| P | phosphorus | |
| PA | pulse angle; → φ | |
| PAT | parallel acquisition technique | |
| PBP | percentage of baseline at peak | |
| PC | phase contrast | |
| PCA | phase-contrast angiography | |
| PC-MRA | phase-contrast MR angiography | |
| PD | proton density; → ρ | |
| PEAR | phase-encoded artifact reduction | |
| PET | positron emission tomography | |
| PFI | partial flip imaging | |
| PILS | parallel imaging with localized sensitivities | |
| PION | poly-crystalline iron oxide nano-compound | |
| pixel | picture element | |
| PPA | partially parallel acquisition | |
| ppm | parts per million | |
| PRESS | point resolved spectroscopy | |
| PRESTO | principle of echo shifting with train of observation | |
| PS | [1] partial saturation; [2] presaturation | |
| PSIF | reverse fast imaging with steady precession | |
| PW-MR | pulsed wave magnetic resonance | |
| SAR | (1) specific absorption rate (2) saturation recovery single shot acquisition | |
| SAPPHIRE | saturation pulse prepared heart rate independent inversion recovery | |
| SASHA | specific absorption rate | |
| SE | spin echo | |
| SE-CSI | spin-echo chemical shift imaging | |
| SENSE | sensitivity encoding | |
| S-GRE | spoiled gradient echo | |
| SI | signal intensity | |
| ShMOLLI | shortened modified LL IR technique | |
| SHORT | short repetition technique | |
| SMASH | (1) short minimum-angle shot; (2) simultaneous acquisiton of spatial harmonics | |
| SNR (S/N) | signal-to-noise ratio | |
| SPECT | single-photon emission computed tomography | |
| SPGR | spoiled gradient-recalled | |
| SPIO | superparamagnetic iron oxide (nanoparticles) | |
| SR | saturation recovery (better: PS - partial saturation) | |
| SS | steady state | |
| SSFP | steady-state free precession | |
| STAGE | small tip angle gradient echo | |
| STAGE:T1W | small tip angle gradient echo: T1-weighted | |
| STAR | signal targeting with alternating radiofrequency | |
| STEAM | stimulated echo acquisition mode | |
| STEP | stimulated echo progressive imaging | |
| STERF | steady-state technique with refocused free induction decay | |
| STEV | stimulated echo volumetry | |
| STIR | short TI inversion recovery | |
| SVS | single voxel spectroscopy | |