Optical coherence tomography: basics, current application and future potential

Calcification is a risk factor for intracranial in-stent restenosis: an optical coherence tomography study

BACKGROUND

The frequent occurrence of calcification in intracranial artery stenosis increases the risk of ischemic stroke. In previous cases, we have observed a possible relationship between calcification and intracranial in-stent restenosis (ISR) using optical coherence tomography (OCT). Therefore, our study aimed to demonstrate the relationship between intracranial calcification and ISR with a larger sample size.

METHODS

For our study patients who underwent OCT for intracranial artery stenosis before stenting were included from May 2020 to October 2022. Follow-up assessments were performed using transcranial color-coded duplex (TCCD) sonography ultrasonography to detect cases of ISR.

RESULTS

We recruited 54 patients, 15 of them were excluded as they did not meet the study criteria. Our study included 39 patients, of whom 21 had calcification, and 18 did not. The results of our study revealed a significant association between calcification and intracranial ISR (9 (42.86) vs 2 (11.11), p=0.0375). Notably, patients with macrocalcification were more likely to undergo ISR than patients with spotty calcification (77.78% vs 22.22%, p=0.03).

CONCLUSION

OCT imaging demonstrates that calcification is an essential risk factor for intracranial ISR. These findings have important implications for individualized treatment. They provide valuable insights for optimizing stent design and exploring potential mechanisms of intracranial ISR.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier: NCT05550077.

The Usefulness of Optical Coherence Tomography in Disease Progression Monitoring in Younger Patients with Relapsing-Remitting Multiple Sclerosis: A Single-Centre Study

The purpose of the study was to assess the usefulness of optical coherence tomography (OCT) in the detection of the neurodegenerative process in younger patients with multiple sclerosis (MS). The study group consisted of 61 patients with a relapsing remitting course of MS (mean age 36.4 ± 6.7 years) divided into two groups: short (≤5 years) and long (>10 years) disease duration. OCT, P300 evoked potential, Montreal Cognitive Assessment, and performance subtests (Picture Completion and Digit Symbol) of the Wechsler Adult Intelligence Scale were performed in all patients. Mean values of most parameters assessed in OCT (pRNFL Total, pRNFL Inferior, pRNFL Superior, pRNFL Temporalis, mRNFL, GCIPL, mRNFL+GCIPL) were significantly lower in MS patients in comparison to controls. And in patients with longer disease duration in comparison to those with shorter. Most OCT parameters negatively correlated with the EDSS score (p < 0.05). No significant correlation was found between OCT results and both P300 latency and the results of psychometric tests. OCT, as a simple, non-invasive, quick, and inexpensive method, could be useful for monitoring the progression of disease in MS patients.

Macrocalcification of intracranial vertebral artery may be related to in-stent restenosis: lessons learned from optical coherence tomography

BACKGROUND

Calcification has been proven to be a marker of atherosclerosis and is related to an increased risk of ischemic stroke. Additionally, calcification was reported to be prevalent in patients with stenotic lesions of the intracranial vertebral artery. Thus, reliable imaging facilities for evaluating plaque calcification have remarkable significance in guiding stenting and predicting patient outcomes. Optical coherence tomography (OCT) has a unique advantage in its ability to detect calcium and to achieve three-dimensional volumetric calcium characterization.

METHODS

From March 2017 to September 2018, seven cases of calcified lesions with intracranial vertebral artery stenosis were investigated using OCT, before and after the placement of an Apollo balloon-mounted stent. Transcranial color-coded duplex sonography was performed to identify restenosis with a mean follow-up time of 13.3 months in this case series.

RESULTS

All calcified lesions were evaluated quantitatively and qualitatively using OCT. Among all cases, five had macrocalcifications and two had spotty calcifications. Severe in-stent restenosis was observed in two cases, both with macrocalcifications.

