Bakker C J, Hoogeveen R M, Viergever M A
Department of Radiology, Image Sciences Institute, University Hospital Utrecht, The Netherlands.
J Magn Reson Imaging. 1999 Jan;9(1):119-27. doi: 10.1002/(sici)1522-2586(199901)9:1<119::aid-jmri16>3.0.co;2-f.
Our aim is to describe and demonstrate the steps we have found to be useful in the construction and evaluation of protocols for triggered and nontriggered measurement of blood flow by two-dimensional phase-contrast magnetic resonance angiography (MRA). To achieve this goal, we start with a survey of factors governing the accuracy (validity) and precision (repeatability) of MR flow measurements. This knowledge, combined with prior information regarding the diameter of the target vessel and the prevailing flow conditions, is then employed to define a protocol for measuring flow with negligible systematic error. In the absence of a gold standard for in vivo flow measurements, the protocol is subsequently validated for a range of flow conditions by representative phantom experiments. Precision is then calculated from the signal-to-noise ratio (SNR) of blood in the accompanying magnitude images or, less conveniently, estimated from the standard deviation of repeated measurements. The desired precision is finally achieved by adjusting the appropriate SNR parameters. All steps involved in protocol development are demonstrated for both flow-independent and flow-dependent acquisitions.
我们的目的是描述并展示我们发现的在通过二维相位对比磁共振血管造影（MRA）进行触发式和非触发式血流测量的方案构建与评估中有用的步骤。为实现这一目标，我们首先对影响磁共振血流测量准确性（有效性）和精密度（可重复性）的因素进行综述。然后，将这些知识与关于目标血管直径和当前血流状况的先验信息相结合，用于定义一个系统误差可忽略不计的血流测量方案。由于缺乏体内血流测量的金标准，随后通过代表性的体模实验在一系列血流状况下对该方案进行验证。然后根据伴随的幅度图像中血液的信噪比（SNR）计算精密度，或者不太方便地从重复测量的标准差估计精密度。最后通过调整适当的SNR参数实现所需的精密度。针对与血流无关和与血流相关的采集，展示了方案开发中涉及的所有步骤。
