Vessel-selective 4D MRA based on ASL might potentially show better performance than 3D TOF MRA for treatment evaluation in patients with intra-extracranial bypass surgery: a prospective study

Objectives To compare bypass patency and intracranial collaterals from the external carotid artery (ECA) by four-dimensional MR angiography (MRA) based on super-selective pseudo-continuous arterial spin labeling (pCASL) combined with the keyhole and view-sharing techniques (4D-sPACK) versus three-dimensional time-of-flight (3D TOF) MRA in patients with extra-intracranial revascularization. Methods The MR data of 45 patients administered bypass surgery were collected. The image quality of 4D-sPACK was evaluated using a 4-point grading system according to whether the diagnosis of intracranial collaterals was affected. Anastomosis patency and intracranial collateral visualization from ECA were assessed by two radiologists on 4D-sPACK and 3D TOF MRA, with digital subtraction angiography (DSA) findings as reference. Intracranial collateral assessment employed another 4-point grading system according to the number of vessels shown. Interobserver agreement was assessed with the weighted kappa statistic. Results Fifty hemispheres in 43 patients were included. The image quality of 4D-sPACK was good in 47 (47/50, 94.0%) hemispheres. 4D-sPACK had a higher sensitivity than 3D TOF MRA (97.73% vs 79.55%) for visualizing anastomoses. There were significant differences between 4D-sPACK (scores, 3.22 ± 1.15) and 3D TOF MRA (scores, 1.80 ± 0.67) in the visualization of intracranial collaterals from ECA ( p