Martos J, Nägele T, Klose U, Petersen D, Voigt K
National Institute of Neurosurgery, Budapest, Hungary.
Eur Radiol. 1996;6(4):489-93. doi: 10.1007/BF00182478.
This study addressed the use of 3D MR angiography with flip angles (FAs) linearly varying across the excitation volume in order to diminish spin saturation. The shape of the ramp profile was varied to optimize the method for different regions and pathological alterations. Radio frequency pulses with ramp-shaped excitation profiles were generated using Fourier transformation and integrated into a flow-compensated 3D-FISP sequence. With the use of ramp-shaped excitation profiles good results were obtained for intracranial arteries as well as for neck arteries (i.e. carotid and vertebral arteries) which were demonstrated in 6 healthy volunteers and in 5 patients with various stenoses and anomalies of the carotid and vertebral arteries. With this technique it was possible to use increased thicknesses of the excitation volume (slab) up to 256 mm. Ramp-shaped excitation pulses with linearly increasing FAs in main flow direction can provide improved contrast of the vessel parts located distally to the entry side of the slab. Although this method has no advantage concerning complex flow or other dephasing effects; its particular effectiveness lies in the reduction of spin saturation.
本研究探讨了使用翻转角（FA）在激发容积内线性变化的三维磁共振血管造影术，以减少自旋饱和。斜坡轮廓的形状有所变化，以便针对不同区域和病理改变优化该方法。利用傅里叶变换生成具有斜坡状激发轮廓的射频脉冲，并将其整合到流动补偿三维快速成像稳态进动序列中。通过使用斜坡状激发轮廓，在6名健康志愿者以及5名患有各种颈动脉和椎动脉狭窄及异常的患者中，颅内动脉和颈部动脉（即颈动脉和椎动脉）均获得了良好结果。采用该技术可以使用厚度增加至256毫米的激发容积（层面）。在主流方向上具有线性增加FA的斜坡状激发脉冲能够改善位于层面入口侧远端的血管部分的对比度。尽管该方法在复杂血流或其他去相位效应方面没有优势；但其独特的有效性在于减少自旋饱和。
