slew rate
Rate at which the MR gradient field changes, measured in T/m/s. Defines how fast the gradient can switch between values within a pulse sequence. Paired with gradient strength (mT/m) as the two physics specs that bound advanced-application capability on a given platform.
Why it matters to buyers: Higher slew rate = faster echo-planar imaging (DWI, fMRI), better cardiac gating, shorter exam times, finer diffusion-encoding capability. Slew rate plus gradient amplitude together determine whether the platform can run high-end neuro applications cleanly. Typical tiers: 100–125 T/m/s on 1.5T workhorse, 150–200 T/m/s on premium 3T, 200+ on research.
Why it matters to engineers: Limited by peripheral nerve stimulation (PNS) thresholds — can't just turn slew rate up indefinitely without exceeding regulatory limits on dB/dt. Gradient amplifier (GPA) duty cycle and gradient-coil cooling are the practical limits in service. Exceeding duty cycle cooks the amplifier or coil.