Clinical utility of intravascular ultrasound in brachiocephalic artery stenting

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Introduction

Cerebrovascular diseases remain leading causes of death and permanent disability worldwide [1]. A significant proportion of ischemic strokes — 15–40% according to various estimates — are attributable to atherosclerotic lesions of the brachiocephalic arteries (internal carotid arteries (ICAs) and vertebral arteries (VAs)), mediated by atherothrombosis, artery-to-artery embolism, and hemodynamic insufficiency [2]. In addition to adequate medical therapy (antiplatelet, lipid-lowering, etc.), prevention of cerebral ischemia in patients with significant ICA/VA stenosis widely includes revascularization techniques: carotid endarterectomy (CEA) and carotid angioplasty with stenting (CAS) [3].

Large randomized trials have demonstrated comparable long-term outcomes of CAS and CEA for stroke prevention (5.2% for CAS vs. 4.5% for CEA). However, CAS is associated with a slightly higher rate of periprocedural stroke (4.1% vs. 2.3%), while CEA has a higher rate of myocardial infarction (1.1% vs. 2.3%) [4]. Data from the recently completed CREST-2 trial indicate a lower early postoperative stroke rate after CAS (2.8%) compared to CEA (3.7%) [5]. Nevertheless, embolic complications during endovascular procedures remain a concern. A substantial proportion of patients undergoing carotid stenting show new ischemic lesions on MRI (including clinically silent lesions) compared to those undergoing open surgery [6, 7]. The ICSS-MRI study reported that new ischemic lesions on diffusion-weighted imaging were found in 50% of patients after CAS, compared to 17% after CEA — a threefold higher rate [8]. In other studies, the rate of acute silent ischemic lesions after CAS with embolic protection was 14.89%, with 8.51% located directly in the territory of the treated artery [9]. Moreover, cerebral ischemic events may occur not only intraoperatively but also in the early weeks after the procedure, often due to in-stent thrombosis or embolization of unstable plaque fragments [4]. According to the CREST trial, more than half of all ipsilateral strokes over the 10-year follow-up occurred within the first month after the procedure [10]. Therefore, improving plaque visualization and embolic risk assessment during endovascular intervention is a promising avenue for enhancing the safety of brachiocephalic artery stenting.

In the current paradigm of angioneurology, there is a gradual shift from isolated angiographic assessment of stenosis severity toward comprehensive plaque morphology analysis — both as a diagnostic and prognostic marker for cerebral ischemia and as a potential tool for validating the quality of revascularization techniques. The modern portfolio for imaging atherosclerotic lesions in cerebral arteries includes duplex ultrasound, computed tomography, magnetic resonance imaging, and digital subtraction angiography — the intraoperative gold standard.

Detailed assessment of plaque morphology — ulceration, lipid core, thin fibrous cap — is crucial for predicting embolic complications [11, 12]. However, standard angiography and non-invasive methods do not always reliably identify unstable plaques and often yield errors in stenosis measurement, as confirmed by the CARUS study [13–15]. This issue is particularly pronounced in vertebral artery lesions due to bone overlap [12].

Intravascular ultrasound (IVUS) offers an optimal solution, providing accurate assessment of plaque anatomy and composition. To standardize these data and stratify risk, the PLAQUE-RADS classification is now being actively implemented. A comparative overview of the main cerebrovascular atherosclerosis imaging modalities is presented in Table 1.

 

Table 1. Comparative characteristics of carotid plaque imaging modalities*

Parameter/Imaging modality	Digital subtraction angiography	Duplex ultrasound	High-resolution MRI	IVUS
Stenosis grading	++	+	+	+++
Plaque morphology	–	+	+++	+++
Calcium visualization	+	++	+	++
Remodeling assessment	–	–	++	+++
Invasiveness	++	–	–	+++
Resolution, μm	200–500	150–300	300–500	100–150

Note. *Аdapted from Fernández-Alvarez V, Linares-Sánchez M, Suárez C et al. Novel imaging-based biomarkers for identifying carotid plaque vulnerability. Biomolecules. 2023;13(8):1236. DOI: 10.3390/biom13081236

 

IVUS is a procedure in which a miniature ultrasound transducer is introduced into the vascular lumen, providing tomographic (cross-sectional) imaging of the arterial wall from within [16]. In 1988, P.G. Yock et al. first presented an IVUS transducer as a device for intravascular imaging specifically designed for coronary arteries [17]. Since then, IVUS has been used to assess plaque burden, morphology, and vulnerability, improving risk stratification and therapeutic decision-making. Robust evidence demonstrates that IVUS guidance during percutaneous coronary interventions improves long-term outcomes and reduces restenosis and stent thrombosis rates, particularly in complex lesions [13]. While routine IVUS use during percutaneous coronary interventions reaches 80% in some countries (e.g., Japan, South Korea) and is steadily increasing in the US and Europe (approximately 8–9%), this technology remains rarely used in carotid artery stenting (CAS) [18].

