Jou L D, Saloner D
Department of Radiology, Veteran Administration Medical Center, University of California at San Francisco, 94121, USA.
Med Eng Phys. 1998 Nov-Dec;20(9):643-52. doi: 10.1016/s1350-4533(98)00075-7.
A numerical method to simulate magnetic resonance angiographic images is proposed. The new method greatly simplifies the calculation of the average phase in a voxel, the bottleneck of previous simulations, and reduces the computation time by more than a factor of 5. Both the Navier-Stokes and the Bloch equations are solved on the same mesh to obtain the distributions of the modulus and phase of the magnetization. The data in the frequency domain are reordered according to the gating strategy to generate the final images. Pulsatile flow through a 2D normal carotid bifurcation is considered as a test case. Images for magnetic resonance angiography with an uncompensated gradient waveform, a velocity-compensated gradient waveform and an uncompensated short-TE gradient waveform are compared. Systolic gating images are shown to have degraded image quality. Images acquired with diastolic-gating have little variation in magnetization strength throughout the pulsatile cycle and provide a better representation of the vessel lumen.
提出了一种模拟磁共振血管造影图像的数值方法。新方法极大地简化了体素中平均相位的计算，而这是以往模拟的瓶颈，并将计算时间减少了5倍以上。在同一网格上求解纳维-斯托克斯方程和布洛赫方程，以获得磁化强度模量和相位的分布。频域中的数据根据门控策略重新排序以生成最终图像。将通过二维正常颈动脉分叉的脉动流作为测试案例。比较了具有未补偿梯度波形、速度补偿梯度波形和未补偿短TE梯度波形的磁共振血管造影图像。结果表明，收缩期门控图像的图像质量有所下降。通过舒张期门控采集的图像在整个脉动周期内磁化强度变化很小，能更好地显示血管腔。
