Flow measurement by magnetic resonance: A unique asset worth optimising
Flow measurement by magnetic resonance: A unique asset worth optimising
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DOI：
10.1080/10976640701465090
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发表时间：
2007-01-01
影响因子：
6.4
通讯作者：
Firmin, David N.
中科院分区：
文献类型：
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作者：
Kilner, Philip J.;Gatehouse, Peter D.;Firmin, David N.
心血管磁共振（CMR）系统的用户和制造商可能拥有无与伦比的资产。通过横切大动脉的平面进行速度的相位对比标测应提供心输出量、分流流量、主动脉或肺动脉返流以及间接二尖瓣返流的最准确测量。但现实情况是，相位对比速度标测仍然没有得到充分利用，并且在一些CMR用户和转诊临床医生的眼中可能已经变得不可信。即使使用了适当的采集方法，由于涡流或未校正的伴随梯度引起的背景相位误差，也可能导致某些CMR系统上的流量测量不准确。这些误差可能会严重影响分流或分流流量的测量，应通过适当的硬件和软件设计将这些误差降至最低或进行校正。如果没有，则可以通过在静态体模上重复相同的速度采集并从临床采集的速度中减去相应的表观体模速度来检测和校正不准确性。为了准确测量主动脉瓣返流或二尖瓣流入，需要相对于瓣膜的循环位移的运动跟踪和速度校正，但是很少有商业系统提供这种设施。射流速度的测量提出了不同的挑战，主要涉及相对于窄射流的体素的大小和位置。意识到潜在的问题和协调一致的努力，以优化需要从制造商和用户，使适当的使用相衬流量测量心血管磁共振的独特优势。
Users and manufacturers of cardiovascular magnetic resonance (CMR) systems have, potentially, an unrivalled asset. Phase contrast mapping of velocities through planes transecting the great arteries should provide the most accurate measurements available of cardiac output, shunt flow, aortic or pulmonary regurgitation and, indirectly, of mitral regurgitation. But the reality is that phase contrast velocity mapping remains under-used, and may have become discredited in the eyes of some CMR users and referring clinicians. Even when appropriate methods of acquisition have been used, there can be inaccuracies of flow measurement on some CMR systems caused by background phase errors due to eddy currents or uncorrected concomitant gradients. Measurements of regurgitant or shunt flow can be seriously affected by these errors which should be minimised or corrected by appropriate hardware and software design. If they have not been, inaccuracies can be detected and corrected by repeating identical velocity acquisitions on a static phantom, and subtracting the corresponding apparent phantom velocities from those of the clinical acquisition. For accurate measurements of aortic regurgitation or mitral inflow, motion tracking and velocity correction with respect to the cyclic displacements of the valves are needed, but few if any commercial systems provide this facility. Measurements of jet velocity pose different challenges, mainly related to the size and placement of voxels relative to a narrow jet. Awareness of the potential problems and concerted efforts towards optimisation are needed from manufacturers and users to make appropriate use of phase contrast flow measurement-a unique strength of cardiovascular magnetic resonance.