Fontaine A A, Heinrich R S, Walker P G, Pedersen E M, Scheidegger M B, Boesiger P, Walton S P, Yoganathan A P
Cardiovascular Fluid Mechanics Laboratory, Georgia Institute of Technology, Altanta, GA, USA.
J Heart Valve Dis. 1996 Jan;5(1):66-73.
The non-invasive, in-vivo assessment of prosthetic valve function is compromised by the lack of accurate measurements of the transvalvular flow fields or hemodynamics by current techniques. Short echo time magnetic resonance imaging (MRI) may provide a method for the non-invasive, in vivo assessment of prosthetic valve function by accurately measuring changes in the transvalvular flow fields associated with normal and dysfunctional prosthetic valves. The objectives of these in vitro experiments were to investigate the potential for using MRI as a tool to measure the complex flow fields distal to replacement heart valves, and to assess the accuracy of MRI velocity measurements by comparison with Laser Doppler Anemometry (LDA), a gold standard.
The velocity fields downstream of tilting disc, bileaflet, ball and cage, and pericardial tissue valves were measured using both three-component LDA and MRI phase velocity encoding under a steady flow rate of 22.8 l/min, simulating peak systolic flow. The valves were tested under normal and stenotic conditions to assess the MRI capabilities under a wide range of local flow conditions, velocities and turbulence levels. A new short echo time MRI technique (FAcE), which allowed velocity measurements in stenotic jets with high turbulence, was tested.
Good overall agreement was obtained between the MRI velocity measurements and the LDA data. The MRI velocity measurements adequately reproduced the spatial structure of the flow fields. In most cases peak velocities were accurately measured to within 15%.
The results indicate that the FAcE MRI method has the potential to be used as a diagnostic tool to assess prosthetic valve function.
目前的技术缺乏对跨瓣流场或血流动力学的准确测量，这使得人工瓣膜功能的非侵入性体内评估受到影响。短回波时间磁共振成像（MRI）或许能通过精确测量与正常及功能异常人工瓣膜相关的跨瓣流场变化，为人工瓣膜功能的非侵入性体内评估提供一种方法。这些体外实验的目的是研究将MRI用作测量人工心脏瓣膜远端复杂流场的工具的潜力，并通过与金标准激光多普勒测速仪（LDA）比较来评估MRI速度测量的准确性。
在22.8升/分钟的稳定流速下，使用三分量LDA和MRI相速度编码测量倾斜盘式、双叶式、球笼式和心包组织瓣膜下游的速度场，模拟收缩期峰值血流。在正常和狭窄条件下对瓣膜进行测试，以评估在各种局部血流条件、速度和湍流水平下MRI的能力。测试了一种新的短回波时间MRI技术（FAcE），该技术能够在高湍流的狭窄射流中进行速度测量。
MRI速度测量结果与LDA数据总体吻合良好。MRI速度测量充分再现了流场的空间结构。在大多数情况下，峰值速度的测量精度在15%以内。
结果表明，FAcE MRI方法有潜力用作评估人工瓣膜功能的诊断工具。
