Time-resolved contrast-enhanced pulmonary MR angiography using sensitivity encoding (SENSE)

Purpose: To evaluate the relationship between gadolinium concentration and signal-to-noise ratio (SNR) on sensitivity encoding (SENSE) images, and determine the appropriate bolus injection protocol for visualizing pulmonary circulation. Materials and Methods: Eighteen different gadolinium concentration phantoms (0, 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5, 2.0, 5.0, 10.0, 20.0, 30.0, 50.0, and 100.0 mmol/L) were analyzed to determine the relationship between gadolinium concentration and SNR on SENSE images in a phantom study. In an in vivo study, 3 mL (protocol A) or 6 mL (protocol B) of Gd-DTPA BMA at 3 mL/second, and 5 mL of Gd-DTPA BMA at 5 mL/second (protocol C) were administered to eight normal volunteers for contrast-enhanced (CE) pulmonary MR angiography (MRA) with SENSE. The peak SNRs of pulmonary parenchyma and the difference in SNR between pulmonary artery (PA) and pulmonary vein (PV) at peak SNR in the PA were statistically evaluated. Results: For each flip angle at each gadolinium concentration. the SNRs and contrast-to-noise ratios (CNRs) of the SENSE images were significantly lower than those acquired with a nonparallel imaging technique (P < 0.05). The peak SNR of the pulmonary parenchyma, and differences in SNR between the PA and PV at the peak SNR of the PA obtained with a 5-mL/second bolus injection protocol were found to be significantly higher than those obtained with other protocols (P < 0.05). Conclusion: 3D-CE-MRA using SENSE demonstrated linearity between gadolinium concentration and SNR, and resulted in MRA with high spatial and temporal resolution with the aid of a sharp bolus injection protocol.