BACKGROUND Susceptibility weighted imaging (SWI) combines phase with magnitude information to better image sub-voxel veins. Recently, it has been extended to image very small sub-voxel arteries and veins by injecting intravenously the ultra-small superparamagnetic iron oxide, Ferumoxytol. OBJECTIVE To determine practical experimental imaging parameters for sub-voxel cerebral vessels at 7 T. METHODS Six Wistar-Kyoto rats aged 7-13 weeks were imaged. For a given spatial resolution, SWI was acquired pre- and post- Ferumoxytol with doses of 2, 4, 6 and 8 mg/kg and echo times (TEs) of 5, 10 and 15 ms at each dose. The spatial resolutions of 62.5 × 125 × 250 μm3 (acquisition time of 7.5 min) and 62.5 × 62.5 × 125 μm3 (30 min) were used. Both SWI and quantitative susceptibility mapping (QSM) data were analyzed. Contrast-to-noise ratio (CNR) was measured and used to determine the optimal practical imaging parameters for detection of small cortical penetrating arteries. RESULTS For a given spatial resolution with an aspect ratio (frequency: phase: slice) of 2:4:8 relative to the vessel size, we found the TE-dose index (TE x dose) must be at least 40 ms·mg/kg for both SWI and QSM to reveal the most vessels. The higher the TE-dose index, the better the image quality for both SWI and QSM up to 60 ms·mg/kg. CONCLUSIONS There is an optimal TE-dose index for improved visualization of sub-voxel vessels. Choosing the smallest TE and the largest allowed dose made it possible to run the sequence efficiently. In practice, the aspect ratio of 2:4:8 and the TE-dose index ranging from 40 to 60 ms·mg/kg provided the optimal and most practical solution.

中文翻译：

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在7 T时使用USPIO增强的药敏加权MRI检测亚体素微脉管系统。

背景技术磁化加权成像（SWI）将相位与幅度信息相结合以更好地成像亚体素静脉。最近，它已经通过静脉内注射超小型超顺磁性氧化铁Ferumoxytol扩展到非常小的体素下动脉和静脉的图像。目的确定7 T时体素下脑血管的实际实验成像参数。方法对6只7-13周大的Wistar-Kyoto大鼠进行成像。对于给定的空间分辨率，在费洛美托尔前后分别获得SWI，剂量分别为2、4、6和8 mg / kg，每个剂量的回声时间（TEs）为5、10和15 ms。使用的空间分辨率为62.5×125×250μm3（采集时间为7.5分钟）和62.5×62.5×125μm3（30分钟）。分析了SWI和定量磁化图（QSM）数据。测量对比度和噪声比（CNR），并将其用于确定检测皮质小动脉的最佳实用成像参数。结果对于给定的空间分辨率（相对于血管尺寸，纵横比（频率：相位：切片）为2：4：8），我们发现TE剂量指数（TE x剂量）必须至少为40 ms·mg / SWI和QSM的公斤数显示最多的船只。TE剂量指数越高，在60 ms·mg / kg以下的SWI和QSM图像质量都越好。结论有一个最佳的TE剂量指数可改善亚体素血管的可视化。选择最小的TE和最大允许剂量使高效运行序列成为可能。在实践中，长宽比为2：4：8，TE剂量指数范围为40至60 ms·mg / kg，是最佳且最实用的解决方案。