The goal of this clinical trial is to learn whether a coated flow diverter leads to fewer in-stent narrowings (in-stent stenosis) than an otherwise identical uncoated flow diverter when used to treat intracranial aneurysms in routine clinical care. The main questions it aims to answer are:

Does the coated flow diverter reduce the rate and severity of in-stent stenosis compared with the uncoated flow diverter?

Are there differences in angiographic aneurysm occlusion and procedure-related complications between the two devices?

Researchers will compare treatment with the coated flow diverter (Derivo 2 heal) to the uncoated flow diverter (Derivo 2).

Participants will:

Receive endovascular treatment of their intracranial aneurysm with one of the two flow diverters assigned by randomization

Receive standard antiplatelet medication and follow-up imaging as part of routine care

This investigator-initiated, prospective, single-center randomized clinical study compared a surface-modified flow diverter (Derivo 2 heal; Acandis, Germany) with the corresponding uncoated device (Derivo 2) in the endovascular treatment of unruptured saccular internal carotid artery (ICA) aneurysms in routine clinical care. After confirmation of eligibility and written informed consent, patients were randomized in a 1:1 ratio to receive either the coated or uncoated flow diverter using a computer-generated permuted block randomization scheme with variable block sizes. Allocation concealment was ensured using sequentially numbered, opaque, sealed envelopes prepared by an independent study coordinator. Device diameter and length were selected according to a predefined institutional sizing standard based on angiographic measurements, independent of treatment allocation.

All procedures were performed under general anesthesia via a transfemoral approach using standard technique. No adjunctive coiling and no balloon angioplasty were performed. All participants received dual antiplatelet therapy with aspirin 100 mg/day and clopidogrel 75 mg/day initiated at least 3 days before the procedure and continued for at least 12 months; platelet function testing was not routinely performed.

Angiographic follow-up was scheduled at 3 and 9 months using digital subtraction angiography (DSA). In-stent stenosis (ISS) was defined as a segmental reduction of the contrast-filled parent vessel lumen within the stented segment compared with the immediate post-procedural angiogram. Because absolute calibration is limited in 2D projection imaging, ISS severity was assessed using a standardized ratio-based approach: the vessel diameter at the site of maximal stenosis was related to a reference segment in the petrous ICA, and the resulting ratio was compared with the corresponding ratio on the immediate post-procedural angiogram to quantify relative luminal narrowing over time. For descriptive purposes, high-grade ISS (>50%) was recorded. In addition, ISS was morphologically categorized as stenosis associated with visible stent deformation (e.g., focal flattening, incomplete expansion, segmental collapse, fish-mouth configuration) versus stenosis without visible deformation, the latter interpreted as predominantly related to intimal hyperplasia.

Aneurysm occlusion was assessed on follow-up DSA using the O'Kelly-Marotta (OKM) grading scale. Complete occlusion was predefined as OKM grade D (no residual aneurysm filling). Clinical events and adverse events were prospectively recorded during the periprocedural period and follow-up visits.

The primary objective was to compare the incidence and severity of ISS between the coated and uncoated flow diverter groups over time. Secondary objectives included comparison of aneurysm occlusion rates and evaluation of relationships between angiographic outcomes and device- or vessel-related factors.

Inclusion Criteria:

• Adults aged ≥18 years
• Unruptured, saccular aneurysm of the internal carotid artery (ICA) suitable for single-device flow diverter treatment
• Availability of angiographic follow-up imaging at both 3 and 9 months

Exclusion Criteria:

• Fusiform or dissecting aneurysms
• Requirement for multiple flow diverter implantation
• Previous treatment of the target aneurysm
• Contraindications to dual antiplatelet therapy

Individual participant data will not be shared due to local data protection regulations and because participant consent did not include public sharing of individual-level clinical and imaging data. Aggregated results will be reported in publications.