Purpose: To prospectively evaluate the technical feasibility and relative performance of pulmonary time-resolved MR angiography (MRA) and pulmonary artery (PA) flow quantification at 3.0T vs. 1.5T.
Materials and Methods:Time-resolved contrast-enhanced (CE) MRA of the pulmonary circulation, and flow quantification of the main PA (MPA) were performed in 14 consecutive adult healthy volunteers at both 1.5 and 3.0 Tesla with nearly identical sequence parameters. Image quality, signal-to-noise ratio (SNR), and quantitative indices of pulmonary perfusion, flow, and velocity were evaluated and compared at both field strengths.Results: Time-resolved pulmonary MRA, perfusion, and flow quantification were successfully performed at both magnetic fields. The results of pulmonary perfusion and flow indices were comparable at both magnetic fields, with no statistically significant difference. The SNR values for vascular structures were higher at 3.0T vs. 1.5T (P ϭ 0.001). The SNR values and the definition scores for parenchymal enhancement were significantly lower (P ϭ 0.008 and 0.001, respectively) at 3.0T.
Conclusion:Time-resolved pulmonary MRA, perfusion, and flow quantification at 3.0T was feasible, with comparable results to 1.5T. The lower parenchymal enhancement at 3.0T is believed to reflect increased susceptibility effects at higher magnetic fields. Further work is needed to fully exploit the potential of pulmonary perfusion imaging at 3.0T and to address the current limitations.Key Words: pulmonary perfusion with MRI; time-resolved pulmonary MRA at 3.0T; pulmonary flow at 3.0T; comparison of 3.0T vs. MRI IS INCREASINGLY being applied to the study of pulmonary vascular anatomy, perfusion, and blood flow. Time-resolved contrast-enhanced magnetic resonance angiography (CE-MRA) in particular is well suited for studying the pulmonary circulation because it offers the potential for simultaneous evaluation of vascular anatomy and dynamic microvascular parenchymal enhancement.Recently, parallel imaging with k-space undersampling has improved the temporal and spatial resolution of time-resolved MRA (1,2) with positive results at 1.5T. Phase-sensitive velocity imaging has been successfully applied to the study of pulmonary artery (PA) blood flow for some time (3,4).With the advent of whole-body, 3.0T MR systems, the promise is that performance and image quality can be even further enhanced. The higher available signal-tonoise ratio (SNR) can be used to support fast imaging tools, improving both spatial and temporal resolution. Also, since the longitudinal relaxation time (T1) of unenhanced blood increases with field strength (5), sensitivity to injected gadolinium (Gd) agents for CE-MRA may be heightened. There are, however, substantial technical challenges presented by MRI at 3.0T. Specific absorption rates (SAR) set lower limits on nominal flip angles, and dielectric resonances and radiofrequency (RF) eddy currents may result in B 1 inhomogeneity, which can negatively impact image quality (6 -8). Magnetic susceptibility eff...