title: On the undersampling strategies to accelerate time-resolved 3D imaging using k-t-GRAPPA.
abstract: The purpose of this study was to explore how to optimally undersample and reconstruct time-resolved 3D data using a k-t-space-based GRAPPA technique. The performance of different reconstruction strategies was evaluated using data sets with different ratios of phase (N(y)) and partition (N(z)) encoding lines (N(y) × N(z) = 64-128 × 40-64) acquired in a moving phantom. Image reconstruction was performed for different kernel configurations and different reduction factors (R = 5, 6, 8, and 10) and was evaluated using regional error quantification and SNR analysis. To analyze the temporal fidelity of the different kernel configurations in vivo, time-resolved 3D phase contrast data were acquired in the thoracic aorta of two healthy volunteers. Results demonstrated that kernel configurations with a small kernel extension yielded superior results especially for more asymmetric data matrices as typically used in clinical applications. The application of k-t-GRAPPA to in vivo data demonstrated the feasibility of undersampling of time-resolved 3D phase contrast data set with a nominal reduction factors of up to R(net) = 8, while maintaining the temporal fidelity of the measured velocity field. Extended GRAPPA-based parallel imaging with optimized multidimensional reconstruction kernels has the potential to substantially accelerate data acquisitions in time-resolved 3D MRI.
authors: Department of Diagnostic Radiology, Medical Physics, University Hospital, Freiburg, Germany. bernd.jung@uniklinik-freiburg.de
authors: Bernd
authors: B
authors: Jung
authors: Aurélien F
authors: AF
authors: Stalder
authors: Simon
authors: S
authors: Bauer
authors: Michael
authors: M
authors: Markl
mesh_terms: D000465:Algorithms; D001011:Aorta / Q000033:anatomy & histology* / Q000502:physiology; D016477:Artifacts; D001783:Blood Flow Velocity; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D013997:Time Factors