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The field strength of the magnet is measured in teslas – and while the majority of systems operate at 1.5 T, commercial systems are available between 0.2 and 7 T. 3T MRI systems, also called 3 Tesla MRIs, have stronger magnets than 1.5 systems and are considered better for images of organs and soft tissue. [7]
A field strength of 1.0–1.5 T is a good compromise between cost and performance for general medical use. However, for certain specialist uses (e.g., brain imaging) higher field strengths are desirable, with some hospitals now using 3.0 T scanners. FID signal from a badly shimmed sample has a complex envelope.
To sensitize MRI images to diffusion, the magnetic field strength (B1) is varied linearly by a pulsed field gradient. Since precession is proportional to the magnet strength, the protons begin to precess at different rates, resulting in dispersion of the phase and signal loss.
These scanners operate at relatively low magnetic field strengths, such as 0.35 T or 0.55 T. Many RT-MRI acquisition sequences, such as bSSFP, experience significant off-resonance effects. Off-resonance effects increase linearly with B0 field strength, so minimizing B0 also minimizes these effects that can lead to artifacts and image distortion ...
Example 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, [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 ...
Thus, the relaxation rate as a function of the magnetic field strength is a fingerprint of the microscopic dynamics. Key Materials science properties are often described in different fields using the terms mobility / dynamics / stiffness / viscosity / rigidity of the sample. These properties are usually dependent on atomic and molecular motion ...
The values in the phase images are constrained from -π to π so if the value goes above π it wraps to -π, inhomogeneities in the magnetic field cause low frequency background gradients. This causes all the phase values to slowly increase across the image which creates phase wrapping and obscures the image.
This page lists examples of magnetic induction B in teslas and gauss produced by various sources, grouped by orders of magnitude. The magnetic flux density does not measure how strong a magnetic field is, but only how strong the magnetic flux is in a given point or at a given distance (usually right above the magnet's surface).