Detector that detects the phase of the signal relative to the phase of a reference oscillator. Phase sensitive detectors are used in MR transmitters (where they form part of the frequency synthesis pathway) and MR receivers (where they are used to down-convert the MR signal to audio-frequencies prior to digitization). This device type includes modulators, demodulators and mixers.

See Quadrature Detector.

Another term for detector, by analogy to broadcast radio receivers. Other terms used for devices of this type include modulators, phase sensitive detector and mixers.

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.

The portion of the MRI equipment that detects and amplifies the RF signals picked up by the receiver coil. Includes a preamplifier, MR signal amplifier, and demodulator. Phase sensitive detectors (electronic device in which the output is dependent on the instantaneous difference in phase between two input signals) are used to down-convert the MR signal to audio-frequencies prior to digitization.

See also MRI Equipment.

The portion of the MRI system that produces the RF current and delivers it to the transmitting coil (antenna). The RF signal produced by the transmitter is used to excite the protons in the imaging volume. Phase sensitive detectors (electronic device in which the output is dependent on the instantaneous difference in phase between two input signals) form part of the frequency synthesis pathway.