RF Design And Safety Of MRI Systems

Electromagnetic simulation software has become an indispensable tool in the development and analysis of magnetic resonance imaging (MRI) systems. Motivated by better image resolution, improved signal to noise ratio (SNR) and reduced scan times, the trend to design systems that operate at higher static (B0) field strengths comes with new challenges. The increase in static field strength implies a proportional increase in the B1 field frequency. As the wavelength becomes comparable to the electrical size of the patient and the MRI geometry, it becomes more difficult to achieve a homogeneous field distribution that is required for good image quality.

The increase in operating frequency also has implications for patient safety as the conductivity of the tissues is proportional to the frequency, making the tissue more susceptible to absorbing EM energy. The close proximity of transmit arrays to the body can also be responsible for higher absorption of the RF energy in the body.