Lesser known MRI risks!
Posted on by Steven Mussey MD
Have a great weekend.
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I did an online search and boy it was hard to delineate the Rf frequencies reliably for a given magnetic field. I was looking for the infamous online calculator but found none. The Rf frequency varies based on the magnetic field strength. All that is based on laws of physics. Basically there is an optimum Rf for a given magnetic field (T for Tesla). Here’s a list: (Don’t hold me to them but it shows a trend.)
Frequency Magnet
64Mhz 1.5 T
128Mhz 2.0 T
200Mhz 4.7 T
298Mhz 7.0 T
447Mhz 10 T
658Mhz 13.5 T
This is from specialists literature and the authors probably assume readers know this stuff offhand. Many times it’s not mentioned but in some articles it is posted what Rf was used. It can be mathematically calculated.
Now from what I searched, the researchers seemed to be trying to limit the Rf energy needed/imparted on living humans with larger magnets. Something about “Rf shimming” which I don’t know what the heck it is. Might be some receive technique so lower power Rf energy can be used. Ah, I notice in some scanners were quoted using 2 kilowatt Rf transmitters. For reference, a microwave oven is at 2,450Mhz and doesn’t use that much Rf power.
Well, after I had an MRI of the left shoulder for impingement, I swear the shoulder felt comfortably warm after the scan. Was nice actually but the relief was short lived. I had two scans of the shoulder and it happened both time. I think it was 3.0 T magnet but I don’t remember the particulars. Might have been 4.7 T. My right ankle had an MRI scan later on and felt warm but not as much as the shoulder.
Also from what I read, the manufacturers have to do safety studies on given hardware and prove to the FDA it’s safe before a device can be improved. They actually have to present studies on everything involved running a scanner.
Yeah I know, we don’t know the “long term” effects but if there are any, I suspect it’s along the lines of X-rays. One wouldn’t want to be irradiated so much over time especially with older X-ray equipment. I don’t think folks get MRI’s that often over time through their lives. If there is any risk, I think it’s less than X-rays and could be negligible.
May be more accurate than you think….. https://research.umn.edu/inquiry/post/u-scientists-scan-worlds-first-105-tesla-human-mri-image