- Artifact
- A feature which appears in an NMR spectrum of a molecule which should not be present based on the chemical structure and pulse sequence used.
[Chapter 7]
- Chemical Screening
- The screening of an applied magnetic field experienced by a nucleus due to the electron cloud around an atom or molecule.
[Chapter 4]
- Chemical Shift
- A variation in the resonance frequency of a nuclear spin due to the chemical environment around the nucleus. Chemical shift is reported in ppm. [Chapter 4]
- Coil
- One or more loops of a conductor used to create a magnetic field. In NMR, the term generally refers to the radiofrequency coil.
[Chapter 7]
- Convolution
- A mathematical operation between two functions.
[Chapter 2]
- Complex Data
- Numerical data with a real and an imaginary component.
[Chapter 2]
- Continuous Wave (CW)
- A form of spectroscopy in which a constant amplitude electromagnetic wave is applied.
[Chapter 3]
- Coordinate Transformation
- A change in the axes used to represent some spatial quantity.
[Chapter 2]
- Cryopumping
- The condensation of air onto a surface cooled by a cryogenic liquid .
[Chapter 8]
- Dephasing Gradient
- A magnetic field gradient used to dephase transverse magnetization.
[Chapter 11]
- Digital Filtering
- A feature found on may newer spectrometers which eliminates wraparound artifacts by filtering out the higher frequency components in the time domain spectrum.
[Chapter 7]
- Doubly balanced mixer
- An electrical device, often referred to as a product detector, which is used in NMR to convert signals from the laboratory frame of reference to the rotating frame of reference.
[Chapter 7]
- Echo
- A form of magnetic resonance signal from the refocusing of transverse magnetization.
[Chapter 6]
- Echo Time ( TE )
- The time between the 90 degree pulse and the maximum in the echo in a spin-echo sequence.
[Chapter 6]
- Exchange, Chemical
- The interchange of chemically equivalent components on a molecule.
[Chapter 3]
- Exchange, Spin
- The interchange of spin state between two nuclei.
[Chapter 3]
- Figure-8 Coil
- A magnetic field gradient coil shaped like the number eight.
[Chapter 7]
- Free induction decay ( FID )
- A form of magnetic resonance signal from the decay of transverse magnetization.
[Chapter 4]
- Fourier transform ( FT )
- A mathematical technique capable of converting a time domain signal to a frequency domain signal and vice versa.
[Chapter 5]
- Gradient ( G )
- A variation in some quantity with respect to another. In the context of NMR, a magnetic field gradient is a variation in the magnetic field with respect to distance.
[Chapter 7]
- Gyromagnetic Ratio
- The ratio of the resonance frequency to the magnetic field strength for a given nucleus.
[Chapter 3]
- Imaginary Component
- The component of a signal perpendicular to the real signal.
[Chapter 5]
- Imaging Sequence
- A specific set of RF pulses and magnetic field gradients used to produce an image.
[Chapter 11]
- Inversion Recovery Sequence
- A pulse sequence producing signals which represent the longitudinal magnetization present after the application of a 180
^{o}inversion RF pulse. [Chapter 6 - Inversion Time (TI)
- The time between the inversion pulse and the sampling pulse(s) in an inversion recovery sequence.
[Chapter 6]
- K-Space
- That image space represented by the time and phase raw data. The Fourier transform of k-space is the magnetic resonance image.
[Chapter 5]
- Larmor frequency
- The resonance frequency of a spin in a magnetic field. The rate of precession of a spin packet in a magnetic field. The frequency which will cause a transition between the two spin energy levels of a nucleus.
[Chapter 3]
- Longitudinal Magnetization
- The Z component of magnetization.
[Chapter 3]
- Lorentzian Lineshape
- A function obtained from the Fourier transform of an exponential function.
[Chapter 5]
- Magnitude
- The length of a magnetization vector. In NMR, the square root of the sum of the squares of the Mx and My components,
*i.e.*the magnitude of the transverse magnetization. [Chapter 2] - Magnetic Resonance Imaging (MRI)
- An imaging technique based on the principles of NMR.
