Components of a magnetic resonance imaging system and their relationship to safety and image quality.

Magnetic resonance imaging (MRI) is a powerful diagnostic tool that can be optimized to display a wide range of clinical conditions. An MRI system consists of four major components: a main magnet formed by superconducting coils, gradient coils, radiofrequency (RF) coils, and computer systems. Each component has safety considerations. Unless carefully controlled, the MRI machine's strong static magnetic field could turn a ferromagnetic object into a harmful projectile or cause vertigo and headache. Switching magnetic fields in the gradients evokes loud noises in the scanner, which can be mitigated by ear protection. Gradients also generate varying magnetic fields that can cause peripheral nerve stimulation and muscle twitching. Magnetic fields produced by RF coils deposit energy in the body and can cause tissue heating (with the potential to cause skin burns). In this review, we provide an overview of the components of a typical clinical MRI scanner and its associated safety issues. We also discuss how the relationship between the scanning parameters can be manipulated to improve image quality while ensuring a safe operational environment for the patients and staff. Understanding the strengths and limitations of these parameters can enable users to choose optimal techniques for image acquisition, apply them in clinical practice, and improve the diagnostic accuracy of an MRI examination.