Some of you may have already been inside an Magnetic Resonance scanner. From the outside it has a pretty simple donut-like shape, like this:
(image from here)
Even though the outside has a fancy minimalist design, the way it works is one of the most sophisticated method's I've ever studied, and I'm far from fully understanding it. Every time I read something on magnetic resonance imaging (MRI), not only I learn something new but also have new questions about it.
Very very very (I really have to emphasize it) briefly, this technique works by placing a human body in a strong magnetic field.
This magnetic field is slightly different from the head to feet, meaning the atoms inside the body will precess (rotate somehow like a spinning top) at different speeds.
Different speeds mean they'll have different resonance frequencies. It is possible to stimulate a number of elements, but because hydrogen is abundant inside the human body and the MR signal is strong, this is the chosen element for stimulation.
When precessing protons are stimulated by radiofrequency pulses, they absorb energy and tend to return to their lowest energy state (oriented along the magnetic field). When releasing energy, protons emit a magnetization signal which can be detected by electromagnetic induction in coils.
After reconstruction from frequency domain, different types of images can be obtained depending on how the protons are stimulated.
New techniques such as diffusion kurtosis imaging may provide new information relevant to clinicians. Scientists all over the world actively investigate new ways to stimulate protons and have different contrast images, new types of information, etc.
Maybe one day I'll get to work on this. So far I analysed DTI images in order to look for differences between Parkinson's disease and healthy subjects, which was a pretty interesting project and in which I've learnt many things.
Suggested reading (online and free): The Basics of MRI by Joseph P. Hornak.
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