Presentations

Hi, this is my first time documenting my work so I need time to get used to this kind of communication. 

I present myself, my name is Davide and I come from Italy. I'm currently studying material engineer at the University of Napoli Federico II. My main subjects of course regard matter from large to the nanoscale, anyway my courses are based largely on physics (and chemistry).

Ok, now I know this project will take some time, and before publishing this first log I've already documented myself more or less on how an MRI works. So I have a general idea of how to proceed. 

A Review of an MRI

An MRI which stands for "Magnetic Resonance Imaging"  is a fascinating device that allows you to take a picture of a slice of your body. Maybe in another log ill explain in detail how it works. Still, the main function in a very simple fashion is to use a strong magnetic field (usually achieved with a superconductor ring) so all the electrons in our body "align" with it. we then send some signal with a specially tuned antenna, therefore we receive back another signal. The final step is to reconstruct the image with some fancy math that involves a Fourier transform. The image is grayscale, and every value corresponds to electron density (aka matter density) so we can discriminate all the different body tissues (skin, bone, brain, organs, fat, muscle, ...).

Obviously in reality an MRI is extremely more complex but we can section it, into individual and independent pieces:

• Main Magnetic Field: I can't afford a big superconductor ring that I must maintain at a temperature of 9.4 Kelvin (-272°C). There are two alternatives, put a current through a wire in a specific geometry or with permanent magnets in a special configuration (we need a homogeneous field over space so there is a specific way to do this). With the superconductor, we can produce a really strong magnetic field in the range of 7 T (Tesla) and even 11 T on recent MRIs. It sounds like a small value but as a reference, the average value of the magnetic field on Earth's surface is 60 milli micro Tesla. The alternatives can produce a field of 0.5-1 T so we call this specific type of MRI "Low Field" or "Ultra Low Field". The question is, why do we need a strong magnetic field? the answer is resolution, the stronger the field higher will be the resolution of our image.
• Auxiliary Magnetic Field: usually said gradient coil. When we align all the electrons with the main field we need to know where an atom is in real space. To do this we need a gradient coil that produces a varying magnetic field in space. For every value of this field, we can relate a position in space. Also, another function is to select a particular slice of our body.
• RF coil: radio frequency coil. It's a radio antenna that can send and receive within a specific narrow bandwidth. The frequency of this antenna depends on the strength of the Main Magnetic field, for a commercial MRI which provides a field of like 7-10 T the frequency of transmission and receive of the RF coil is in the order of 200-300MHz. Sometimes TX (transmission) and RX (receive) are separated in two different antennae so we can get the best tuning for the two of them.

In order to build a complete an functional MRI I need to build this 3 main parts. Of course, there is more to talk about this but in the future, I'm going to cover as much as I can in detail. In the next log I'm going to disscus how i'm going to measure the magnetic field that I will produce in future.