Gradient, PNS and SAR constraints

The checks in pypulseqpp.safety evaluate a finished sequence against stated limits and models. They are design-time estimates. They do not replace the scanner’s own gate before download, nor its hardware monitor during the scan, and they do not establish patient safety.

Checks

Check	Compares	Needs
Gradient amplitude	the largest per-axis gradient amplitude	max_grad from the system limits
Slew rate	the largest per-axis slew rate within a block	max_slew and the gradient raster from the system limits
Gradient continuity	the amplitude step across each block boundary	max_slew and the gradient raster from the system limits
Peripheral nerve stimulation	a nerve model’s response to the slew of each axis	a SAFE or chronaxie model
Mechanical resonance	the windowed gradient amplitude spectrum	a forbidden-band table
Specific absorption rate	window-averaged local and global SAR	virtual observation points, a drive calibration and SAR limits

The first five checks are gradient-derived and evaluate the physical gradient axes; the SAR check is RF-derived and evaluates the RF waveforms and shims. The frames, report units and evaluation intervals common to the checks are in Check conventions.