Poojar Pavan, Geethanath Sairam, Reddy Ashok Kumar, Venkatesan Ramesh
Medical Imaging Research Centre, Dayananda Sagar Institutions, Bangalore, India.
Medical Imaging Research Centre, Dayananda Sagar Institutions, Bangalore, India; Magnetic Resonance Research Center, Columbia University, New York, NY 10027.
Crit Rev Biomed Eng. 2019;47(4):349-363. doi: 10.1615/CritRevBiomedEng.2019029380.
Magnetic resonance imaging is a well-established method for diagnostics and/or prognostics of various pathological conditions. Cartesian k-space trajectory-based acquisition is the popular choice in clinical magnetic resonance imaging, owing to its simple acquisition, reconstruction schemes, and well-understood artifacts. However, non-Cartesian trajectories are relatively more time efficient, with involved methods for image reconstruction. In this review, we survey non-Cartesian trajectories from the standpoint of rapid prototyping and/or implementation. We provide examples of two-dimensional (2D) and 3D non-Cartesian k-space trajectories with analytical equations, merits, limitations, and applications. We also demonstrate implementation of three variants of the 2D radial and spiral trajectories (standard, golden angle, and tiny golden angle), using open-source software. For rapid prototyping, pulse sequences were designed with the help of Pulseq. In-vitro phantom and in-vivo brain data were acquired with three variants of radial and spiral trajectories. The obtained raw data were reconstructed using a graphical programming interface. The signal-to-noise ratios of each of these reconstructions were quantified and assessed.
磁共振成像（MRI）是诊断和/或预测各种病理状况的成熟方法。基于笛卡尔k空间轨迹的采集是临床磁共振成像中的常用选择，这是由于其采集简单、重建方案简单且伪影易于理解。然而，非笛卡尔轨迹在时间效率上相对更高，且涉及图像重建方法。在本综述中，我们从快速原型制作和/或实现的角度审视非笛卡尔轨迹。我们提供具有解析方程、优点、局限性及应用的二维（2D）和三维（3D）非笛卡尔k空间轨迹的示例。我们还展示了使用开源软件实现二维径向和螺旋轨迹的三种变体（标准、黄金角和微小黄金角）。为了进行快速原型制作，借助Pulseq设计了脉冲序列。使用径向和螺旋轨迹的三种变体采集了体外体模和体内脑数据。使用图形化编程接口对获得的原始数据进行重建。对这些重建图像的每个信噪比进行了量化和评估。
