Magnetic field mapping.

Homogeneous radiofrequency magnetic fields are necessary for production of high-quality magnetic images and for most forms of magnetic resonance spectroscopy. It is often convenient to map the radiofrequency homogeneity associated with a resonant device by measuring the magnetic image intensity of an aqueous phantom placed within the resonator. The rf field intensity is not related trivially to the magnetic image intensity, and the relationship is different for different image acquisition methods. In this report relationships between rf field intensity and magnetic image intensity are derived and radio-frequency field maps presented for comparison using (1) an rf probe moved about within the resonant volume, (2) spin-echo images, and (3) small tip angle gradient refocused echo images.