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Medical Imaging CT - T2?

So, this 'T2' thing keeps on being mentioned in my Radiology lectures but it hasn't been explained really well. They keep saying 'bright - H20, T2?'
Could anyone explain this to me?
Original post by MedStudentt
So, this 'T2' thing keeps on being mentioned in my Radiology lectures but it hasn't been explained really well. They keep saying 'bright - H20, T2?'
Could anyone explain this to me?


Unlike plain films and CT which make use of ionising radiation (X-rays), magnetic resonance instead uses the magnetic properties of the body's hydrogen atoms to generate an image. The magnetic field which is applied from the scanner to the body causes the hydrogen protons in your body to become excited and then to relax in different phases. The signal generated from these phases is what produces the image. T1 and T2 weightings are to do with MR imaging, not CT.

In T1 relaxation, structures in the body which are heavy in fat show up brightly on the image. T2 relaxation causes structures with an abundance of water to show up brightly e.g. CSF. The physics behind this is to do with the manner in which the protons spin and how quickly they return to their usual positions after becoming excited, which then determines the features you see on the generated image.

There are other MR sequences as well as T1 and T2 and it's not as simple as "dark CSF on MR = always T1" but this is all really well beyond undergraduate level and is not something they will be asking you about in your exams.

The (simplified) point they're trying to make is that by making use of the different image weightings, it is possible to differentiate pathological changes e.g. because oedema means greater water content, this will show up as brighter on a T2 image vs a T1 which can help you make the diagnosis.
(edited 6 years ago)

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