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The spin-echo effect was discovered by Erwin Hahn when he applied two successive 90° pulses separated by short time period, but detected a signal, the echo, when no pulse was applied. This phenomenon of spin echo was explained by Erwin Hahn in his 1950 paper, [ 5 ] and further developed by Carr and Purcell who pointed out the advantages of ...
Spin echo: T1 weighted: T1: Measuring spin–lattice relaxation by using a short repetition time (TR) and echo time (TE). Lower signal for more water content, [4] as in edema, tumor, infarction, inflammation, infection, hyperacute or chronic hemorrhage. [5] High signal for fat [4] [5] High signal for paramagnetic substances, such as MRI ...
Each of the spin-echo signal is a sinc function of time, which can be described by = Where = + ¯ Here ¯ is the gyromagnetic ratio constant, and is the basic resonance frequency of the spin. Due to the presence of the gradient G , the spatial information r is encoded onto the frequency ω {\displaystyle \omega } .
The spin echo is a 90° pulse followed by a 180° pulse after a time period τ and is applied on the proton, the sensitive nucleus (designated, perhaps counter-intuitively, as the I spin, while the insensitive nucleus is the S spin; note, however, that the original paper on INEPT used the opposite designations). [1] Spin Echo
INEPT is a common building block of NMR experiments to improve 15 N signal. [ 1 ] In Fourier transform NMR spectroscopy and imaging , a pulse sequence describes a series of radio frequency pulses applied to the sample, such that the free induction decay is related to the characteristic frequencies of the desired signals.
This transverse magnetisation refocuses to form a spin echo at a time T E. During the spin echo, a frequency-encoding (FE) or readout gradient is applied, making the resonant frequency of the nuclear magnetization vary with its location in the X direction. The signal is sampled n FE times by the ADC during this period, as represented by the ...
Neutron spin echo is a time-of-flight technique. Concerning the neutron spins it has a strong analogy to the so-called Hahn echo, [13] well known in the field of NMR.In both cases the loss of polarization (magnetization) due to dephasing of the spins in time is restored by an effective time reversal operation, that leads to a restitution of polarization (rephasing).
Higher signal for more water content [1] Low signal for fat in standard Spine Echo (SE), [1] though not with Fast Spin Echo/Turbo Spin Echo (FSE/TSE). FSE/TSE is the standard of care in modern medicine because it is faster. With FSE/TSE, fat has high signal due to disruption of hyperfine J-coupling between adjacent fat protons. [3]