What is the difference between T1 and T2 relaxation times?
T2 relaxation always proceeds at a faster rate than T1 relaxation; thus the the T1 relaxation time is always longer than or equal to T2. To the left is a table listing T1 and T2 values for hydrogen nuclei in various biological tissues.
How are MRI sequences different?
The best way to tell the two apart is to look at the grey-white matter. T1 sequences will have grey matter being darker than white matter. T2 weighted sequences, whether fluid attenuated or not, will have white matter being darker than grey matter.
How does MRI work Physics A level?
Magnetic Resonance Imaging (MRI) works by measuring the way that hydrogen atoms absorb and then relax and re-emit electromagnetic energy. Most of the human body is made up of water molecules, which consist of only hydrogen and oxygen atoms and fat, which also contains hydrogen atoms.
Why is T2 less than T1?
Typically (as shown in the first figure), T2 values of tissue are considerably lower than T1 values, i. e., the transverse magnetization decays quicker than the longitudinal relaxation needs for recovery. For most tissues in vivo, T1 varies between about 300 ms and 3 s, while T2 varies between about 10 ms and 200 ms.
What is a high T1 and T2 signal MRI?
T1 images – 1 tissue type is bright – FAT. T2 images – 2 tissue types are bright – FAT and WATER.
What happens when RF is switched off?
When RF Pulse is switched off, the protons start to realign themselves back in a low energy state or equilibrium state, i.e., the main magnetic field’s direction. This is called relaxation. Relaxation occurs in two different ways, i.e., T1 and T2 relaxation.
What is T1 and T2 physics?
T1-weighted images are produced by using short TE and TR times. The contrast and brightness of the image are predominately determined by T1 properties of tissue. Conversely, T2-weighted images are produced by using longer TE and TR times.