Esaote O-scan eXP, User Manual

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4 / 8 Chapter 2
INHOMOGENEITY - Degree of a lack of homogeneity. For example, the
fractional deviation of the local magnetic field from the average value of
the field.
LONGITUDINAL MAGNETIZATION - Component of the macroscopic
magnetization vector along the static magnetic field.
LOWER LIMB - Includes foot, ankle, calf, and knee, but which excludes the
thigh.
MAGNETIC GRADIENT FIELD - A magnetic field the intensity of which
varies in proportion to the distance from the magnet isocenter. Used to
select the imaging region and encode the MR signal with spatial
information. Such a gradient field is superimposed on the main magnetic
field.
MAGNETIC RESONANCE (MR) - The absorption or emission of
electromagnetic energy by nuclei in a static magnetic field, after
excitation by a suitable RF magnetic field. The peak resonance frequency
is proportional to the magnetic field, and is given by Larmour equation.
Only nuclei with a non-zero spin exhibit nuclear magnetic resonance
(NMR).
MAGNETIC RESONANCE IMAGING - Creation of images of the human
body using Magnetic Resonance. The intensity of an image of a specific
zone depends mainly on the density of the spin and tissue relaxation
times.
MAGNETIZATION - The magnetic polarization of a material produced by a
magnetic field.
MATRIX (RAW DATA) - Matrix whose side is determined by the number of
readout (frequency) sampling points and the number of phase encoding
steps, to yield a desired spatial resolution.
MAXIMUM DISPLAYED IMAGE - The maximum size of the displayed image
is a 140 mm x 140 mm square in order to minimize the displayed area
external to the homogeneity region.
MR ENVIRONMENT - This term refers to the environment present in the
immediate vicinity of the MR system. In particular it refers to the area
within the line at 0.5 mT.
MR MARKER - A marker that is visible in magnetic resonance images that
can be placed on the surface of a patient's body to delineate, or serve as a
reference point with respect to the tissue to be examined.
MR WORKER - person because of his/her profession has to enter the
CONTROLLED ACCESS AREA or equivalent of the MAGNETIC RESONANCE
SYSTEM.
NOISE - A statistic fluctuation of signal intensity that does not contribute
to image information. The factors that determine noise include presence
of the patient in the magnet, electric noise generated by the RF reception
system and external electromagnetic noise.