# What is a spin echo sequence?

## What is a spin echo sequence?

The spin echo sequence is made up of a series of events : 90° pulse – 180° rephasing pulse at TE/2 – signal reading at TE. This series is repeated at each time interval TR (Repetition time). With each repetition, a k-space line is filled, thanks to a different phase encoding.

### What is a spin echo used for?

Spin-echo pulse sequences are one of the earliest developed and still widely used (in the form of fast spin-echo) of all MRI pulse sequences. The pulse sequence timing can be adjusted to give T1-weighted, proton density, and T2-weighted images.

How is spin echo formed?

In fact, spin echoes are formed when two successive RF-pulses of any flip angle are employed! Hahn, in his original paper, used two 90° pulses. When flip angles other than 90° and 180° are employed, the resultant spin echo is sometimes referred to as a Hahn echo.

What is the difference between gradient echo and spin echo?

A spin echo (SE) is produced by pairs of radiofrequency (RF) pulses, whereas a gradient echo (GRE) is produced by a single RF pulse in conjunction with a gradient reversal. The formation of a GRE is illustrated schematically.

## How is spin echo calculated?

Spin-Echo. S = k ρ (1-exp(-TR/T1)) exp(-TE/T2) Inversion Recovery (180-90)

### What is TE and TR?

Repetition Time (TR) is the amount of time between successive pulse sequences applied to the same slice. Time to Echo (TE) is the time between the delivery of the RF pulse and the receipt of the echo signal. Tissue can be characterized by two different relaxation times – T1 and T2.

What is spin echo pulse sequence in MRI?

What are the types of spin echo pulse sequence?

short tau inversion recovery (STIR)

• fluid attenuation inversion recovery (FLAIR)
• turbo inversion recovery magnitude (TIRM)
• double inversion recovery (DIR)
• ## Why is gradient echo faster than spin echo?

Fast spin echo (FSE) uses many successive 180-degree pulses to speed acquisition. The gradient echo (GRE) sequence does not use a 180-degree pulse; dephasing occurs according to T2*, which is much more rapid. The sequence is overall much faster and allows for rapid repetition.

### What type of flip angle is used in spin-echo?

The flip angle is usually at or close to 90 degrees for a spin-echo sequence but is less on gradient-echo sequences, commonly varying over a range of 10 to 80 degrees (usually denoted by α).

Why is gradient echo faster than spin-echo?

What is T1 and T2?

T1 and T2 are technical terms applied to different MRI methods used to generate magnetic resonance images. Specifically, T1 and T2 refers to the time taken between magnetic pulses and the image is taken. These different methods are used to detect different structures or chemicals in the central nervous system.

## What is spin echo pulse sequence?

Spin-echo pulse sequences are one of the earliest developed and still widely used (in the form of fast spin-echo) of all MRI pulse sequences. The pulse sequence timing can be adjusted to give T1-weighted, proton density, and T2-weighted images. Dual echo and multiecho sequences can be used to obtain both proton density…

### What is spin echo in MRI?

Spin echo sequences. Spin-echo pulse sequences are one of the earliest developed and still widely used (in the form of fast spin-echo) of all MRI pulse sequences. The pulse sequence timing can be adjusted to give T1-weighted, proton density, and T2-weighted images. Dual echo and multiecho sequences can be used to obtain both proton density…

What is the spin echo family?

The spin echo family consists of the convention spin echo, the fast spin echo, the inverse recovery sequence, the single shot sequence, DRIVE, and the hydrid sequence. If we take a close look at a pulse sequence diagram, we can see that during the excitation pulse, we need to create resonance that affects only a slice of data.

What are the two variables of interest in spin echo sequences?

The two variables of interest in spin echo sequences are the repetition time (TR) and the echo time (TE). All spin echo sequences include a slice selective 90-degree pulse followed by one or more 180 degree refocusing pulses as shown in the diagrams.