Quote Originally Posted by Ken Fitzgerald View Post
Michael, the sounds you hear are normally caused by the gradient coils changing the main magnetic field in a precise way.

Have you ever seen a child build something with a set of blocks? Imagine your body built out of a child's blocks. Now we'll call those individual blocks voxels. An MRI image is made by the machine causing each voxel to produce its own distinct, individual RF signal. The machine knows in 3-D from where a given RF signal with a specific frequency was produced. The human body is made up primarily water, H2O. The MRI image is made by studying the hydrogen molecules in the body.

Different pulse sequences will produce dramatically different gradient pulses/fields and thus dramatically different sounds.
Fascinating Ken, I had no idea and curiosity made me ask AI. This was the reply and reads like science fiction, at least to me. There are some real smart folks in this world.

“MRI, or Magnetic Resonance Imaging, utilizes powerful magnets and radio waves to generate detailed images of the body's internal structures. Here's how it works:

  1. Alignment of Hydrogen Atoms: The patient lies within a strong magnetic field, which aligns the hydrogen atoms in their body along the magnetic field lines.
  2. Radiofrequency Pulse: A radiofrequency pulse is then applied, causing the aligned hydrogen atoms to absorb energy and temporarily deviate from their aligned positions.
  3. Relaxation: When the radiofrequency pulse is turned off, the hydrogen atoms gradually return to their aligned positions, releasing energy in the form of radio waves.
  4. Signal Detection: Specialized coils detect these emitted radio waves.
  5. Image Reconstruction: A computer processes the signals to construct detailed images of the internal structures based on the behavior of the hydrogen atoms in different tissues. “