3D multi-phase balanced non-steady-state free precession acquisition for multi-parameter mapping

OBJECTIVE: 

This study presents the 3D MP-b-nSSFP sequence for multi-parametric mapping.

METHODS: 

We evaluate several aspects of the 3D implementation, like the type of RF pulse (selective/non-selective), the readout duration, the undersampling pattern, and the acceleration factor. We use undersampled scans with subspace-constrained reconstruction and extended spiral readouts to achieve clinically acceptable scan times. The repeatability and accuracy of the T 1 and T 2 maps are compared with a reference technique in phantom and three volunteer scans.

RESULTS: 

Compared with selective refocusing pulses, we observe lower bias with non-selective pulses, despite modeling the spatially varying effect of the pulses in the fitting process. T 1 and T 2 maps obtained from phantom scans were comparable to the nominal values and those from reference scans. T 1 values in vivo were underestimated compared to the reference scan. The maps with an acquisition matrix of 256 × 256 × 44 and resolution 1 × 1 × 3 mm 3 were acquired in 11 min.

CONCLUSION: 

We show that 3D MP-b-nSSFP can be used for multi-parameter mapping within clinically acceptable scan time. Phantom scans show results in good agreement with reference scan results. However, the in vivo scan underestimated T 1 .