In neurointerventional practice, IVUS has been adopted relatively recently but has already shown promise [16]. Studies indicate that angiography-alone guidance is insufficient: IVUS identifies incomplete stent apposition in approximately 10% of patients after post-dilatation and detects plaque protrusion nearly three times more often than angiography (7.8% vs. 2.6%) [6, 7].

The study aims to review the technical capabilities of IVUS, its role at various stages of brachiocephalic artery stenting, and future directions for this technology in stroke prevention.

Technical capabilities of intravascular ultrasound

The imaging principle of IVUS is based on oscillatory motion (expansion and contraction) of a piezoelectric transducer (crystal), which generates sound waves when electrically excited. After reflection from tissues, a portion of the ultrasound energy returns to the transducer, which generates an electrical impulse that is rendered as an image. Currently, two types of IVUS transducers exist: mechanical (rotating) and electronic phased-array. Mechanical systems provide higher image resolution due to high frequencies (40–60 MHz), making them the clinical gold standard (used in approximately 80–90% of cases). However, they are prone to rotation artifacts and require careful flushing. Phased-array systems are easier to use, have no moving parts, and provide stable imaging without rotation artifacts, but they have lower resolution due to lower frequency (20 MHz) and a larger catheter size. The choice depends on the clinical scenario: mechanical systems are preferred for maximum detail, while phased-array systems are better suited for complex anatomy and rapid acquisition of stable data [19].

IVUS is performed using a catheter-based transducer introduced into the arterial lumen and advanced through the stenotic area. Modern IVUS systems use ultrasound frequencies of 20–60 MHz, providing high spatial resolution (approximately 100 μm) with a penetration depth of 5–10 mm, sufficient for evaluating large arteries. The transducer performs 360° rotational scanning, generating real-time cross-sectional images of the vessel. IVUS acquisition and interpretation during CAS takes approximately 8–10 minutes on average, prolonging the overall procedure by 10.3 ± 5.0 minutes according to the literature. Catheter navigation and image acquisition (pre- and post-stent implantation) require 3–5 minutes, with an additional 2–3 minutes for real-time data interpretation. Thus, a standard CAS procedure lasting 1–2 hours is extended to approximately 1 hour 10 minutes to 2 hours 10 minutes with IVUS [20]. Despite this increase, researchers emphasize that the additional time is clinically negligible compared to the benefits of precise intraoperative assessment of plaque morphology, vessel diameter, and stent apposition. Importantly, with operator experience, IVUS time decreases substantially. IVUS images clearly distinguish the lumen, intima, media, and adventitia, as well as atherosclerotic plaques and their components [16]. The method is highly accurate in determining vessel diameter and luminal area, with measurement errors in the order of tenths of a millimeter — substantially surpassing the accuracy of angiographic assessment [13].

Unlike angiography, IVUS allows examination not only of the arterial lumen but also of the atherosclerotic plaque structure itself. On gray-scale IVUS imaging, different tissues exhibit characteristic echogenicity: the soft lipid component typically appears hypoechoic (dark), fibrous tissue is more echogenic, and calcifications appear bright with acoustic shadowing [16]. This enables intraoperative assessment of plaque composition (predominance of lipid core, presence of calcification, fibrous cap, etc.) and signs of instability — thin or ruptured cap, surface ulceration, heterogeneous structure, sub-surface tears — features invisible on standard angiograms during the procedure [15]. An important advantage is the detection of mural thrombi and dissections, which may occur spontaneously or during the intervention. In certain clinical scenarios, IVUS may modify the treatment approach: visualization of a soft, friable plaque with a large thrombotic component during CAS may guide the choice of a stent with smaller cells or double-layer mesh to prevent embolization, while identification of heavy eccentric calcification may prompt aggressive pre-dilatation or use of a specialized balloon [21]. Another tangible benefit is accurate stent and balloon sizing based on precise measurement of lesion diameter and length: several studies report that IVUS before stent implantation changed the initially planned stent size or type in approximately 15–20% of cases [21].

IVUS enables identification of eccentric stenosis and determination of plaque length — in such cases, selecting a stent capable of full expansion along the major axis of the vessel is critical. Thus, at the planning stage, IVUS provides more reliable guidance for stenting strategy, minimizing the risk of incomplete plaque coverage or inadequate stent expansion [21].

