In an MRI scan, a higher magnetic field requires higher frequency radio waves to resonate with the nuclear type whose density and location is being imaged. What effect does going to a larger magnetic field have on the most efficient antenna to broadcast those radio waves? Does it favor a smaller or larger antenna?

Magnetic field lines are never crossed. The strength of the field is determined by the density of the field lines.

The patient is enveloped by a magnetic field during an MRI scan. As we all know, water includes hydrogen atoms and is abundant in the human body. When a hydrogen atom is put in a magnetic field, it produces radio-frequency pulses because hydrogen acts as a proton.

A different source of the magnetic field is used to change the field. And energy is created when hydrogen is relaxed. This energy is transformed into a picture. The secondary magnetic field in this case adjusts with time as needed. As a result, for a better image, the radio frequency should be consistent.

In this case, a bigger antenna is chosen over a smaller antenna for better transmission.

Therefore, it is preferable to have a larger antenna.