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Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to form images of the organs in the body.
High performance gradient coils used in MRI are typically capable of producing a gradient magnetic field of approximate 30 mT/m or higher for a 1.5 T MRI. The slew rate of a gradient system is a measure of how quickly the gradients can be ramped on or off. Typical higher performance gradients have a slew rate of up to 100–200 T·m −1 ·s ...
T1 weighted: T1: Measuring spin–lattice relaxation by using a short repetition time (TR) and echo time (TE). Lower signal for more water content, [1] as in edema, tumor, infarction, inflammation, infection, hyperacute or chronic hemorrhage. [2] High signal for fat [1] [2] High signal for paramagnetic substances, such as MRI contrast agents [2]
The introduction of FLASH MRI sequences in diagnostic imaging for the first time allowed for a drastic shortening of the measuring times without a substantial loss in image quality. In addition, the measuring principle led to a broad range of completely new imaging modalities.
Spin–lattice relaxation in the rotating frame is the mechanism by which M xy, the transverse component of the magnetization vector, exponentially decays towards its equilibrium value of zero, under the influence of a radio frequency (RF) field in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI).
In magnetic resonance imaging (MRI) and nuclear magnetic resonance spectroscopy (NMR), an observable nuclear spin polarization (magnetization) is created by a homogeneous magnetic field. This field makes the magnetic dipole moments of the sample precess at the resonance frequency of the nuclei. At thermal equilibrium, nuclear spins precess ...
Phase contrast MRI (PC-MRI) is used to measure flow velocities in the body. It is used mainly to measure blood flow in the heart and throughout the body. PC-MRI may be considered a method of magnetic resonance velocimetry. Since modern PC-MRI typically is time-resolved, it also may be referred to as 4-D imaging (three spatial dimensions plus ...
In MRI, T 2-weighted images can be obtained by selecting an echo time on the order of the various tissues' T 2 s. [8] In order to reduce the amount of T 1 information and therefore contamination in the image, excited spins are allowed to return to near- equilibrium on a T 1 scale before being excited again.