introduction

Revascularization is a common treatment strategy in patients with intra-extracranial symptomatic arterial occlusive disease1. Conventional digital subtraction angiography (DSA) is the gold standard reference for evaluating patients with intracranial vasculopathy and is an invasive technique. Four-dimensional (4D) MR angiography (MRA) based on pseudocontinuous ASL (pCASL) combined with the keyhole and view-sharing techniques (4D-PACK) as a nonenhanced method provides better visualization of peripheral arteries compared with dynamic contrast-enhanced MRA in patients with moyamoya disease not treated by surgery2, 3. This study aimed to assess and compare the visualization of bypass patency and intracranial collaterals from the external carotid artery (ECA) by 4D-sPACK versus 3D time-of-flight MRA (3D TOF MRA) in patients with extra-intracranial revascularization. DSA was used as a reference.

Methods

The MRI data of 23 patients who underwent bypass surgery were collected on an Ingenia 3.0T CX scanner (Philips Healthcare, the Netherlands). The image quality of 4D-sPACK was evaluated using a 4-point grading system. Patency of anastomosis was assessed on 4D-sPACK and 3D TOF MRA images using DSA as the gold standard. Visualization of intracranial collateral vessels was assessed with another 4-point grading by two radiologists on the images of 4D-sPACK and 3D TOF MRA using DSA as the reference. The interobserver agreement of intracranial vessel visualization scores was assessed with the weighted kappa statistic.

results

Twenty-seven hemispheres of 22 patients (9 male, age 44 ± 11.72 years) with occlusive intracranial vascular disease were included in the study. The 4D-sPACK images were successfully obtained in 24 (24/27, 88.89%) hemispheres with a higher sensitivity compared with 3D TOF MRA (95.65% vs 78.26%) for visualizing anastomoses. Significant differences were found between 4D-sPACK (scores, 3.10 ± 1.20) and 3D TOF MRA (scores, 1.67 ± 0.62) in the visualization of intracranial collaterals from the ECA obtained using DSA as a reference (P < 0.001). The interobserver agreement for intracranial collateral assessment was almost substantial for 4D-sPACK (kappa = 0. 719) and 3D TOF MRA (kappa = 0.801).

conclusion

The 4D-sPACK provided better performance than 3D TOF MRA in the treatment evaluation of patients after bypass surgery, and it had high consistency with DSA. Hence, 4D-sPACK could serve as a novel noninvasive method to visualize flow dynamics when labeling the ECA and to evaluate the patency of anastomoses and intracranial collaterals in patients with bypass surgery.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (81720108022 B.Z., 81971596, X.Z., 82071904, Z.Q.); Supported by the Fundamental Research Funds for the Central Universities, Nanjing University (2020-021414380462); The key project of Jiangsu Commission of Health (K2019025); Key medical talents of the Jiangsu province, the "13th Five-Year" health promotion project of the Jiangsu province (ZDRCA2016064); Jiangsu Provincial Key Medical Discipline (Laboratory) (ZDXKA2016020); the project of the sixth peak of talented people (WSN -138).