基于k空间加速采集的磁共振成像技术

Development of Fast Magnetic Resonance Imaging Techniques Based on k-space Accelerated Collection

磁共振成像(MRI)已成为临床医学影像检查的重要手段之一。然而,由于k空间信号采集受奈奎斯特(Nyquist)采样定理限制,其成像速度仍然较低。在一定的主磁场和梯度场条件下,要获得具有实用价值的高分辨率图像必须进行较长时间的信号采集。为实现磁共振快速动态成像,除提高主磁场强度、梯度强度及其切换率以外,还可以通过一定的数学方法,在稀疏采样的情况下使最终重建图像数据满足奈奎斯特采样定理,从而减少k空间信号采集的数量,缩短信号采集时间。随着研究的深入,许多基于k空间数据共享和欠采样的快速磁共振成像方法被提出,如半傅里叶成像、钥孔成像、并行成像、部分可分离函数(PSF)等。在描述k空间填充方式的基础上,对这些快速成像技术进行综述。

Magnetic resonance imaging（MRI） is one of the most important non-invasive diagnostic tools in routine clinical examination.However,the temporal resolution is still low due to the limitation of Nyquist sampling theorem in k-space signal acquisition.Under the conditions of certain magnetic and gradient field,it takes a long time for signal acquisition to obtain a high resolution image with clinical value.In addition to enhancing the strength of main magnetic field and gradient as well speeding gradient field switch,some mathematical methods have been used to reduce the amount of k-space signal acquisition to shorten MR imaging time.Although under sparse sampling,the final reconstructed image data could be satisfied with Nyquist sampling theorem through these mathematical methods.Furthermore,many fast MRI methods based on data sharing and undersampling of k-space were proposed,such as half-Fourier imaging,keole imaging,parallel imaging,partially separable functions（PSF） and so on.In this review,several typical fast imaging methods were summarized and discussed based on k-space sampling techniques.