Comments on: MRIs and store alarms http://www.kevinmd.com/blog/2007/07/mris-and-store-alarms.html Tue, 14 Feb 2012 11:46:00 +0000 hourly 1 By: Robhttp://www.kevinmd.com/blog/2007/07/mris-and-store-alarms.html#comment-77853 Rob Wed, 18 Jul 2007 22:17:00 +0000 http://clients.emmense.com/kevinmd/2007/07/mris-and-store-alarms.html#comment-77853 Of course I was joking, you goof!! Of course I was joking, you goof!!

]]> By: Anonymoushttp://www.kevinmd.com/blog/2007/07/mris-and-store-alarms.html#comment-77841 Anonymous Wed, 18 Jul 2007 16:52:00 +0000 http://clients.emmense.com/kevinmd/2007/07/mris-and-store-alarms.html#comment-77841 I hope Dr Rob was just joking, because he obviously has no clue as to how MRI works.<br/><br/>MRI does NOT "cause your RBCs to line up" in fact MRI has no effect at the cellular level, only the atomic level. It wont cause anything to "line up" other than the magnetic axis of the hydrogen protons in your body.<br/><br/>Even then, the number of excess spins being lined up in the external magnetic field of the scanner is on the order of 1 in 1 million. So the effect is barely noticeable. Thats why the sensitivity of MRI is so poor relative to PET or other nuclear imaging techniques.<br/><br/>As soon as the magnet shuts off, the hydrogen proton spins decay to their previous equilibrium, leaving no "memory" of you being magnetized. Thats why theoretically you could have an infinite number of MRIs with no lasting effects to your body.<br/><br/>The only exception to this rule as stated in the article is iron overload states, which can become temporarily polarized by the external magnetic field imposed by the MR scanner. <br/><br/>But even this too decays with time, it just takes longer than the normal hydrogen proton decay curve. I hope Dr Rob was just joking, because he obviously has no clue as to how MRI works.

MRI does NOT “cause your RBCs to line up” in fact MRI has no effect at the cellular level, only the atomic level. It wont cause anything to “line up” other than the magnetic axis of the hydrogen protons in your body.

Even then, the number of excess spins being lined up in the external magnetic field of the scanner is on the order of 1 in 1 million. So the effect is barely noticeable. Thats why the sensitivity of MRI is so poor relative to PET or other nuclear imaging techniques.

As soon as the magnet shuts off, the hydrogen proton spins decay to their previous equilibrium, leaving no “memory” of you being magnetized. Thats why theoretically you could have an infinite number of MRIs with no lasting effects to your body.

The only exception to this rule as stated in the article is iron overload states, which can become temporarily polarized by the external magnetic field imposed by the MR scanner.

But even this too decays with time, it just takes longer than the normal hydrogen proton decay curve.

]]>