Rationale and objectives: We sought to optimize the dosage of a paramagnetic contrast medium (CM) for the quantification of pulmonary blood flow and volume by contrast-enhanced dynamic magnetic resonance imaging (MRI) using a parallel imaging technique and to prove the feasibility of the approach in healthy volunteers.
Methods: In a phantom study, the dependency of signal increase on different concentrations of the CM gadodiamide was evaluated by means of an ultra-fast MRI sequence with a generalized autocalibrating partially parallel acquisition technique (acceleration factor = 2). Using the same sequence, measurements were performed in a healthy volunteer after administration of different CM dosages for contrast dosage optimization in vivo. Finally, perfusion measurements were performed in 16 healthy volunteers after the administration of the optimal CM dose. Signal-time curves were evaluated from the pulmonary artery and from predefined regions of the lung. Pulmonary regional blood volume (RBV) and flow (RBF) were estimated using an open 1-compartment model.
Results: Phantom studies yielded a linear signal increase up to a concentration of 5.0 mmol/L gadodiamide. Results of contrast dosage optimization in vivo showed that the maximum CM dose providing a linear relationship between signal increase and CM concentration in the pulmonary artery of a healthy volunteer was approximately 0.05 mmol/kg-bw. Quantification of pulmonary blood volume and flow was reproducible in healthy volunteers, yielding mean values for the upper lung zones of 7.1 +/- 2.3 mL/100 mL for RBV and 197 +/- 97 mL/min/100 mL for RBF and for lower lung zones, 12.5 +/- 3.9 mL/100 mL for RBV and 382 +/- 111 mL/min/100 mL for RBF.
Conclusions: If an adequate amount of gadodiamide and fast MR sequences are used, quantification of pulmonary blood flow and volume is feasible.