Magnetic Resonance Imaging of Pulmonary Ventilation

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Abstract
The authors investigate whether a modified gadolinium (Gd)-DTPA formulation can be aerosolized and used as a contrast agent for magnetic resonance (MR) ventilation imaging of the lungs. Gadolinium-DTPA (gadopentetate dimeglumine, Schering AG, Berlin, Germany, 100 mmol Gd/L) was modified by addition of mannitol (Sigma, Deisenhofen, Germany, 10 mg/mL) and the surface active detergent Lutrol F68 (BASF, Mannheim, Germany, 2 mg/mL). The imaging was performed in an anesthetized rat model after inhalation of the contrast agent aerosol (PulmoSonic, De Vilbiss, Germany, 10-minute nebulization). T1-weighted spin echo images (repetitive time [TR]/echo time [TE] = 40/3 mseconds) were acquired at 2 T (SIS 85; Sisco, Fremont, CA) before and as long as 120 minutes after administration of the contrast agent. The modified Gd-DTPA aerosol elicited high and relatively homogeneous enhancement of the lung directly after nebulization. The enhancement was more pronounced than that obtained with a Gd-DTPA formulation without additives. Gadolinium-DTPA-based aerosol appears to be a suitable contrast agent for MR ventilation imaging in an experimental animal model. Modification by mannitol (to increase proton density through a slight additional osmotic effect) and a detergent (to reduce droplet size by decreasing surface tension) is suitable and effective in increasing signal intensity compared with Gd-DTPA without modification.