Magnetic Resonance Imaging (MRI)
A non-invasive medical imaging modality utilizing powerful magnetic fields, radiofrequency (RF) pulses, and nuclear magnetic resonance (NMR) of hydrogen protons to image soft tissue.
Governing formula
Larmor Frequency ν₀ = (γ / 2π) B₀ (γ_proton ≈ 42.58 MHz/T)
SI unit
Tesla B₀ (~1.5–3.0 T) & MHz
In depth
Proton spins align in strong static magnetic field B₀. Resonant RF pulses tip proton magnetization; as spins relax back (T1 longitudinal and T2 transverse relaxation times), they emit RF signals detected by receiver coils, reconstructed into high-contrast soft tissue 3D images.
Examples in the real world
Brain MRI scans differentiating grey matter, white matter, and brain tumors based on T1 and T2 relaxation time differences.