Effects of Refocusing Flip Angle Modulation and View Ordering in 3D Fast Spin Echo

Magn Reson Med. 2008 Sep;60(3):640-9. doi: 10.1002/mrm.21680.

Abstract

Recent advances have reduced scan time in three-dimensional fast spin echo (3D-FSE) imaging, including very long echo trains through refocusing flip angle (FA) modulation and 2D-accelerated parallel imaging. This work describes a method to modulate refocusing FAs that produces sharp point spread functions (PSFs) from very long echo trains while exercising direct control over minimum, center-k-space, and maximum FAs in order to accommodate the presence of flow and motion, SNR requirements, and RF power limits. Additionally, a new method for ordering views to map signal modulation from the echo train into k(y)-k(z) space that enables nonrectangular k-space grids and autocalibrating 2D-accelerated parallel imaging is presented. With long echo trains and fewer echoes required to encode large matrices, large volumes with high in- and through-plane resolution matrices may be acquired with scan times of 3-6 min, as demonstrated for volumetric brain, knee, and kidney imaging.

MeSH terms

  • Algorithms
  • Fourier Analysis
  • Humans
  • Image Enhancement / methods
  • Magnetic Resonance Imaging / methods*