Frequency-domain optical coherence tomography assessment of very late vascular response after carotid stent implantation

A neurovascular high-frequency optical coherence tomography system enables in situ cerebrovascular volumetric microscopy

Intravascular imaging has emerged as a valuable tool for the treatment of coronary and peripheral artery disease; however, no solution is available for safe and reliable use in the tortuous vascular anatomy of the brain. Endovascular treatment of stroke is delivered under image guidance with insufficient resolution to adequately assess underlying arterial pathology and therapeutic devices. High-resolution imaging, enabling surgeons to visualize cerebral arteries' microstructure and micron-level features of neurovascular devices, would have a profound impact in the research, diagnosis, and treatment of cerebrovascular diseases. Here, we present a neurovascular high-frequency optical coherence tomography (HF-OCT) system, including an imaging console and an endoscopic probe designed to rapidly acquire volumetric microscopy data at a resolution approaching 10 microns in tortuous cerebrovascular anatomies. Using a combination of in vitro, ex vivo, and in vivo models, the feasibility of HF-OCT for cerebrovascular imaging was demonstrated.

Optical Coherence Tomography for Intracranial Aneurysms: A New Method for Assessing the Aneurysm Structure

BACKGROUND

There is a lack of precise methods for predicting the risk of aneurysm rupture. Therefore, prophylactic treatment is used, which leads to unnecessary potential complications. A new modality enabling a more accurate risk assessment is needed. Optical coherence tomography (OCT) is a new-generation imaging technology that has astonishing resolution for vascular imaging. In this study, OCT was used for the evaluation of intracranial aneurysms.

METHODS

In vivo OCT imaging was performed for aneurysms induced in 6 rabbits and in 9 intracranial aneurysm patients. Catheters were cut short to prevent any extra length from damaging aneurysms and tissues. Images of both the parent artery and the aneurysm at multiple viewing angles were obtained using rotational OCT scanning.

RESULTS

The OCT images of rabbits correlated well with histologic sections. The 3-layered architecture of the parent arteries was explicitly shown. Ruptured intracranial aneurysms manifested complete breakdown of the wall structure; however, this was not observed in any unruptured aneurysms. The OCT images of unruptured intracranial aneurysms demonstrated a trend of degradation by showing the gradual disappearance of the demarcation between the layers or incomplete apoptosis in layer structures.

CONCLUSION

OCT is the most precise imaging modality because it provides detailed information regarding the aneurysm structures, thus enabling more distinct insight into the vascular construction of intracranial aneurysms.

Collar Sign in Incompletely Occluded Aneurysms after Pipeline Embolization: Evaluation with Angiography and Optical Coherence Tomography

BACKGROUND AND PURPOSE

Flow diversion with the Pipeline Embolization Device has emerged as an attractive treatment for cerebral aneurysms. Processes involved in aneurysm occlusion include changes in intra-aneurysmal hemodynamics and endothelialization of the device. Here, we call attention to a radiographic sign not previously reported that is detected in incompletely occluded aneurysms after treatment with the Pipeline Embolization Device at angiographic follow-up and referred to as the "collar sign."

MATERIALS AND METHODS

A retrospective review of all patients who underwent placement of a Pipeline Embolization Device for cerebral aneurysms between January 2014 and May 2016 was performed. All aneurysms found to show the collar sign at follow-up were included. Optical coherence tomography was performed in 1 case.

RESULTS

One hundred thirty-five aneurysms were treated in 115 patients. At angiographic follow-up, 17 (10.7%) aneurysms were found to be incompletely occluded. Ten (58.8%) of these aneurysms (average diameter, 7.9 ± 5.0 mm) were found to have the collar sign at angiographic follow-up (average, 5.5 ± 1.0 months). Four (40.0%) of the aneurysms underwent a second angiographic follow-up (average, 11.0 ± 0.9 months) after treatment, and again were incompletely occluded and showing the collar sign. Two patients underwent retreatment with a second Pipeline Embolization Device. Optical coherence tomography showed great variability of endothelialization at the proximal end of the Pipeline Embolization Device.

CONCLUSIONS

The collar sign appears to be indicative of endothelialization, but continued blood flow into the aneurysm. This is unusual given the processes involved in aneurysm occlusion after placement of the Pipeline Embolization Device and has not been previously reported.

Optical coherence tomography of traumatic aneurysms of the internal carotid artery: report of 2 cases

The pathophysiology of extracranial traumatic aneurysm formation has not been fully elucidated. Intraarterial optical coherence tomography (OCT), an imaging modality capable of micrometer cross-sectional resolution, was used to evaluate patients presenting with saccular traumatic aneurysms of the internal carotid artery (ICA). Two consecutive trauma patients diagnosed with saccular traumatic aneurysms of the cervical ICA, per the institutional screening protocol for traumatic cerebrovascular injury, underwent digital subtraction angiography (DSA) with OCT. Optical coherence tomography demonstrated disruption of the intima with preservation and stretching of the more peripheral layers. In 1 patient the traumatic aneurysm was associated with thrombus formation and a separate, more proximal dissection not visible on CT angiography (CTA) or DSA. Imaging with OCT indicates that saccular traumatic aneurysms may develop from disruption of the intima with at least partial preservation of the media and adventitia. This provides in vivo evidence that saccular traumatic aneurysms result from a partial arterial wall tear rather than complete disruption. Interestingly, OCT was also able to detect arterial injury and thrombi not visible on CTA or DSA.

Optical coherence tomography of the intracranial vasculature and Wingspan stent in a patient

A 67-year-old man with medically refractory vertebrobasilar insufficiency and short segment occlusions of the intracranial vertebral arteries was treated with angioplasty and stent placement. Fifteen hours after the procedure the patient developed symptoms of posterior fossa ischemia and repeat angiography showed thrombus formation within the stent which was treated with thrombolytic and aggressive antiplatelet therapy. Angiography revealed lysis of the clot, but concerns regarding the mechanism of the thrombotic phenomenon prompted frequency-domain optical coherence tomography (FDOCT) assessment. FDOCT provided excellent visualization of the stent and vessel wall interactions, as well as excluding residual flow-limiting stenosis, obviating the need for further intervention. The potential utility of FDOCT in the evaluation of intracranial atherosclerotic disease and additional intracranial applications are discussed.

Surgery Versus Stenting in Symptomatic Patients

Symptomatic carotid artery stenosis is an important cause of stroke with significant morbidity and mortality. Revascularization with carotid endarterectomy reduces the recurrence of stroke and until recently was considered the gold standard of therapy. Carotid artery stenting has emerged as an alternative method of revascularization in both high-risk and standard-risk patients. This review appraises the role of surgery versus stenting for patients with symptomatic carotid stenosis.