The transverse relaxation time, this is due to the lack of,
is the decay of magnetization due to interaction between nuclei, and
this is described by a time constant T2.
And this is due to this lack of phase coherence, and we see this illustrated.
And T2 is how long it takes for
us to go down from 100% down to 37%.
By altering how often we excite the nuclei, which is measured by something
called the TR, and how soon after excitation we begin data collection,
this is something called TE, we can control which characteristic of the image
is emphasized, whether it's T1, or T2, or whatnot.
And so the key to this measure signals approximately equal to the following
equation is M knot, which is the core net magnetization,
times a term that depends on TR and T1.
And remember, TR is something that we can control.
And, a second term that depends on TE and T2.
And again, TE is something that we can control.
And, in contrast, T1 and T2 are tissue properties.
So, the goal of MRI is to construct an image, or
a matrix of numbers that correspond to spatial locations.
And so, the image depicts the spatial distribution of some property of
the nuclei within the sample.