Accuracy of optical coherence tomography imaging in assessing aneurysmal remnants after flow diversion

Imaging follow-up of unruptured intracranial aneurysms treated with flow diverter: Insights from a French collaborative survey

PURPOSE

The absence of standardized guidelines for imaging follow-up of unruptured intracranial aneurysms treated with flow diverters (FD) results in significant variability across centers. This survey aims to provide a comprehensive overview of current imaging follow-up practices in French academic centers.

METHODS

In April 2024, a 49-question survey was distributed to interventional neuroradiology centers in France through the trainee-led research collaborative network, Jeunes En Neuroradiologie Interventionnelle-Research Collaborative (JENI-RC). The survey covered follow-up protocols for digital subtraction angiography (DSA), magnetic resonance imaging (MRI), and computed tomography (CT), as well as potential modifications for specific cases.

RESULTS

Twenty interventional neuroradiology centers responded to the survey. Most centers (n = 14, 70 %), conducted a single systematic DSA either at 6 or 12 months post-procedure. In most centers (n = 13, 65 %), a second DSA was scheduled only based on the results of the first, specifically in cases of non-occluded aneurysm, intimal hyperplasia, or in-stent stenosis. MRI follow-up varied, with most centers (n = 12, 60 %) performing three MRIs over five years. Only two centers included CT scans in their protocols.

CONCLUSION

This survey highlights the substantial heterogeneity in imaging follow-up protocols for FD-treated unruptured intracranial aneurysms among French academic centers. The findings underscore the urgent need for standardized guidelines to harmonize practices, optimize patient outcomes, and improve resource utilization. Additionally, innovations in FD technology, advancements in MRI sequences, and the advent of photon-counting CT will likely influence follow-up practices in the near future.

Optical Coherence Tomography in Cerebrovascular Disease: Open up New Horizons

Optical coherence tomography (OCT), based on the backscattering or reflection of near-infrared light, enables an ultra-high resolution of up to 10 μm. The successful application of OCT in coronary artery diseases has sparked increasing interest in its implementation in cerebrovascular diseases. OCT has shown promising potential in the atherosclerotic plaque structure characterization, plaque rupture risk stratification, pre-stenting and post-stenting evaluation, and long-term follow-up in extracranial and intracranial atherosclerotic stenosis (ICAS). In hemorrhagic cerebrovascular diseases, OCT plays an important role in the structure evaluation, rupture risk stratification, and healing and occlusion evaluation following initial treatment in intracranial aneurysms (IAs). In this study, we summarized the applications of OCT in the diagnosis, treatment, and follow-up of cerebrovascular diseases, especially in ICAS and IAs. The current limitations and future directions of OCT in the endovascular treatment of cerebrovascular diseases were also discussed.

Imaging of intracranial aneurysms in animals: a systematic review of modalities

Intracranial aneurysm (IA) animal models are paramount to study IA pathophysiology and to test new endovascular treatments. A number of in vivo imaging modalities are available to characterize IAs at different stages of development in these animal models. This review describes existing in vivo imaging techniques used so far to visualize IAs in animal models. We systematically searched for studies containing in vivo imaging of induced IAs in animal models in PubMed and SPIE Digital library databases between 1 January 1945 and 13 July 2022. A total of 170 studies were retrieved and reviewed in detail, and information on the IA animal model, the objective of the study, and the imaging modality used was collected. A variety of methods to surgically construct or endogenously induce IAs in animals were identified, and 88% of the reviewed studies used surgical methods. The large majority of IA imaging in animals was performed for 4 reasons: basic research for IA models, testing of new IA treatment modalities, research on IA in vivo imaging of IAs, and research on IA pathophysiology. Six different imaging techniques were identified: conventional catheter angiography, computed tomography angiography, magnetic resonance angiography, hemodynamic imaging, optical coherence tomography, and fluorescence imaging. This review presents and discusses the advantages and disadvantages of all in vivo IA imaging techniques used in animal models to help future IA studies finding the most appropriate IA imaging modality and animal model to answer their research question.

Correlation between intracranial vertebral artery stenosis diameter measured by digital subtraction angiography and cross-sectional area measured by optical coherence tomography

Background

Intracranial vertebral artery (V4 segment) stenosis quantification traditionally uses the narrowest stenosis diameter. However, the stenotic V4 lumen is commonly irregularly shaped. Optical coherence tomography (OCT) allows a more precise calculation of V4 geometry. We compared the narrowest diameter stenosis (DS), measured by digital subtraction angiography (DSA), with the area stenosis (AS), measured by OCT. We hypothesized that DS is the gold standard for measuring the degree of stenosis.

Methods

Five neuroradiologists evaluated 49 stenosed V4 segments in a blinded protocol. V4 stenosis was measured in millimeters on DSA at its narrowest diameter. OCT was used to estimate the cross-sectional luminal area. We also used automated software to measure DS. Three different angles (anterior, lateral, and oblique views) were used for calculations, and the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and Warfarin–Aspirin Symptomatic Intracranial Disease (WASID) methods were used in all measurements. Spearman’s R values were calculated. Non-linear regression analysis was performed between the DS and AS, with statistically different correlations.

Results

A high correlation was observed between the WASID and NASCET methods to measure DS with observer measurement and automated software. A good correlation was found between DS measured by observers and AS measured by OCT. Non-linear regression analysis showed that only observer measurement using the oblique view and the WASID method could attain statistically significant differences, but it was weak (r=0.389).

Conclusion

Measurement of the narrowest diameter was not a reliable predictor of the cross-sectional area of V4 stenosis. Larger studies are therefore needed to develop a new evaluation system based on V4 stenosis.