Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
AJR Am J Roentgenol. 2011 Aug;197(2):374-82. doi: 10.2214/AJR.10.5724.
The purpose of this study was to improve the blood-pool signal-to-noise ratio (SNR) and blood-myocardium contrast-to-noise ratio (CNR) of slow-infusion 3-T whole-heart coronary MR angiography (MRA).
In 2D sensitivity encoding (SENSE), the number of acquired k-space lines is reduced, allowing less radiofrequency excitation per cardiac cycle and a longer TR. The former can be exploited for signal enhancement with a higher radiofrequency excitation angle, and the latter leads to noise reduction due to lower data-sampling bandwidth. Both effects contribute to SNR gain in coronary MRA when spatial and temporal resolution and acquisition time remain identical. Numeric simulation was performed to select the optimal 2D SENSE pulse sequence parameters and predict the SNR gain. Eleven patients underwent conventional unenhanced and the proposed 2D SENSE contrast-enhanced coronary MRA acquisition. Blood-pool SNR, blood-myocardium CNR, visible vessel length, vessel sharpness, and number of side branches were evaluated.
Consistent with the numeric simulation, using 2D SENSE in contrast-enhanced coronary MRA resulted in significant improvement in aortic blood-pool SNR (unenhanced vs contrast-enhanced, 37.5 ± 14.7 vs 121.3 ± 44.0; p < 0.05) and CNR (14.4 ± 6.9 vs 101.5 ± 40.8; p < 0.05) in the patient sample. A longer length of left anterior descending coronary artery was visualized, but vessel sharpness, coronary artery coverage, and image quality score were not improved with the proposed approach.
In combination with contrast administration, 2D SENSE was found effective in improving SNR and CNR in 3-T whole-heart coronary MRA. Further investigation of cardiac motion compensation is necessary to exploit the SNR and CNR advantages and to achieve submillimeter spatial resolution.
本研究旨在提高 3T 全心脏冠状动脉磁共振血管造影（MRA）慢注射时的血池信噪比（SNR）和血心肌对比噪声比（CNR）。
在二维灵敏度编码（SENSE）中，减少采集的 K 空间线数量，从而使每个心动周期的射频激发更少，TR 更长。前者可通过更高的射频激发角进行信号增强，后者由于数据采样带宽较低而导致噪声降低。当空间和时间分辨率以及采集时间保持相同时，这两种效应都会导致冠状动脉 MRA 的 SNR 增益。数值模拟用于选择最佳的 2D SENSE 脉冲序列参数并预测 SNR 增益。11 例患者进行了常规未增强和拟议的 2D SENSE 对比增强冠状动脉 MRA 采集。评估血池 SNR、血心肌 CNR、可见血管长度、血管锐利度和侧支数量。
与数值模拟一致，在对比增强冠状动脉 MRA 中使用 2D SENSE 可显著提高主动脉血池 SNR（未增强与增强，37.5±14.7 与 121.3±44.0；p<0.05）和 CNR（14.4±6.9 与 101.5±40.8；p<0.05）。可显示更长的左前降支冠状动脉，但血管锐利度、冠状动脉覆盖率和图像质量评分并未因该方法而改善。
结合对比剂给药，发现 2D SENSE 可有效提高 3T 全心脏冠状动脉 MRA 的 SNR 和 CNR。需要进一步研究心脏运动补偿，以充分利用 SNR 和 CNR 优势并实现亚毫米空间分辨率。
