What is spin echo in NMR?
In magnetic resonance, a spin echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. Modern nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) make use of this effect.
What is diffusion NMR?
The diffusion NMR technique is often referred to as Self-Diffusion (SD)-NMR or Diffusion Ordered SpectroscopY (DOSY). This is achieved by combining radio-frequency pulses as used in routine NMR spectroscopy with magnetic field gradients that encode spatial information.
What is the purpose of spin echo?
The “spin-echo” pulse sequence [9,10,11] is used to obtain a signal by means of a 90º excitation pulse and a 180º inversion pulse, which were sent to the nuclei of hydrogen atoms of the tissues present in the region to be analyzed (Figure 2).
What is 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 the difference between spin echo and fast spin echo?
Fast spin echo offers increased resolution in a comparable time to conventional spin echo by increased number of excitations and finer matrix size, thus improving the signal-to-noise ratio and spatial resolution, respectively.
What is the difference between spin echo and gradient 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 does an NMR work?
How Does NMR Actually Work? When molecules are placed in a strong magnetic field, the nuclei of some atoms will begin to behave like small magnets. If a broad spectrum of radio frequency waves are applied to the sample, the nuclei will being to resonate at their own specific frequencies.
What are the types of spin echo pulse sequence?
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.
What is fast spin echo?
Fast or turbo spin echo (FSE/TSE) is an adaptation of conventional spin-echo (SE) acquisition technique designed to reduce imaging time. It has largely supplanted the original spin-echo technique due to vastly improved imaging speed.
What is the primary advantage of gradient echo over spin echo imaging?
The common characteristic of the gradient echo imaging methods is that a magnetic field gradient is used to produce the echo event rather than a 180° RF pulse, as is used in the spin echo methods. One of the principal advantages of the gradient echo process is that it is a relatively fast imaging method.