Introduction

Magnetic resonance angiography (MRA), as a non-invasive vascular imaging method, has been widely applied in clinical practice, providing rich imaging data for the diagnosis of vascular diseases. However, due to the narrow diameter, tortuous route of coronary arteries, and the interference of respiration and heartbeat during scanning, MRCA has always been a very difficult and challenging task. An improved 3D B-TFE sequence is often used for MRCA in 3.0T MR systems[1,2]. B-TFE sequence, which has high scanning speed, slight motion artifact and high blood signal[5], is suitable for MRCA and has become a common scanning method[6]. However, B-TFE is often not ideal in fat suppression, relatively sensitive to the uneven B0 field strength so that the image quality will be spoiled to a large extent. mDIXON has high signal to noise (SNR), uniform fat suppression, and high scanning speed combined with compressed SENSE technology. In recent years, mDIXON has been applied to MRCA more than before[3,4].Therefore, in order to choose more appropriate imaging techniques, we conducted a comparative study of MRCA with two different methods.

Methods

12 healthy young volunteers(7 males and 5 females, aged range from 21 to 22) were scanned using B-TFE sequence and mDIXON sequence on 3.0T scanner (Ingenia CX, Philips, Netherlands) with a 32-channel coils in May 2021. Scaning parameters are recommended by Philips as shown in table 1.The coronary artery images were post-processed in ISP9 workstation （Philips, Netherlands) with surface reconstruction, maximum intensity projection, VR, etc, and evaluated with the original axial bitmap.Referring to the coronary artery segmentation method of the American College of Cardiology, this study mainly analyzed left main artery(LM), right coronary atery (RCA) including proximal, middle and distal segments,The left anterior descending branch(LAD) including proximal and middle segments, and the left circumflex branch (LCX) including proximal and middle segments.Subjective image quality was evaluated by referring to the Likert scoring method from 1point to 4 points. Among the above 8 study segments, 5 segments with scores greater than 3 were classified as qualified image quality.SNR= vascular signal intensity/background noise, CNR= (vascular signal intensity value - surrounding tissue signal intensity value)/background noise. Observe each segment of coronary artery, subjective diagnosis was divided into two types: no obvious stenosis, obvious stenosis.The measurement data were expressed as mean ± standard deviation.Wilcoxon rank sum test was used for subjective score data of coronary artery image quality, and T test was used for objective score data of SNR and CNR. P<0.05 was considered statistically significant.

Results

11 healthy young volunteers was included with qualified MRCA image quality. One failed due to claustrophobia.The heart rate of 11 healthy young volunteers was 53-92 beats/min, with an average of 65 beats/min.The subjective evaluation mean value of B-TFE in coronary artery imaging was higher than that of mDixon sequence, but the difference was not statistically significant.Shown in table 2.SNR and CNR scores of mDIXON sequence were higher than those of B-TFE sequence, and the difference was statistically significant. As shown in table 3.None of the 11 healthy adults underwent DSA or CTA examination.Coronary MRA abnormalities were mainly manifested as vascular stenosis, the number of occurrences is shown in Table 4.

Discussion

B-TFE can eliminate phase interference and retain magnetic resonance signal to the maximum extent[5].mDIXON can stably complete a wide range of water lipid separation and achieve good fat suppression[7].The results showed that the application of B-TFE and mDIXON sequences in MRCA can achieve satisfy imaging results, as shown in figure 1.11 from 12 healthy young volunteers complete the examination, with the subjective scores mostly above 3 points. mDIXON had blurred coronary artery edge and lower subjective quality score, while B-TFE had clear coronary artery edge and higher subjective quality score.B-TFE[5] utilized every TI interval to increase the ratio of T2/T1 relaxation time indicating that blood vessels have a very high contrast with soft tissue, and the image SNR is high. However, our examination showed that SNR and CNR of MRCA of mDixon sequence had relatively high absolute values, and the difference between the two sequences was statistically significant, which may be related to the characteristics of uniform fat suppression.MRCA sequences of mDIXON and B-TFE also showed a large number of vascular imaging abnormalities, and their manifestations were diverse, suggesting that the two examination methods need to be greatly improved.In addition, the sample size is small, and MRCA lacks the gold standard control.These may have had an impact on the results

Conclusion

3T MRCA using 3D B-TFE or mDIXON sequences can be used for coronary artery images. mDIXON sequence is a powerful alternative to B-TFE sequence. In addition, compressed SENSE technology can be used in mDIXON sequence and the scanning time is significantly shortened, suggesting that mDIXON sequence is potentially a promising and valuable MRCA imaging technique.

Acknowledgements

No acknowledgement found.

References

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