Chen Yue, Kwok Ka-Wai, Tse Zion Tsz Ho
College of Engineering, The University of Georgia, Athens, GA, USA.
Ann Biomed Eng. 2014 Sep;42(9):1823-33. doi: 10.1007/s10439-014-1049-x. Epub 2014 Jun 24.
Magnetic resonance imaging allows for visualizing detailed pathological and morphological changes of soft tissue. MR-conditional actuations have been widely investigated for development of image-guided and robot-assisted surgical devices under the Magnetic resonance imaging (MRI). This paper presents a simple design of MR-conditional stepper motor which can provide precise and high-torque actuation without adversely affecting the MR image quality. This stepper motor consists of two MR-conditional pneumatic cylinders and the corresponding supporting structures. Alternating the pressurized air can drive the motor to rotate each step in 3.6° with the motor coupled to a planetary gearbox. Experimental studies were conducted to validate its dynamics performance. Maximum 800 mN m output torque is achieved. The motor accuracy independently varied by two factors: motor operating speed and step size, was also investigated. The motor was tested within a 3T Siemens MRI scanner (MAGNETOM Skyra, Siemens Medical Solutions, Erlangen, Germany) and a 3T GE MRI scanner (GE SignaHDx, GE Healthcare, Milwaukee, WI, USA). The image artifact and the signal-to-noise ratio (SNR) were evaluated for study of its MRI compliancy. The results show that the presented pneumatic stepper motor generated 2.35% SNR reduction in MR images. No observable artifact was presented besides the motor body itself. The proposed motor test also demonstrates a standard to evaluate the pneumatic motor capability for later incorporation with motorized devices used under MRI.
磁共振成像能够可视化软组织的详细病理和形态变化。在磁共振成像（MRI）环境下，为了开发图像引导和机器人辅助手术设备，对磁共振条件驱动进行了广泛研究。本文提出了一种简单的磁共振条件步进电机设计，该电机能够提供精确且高扭矩的驱动，同时不会对磁共振图像质量产生不利影响。这种步进电机由两个磁共振条件气动缸和相应的支撑结构组成。通过交替施加压缩空气，可以驱动电机以3.6°的步距角逐步旋转，电机与行星齿轮箱相连。进行了实验研究以验证其动力学性能。实现了最大800 mN·m的输出扭矩。还研究了电机精度独立变化的两个因素：电机运行速度和步距大小。该电机在一台3T西门子磁共振成像扫描仪（MAGNETOM Skyra，西门子医疗解决方案公司，德国埃尔朗根）和一台3T通用电气磁共振成像扫描仪（GE SignaHDx，通用电气医疗集团，美国威斯康星州密尔沃基）内进行了测试。评估了图像伪影和信噪比（SNR），以研究其磁共振兼容性。结果表明，所提出的气动步进电机在磁共振图像中导致信噪比降低了2.35%。除了电机本体本身外，未观察到明显的伪影。所提出的电机测试还展示了一种评估气动电机能力的标准，以便日后与磁共振成像环境下使用的电动设备相结合。
