Table 4.

Comparison of 2D and 4D flow assessment of PI and mean flow.

Vessel	Subject group	Mean difference (4D – 2D)		Standard deviation of difference
		PI	Mean flow (ml/s)	PI	Mean flow (ml/s)
RMCA	HV	−0.17**	0.72**	0.16	0.72
	P	−0.15***	0.17	0.09	0.50
RACA	HV	−0.14*	0.34*	0.20	0.42
LACA	HV	−0.11	0.35	0.18	0.54
SSS	HV	−0.02	0.46**	0.06	0.44
	P	0.00	0.34*	0.07	0.45
StS	HV	0.03	−0.04	0.15	0.38
	P	−0.03	0.16	0.09	0.24

2D/4D method comparisons of PI and mean flow measurements across intracranial vessels, assessed using paired t-tests and Bland-Altman statistics. *p < 0.05, **p < 0.01, ***p < 0.001. RMCA, right middle cerebral artery; RACA/LACA, right/left anterior cerebral artery; SSS, superior sagittal sinus; StS, straight sinus; HV, healthy volunteers; P, patients (with sporadic small vessel disease).