During stenting, IVUS can be used for navigation and step-by-step outcome assessment. Post-stent IVUS serves several purposes:

1. Verification of full stent expansion — measurement of the minimum luminal area within the stent, compared with the expected vessel diameter. If a segment with incomplete expansion is detected, additional balloon dilatation is performed (which often increases luminal area by 20–30% on IVUS) [16].
2. Detection of plaque protrusion — penetration of atheromatous material through the stent struts into the lumen. IVUS clearly visualizes such fragments as echogenic structures within the stent lumen. According to studies, plaque protrusion occurs in approximately 5–10% of carotid stenting patients, with most cases undetected by angiography [4]. For example, N. Shinozaki et al. found plaque protrusion on IVUS in 7.8% of patients, compared to only 2.6% on angiography alone [4]. Such complications require additional post-dilatation or placement of a second stent [4]. Appropriate correction of detected protrusion — all cases were resolved by repeat dilatation or stent-in-stent technique — prevented early postoperative strokes in all affected patients [4]. K. Yamada et al. showed that pre-procedural IVUS improves detection of complex plaques and reduces the rate of new lesions on post-operative diffusion-weighted MRI by 25–40% [7, 22].
3. Intraoperative visualization of intimal tears and false lumen formation when carotid artery dissection is suspected [16].

Angiography alone often provides inadequate assessment of stent expansion. In coronary stenting, IVUS-guided optimization of stent expansion is known to significantly reduce restenosis and thrombosis risk, particularly in complex cases [13].

If suboptimal stent expansion is identified, the operator may immediately perform additional high-pressure balloon post-dilatation or place a second "stent-in-stent" to reinforce the result [4]. Similarly, in ostial vertebral artery lesions, IVUS helps differentiate true atherosclerotic stenosis from, for example, extrinsic compression or vessel tortuosity, since in the latter case significant plaque may be absent on intravascular imaging [23]. Thus, by complementing standard angiography, IVUS provides a more comprehensive assessment of the lesion before active manipulation (pre-dilatation, stenting, and post-dilatation).

After all maneuvers, a final IVUS run is performed to confirm optimal stent expansion (minimal residual stenosis), adequate stent apposition, absence of plaque protrusion, and satisfactory flow restoration [16]. Thus, IVUS during carotid or vertebral stenting enables intraoperative detection of the above complications and timely intervention, reducing the risk of both acute and long-term adverse events.

In some cases, IVUS is also used at follow-up to assess stent status. H. Matsumoto et al. used IVUS to monitor neointimal formation (restenosis) in carotid stents, demonstrating varying degrees of intimal hyperplasia at 6 months post-stenting and certain design-related features of different stent types [24]. In 2016, M. Kawasaki et al. showed a 3- to 4-fold reduction in clinically significant restenosis (> 50%) in the IVUS-assisted group [25].

Nevertheless, routine invasive follow-up after stenting is not standard practice; duplex ultrasound remains the standard of care.

For in-depth analysis, advanced IVUS modalities are available. For example, virtual histology IVUS (VH-IVUS) performs computer-based classification of echo signals and color-codes the image according to tissue type (fibrous, fibro-fatty, lipid core, calcium) (Table 2; Fig. 1) [26, 27]. This method has shown good correlation with native histology — overall accuracy for predicting plaque composition was 93.5% for fibrous tissue, 94.1% for fibro-fatty tissue, 95.8% for necrotic core, and 96.7% for calcified areas, with sensitivity and specificity ranging from 72% to 99% [21]. Thus, real-time (intraoperative) IVUS provides valuable information on atherosclerotic plaque morphology in situ.

 

Table 2. Comparative characteristics of histological examination and VH-IVUS color classification (adapted from [26])

Tissue type	Histology of plaques using Movat's pentachrome stain	VH-IVUS color
Fibrous	Densely packed collagen	Dark green
Fibro-fatty	Collagen with interspersed lipids	Light green
Necrotic core	Foam cells, cholesterol clefts, and microcalcifications	Red
Calcium	Calcific deposits without necrosis	White

 

Fig. 1. Schematic of VG-IVUS (A) and VG-IVUS image (B), adapted from [26].

 

Of note, the largest body of evidence on IVUS efficacy has been accumulated for carotid artery stenting, while experience with vertebral artery stenosis is described in isolated reports. Nevertheless, the principles are similar: in ostial VA stenting, IVUS allows accurate measurement of the ostial diameter (often differing from angiographic estimates), determination of plaque length, and post-stent verification of full expansion and absence of dissection at the proximal edge in the subclavian artery [28]. Another report describes spontaneous VA dissection: IVUS-guided stenting confirmed correct coverage of the dissection site and the true lumen [28]. These examples highlight the potential diagnostic value of IVUS in treating extracranial arteries of various locations.