[Chapter 11]
- Negative Frequency Artifact
- The appearance of smaller in amplitude peaks in one half of the spectrum which are the mirror image of ones in the opposite half.
[Chapter 8]
- Net Magnetization Vector
- A vector representing the sum of the magnetization from a spin system.
[Chapter 3]
- Nuclear Magnetic Resonance (NMR)
- A spectroscopic technique used by scientists to elucidate chemical structure and molecular dynamics.
[Chapter 1]
- Pixel
- Picture element.
[Chapter 1]
- Precess
- A rotational motion of a vector about the axis of a coordinate system where the polar angle is fixed and the azmuthal angle changes steadily.
[Chapter 3]
- Proportionality Constant
- A constant used to convert one set of units to another.
[Chapter 8]
- Pulse Sequence
- A series of RF pulses and/or magnetic field gradients applied to a spin system to produce a signal whose behavior gives information about some property of the spin system.
[Chapter 4]
- Quadrature Detection
- Detection of Mx and My simultaneously as a function of time.
[Chapter 9]
- Radio Frequency
- A frequency band in the electromagnetic spectrum with frequencies in the millons of cycles per second.
[Chapter 3]
- Raw data
- The Mx and My data as a function of time and/or other parameters in an NMR pulse sequence. This is also called k-space data.
[Chapter 10]
- Real
- The component of a signal perpendicular to the imaginary signal.
[Chapter 2]
- Repetition Time
- The time between repetitions of the basic sequence in a pulse sequence.
[Chapter 6]
- Resonance
- An exchange of energy between two systems at a specific frequency.
[Chapter 3]
- RF Coil
- An inductor-capacitor resonant circuit used to set up B
_{1}magnetic fields in the sample and to detect the signal from the sample. [Chapter 7] - RF Pulse
- A short burst of RF energy which has a specific shape.
- Rotation Matrix
- A matrix used to describe the rotation of a vector.
[Chapter 3]
- Sample Probe
- That portion of the NMR spectrometer containing the RF coils and into which the sample is placed.
[Chapter 7]
- Saddle Coil
- A coil geometry which has two loops of a conductor wrapped around opposite sides of a cylinder.
[RF: Chapter 7]
- Spin
- A fundamental property of matter responsible for NMR and MRI.
[Chapter 3]
- Spin Density
- The concentration of spins.
[Chapter 6]
- Spin-Echo
- An NMR sequence whose signal is an echo resulting from the refocusing of magnetization after the application of 90
^{o}and 180^{o}RF pulses. [Chapter 6] - Spin-Lattice Relaxation
- The return of the longitudinal magnitization to its equilibrium value along the +Z axis.
[Chapter 3]
- Spin-Lattice Relaxation Time ( T
_{1}) - The time to reduce the difference between the longitudinal magnitization and its equilibrium value by a factor of e.
[Chapter 3]
- Spin Packet
- A group of spins experiencing the same magnetic field.
[Chapter 3]
- Spin-Spin Relaxation
- The return of the transverse magnitization to its equilibrium value (zero).
[Chapter 3]
- Spin-Spin Relaxation Time
- The time to reduce the transverse magnetization by a factor of e.
[Chapter 3]
- Sinc Pulse
- An RF pulse shaped like Sin(x)/x.
[Chapter 5]
- Superconduct
- To have no resistance. A perfect superconductor can carry an electrical current without losses.
[Chapter 7]
- T
_{2}* - Pronounced T-2-star. The spin-spin relaxation time composed of contributions from molecular interactions and inhomogeneities in the magnetic field.
[Chapter 3]
- Timing Diagram
- A multiaxis plot of some aspects of a pulse sequence as a function of time.
[Chapter 6]
- Transverse magnetization
- The XY component of the net magnetization.
[Chapter 3]

Copyright © 1997-99 J.P. Hornak.

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