Zhang Qiang, Chen Zhensen, Chen Shuo, Liu Xinke, Ning Jia, Han Yongjun, Chen Li, He Le, Zhao Xihai, Xiong Yuhui, Guo Hua, Yuan Chun, Li Rui, Chen Huijun
Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China.
Vascular Imaging Laboratory, Department of Radiology, University of Washington, Seattle, WA, USA.
Magn Reson Imaging. 2020 Feb;66:199-207. doi: 10.1016/j.mri.2019.09.001. Epub 2019 Sep 4.
To theoretically compare the MR angiography (MRA) contrast mechanism of Time of Flight (TOF) and Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) for intracranial artery imaging with in-vivo validation.
The contrast ratio (CR) of SNAP and TOF was simulated under different blood velocities and travel distance that the blood had flown through. The CR and the slope of CR with respect to blood velocity of SNAP and TOF were compared in theoretical simulation. Two healthy subjects (a 60 years old female and a 29 years old male) were imaged on a 3 T MR scanner with SNAP, TOF and phase contrast (PC) images as the validation set. The measured CR from the images in validation set was compared with the theoretically simulated CR by Person's correlation coefficient. The ratio of CR difference to velocity difference in the validation set was compared between TOF and SNAP with Student's t-test. Thirty patients (21 males, age: 48 ± 13.8 years) with carotid artery atherosclerotic plaque were imaged with both TOF and SNAP as the comparison test. Between TOF and SNAP, the CR and total artery length were compared with Student's t-test, and the prevalence of stenosis was compared with Cohen's kappa in comparison test.
The theoretically simulated CR was significantly correlated with in-vivo measured CR from the validation set for TOF (p < 0.001) and SNAP (p < 0.001). The simulation revealed that the CR of SNAP was higher than that of TOF when the blood velocity and travel distance were within the range to have effective MRA contrast. Similarly, the in-vivo comparison test showed that SNAP had higher CR (p < 0.001 for all tested intracranial arteries) and longer total artery length (1.4 ± 0.4 m vs 1.2 ± 0.2 m, p < 0.001) than TOF. The stenosis detection performance was similar between TOF and SNAP (Cohen's kappa 0.72; 95% confidence interval: 0.51-0.93). Moreover, compared with TOF, SNAP showed higher slope of CR with respect to velocity in simulation (0.06 ± 0.02 s/cm vs 0.02 ± 0.05 s/cm, p < 0.001), and higher ratio of CR difference to velocity difference in validation test (0.47 ± 0.38 s/cm vs 0.19 ± 0.38 s/cm, p = 0.001).
Compared with TOF, the SNAP shows better performance to visualize distal intracranial artery and worse performance to visualize ICA, and is more sensitive to blood velocity.
从理论上比较飞行时间法（TOF）和同步非对比血管造影及斑块内出血（SNAP）的磁共振血管造影（MRA）对比机制用于颅内动脉成像，并进行体内验证。
在不同血流速度和血流经过的行程距离下模拟SNAP和TOF的对比率（CR）。在理论模拟中比较SNAP和TOF的CR以及CR相对于血流速度的斜率。两名健康受试者（一名60岁女性和一名29岁男性）在3T MR扫描仪上进行成像，获取SNAP、TOF和相位对比（PC）图像作为验证集。通过Person相关系数将验证集中图像测量得到的CR与理论模拟的CR进行比较。采用Student t检验比较TOF和SNAP在验证集中CR差异与速度差异的比值。对30例（21例男性，年龄：48±13.8岁）患有颈动脉粥样硬化斑块的患者进行TOF和SNAP成像作为对比试验。在TOF和SNAP之间，采用Student t检验比较CR和总动脉长度，并采用Cohen卡方检验比较狭窄患病率。
理论模拟的CR与TOF（p<0.001）和SNAP（p<0.001）验证集的体内测量CR显著相关。模拟显示，当血流速度和行程距离在产生有效MRA对比的范围内时，SNAP的CR高于TOF。同样，体内对比试验表明，SNAP的CR更高（所有测试颅内动脉p<0.001），总动脉长度更长（1.4±0.4m对1.2±0.2m，p<0.001）。TOF和SNAP之间的狭窄检测性能相似（Cohen卡方值0.72；95%置信区间：0.51 - 0.93）。此外，与TOF相比，SNAP在模拟中显示出更高的CR相对于速度的斜率（0.06±0.02s/cm对0.02±0.05s/cm，p<0.001），在验证试验中显示出更高的CR差异与速度差异的比值（0.47±0.38s/cm对0.19±0.38s/cm，p = 0.001）。
与TOF相比，SNAP在显示颅内远端动脉方面表现更好，在显示颈内动脉方面表现更差，并且对血流速度更敏感。
