Volume 10 Supplement 1

Abstracts of the 11th Annual SCMR Scientific Sessions - 2008

Open Access

2117 High-resolution 3D free-breathing coronary MR angiography using wideband SSFP at 3 Tesla

  • Hsu-Lei Lee1,
  • Ajit Shankaranarayanan2,
  • Gerald M Pohost3 and
  • Krishna S Nayak1
Journal of Cardiovascular Magnetic Resonance200810(Suppl 1):A386

https://doi.org/10.1186/1532-429X-10-S1-A386

Published: 22 October 2008

Introduction

Steady-state free precession (SSFP) imaging at 3 T can be used to generate coronary artery images with substantially higher signal to noise ratio (SNR) and blood-myocardium contrast to noise ratio (CNR) compared to 1.5 T, but is limited by potentially severe off-resonance artifacts [1]. The need for a short TR (to avoid banding) limits the spatial resolution to > 1 mm using conventional gradients, making it difficult to achieve the sub-millimeter resolution needed for accurately evaluating coronary artery stenoses.

Wideband SSFP uses two alternating repetition times to increase the band spacing in the steady-state frequency response, with a modest sacrifice in SNR [2]. It can suppress off-resonance related artifacts in cardiac imaging for a given spatial resolution. We demonstrate the application of wideband SSFP to 3D free-breathing coronary artery imaging at 3 T, and compare results with conventional SSFP at 3 T.

Methods

Experiments were performed on a Signa Excite HD 3 T scanner (GE Healthcare, Waukesha, WI) with gradients capable of 40 mT/m amplitude and 150 mT/m/ms slew rate, using an 8-channel phased-array cardiac coil. Three healthy volunteers were scanned after providing informed consent. Navigator-gated sequences, illustrated in Figure 1, were used to image the LMCA and proximal LAD in mid-diastole. A conventional cylindrical navigator (4.3 ms excitation), is followed by a spectrally-selective fat saturation pulse, and a Kaiser-Bessel RF ramp to quickly align magnetization with the steady-state. 3DFT image acquisition used a segmented interleaved sequential phase-encoding order. Imaging parameters were: FOV = 26 × 26 × 1.8 cm3, resolution = 0.68 × 1.0 × 1.0 mm3, flip angle = 55°, TR/TRs = 3.9/2.4 ms for wideband SSFP and TR = 3.9 ms for conventional SSFP. 3D image reformation was performed off-line.

Figure 1

Results and discussion

Figure 2 shows 3-D reformatted LAD images from one volunteer. A resolution of 0.68 × 1.0 × 1.0 mm3 was achieved at 3 T with a wideband SSFP sequence in 5 minutes (Figure 2a). Figure 2b shows a conventional SSFP image with the same spatial resolution and TR (3.9 ms), where banding artifacts obstruct the assessment of vessels of interest. Wideband SSFP with TR/TRs = 3.9/2.4 ms is expected to have a 24% wider null-to-null spacing (~317 Hz) compared to SSFP and this increased bandwidth removes the off-resonance artifacts from the region of interest.
Figure 2

We demonstrate sub-millimeter resolution 3D SSFP coronary artery imaging at 3 Tesla using the wideband SSFP technique. Images of the LMCA and proximal LAD were obtained with 0.68 × 1.0 × 1.0 mm resolution and without the banding artifacts experienced by conventional SSFP.

Summary

We have demonstrated wideband SSFP in free-breathing 3D coronary artery MR imaging at 3 T. A spatial resolution of 0.68 × 1.0 × 1.0 mm3 was achieved without the banding artifacts experienced by conventional SSFP with excellent coronary artery imaging.

Authors’ Affiliations

(1)
Department of Electrical Engineering, University of Southern California
(2)
Global Applied Science Lab, GE Healthcare
(3)
Division of Cardiovascular Medicine, University of Southern California

References

  1. Bi X, Deshpande V, Simonetti O, Laub G, Li D: Three-Dimensional Breathhold SSFP Coronary MRA: A Comparison Between 1.5 T and 3.0 T. J Magn Reson Imag. 2005, 22: 206-212. 10.1002/jmri.20374.View ArticleGoogle Scholar
  2. Nayak Krishna, Lee Hsu-Lei, Hargreaves Brian, Hu Bob: Wideband SSFP: Alternating Repetition Time Balanced Steady State Free Precession with Increased Band Spacing. Magn Reson Med.Google Scholar

Copyright

© Lee et al; licensee BioMed Central Ltd. 2008

This article is published under license to BioMed Central Ltd.

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