Radiology: 7T MRA outperforms 3T
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| Sinoatrial nodal artery and a proximal branch of the RCA in a healthy 28-year-old man. At 7T, there is not much difference in signal intensity between the blood pool and the myocardium. Image Source: Radiology |
Only about 40 7T MRI systems are available for human use, and no studies have compared this high-field-strength of cardiac MR with 3T MR, Saskia G. C. van Elderen, MD, of Leiden Medical Center in Leiden, the Netherlands, and colleagues claimed. "[T]he purpose of our study was to objectively compare quantitative parameters related to image quality attained at coronary MR angiography of the right coronary artery (RCA) performed at 7T and 3T."
The researchers performed both 3T and 7T MRA on 10 healthy young adults, measuring the following parameters in the right coronary artery: contrast-to-noise ratio (CNR) between the blood pool and the epicardial fat; signal-to-noise ratio (SNR) of the blood pool; vessel sharpness and diameter of the first four cm; and visible vessel length.
7T MRA significantly outperformed 3T across several parameters measured, while 3T did not demonstrate significant image enhancements across any parameters. The researchers measured the mean CNR between the blood pool and the epicardial fat for 7T at 87.5 and 51.7 for 3T. RCA vessel sharpness was measured at 58.3 percent with 7T and 49.7 percent with 3T. No statistically significant differences were observed between vessel length, vessel diameter, navigator efficiency or data acquisition.
The mean SNR of the blood pool was measured to be 60 percent higher with 7T (109.2) than with 3T (66.9), though the authors noted that a twofold increase was predicted. They attributed this smaller-than-expected increase to an inferior transmit-receive coil used in the 7T system (the 7T coil was built at the researchers' institution), saying that the improved performance but lower than expected SNR demonstrated the "need for further development in coil technology" to advance 7T MR use. "Future work will concentrate on refinements in coil technology and contrast generation to support concomitant imaging of the left coronary system."
The authors concluded that in their study, "quantitative parameters related to image quality attained at 7T equal or surpass those from 3T. Our results clearly warrant further evaluation in patients with coronary artery disease to assess the potential of our 7T approach for the visualization of luminal RCA disease."