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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 ...
The major components of an MRI scanner are the main magnet, which polarizes the sample, the shim coils for correcting shifts in the homogeneity of the main magnetic field, the gradient system which is used to localize the region to be scanned and the RF system, which excites the sample and detects the resulting NMR signal. The whole system is ...
To use the technique, the gradient coils in the MRI equipment need to be driven with special pulse sequences, designed for specific tissues, that "tags" deformation of the tissue, such that tissue that deforms more is brighter, or darker, as needed. Using a baseline measurement of normal deformation, the measurements can show unusual amounts of ...
Radiofrequency coils (RF coils) are the receivers, and sometimes also the transmitters, of radiofrequency (RF) signals in equipment used in magnetic resonance imaging (MRI). The MR signal in MRI is produced by the process of resonance, which is the result of radiofrequency pulses.
Magnetic field gradient: High gradient focus of magnetic resonance in a smaller volume (smaller point spread function), results in a better spatial resolution. The gradients for MRM are typically 50 to 100 times those of clinical systems. However, the construction of radio frequency (RF) coils used in MRM does not allow ultrahigh gradients.
A Maxwell coil is a device for producing a large volume of almost constant (or constant-gradient) magnetic field. It is named in honour of the Scottish physicist James Clerk Maxwell . A Maxwell coil is an improvement of a Helmholtz coil : in operation it provides an even more uniform magnetic field (than a Helmholtz coil), but at the expense of ...
An MRI artifact is a visual artifact ... the cause might be either a damaged gradient coil or an abnormal current passing through the gradient coil. [1] RF (B1 ...
Gradient echo sequences present shorter echo times since only one RF pulse is required for each sequence. [12] Modern fast-switching gradient coils also require increasing the slew rate, allowing for faster changes in gradient echo sequences and decreasing the repetition time. [13] Rectilinear sampling of the k-space