What is CPMG pulse sequence?
A sequence of pulses used for spin-echo experiments in nuclear magnetic resonance (NMR) in which the initial pulse is 90° followed by a series of 180° pulses. A CPMG sequence is designed so that the spin echoes die away exponentially with time.
What is excitation pulse in MRI?
Introduction. SLICE-SELECTIVE radio-frequency (RF) excitation pulses are ubiquitous throughout magnetic resonance imaging (MRI). They are widely used to excite only those magnetic spins within a thin slice of tissue while leaving spins outside the slice in alignment with B0, the system’s magnetic main field.
What is gradient pulse in MRI?
The gradient echo is generated by the frequency-encode gradient, except that it is used twice in succession, and in opposite directions: it is used in reverse at first to enforce transverse dephasing of spinning protons and then right after, it is used as a readout gradient (like in spin-echo MRI) to re-align the …
What is MRI spin-echo?
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 T2 relaxation time in MRI?
T2 Relaxation: Definition Thus T2 is the time required for the transverse magnetization to fall to approximately 37% (1/e) of its initial value. Synonyms for T2 relaxation are transverse relaxation and spin-spin relaxation.
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 pulse sequence diagram?
A pulse sequence diagram (PSD) illustrates the sequence of events that occur during magnetic resonance imaging (MRI). It is a timing diagram showing the radio frequency (RF) pulses, gradients, and echoes.
What is gradient sequence?
Gradient echo sequences (GRE) are an alternative technique to spin-echo sequences, differing from it in two principal points: utilization of gradient fields to generate transverse magnetization. flip angles of less than 90°
What is CPMG NMR?
The CPMG (Carr-Purcell-Meiboom-Gill) pulse train is a fundamental component of pulse sequences used for the measurement of dynamic processes by NMR spectroscopy. This simple modification compensated for imperfections in the 180° pulses that would otherwise have accumulated over the course of the pulse train.
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.