Measurements of the radiofrequency field in magnetic resonance coils

Abstract
This design note describes an inexpensive system used to control the radiofrequency field generated by magnetic resonance coils. The device is built around three main modules, a sequencer, a modulator and a phase-sensitive detector. This system permits one to detect the radiofrequency field at each point of the region of interest using a pick-up coil, without the requirement of a magnetic resonance spectrometer. Examples of radiofrequency field distributions obtained at 85 MHz are given.