Tuning Into the Heart
Having a magnet is not enough. To get information out of the heart, we must give energy to the protons. We do this using a B₁ Field (an RF pulse).
The Tuning Rule
Energy only transfers from the pulse to the protons if their frequencies match exactly. This is Resonance. Think of it like pushing a child on a swing—you must push at the exact right moment to build momentum.
In clinical scanning, the "Radio Station" (Larmor Frequency) for a 1.5T magnet is ~63.9 MHz. For a 3.0T magnet, it's ~127.8 MHz.