Oshinski J N, Ku D N, Pettigrew R I
Department of Radiology, Emory University School of Medicine, Atlanta, GA 30322, USA.
Magn Reson Med. 1995 Feb;33(2):193-9. doi: 10.1002/mrm.1910330208.
Studies of flow in a 90%-stenosis phantom were conducted to elucidate the parameters and mechanisms responsible for signal loss in MR angiographic images. The studies independently evaluated the effect of velocity, Reynolds number, turbulent fluctuation velocity, and turbulence intensity on the amount of post-stenotic signal loss. Results suggested that the magnitude of the turbulent fluctuation velocity, not merely the presence of turbulence or the intensity of turbulence, was the parameter that determined the extent of the signal loss. The study suggests that future flow phantom studies should be conducted with fluids having physiologic velocities and viscosities to obtain accurate levels of turbulent fluctuation velocities and hence reproduce results of in-vivo signal-loss patterns. The mechanism for signal loss is that the temporal and spatial variations of the turbulent fluctuation velocity cause a range of phases to be present within a voxel. Examination of the theoretical aspects of fluid turbulence suggest that shortening gradient durations and imaging during diastole may help reduce signal loss.
对90%狭窄模型中的血流进行了研究，以阐明磁共振血管造影图像中信号丢失的参数和机制。这些研究独立评估了速度、雷诺数、湍流脉动速度和湍流强度对狭窄后信号丢失量的影响。结果表明，决定信号丢失程度的参数是湍流脉动速度的大小，而不仅仅是湍流的存在或湍流强度。该研究表明，未来的血流模型研究应使用具有生理速度和粘度的流体进行，以获得准确的湍流脉动速度水平，从而重现体内信号丢失模式的结果。信号丢失的机制是湍流脉动速度的时空变化导致体素内存在一系列相位。对流体湍流理论方面的研究表明，缩短梯度持续时间和在舒张期成像可能有助于减少信号丢失。
