Inflow Quantification in Three-Dimensional Cardiovascular MR Imaging

Purpose: To investigate blood inflow enhancement (or lack thereof) in three-dimensional (3D) cardiovascular MR for both single phase whole-heart and cine biventricular functions. Materials and Methods: A 3D imaging sequence is proposed in which radiofrequency excitation gradient is changed without modifying image acquisition or phase/slice encoding. This imaging sequence enables direct inflow measurement while retaining static voxel signal-to-noise ratio. Inflow measurements were performed for both spoiled gradient-echo (GRE) imaging and balanced steady-state free precession (SSFP) in 18 healthy subjects. Results: For single phase imaging, increasing slab thickness from 3 to 10 cm lead to 73% and 59% reductions in contrast-to-noise ratio (CNR) with GRE and SSFP, respectively. For cine acquisitions, systolic CNR was reduced by 85% and 50% for the GRE and SSFP acquisitions, respectively, while diastolic CNR was reduced by 64% and 42%. Conclusion: There is significant loss of CNR between blood and myocardium when using larger 3D slabs due to saturation of inflowing spins. The loss of contrast is less pronounced for SSFP than for GRE, though both acquisition techniques suffer.