MR imaging -- the banging

Sound of Science  @jeffreyFDunn

 What strikes you most about your MRI scan? I’m betting that a big part of the experience is the sound of the scans--the noise, the banging.

I do research with MRI’s, and the banging has become one of those background noises that are part of the lab. They are kind of comforting. Everything is working, data is being collected. I’m hoping that if you have a better understanding of what the sound is, then you can begin to share my attitude about the banging, making your MRI experience less stressful. The sounds are caused by the interaction between the structure holding the large magnet, and the structure holding the room temperature electromagnets. These latter components of the MRI create a gradient of magnetic field across the bore. As a result, they are called gradients. The strength and direction of the gradients change in complex ways as the scans are collected. The sounds are caused by torsion between the two magnets. It’s the same kind of stress you get if you hold two bar magnets parallel to each other, the ends try to repel. As the gradients change direction, you get different stresses in the structure of the MRI and you get a bang. The loudness relates to the strength and pattern. You can tell what MRI image is being collected by the sound of the gradients---the sound of science!