Reed F. Busse PhD, Abstract Co-Author: Employee, General Electric Company

Kang Wang MS, Abstract Co-Author: Nothing to Disclose

James Holmes MS, Presenter: Employee, General Electric Company

Jean Helen Brittain PhD, Abstract Co-Author: Employee, General Electric Company

Christopher Jean-Pierre Francois MD, Abstract Co-Author: Research agreement, General Electric Company

Frank R. Korosec PhD, Abstract Co-Author: Nothing to Disclose

Dynamic MRA provides visualization of contrast kinetics in arteries and veins, enabling assessment of vascular disease. Clinical demand for simultaneously high spatial and temporal resolution has been a challenge. To provide the robustness of accelerated Cartesian approaches (e.g. CAPR) with the improved temporal fidelity of constrained projection approaches (e.g. HYPR), a new technique is presented in which Cartesian data are acquired in an Interleaved Variable Density (IVD) fashion, then a series of time-resolved 3D images are produced by a parallel imaging Highly-constrained Cartesian Reconstruction (HYCR) algorithm.

The IVD method acquires an under-sampled set of phase encode views. Compared to a Nyquist-sampled set, IVD pattern is sub-sampled first in a regular 2x2 parallel imaging (PI) pattern, then in a pseudo-random pattern with higher density in the center of k-space. A set of N such patterns interleave, thus data averaged over N frames have regular 2x2 subsampling. The HYCR algorithm multiplies a high spatial-resolution constraining image by a high temporal-resolution weighting image. The constraining image is reconstructed from data averaged over N time frames, using 2D PI and Homodyne. The weighting image is the ratio of two images: one reconstructed from data acquired in a single time frame, and the other from the averaged data subsampled at the same locations. Feasibility was assessed in normal volunteers, using a GE 3T MR750 system. The study protocol was IRB approved and informed consent was obtained from all volunteers. Images were acquired at 1.0 mm3 isotropic resolution over an FOV of 480 (S/I) × 290 (L/R) × 120 (A/P) mm3, with time frames resolved at 6.4 seconds per frame.

Comparison of images reconstructed from the same data by HYCR and view-sharing demonstrated similar high image quality. Contrast arrival, assessed in small vessels, exhibited steeper rise times with the HYCR method, suggesting improved temporal fidelity (less temporal blur).

The experiments demonstrated that the technique is capable of producing high resolution and high SNR images while providing high temporal resolution in small enhancing vessels.

High spatial- and high temporal-resolution provided by the IVD HYCR method enables the dynamics of smaller vessels to be visualized with improved temporal fidelity.

Busse, R, Wang, K, Holmes, J, Brittain, J, Francois, C, Korosec, F, Dynamic MR Angiography with Interleaved Variable Density Sampling and Highly Constrained Cartesian Reconstruction.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9008771.html