Physics Just the Basics Series #03 - The MRI Hardware-Physics Just the Basics

Video Transcription

Video Summary

The webinar introduced the basics of MRI hardware and how it affects image acquisition, safety, and image quality. Dr. Salerno reviewed the three main MRI components: the main magnet, RF coils, and gradient coils. He explained the types of magnets used in MRI, emphasizing that clinical scanners are usually superconducting magnets cooled by liquid helium and always “on.” He also covered magnet safety, including projectile risks and MRI safety zones.<br /><br />The talk then described RF coils, which transmit and receive radiofrequency signals at the Larmor frequency. He distinguished between body coils and receive-only array coils, and explained SAR-related heating limits and safety concerns. Next, he discussed gradient coils, which create spatial encoding by varying magnetic fields across space. Their amplitude and slew rate determine performance, but rapid switching can cause peripheral nerve stimulation.<br /><br />Finally, he explained pulse sequences, analog-to-digital conversion, Fourier reconstruction, and shimming, including passive and active higher-order shimming to improve field homogeneity. The session concluded with a Q&A on coils, shimming, pacemakers, pregnancy, quenching, and emerging MRI technologies.

Keywords

MRI hardware

image acquisition

magnet safety

RF coils

gradient coils

pulse sequences

Fourier reconstruction

shimming

superconducting magnets