MRI Spin echo sequence and STIR

In summary: The signal is highest at TE when the protons are in coherence, meaning they are aligned and produce a strong signal. In STIR, a 90 degree read out pulse is given at the Time to Inversion (TI), which is the point where the magnetization of fat tissue is zero. This allows for better suppression of fat signal in the resulting image. When the 90 degree pulse is given, the magnetization (Mz) is transferred to the transverse magnetization (Mxy) plane, and since Mz is zero at TI, Mxy can also be zero. This technique is used to create a null point for fat signal, improving image contrast.
  • #1
yephonethaw
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I would like to ask a question about MRI Spin echo sequence. after first 90 degree RF pulse, the free induction decay occurs. And 180degree refocusing pulse is given again. And echo signal is obtained at TE. My question is that is the the signal highest when the protons are back again in coherence or when they are dephasing again?
 
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  • #2
yephonethaw said:
My question is that is the the signal highest when the protons are back again in coherence or when they are dephasing again?
The signal is the highest at TE, which is when they are in coherence.
 
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  • #3
In STIR, 90 degree read out pulse is given at Time to inversion TI( short TI) where the Mz of fat tissue is zero(null point). After giving 90 defree pulse ,Mz is transferred to Mxy plane and since Mz is zero, can Mxy be also zero?

<< Mentor Note -- related question merged into the OP's existing thread >>
 
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  • #4
I don't understand the highlighted words and the figure.When 90degree RF pulse is given, is Mz which is zero moved back to -Mz or still staying at transverse magnetization plane?
 

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  • #5
yephonethaw said:
After giving 90 defree pulse ,Mz is transferred to Mxy plane and since Mz is zero, can Mxy be also zero?
Yes, that is the basis of most magnetization preparation techniques.
 

Related to MRI Spin echo sequence and STIR

1. What is an MRI Spin echo sequence?

An MRI Spin echo sequence is a type of magnetic resonance imaging (MRI) technique that uses a series of radiofrequency pulses and magnetic field gradients to generate high-resolution images of the body's tissues. It is based on the principle of spin echo, where the hydrogen atoms in the body's tissues are excited and then emit a signal that is measured and converted into an image.

2. How does an MRI Spin echo sequence work?

The first step in an MRI Spin echo sequence is to apply a strong magnetic field to align the hydrogen atoms in the body's tissues. Then, a radiofrequency pulse is applied, causing the atoms to absorb energy and become excited. As the atoms return to their original state, they emit a signal that is measured and converted into an image. The process is repeated multiple times to create a series of images that can be used to construct a 3D image of the body's tissues.

3. What is the purpose of STIR in MRI Spin echo sequence?

STIR (short tau inversion recovery) is a type of MRI technique that is often used in conjunction with an MRI Spin echo sequence. It is designed to suppress the signal from fat tissues, making it easier to distinguish between different types of tissues in the body. This can be particularly useful in visualizing bone fractures, tumors, and areas of inflammation.

4. Is an MRI Spin echo sequence safe?

Yes, an MRI Spin echo sequence is generally considered to be a safe imaging technique. It does not use ionizing radiation, unlike other imaging methods such as X-rays and CT scans. However, it is important to inform your doctor or MRI technologist if you have any metal implants or devices in your body, as these can be affected by the strong magnetic field used in MRI.

5. What are the advantages of MRI Spin echo sequence over other imaging techniques?

MRI Spin echo sequence offers several advantages over other imaging techniques. It produces high-resolution images that can show detailed anatomical structures and soft tissues. It is also non-invasive and does not use radiation, making it a safer option for imaging. Additionally, MRI can provide information about the function and metabolism of tissues, which can be helpful in diagnosing certain conditions.

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