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.

Quick Overview
Please note that there are different common names for this artifact.

The received radio frequency signal is too strong, parts of the signal get lost by converting from analog to digital, resulting in a washed out image.

Auto-prescanning usually adjusts the amplification at the receiver in a way, that the received signal could be processed without any loss. Else the receiver gain must be corrected manually.

See also Data Clipping Artifact, Artifact Overview and Artifacts Reduction Index.

(Mn-DPDP) This agent, mangafodipir trisodium, is a hepatocyte specific MRI contrast agent. Manganese is very toxic, so it has to be chelated and put in the form of a vitamin B6 analog, which is taken up by normal hepatocytes to some extent.
Teslascan® was developed in the early 1980's, went through clinical trials in the early 1990's, and was approved in 1997. One problem with assessing the efficacy of this agent is the fact that the phase III trials finished in the early 1990's, and the techniques used for MR today are very different from the techniques used almost a decade ago.
This contrast agent shortens the T1 relaxation time. On T1 weighted pictures it makes a normal liver look brighter. Since metastases, for example, do not generally take up this agent, the contrast between the enhancing liver and the non-enhancing lesions will increase on T1 weighted pictures. It does not have much effect on T2 weighted images.