Katie41 wrote:here is an explanation of MRIs, as I understand them. MRIs of the brain pull apart the water molecules. The hydrogen and oxygen molecules then have to work their way back together to reform the water molecule. Each MRI makes it more difficult for them to do that.
This sounds like nonsense. If the MRI did break the covalent bonds between the hydrogen and oxygen in water, I would think you'd have some very immediate detrimental effects in the brain.
MRIs don't work by pulling apart the water molecules. The large field magnetic of the MRI causes nuclei of atoms to align with the field and to start to precess, or spin like a top. Then a radio frequency is applied, at the same frequency of this precession. The effect is to cause the magnetic moment of the nuclei to flip. The RF signal is turned off, and the time it takes the nuclei to return to equilibrium is measured. The precession frequency is different for different atoms; most MRIs look at the hydrogen atom, since water is the most abundnant molecule in human tissue. But the molecules remain intact.
I'm interested in what you read about the harmful effects of 7T machines. While I don't buy the previous explanation, I have been wondering if anyone has looked at the possible effects of putting someone in a high strength magnetic field.