The _________ is defined as the resonant frequency, and is equal to the product of the magnetic field and the gyromagnetic ratio.

The precessional frequency is indeed defined as the resonant frequency in magnetic resonance imaging (MRI) and is equal to the product of the magnetic field strength and the gyromagnetic ratio. This frequency is crucial because it determines how nuclei, like hydrogen protons, will precess when placed in a magnetic field.

In the context of MRI, the precessional frequency allows for the tuning of RF pulses to excite nuclei at the correct frequency so that images can be acquired. The gyromagnetic ratio is a unique constant for each type of nucleus, reflecting how strongly it interacts with magnetic fields. When multiplied by the strength of the applied magnetic field, this ratio gives the precise frequency at which the nuclei will resonate, enabling effective imaging based on their response to magnetic fields.

Understanding precessional frequency is fundamental to MRI technology, guiding not only how images are formed but also impacting sequence design, timing, and the specific interactions leveraged to distinguish between different types of tissue.