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  • Oral presentation
  • Open Access

Coronary magnetic resonance angiography at 7 Tesla: a quantitative comparison with results at 3 Tesla

  • 1,
  • 1,
  • 1,
  • 2,
  • 1,
  • 2,
  • 1 and
  • 1
Journal of Cardiovascular Magnetic Resonance201012 (Suppl 1) :O88

https://doi.org/10.1186/1532-429X-12-S1-O88

  • Published:

Keywords

  • Magnetic Resonance Angiography
  • Right Coronary Artery
  • Coil Design
  • Magnetic Resonance Angiography Image
  • Healthy Adult Subject

Introduction

Commercial 7 Tesla(T) systems have recently become available for human use. Our initial results have shown feasibility of right coronary artery(RCA) magnetic resonance angiography(MRA) at 7 T[1]. Since then, we have optimized the RF coil design, resulting in significantly improved image quality at 7 T.

Purpose

To quantitatively compare same-subject signal-to-noise(S/N), coronary vessel length, vessel sharpness, acquisition time and navigator efficiency of right coronary MRA at 7 T and 3 T.

Methods

Eight healthy adult subjects (mean age 23 ± 3 years, 5 men) underwent vector ECG-triggered, navigator gated and corrected free-breathing 3D MRA of the RCA at 7 T and 3 T. At 7 T a quadrature loop-pair (two 15 cm elements) was constructed, and the 2D selective respiratory navigator was localized at the lung-heart interface. At 3 T, a commercial 6-element cardiac receive array was used with body-coil transmit. A 3D segmented k-space gradient echo technique was combined with spectrally selective adiabatic inversion-recovery magnetization fat saturation. At 3 T, coronary MRA were obtained with the navigator localized at the lung-heart interface and at the lung-liver interface, respectively. The scan parameters at both field strengths were as similar as possible (Table 1). The S/N in the bloodpool of the aortic root near the RCA offspring, coronary vessel length, vessel sharpness, acquisition time and navigator efficiency were compared using Wilcoxon matched-pairs test. For visualization, reformatting with the 'Soapbubble'-tool was utilized.
Table 1

Scan parameters

Field strength and sequence

7 Tesla, 3D gradient echo

3 Tesla, 3D gradient echo

3 Tesla, 3D gradient echo

Navigator

Heart

Diaphragm

Heart

Coil

Quadrature loop

6 element array

6 element array

TR/TE/TI fat suppress (ms)

4.3/1.38/200

4.3/1.38/150

4.3/1.38/150

Voxel size (mm3)

0.82 × 0.86 × 2.00

0.82 × 0.86 × 2.00

0.82 × 0.86 × 2.00

No. slices

30

30

30

FOV (mm2)

420 × 268

420 × 269

420 × 269

Matrix

512 × 312

512 × 312

512 × 312

Tip angle (°)

15

15

15

Acquisition window (ms)

107

108

108

Results

In Figure 1, RCAs obtained in the same subject at 7 T(Figure 1a) and 3 T (Figure 1b) are shown. The corresponding quantitative findings averaged over all subjects are listed in Table 2. The S/N was very similar at both field strengths and visible RCA vessel length was slightly lower at 7 T, but not statistically significant. Vessel sharpness obtained at 7 T was significantly higher compared to that at 3 T (p < 0.03). The scanning time for all 3D acquisitions was identical. There was a tendency for reduced navigator efficiency at 7 T which was not statistically significant, however. These findings apply for both the diaphragmatic navigator as well as for that localized at the heart with a trend for a lower S/N at 3 T for the navigator localized at the lung-heart interface.
Table 2

Quantitative findings, *significantly different from 7 T (p < 0.05)

 

7 T

3 T: navigator on diaphragm

3 T: navigator on heart

S/N blood

49.2 ± 30.9

46.1 ± 13.6

38.2 ± 14.2

RCA vessel length (cm)

7.21 ± 2.50

8.48 ± 3.06

8.46 ± 2.84

RCA vessel sharpness (%)

58.94 ± 9.27

48.35 ± 6.45*

48.92 ± 9.62*

Acquisition time (sec)

414 ± 144

478 ± 214

470 ± 173

Navigator efficiency (%)

57 ± 20

48 ± 15

48 ± 15

Figure 1

Conclusion

Using a quadrature transmit/receive coil at 7 T, it was shown that 7 T coronary MRA image quality has already begun to approach that at 3 T while vessel sharpness is already significantly improved. With future incorporation of technology such as larger transmit arrays we anticipate that the image quality at 7 T will continue to improve at rapid pace.

Authors’ Affiliations

(1)
LUMC, Leiden, Netherlands
(2)
Johns Hopkins University, Baltimore, MD, USA

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