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

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

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)
figure1

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.

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Correspondence to Saskia GC van Elderen.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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van Elderen, S.G., Versluis, M.J., Westenberg, J.J. et al. Coronary magnetic resonance angiography at 7 Tesla: a quantitative comparison with results at 3 Tesla. J Cardiovasc Magn Reson 12, O88 (2010). https://doi.org/10.1186/1532-429X-12-S1-O88

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Keywords

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