(TD) The difference in time between radio frequency spin echo (TER) and gradient echo (TE) when the RF and gradient echoes are not coincident.

The coil of the RF transmitter, inside the MR imager is used in excitation of the spins. Also called transmit-only coil it is used to create the B1 field. As a radio frequency generator send this coil bursts of RF pulses. These pulses serve to disturb the spins in the patient.

Trigonometric functions are mathematical functions of an angle. There are six basic trigonometric functions (Sine (sin), Cosine (cos), Tangent (tan), Cotangent (cot), Secant (sec), Cosecant (cosec)), commonly defined as ratios of two sides of a right triangle. Used in MRI for Cartesian sampling, to describe radio frequency signals, etc.

Radio frequency coil that surrounds either the whole body, or one specific region, such as the head or a knee. Volume coils have a better RF homogeneity than surface coils, which extends over a large area. The most commonly used design is a (birdcage) bird cage coil. This consists of a number of wires running along the z-direction, arranged to give a cosine current variation around the circumference of the coil. It is possible to use the same coil to transmit and receive, or to use two separate coils. The largest volume coil, the body coil is typically a transmit and receive coil. If two separate coils are used, works the body coil as the transmitter and a smaller coil as the receiver.

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

Pacemaker lead wires, ECG, and plethysmographic cables can also as surface-coil connections act as antennae. Usually the materials of such wires are not ferromagnetic.

Gradient and radio frequency fields may induce current into these wires and thus cause fibrillations and burns. This presents a risk to the patient and must be eliminated before the examination. The risk of heating during the MRI scan is dependent on the length and the material of these wires as well as the used field strength. If these wires are outside the RF field there is no risk of heating to expect.