摘要
Patients undergoing Magnetic Resonance Imaging (MRI) are exposed to strong, non-uniform static magnetic fields outside of the central imaging region, in which the movement of the body may induce electric currents in tissues which could possibly be harmful. The purpose of this study was to re-evaluate existing clinical protocols by determining the induced electromagnetic (EM) fields in MRI spine examinations. The study covered 120 MRI spine examinations at the MRI Unit of a hospital in Accra, Ghana. A numerical model based on Faraday’s equation was developed using the finite difference method (FDM) and MATLAB software to compute, first, a test simulation of induced EM field intensities and then actual measurements of induced fields on the spine. The simulation results were peak induced electric field, 0.39 V/m and current density, 0.039 A/m2. Patient results were;calculated maximum velocity, 0.29 m/s;peak induced electric field strength, 0.44 V/m, and current density, 0.043 A/m2. The levels of induced EM-fields were such that they would not pose any potential health hazards to the patients as these values were well below the recommended guidance levels set by the Directive IEC 60601-2-33 of the European Parliament.
Patients undergoing Magnetic Resonance Imaging (MRI) are exposed to strong, non-uniform static magnetic fields outside of the central imaging region, in which the movement of the body may induce electric currents in tissues which could possibly be harmful. The purpose of this study was to re-evaluate existing clinical protocols by determining the induced electromagnetic (EM) fields in MRI spine examinations. The study covered 120 MRI spine examinations at the MRI Unit of a hospital in Accra, Ghana. A numerical model based on Faraday’s equation was developed using the finite difference method (FDM) and MATLAB software to compute, first, a test simulation of induced EM field intensities and then actual measurements of induced fields on the spine. The simulation results were peak induced electric field, 0.39 V/m and current density, 0.039 A/m2. Patient results were;calculated maximum velocity, 0.29 m/s;peak induced electric field strength, 0.44 V/m, and current density, 0.043 A/m2. The levels of induced EM-fields were such that they would not pose any potential health hazards to the patients as these values were well below the recommended guidance levels set by the Directive IEC 60601-2-33 of the European Parliament.
