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  • Open Access

Coronary MRA at 3 T using 3d multi-interleaved multi-echo acquisition with varpro fat-water separation

  • 1,
  • 1,
  • 2,
  • 1,
  • 3,
  • 4 and
  • 1
Journal of Cardiovascular Magnetic Resonance201012 (Suppl 1) :P42

  • Published:


  • Right Coronary Artery
  • Contrast Agent Administration
  • Coronary Artery Image
  • Navigator Efficiency
  • Parallel Imaging Factor


Coronary MR Angiography is a valuable tool for non-invasive assessment of coronary arteries. Presently, contrast-enhanced, fat-saturated, ECG-triggered and navigator-gated 3D spoiled gradient-echo sequence is employed for whole-heart Coronary MRA at 3 T[1]. However, large static field variations at 3 T frequently result in non-uniform fat-suppression over the field-of-view (FOV), obscuring the delineation of coronary arteries. Multi-echo Dixon approaches utilizing iterative decomposition have been shown to provide robust fat-water separation even in the presence of large field inhomogeneities. In this study, an ECG-triggered navigator-gated 3D spoiled gradient-echo multi-interleaved multi-echo (GRE-MEMI) pulse sequence is introduced which utilizes VARPRO[2] fat-water separation to achieve reliable fat-suppression and provides enhanced visualization of coronary arteries.


A 3D GRE-MEMI sequence (Fig. 1) was implemented on a 3 T whole-body MR scanner (MAGNETOM Trio, Siemens AG) with support for navigator-gating and ECG-triggering. Water-only and fat-only images were reconstructed using VARPRO. Four healthy volunteers were imaged pre- and during contrast agent administration targeting right coronary artery (RCA). Typical imaging parameters for pre-contrast GRE-MEMI scan are listed in Table 1. Additionally, a conventional single-echo fat-saturated GRE scan was acquired for comparison. Thereafter, 0.2 mmol/kg Gd-DTPA (Magnevist®, Bayer Healthcare) was slowly injected at a rate of 0.3 ml/s followed by 20 ml of saline solution injected at the same rate. GRE-MEMI acquisition with inversion preparation (TI = 300 ms) was started 30 s after injection.
Table 1

Typical imaging parameters for conventional 3D fat-saturated GRE and 3D GRE-MEMI measurements.

Paramater name

Fat-saturated GRE


No. of Echoes




1.54 ms

1/2/3/4 = 1.35/2.47/3.6/4.7 2 ms


3.4 ms

5.42 ms

Flip angle




1.3 mm × 1.3 mm × 1.5 mm

1.3 mm × 1.3 mm × 1.5 mm

No. of Slices



Parallel acquisition/acceleration/reference lines



Figure 1
Figure 1

Pule Sequence Diagram for 3D ECG-triggered, navigator gated, spoiled gradient echo sequence with multi-echo multi-interleave readout (GRE-MEMI). Multiple echoes are used during reconstruction by VARPRO for iterative water-fat decomposition. No fat-saturation prepulse is applied separately. Multi-interleaved scheme achieves shorter echo time increments between multiple echoes, which improves the fat-water separation.


Targeted RCA images were successfully acquired in all volunteers with effective fat-water separation. The average total imaging time was 8.93 ± 1.2 min with navigator efficiency of 33.8 ± 4.6%. Fig. 2 shows pre-contrast coronary artery images from a healthy volunteer. Conventional fat-saturation yields suboptimal fat-suppression whereas robust fat-suppression is evident in water-only images which provide clear depiction of coronary artery. Fig. 3 illustrates enhanced contrast-to-noise with the use of contrast agent.
Figure 2
Figure 2

Conventional fat saturation (chemical selective saturation) image (a) and fat-water separated images (b, c) from a targeted right coronary artery (RCA) measurement at 3 T in a healthy volunteer without any contrast agent administration. Conventional fat saturation yields suboptimal results in some areas (a - red arrows), however, robust fat suppression is achieved over the entire FOV using the proposed technique. Moreover, the use of multiple echoes increases the signal-to-noise ratio (SNR). Water-only (d) and fat-only (e) pre-contrast images from another health subject demonstrate excellent fat suppression and clearly depict RCA (red arrows).

Figure 3
Figure 3

Water-only (a) and fat-only (b) images acquired from a healthy subject during slow infusion of contrast media. Note that water and fat signals are effectively separated and the RCA (a - red arrows) is sharply delineated. Compared to pre-contrast GRE measurements, use of contrast agent increases contrast-to-noise ratio between blood and background tissues.


3D GRE-MEMI sequence was successfully utilized for targeted fat-water separated coronary artery imaging in healthy volunteers. VARPRO fat-water separation provides reliable fat-suppression at 3 T and improves the delineation of coronary arteries. Moreover, without the use of a fat-saturation prepulse, readout duration within a heartbeat can be extended to cover the entire quiescent period without any degradation in fat-suppression. Multi-echo acquisition results in increased acquisition time, however, the resulting water-only image provides the benefit of increased SNR due to intrinsic averaging effect of fat-water separation. Further improvement in acquisition speed using higher parallel imaging factors is required to achieve 3D whole-heart coverage.

Authors’ Affiliations

Siemens Healthcare, Chicago, IL, USA
University of Illinois at Urbana-Champaign, Urbana, IL, USA
Royal Brompton And Harefield NHS Foundation Trust, London, UK
National Institutes of Health/NHLBI, Bethesda, MD, USA


  1. Bi X et al: MRM. 2007, 58:Google Scholar
  2. Hernando D et al: MRM. 2008, 59:Google Scholar


© Shah et al; licensee BioMed Central Ltd. 2010

This article is published under license to BioMed Central Ltd.