Application value of phase contrast MR angiography in assessment of the functional posterior communicating artery in patients with posterior circulation ischemia

Objective To investigate the application value of phase contrast MR angiography (PC MRA) in quantitative assessment for the hemodynamic features of functional posterior communicating artery (F-PCoA) in the patients with posterior circulation ischemia (PCI). Methods Data of PC MRA in our Hospital from April 2015 to March 2017 were collected retrospectively. Twenty-six patients (PCI group) were diagnosed as PCI with F-PCoA, and other 25 patients were defined as non-PCI group including 10 patients with F-PCoA (non-PCI group 1) and 15 patients without F-PCoA (non-PCI group 2). The cross-sectional area, mean flux, mean velocity, minimum flux, maximum flux, minimum velocity, and maximum velocity were recorded, and the peak height of flux (maximum flux-minimum flux) and peak height of velocity (maximum velocity - minimum velocity) of basilar artery (BA) were calculated. The subtype, cross-sectional area, mean flux, mean velocity, blood flow direction, and absolute flux of F-PCoA in anterior-posterior direction(sum of both sides)were recorded and analyzed statistically. Results The F-PCoA of 36 cases in PCI group and non-PCI group 1 were divided into three types: type A: the F-PCoA was consistent with anatomical posterior communicating artery (A-PCoA), accounting for 83.3%(30/36 cases); type B: the F-PCoA was not consistent with A-PCoA, accounting for 13.9%(5/36 cases);and type C: a mixed type with the F-PCoA was consistent with A-PCoA in only one side, accounting for 2.8%(1/36 cases). There were no significant differences in the composition of F-PCoA subtype (χ2=0.609, P=0.737) and the absolute flux of F-PCoA in anterior-posterior direction(t=-0.576, P=0.568) between PCI group and non PCI group 1. It could be unidirectional or bidirectional blood flow forasingle F-PCoA during a cardiac cycle. The blood flow direction of bilateral F-PCoA was similar or not in one single case. The obviously main wave peak of the absolute flux curve of F-PCoA in anterior-posterior direction in PCI group were observed. There was a significant difference in the cross-sectional area of BA between non PCI group 1 and 2(t=-2.856, P=0.009), however no significant differences were found in the genders, mean flux, mean velocity, minimum flux, maximum flux, peak height of flux, minimum velocity, maximum velocity, and peak height of velocity of BA. Conclusions PC MRA can be used to quantificationally assess the hemodynamic characteristics of F-PCoA such as flow direction, velocity and flux direction, absolute flux in anterior-posterior direction and morphological changes of F-PCoA, which may provide more information for the PCI diagnosis and treatment. Key words: Brain ischemia; Haemodynamics; Magnetic resonance imaging