Depending on the type of the RF coil, tuning and matching of the coil is required when the load of the sample has changed between consecutive imaging or spectroscopy studies.

Tuning shifts the resonance frequency of the coil, while matching adapts the impedance of the coil to the impedance of the transmission/reception chain.

Correct tuning and matching reduces the reflection of RF power during transmission and increases the sensitivity (SNR) during signal reception. It is therefore most important for the coil receiving the signal and less for the transmission coil in a cross coil configuration.

For transmission coils in a cross coil configuration, a mismatch of the transmission coils results in a small increase in RF power needed without any impact on the image quality, because the RF Reference Power calibration (see ParaVision Manual) is done under the mismatched condition resulting in a higher Reference Power. The power required for the flip angle used in the MR experiment is then calculated based on the Reference Power and therefore, the desired flip-angles are still correct. The latter are of relevance for the MR experiment.

 

Tuning and matching of a RF coil needs to be performed exactly with the sample and setup that is used when scanning. The so called “wobble curve” is displayed on the RF interface display as soon as the wobble process has been started in ParaVision. The example below shows different situations:

 

The following sub-chapters provide the general workflow for the tune procedures of different families of RF coils. Please check the coil-specific user manual for dedicated procedures that are not described in this manual.