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Quadrature CoilInfoSheet: - Coils -
etc.MRI Resource Directory:
 - Coils -
A coil that produces an RF field with circular polarization. The RF power received from the RF power amplifier comes in two signals (quadrature detection), which have a phase difference of 90°. The RF transmit coil converts the power into a circularly polarized RF magnetic field.
Quadrature coils can be used as both, transmit and/or receive coil. When used as a transmitter coil a factor of two power reduction over a linear coil results; as a receiver an increase in SNR of up to a factor of √2, can be achieved.

See also the related poll result: '3rd party coils are better than the original manufacturer coils'

• View the DATABASE results for 'Quadrature Coil' (2).Open this link in a new window

Further Reading:
  News & More:
Thursday, 26 August 1999   by    
Tech Spotlight: How to calibrate an MRI RF amplifier
Saturday, 1 December 2012   by    
Quadrature Detection
Quadrature detection is used in magnetic resonance imaging as well as in Doppler ultrasound and is also called quadrature demodulation or phase quadrature technique.
With this phase sensitive demodulation technique the complex demodulated signal is separated into two components. One is called the real channel; the second part is called the imaginary channel and is located 90° away from the real channel. The signals from both channels are combined to produce a single set of quadrature detected real and imaginary spectra. In MRI, the parts of the demodulated MR signal are further processed by Fourier transformation analysis. All information on the MR signal components e.g. amplitude, phase, and frequency is given by this quadrature detection combined with Fourier analysis.

• View the DATABASE results for 'Quadrature Detection' (2).Open this link in a new window

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Quadrature Detector
The quadrature detector is a part of the receiver that converts the high-frequency MRI signal to a lower frequency. This phase sensitive detector or demodulator detects the components of the signal in phase with a reference signal and 90° out of phase with the reference signal. The modulated signal contains i.e. the frequency range across the field of view encoded by the frequency encoding gradient. This may be performed by either analog or digital means.

• View the DATABASE results for 'Quadrature Detector' (7).Open this link in a new window

Quadrupole ArtifactInfoSheet: - Artifacts -
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
Quick Overview

Artifact Information
NAME Quadrupole artifact
DESCRIPTION Signal loss, intensity variations
REASON B1 disturbance

Fat suppression (SPIR or FatSat) is very critical to the magnetic field homogeneity. Eddy currents in the patient results in B1 disturbance from left to right and from anterior to posterior. The artifact is seen as signal intensity variations with SPIR, like a signal intensity loss diagonal in the image. The short T1 inversion recovery (STIR) sequence is due to another type of fat suppression insensitive to this artifact.

Image Guidance
Take short T1 inversion recovery (STIR) instead spectral presaturation inversion recovery (SPIR) for fat suppression.
Quadrupole Moment
A measure of the non-spherical distribution of electrical charge possessed by nuclei with a nuclear spin number greater than 1/2. The resulting interaction with electric field gradients in the molecule can lead to a shortening of relaxation times and a broadening of spectral lines.
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