What is gradient echo echo planar imaging?
Echo planar imaging (EPI) is performed using a pulse sequence in which multiple echoes of different phase steps are acquired using rephasing gradients instead of repeated 180-degree radiofrequency pulses following the 90°/180° in a spin echo sequence.
What is planar imaging?
Planar imaging is the acquisition of 2D nuclear images, similar to plain films in x-ray imaging.
What is echo MRI?
In MRI, an echo is the emission of energy in form of an electromagnetic resonance signal of a nuclei after its excitation. At this point spins are back in phase again and the signal is measured.
What is DWI MRI for?
DWI is commonly used to detect and stage tumors, and also to monitor tumor response to treatment over time. DWI can also be collected to visualize the whole body using a technique called ‘diffusion-weighted whole-body imaging with background body signal suppression’ (DWIBS).
What is the EPI factor?
The number of k-space lines (echoes) collected in a single shot is called the “Echo Train Length (ETL)” by GE and Canon; the “EPI factor” by SIemens and Philips; and the “shot factor” by Hitachi. The regions of k-space divided up by each shot of a multi-shot sequence are called segments.
What is a planar study?
The study of theoretical “mathemagic”. Planar Studies is built upon formulae and proofs so strong that they can alter the nature of reality and break its bounds. Planar Mages use magic to perform their calculations, but their formulas themselves operate on physical laws, rather than magic.
What is echo time?
Echo time is the time at which the electrical signal induced by the spinning protons is measured. A long echo time results in reduced signal in tissues like white matter and gray matter since the protons are more likely to become out of phase.
What is echo 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 signal dropout MRI?
Purpose: In diffusion MRI, dropout refers to a strong attenuation of the measured signal that is caused by bulk motion during the diffusion encoding. When left uncorrected, dropout will be erroneously interpreted as high diffusivity in the affected direction.
Why do we use gradient echo?
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 echo planar imaging?
Pulse Sequences Echo-planar imaging (EPI) is a fast-imaging technique whereby a two-dimensional (2-D) image can be obtained in less than a second, by quickly switching the magnetic gradients back and forth after a single excitation pulse.
What is the difference between echo planar MRI and SPECT MRI?
It is more sensitive than SPECT and can be used to detect neurotransmitter activity, with appropriate isotopes, as well as local metabolism. Echo-planar MRI is a variation of MRI technique and can be used to detect variations in oxyhaemoglobin and deoxyhaemoglobin, which relate to tissue oxygen uptake and, therefore, to metabolic rate.
What is the difference between single-shot and multi-shot echo planar imaging?
In a single-shot echo planar sequence, the entire range of phase encoding steps, usually up to 128, are acquired in one TR. In multi-shot echo planar imaging, the range of phase steps is equally divided into several “shots” or TR periods. For example an image with 256 phase steps could be divided into 4 shots of 64 steps each.
What are microbleeds on a planar MRI scan?
Echo planar MRI scans often show small old lesions that image as discrete, black, usually round abnormalities. These black regions indicate that hemosiderin or blood is present. Some of these discrete black images are small blood vessels cut transversely. These abnormalities are often referred to as microbleeds.