sollte beurteilt und die Signalcharakteristika mit 1,5 Tesla verglichen werden. Material und Methoden: 13 Probanden unterzogen sich einer sauerstoffverstärkten MRT-Untersuchung bei 1,5 und 3 T mit einer koronar orientierten T 1-gewichteten, einschichtigen, nichtselektiven Inversion-Recovery-Half-Fourier-Fast-Spin-Echo-Sequenz mit Atem- und EKG-Triggerung. Je 40 Einzelmessungen wurden unter Raumluftatmung und unter Sauerstoffatmung (15 l/min über eine Atemmaske) durchgeführt. Das Signal-Rausch-Verhältnis (SNR) von Lungengewebe wurde mithilfe eines Differenzbildverfahrens ermittelt. Die Bildqualität der Einzelakquisitionen wurde visuell beurteilt. Der Mittelwert des sauerstoffvermittelten relativen Signalanstiegs und sein regionaler Variationskoeffizient wurden berechnet und der Signalanstieg in Parameterkarten farbcodiert dargestellt. Verteilung und Heterogenität des Signalanstiegs in den Parameterkarten bei beiden Feldstärken wurden visuell verglichen. Ergebnisse: Der mittlere relative Signalanstieg durch Sauerstoffatmung betrug 13 % (± 5.6 %) bei 1,5 T und 9.0 % (± 8.0 %) bei 3 T. Ein signifikant höherer Wert des regionalen Variationskoeffizienten zeigte sich bei 3 T. Auf den Parameterkarten zeigte sich visuell und quantitativ bei 3 T eine deutlich inhomogenere Verteilung des Signalanstiegs. Das SNR unterschied sich bei den beiden Feldstärken nicht signifikant, war jedoch bei 3 T tendenziell (um ca. 10 %) höher. Schlussfolgerung: Die sauerstoffverstärkte MRT-Bildgebung der Lunge lässt sich prinzipiell bei 3 T durchführen, wenngleich der Signalanstieg bei 3 T derzeit im Vergleich zu 1,5 T heterogener und etwas geringer ist.

Abstract

Purpose: To assess the feasibility of oxygen-enhanced MRI of the lung at 3 Tesla and to compare signal characteristics with 1.5 Tesla. Materials and Methods: 13 volunteers underwent oxygen-enhanced lung MRI at 1.5 and 3 T with a T 1-weighted single-slice non-selective inversion-recovery single-shot half-Fourier fast-spin-echo sequence with simultaneous respiratory and cardiac triggering in coronal orientation. 40 measurements were acquired during room air breathing and subsequently during oxygen breathing (15 L/min, close-fitting face-mask). The signal-to-noise ratio (SNR) of the lung tissue was determined with a difference image method. The image quality of all acquisitions was visually assessed. The mean values of the oxygen-induced relative signal enhancement and its regional coefficient of variation were calculated and the signal enhancement was displayed as color-coded parameter maps. Oxygen-enhancement maps were visually assessed with respect to the distribution and heterogeneity of the oxygen-related signal enhancement at both field strengths. Results: The mean relative signal enhancement due to oxygen breathing was 13 % (± 5.6 %) at 1.5 T and of 9.0 % (± 8.0 %) at 3 T. The regional coefficient of variation was significantly higher at 3 T. Visual and quantitative assessment of the enhancement maps showed considerably less homogeneous distribution of the signal enhancement at 3 T. The SNR was not significantly different but showed a trend to slightly higher values (increase of about 10 %) at 3 T. Conclusion: Oxygen-enhanced pulmonary MRI is feasible at 3 Tesla. However, signal enhancement is currently more heterogeneous and slightly lower at 3 T.

Key words

3 Tesla MRI - oxygen-enhanced lung MRI - lung MRI - high-field lung MRI

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