TABLE 6:

Change between postcontrast and precontrast vascular signal grades in all segments and regions

Vascular Signal Grade Change	Frequency
Vascular Signal Grade Change	BA	ACA	ICA	M1	M2	P1–P2	P3	Total
	All Vessels
NR to readable	0	0	0	0	1	0	0	1
Two-grade increase	0	1	2	0	2	0	2	7
One-grade increase	0	0	6	4	10	2	3	25
No change	40	39	72	71	63	69	75	429
One-grade decrease	0	0	0	4	4	8	0	16
Two-grade decrease	0	0	0	1	0	1	0	2
Total	40	40	80	80	80	80	80	480
	Only Abnormal Vessels on the Precontrast Angiograms
NR to readable	0	0	0	0	1	0	0	1
Two-grade increase	0	1	2	0	2	0	2	7
One-grade increase	0	0	6	4	10	2	3	25
No change	0	0	0	8	7	0	0	15
One-grade decrease	0	0	0	2	0	0	0	2
Two-grade decrease	0	0	0	0	0	0	0	0
Total	0	1	8	14	20	2	5	50