Overall, IVUS during brachiocephalic artery stenting significantly enhances procedural information and safety. IVUS enables precise pre-procedural assessment of lesion anatomy, facilitates optimal stent implantation, prevents technical complications, and confirms a satisfactory final result. In other words, this technology supports decision-making at all stages of CAS: preoperatively — in assessing wall pathology and plaque nature; intraoperatively — in visualizing dissections, protrusions, and stenosis morphology; and postoperatively — in confirming stenting success [16]. Ultimately, this is aimed at reducing the risk of stroke — both procedure-related and stent-related [6]. Although IVUS increases the cost of the procedure, cost-effectiveness analyses indicate that preventing even one severe periprocedural stroke or repeat revascularization for restenosis is economically justified, particularly given the substantial burden on healthcare systems [29–32].

Conclusion

Stenting of extracranial arteries is an effective method for preventing ischemic stroke, but its success largely depends on procedural precision and imaging quality. IVUS provides a direct "inside-out" view of the atherosclerotic plaque and the vessel wall, enabling accurate measurement of diameter and stenosis area, determination of plaque structure and stability, confirmation of complete lesion coverage by the stent, timely detection of dangerous complications (plaque protrusion, dissection, incomplete stent expansion), and immediate correction. IVUS facilitates a transition from a standard protocol to a personalized approach. Numerous clinical observations confirm that IVUS use improves stenting quality and may reduce embolic complications. Its role spans all stages — from preoperative diagnosis to outcome control — making it a versatile tool for the X-ray endovascular surgeon. The main barriers to broader adoption are economic and educational. Standardized protocols for IVUS image interpretation in the brachiocephalic territory, along with training programs for endovascular surgeons, need to be developed and validated. A key step toward definitive acceptance will be the results of large multicenter randomized trials evaluating the impact of IVUS on endpoints — death and stroke.

IVUS implementation has already provided new insights into complication mechanisms, revealing a much higher frequency of plaque protrusion than previously estimated by angiography, and has stimulated refinements in carotid stenting technique. Future directions include integration with other modalities (3D imaging, combined catheters) and the use of artificial intelligence for automated analysis — all of which could make the procedure safer and more predictable. At present, recommendations for routine IVUS in carotid and vertebral stenting are still evolving, but it is already clear that in complex cases the technology provides tangible benefit. With increasing equipment availability and growing operator experience, wider adoption of IVUS-guided navigation in endovascular surgery can be expected. An ideal algorithm would be: ultrasound screening → plaque MRI for preoperative risk stratification and planning → IVUS navigation during the procedure → follow-up ultrasound. Each modality occupies its niche in the diagnostic pathway. Thus, IVUS has proven itself as a potential tool for enhancing the efficacy and safety of brachiocephalic artery stenting. Further implementation of IVUS is an important step toward reducing stroke risk and improving outcomes in patients with cerebrovascular disease.

About the authors

Vladislav A. Annushkin

Russian Center of Neurology and Neurosciences

Author for correspondence.
Email: annushkin@neurology.ru
ORCID iD: 0000-0002-9120-2550

Cand. Sci. (Med.), Researcher, 1st Neurology Department, Institute of Clinical and Preventive Neurology

Russian Federation, Moscow

Anton A. Raskurazhev

Russian Center of Neurology and Neurosciences

Email: annushkin@neurology.ru
ORCID iD: 0000-0003-0522-767X

Cand. Sci. (Med.), Senior Researcher, 1st Neurology Department, Institute of Clinical and Preventive Neurology

Russian Federation, Moscow

Ivan A. Sinitsyn

Russian Center of Neurology and Neurosciences

Email: annushkin@neurology.ru
ORCID iD: 0000-0001-6862-6980

Interventional Radiologist, Department of X-Ray Surgical Methods of Diagnostics and Treatment, Institute of Functional Surgery

Russian Federation, Moscow

Vladimir L. Shchipakin

Russian Center of Neurology and Neurosciences

Email: annushkin@neurology.ru
ORCID iD: 0000-0003-1428-2769

Cand. Sci. (Med.), Head, Department of X-Ray Surgical Methods of Diagnostics and Treatment, Institute of Functional Surgery

Russian Federation, Moscow

Victor A. Lukyanchikov

Russian Center of Neurology and Neurosciences

Email: annushkin@neurology.ru
ORCID iD: 0000-0003-4518-9874

Dr. Sci. (Med.), Deputy Director, Institute of Functional Neurosurgery

Russian Federation, Moscow

Мarine M. Tanashyan

Russian Center of Neurology and Neurosciences

Email: annushkin@neurology.ru
ORCID iD: 0000-0002-5883-8119

Dr. Sci. (Med.), Professor, Full Member of the RAS, Head, 1st Neurology Department, Deputy Director for Science

Russian Federation, Moscow

References

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