Table 2.

Definitions of perfusion metrics

Metric	Definition	Unit
Ingress
${\mathrm{I}}_{\max }$	Maximum intensity	AU
Onset	Time when intensity exceeds 5% of maximum	s
Rise time	Time from 10% to 90% of maximum	s
Inflow slope	Rate of intensity increase (10%–90%)	AU/s
TTP	Time from onset to maximum	s
${\mathrm{T}}_{1/2}$	Time from onset to 50% of maximum	s
${\mathrm{AUC}}_{50\%}$	Area under curve from onset to 50% of maximum	AU
${\mathrm{AUC}}_{100\%}$	Area under curve from onset to maximum	AU
Egress
${\mathrm{T}}_{80\%}$	Time to drop from maximum to 80%	s
Outflow slope	Rate of intensity decrease (max $\to$ 80%)	AU/s
${\mathrm{I}}_{\mathrm{end}}$	Relative intensity at end of recording	AU
Perfusion indices
TR	${\mathrm{T}}_{1/2}$/TTP	/
Inflow/Outflow ratio	Inflow slope/Outflow slope	/