Photon-counting CT for Intracranial Stent Assessment

Intracranial atherosclerotic stenosis is one of the major causes of ischemic stroke worldwide. Percutaneous transluminal angioplasty and stenting (PTAS) has been widely applied for selected patients with severe intracranial arterial stenosis. Long-term surveillance after stent implantation is important because in-stent restenosis, incomplete stent expansion, incomplete stent apposition, and other stent-related abnormalities may affect clinical outcomes.

Digital subtraction angiography (DSA) is currently considered the reference standard for evaluating intracranial stent patency. However, DSA is an invasive examination requiring arterial catheterization and carries risks including vascular complications and radiation exposure. Therefore, a reliable noninvasive imaging method for intracranial stent follow-up is clinically desirable. Conventional energy-integrating detector CT angiography (EID-CTA) may be limited in intracranial stent evaluation because of metal-related artifacts, particularly blooming artifact and beam-hardening effects.

Photon-counting detector CT (PCD-CT) represents a new generation of CT technology with improved spatial resolution, reduced electronic noise, and enhanced material separation capabilities. Ultra-high-resolution PCD-CT angiography may overcome limitations of conventional CTA and improve visualization of intracranial stent structures.

This prospective observational diagnostic study will include patients with intracranial arterial stents who undergo follow-up UHR PCD-CTA examinations. For patients who undergo DSA within a predefined interval, the findings of UHR PCD-CTA will be compared with DSA.

The results of this study may help determine the clinical value of UHR PCD-CTA as a noninvasive alternative or complementary imaging method for intracranial stent surveillance.

Inclusion criteria

• Age ≥18 years;
• Patients with previously implanted intracranial arterial stents;
• Undergoing follow-up CTA examination;
• Available imaging data for analysis.

Exclusion criteria

• Severe motion artifacts;
• Poor contrast enhancement;
• Incomplete clinical or imaging data.