Department of Diagnostic Radiology, Philipps University, Marburg, Germany.
Magn Reson Imaging. 2013 May;31(4):545-9. doi: 10.1016/j.mri.2012.10.023. Epub 2012 Dec 5.
Time-of-flight (ToF) and phase contrast (PC) magnetic resonance angiographies (MRAs) are noninvasive applications to depict the cerebral arteries. Both approaches can image the cerebral vasculature without the administration of intravenous contrast. Therefore, it is used in routine clinical evaluation of cerebrovascular diseases, e.g., aneurysm and arteriovenous malformations. However, subtle microvascular disease usually cannot be resolved with standard, clinical-field-strength MRA. The purpose of this study was to compare the ability of ToF and PC MRA to visualize the cerebral arteries at increasing field strengths.
The Institutional Review Board-approved study included eight healthy volunteers (age: 36 ± 10 years; three female, five male). All subjects provided written informed consent. ToF and PC MRAs were obtained at 1.5, 3 and 7T. Signal intensities of the large, primary vessels of the Circle of Willis were measured, and signal-to-noise ratios were calculated. Visualization of smaller first- and second-order branch arteries of the Circle of Willis was also evaluated.
The results show that both ToF and PC MRAs allow the depiction of the large primary vessels of the Circle of Willis at all field strengths. Ultrahigh field (7T) provides only small increases in the signal-to-noise ratio in these primary vessels due to the smaller voxel size acquired. However, ultrahigh-field MRA provides better visualization of the first- and second-order branch arteries with both ToF and PC approaches. Therefore, ultrahigh-field MRA may become an important tool in future neuroradiology research and clinical care.
时飞（ToF）和相位对比（PC）磁共振血管造影（MRA）是无创应用程序，用于描绘大脑动脉。这两种方法都可以在不静脉注射对比剂的情况下对脑血管成像。因此，它用于常规的脑血管疾病评估，例如动脉瘤和动静脉畸形。然而，标准的临床场强 MRA 通常无法解决细微的微血管疾病。本研究的目的是比较 ToF 和 PC MRA 在增加场强下可视化大脑动脉的能力。
该机构审查委员会批准的研究包括 8 名健康志愿者（年龄：36 ± 10 岁；3 名女性，5 名男性）。所有受试者均提供书面知情同意书。在 1.5、3 和 7T 处获得 ToF 和 PC MRA。测量了 Willis 环的大、主要血管的信号强度，并计算了信噪比。还评估了 Willis 环的较小一级和二级分支动脉的可视化情况。
结果表明，ToF 和 PC MRA 均可在所有场强下描绘 Willis 环的大主要血管。超高场（7T）由于采集的体素尺寸较小，仅对这些主要血管的信噪比略有提高。然而，超高场 MRA 可通过 ToF 和 PC 方法更好地可视化一级和二级分支动脉。因此，超高场 MRA 可能成为未来神经放射学研究和临床护理的重要工具。
