Table 1:

Assessment criteria for vessel type seen during intravascular injection

Score	Vessel	Suggestive Features
5	Definite vein	Flow into a specific, anatomically identifiable venous structure
4	Probable vein	Flow into region of known venous structure, flow predominantly away from spinal canal, delayed washout
3	Indeterminate	Not meeting criteria for other categories
2	Probable artery	Flow into region of known arterial structure, flow predominantly toward the spinal canal, rapid washout
1	Definite artery	Flow into a specific, anatomically identifiable arterial structure