Amide proton transfer-weighted magnetic resonance imaging for the diagnosis of symptomatic chronic intracranial artery stenosis: a feasibility study

Background: Hemodynamic changes after intracranial artery stenosis (ICAS) or occlusion are important causes of metabolic alterations in tissue. This study aimed to explore the feasibility of using amide proton transfer-weighted (APTw) magnetic resonance imaging (MRI) to diagnose patients with symptomatic chronic ICAS based on pH variations caused by metabolite damage. Methods: Sixty-seven patients with clinically confirmed unilateral anterior circulation ICAS (& GE;70% arterial narrowing) and 20 healthy volunteers were recruited for the study. Each patient underwent an MRI examination including a T2 fluid-attenuated inversion recovery (T2-FLAIR) sequence, spin-echo echo-planar diffusion-weighted imaging (DWI), three-dimensional pseudo-continuous arterial spin labeling (pcASL), and an APTw sequence. Areas with abnormal perfusion and APTw effects were defined as perfusion/ pH matched areas; areas with abnormal perfusion but normal APTw effects were defined as perfusion/pH unmatched areas; the contralateral mirror areas were defined as the normal areas. Regions of interest (ROIs) were selected within these three areas, and the corresponding apparent diffusion coefficient (ADC), cerebral blood flow (CBF), and magnetization transfer ratio asymmetry (MTRasym) were measured. Results: High intraclass correlation coefficient (ICC) values (0.78 <_ ICCs <_0.97; P < 0.05) were observed between the two radiologists who independently performed the data analysis. Significant differences were found in CBF and MTRasym between the perfusion/pH matched, perfusion/pH unmatched, and normal areas [F(2,64)=288.5, 163.5; both P < 0.05], but the ADC values were comparable between the three [F(2,64)=2.11; P > 0.05]. Spearman correlation analysis revealed no significant correlation between changes in MTRasym and CBF (P > 0.05). Finally, APTw showed a robust performance in diagnosing symptomatic chronic ICAS, with an area under the receiver operating characteristic curve (ROC) of 0.953 (sensitivity 97.01%; specificity 85.07%; cut-off value 1.005%). Conclusions: The present study has demonstrated that metabolic alterations are present in patients with symptomatic chronic ICAS. Our findings illustrate that APTw imaging could potentially serve as an effective method to provide a robust clinical diagnosis for patients with symptomatic chronic ICAS.