Evaluation of actuation compatibility and homogeneities for MRI-powered ferromagnetic sphere

Abstract

MR-compatibility actuations have been widely investigated for the development of robot-assisted devices under the magnetic resonance imaging (MRI). Ferromagnetic components of MRI-powered can be manipulated remotely using the magnetic force or torque induced by MRI or magnetic field environment. However, (1) numerical analysis of the related factors, geometry and magnitude, influencing the ferromagnetic components, and (2) field non-homogeneities when placed in a uniform main magnetic field B₀ are rarely reported. To address the relationship between magnetic force/torque and parameters, different radii of ferromagnetic spheres are required to exert magnetic force and torque with variable magnetic field. Comparison of the field homogeneities error (FHE) under various locations and parameters was investigated. In this study, we present the equivalent model of magnetic field and compare the magnetic force and torque of ferromagnetic sphere under different conditions and provide a safety distance of drive source (ferromagnetic sphere). The numerical models between parameters are established and significant factors were analyzed. Through various parameters of the ferromagnetic sphere, the performance of the numerical model in the magnetic field was evaluated. Cubic polynomial equations were developed to relate magnetic properties of ferromagnetic sphere with R² > 0.9506. Field homogeneity was not significantly affected when actuation source was installed in 32 cm away from the isocenter.

Keywords:

• FEM
• field homogeneities
• MRI-compatibility
• MRI-powered
• magnetic actuation
• numerical model

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Funding

This work was supported by National Natural Science Foundation of China [Grant No. 51605385] and Fundamental Research Funds for the Central Universities (3102015JCS050-10), Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University (CX201515) and the State Scholarship Fund of China (No. 201506290164) from Chinese Scholarship Council.