CONCLUSIONS

This study suggests a potential relationship between macrocalcifications and the risk of in-stent restenosis of the intracranial vertebral artery. These preliminary findings obtained from a limited sample should be verified by prospective large-scale studies.

Optical Coherence Tomography for Neurovascular Disorders

Diagnosis of cerebrovascular disease includes vascular neuroimaging techniques such as computed tomography (CT) angiography, magnetic resonance (MR) angiography (with or without use of contrast agents) and catheter digital subtraction angiography (DSA). These techniques provide mostly information about the vessel lumen. Vessel wall imaging with MR seeks to characterize cerebrovascular pathology, but with resolution that is often insufficient for small lesions. Intravascular imaging techniques such as ultrasound and optical coherence tomography (OCT), used for over a decade in the peripheral circulation, is not amendable to routine deployment in the intracranial circulation due to vessel caliber and tortuosity. However, advances in OCT technology including the probe profile, stiffness and unique distal rotation solution, holds the promise for eventual translation of OCT into the clinical arena. As such, it is apropos to review this technology and present the rationale for utilization of OCT in the cerebrovasculature.

Optical coherence tomography and plaque morphology for revascularization of the superficial femoral artery

Background

The optical coherence tomography (OCT) catheter, Ocelot (Avinger Inc., Redwood City, CA), has been utilized to cross Trans-Atlantic Inter-Society Consensus Document (TASC) D lesions. Studies have assessed the characteristics of high-risk plaques in the carotid artery, but few, if any data exist evaluating OCT and plaque morphology in the superficial femoral artery (SFA). This study assessed SFA plaque morphology using OCT and lesion crossing success in chronic total occlusions (CTOs).

Methods

We reviewed patients who underwent attempted infrainguinal revascularization with TASC D CTOs using the Ocelot catheter between June 2014 and June 2018, and recorded demographic information, smoking status, and medical comorbidities. A matched cohort of 44 successfully crossed lesions was compared to 44 that failed; images insufficient for analysis were excluded. The morphology of the plaque was studied using OCT at the proximal cap, midpoint of the lesion, and the distal cap. Morphologic data studied included the intima-media thickness ratio, cross-sectional area of the plaque, and gray-scale median of the plaque.

Results

A total of 140 patients who underwent lower extremity procedures for TASC D lesions of the SFA with OCT imaging were reviewed with a crossing rate of 69.0%. No significant differences were found between crossed and uncrossed lesions for intima-media thickness or cross-sectional area at the proximal cap, the midpoint, or the distal cap. A lower gray-scale median at the proximal cap was associated with the ability to cross the chronic SFA occlusion (P=0.05). Subgroup analysis stratified by smoking and calcium content also demonstrated that a lower gray-scale median at the proximal cap was associated with the ability to cross the chronic SFA occlusion (P=0.01 and P=0.04, respectively).

Conclusions

Lower gray-scale median at the proximal cap of a chronic SFA occlusion calculated using OCT images was associated with the ability to successfully cross the lesion. Higher plaque gray-scale median is correlated with increased calcium, greater fibrous tissue, and signal-rich plaques. Gray-scale median in the proximal cap is useful marker to determine plaque composition and subsequent technical success for crossing chronic SFA occlusions. Further studies are needed to fully determine the utility of OCT images to predict successful endovascular revascularization of chronic SFA occlusions.

Evaluation of Crack Formation and Propagation with Ultrasonic Root-End Preparation and Obturation Using a Digital Microscope and Optical Coherence Tomography

OBJECTIVE

This study is aimed at determining (1) the effect of root-end resection, ultrasonic root-end preparation, and root-end filling on the incidence of crack formation and propagation by using a digital microscope (DM) and optical coherence tomography (OCT) and (2) the performance of OCT on the detection of cracks by comparing with microcomputed tomography (micro-CT) as a reference standard.

METHODOLOGY

Thirty extracted lower incisors were endodontically treated and subjected to root-end resection and ultrasonic root-end cavity preparation. Then, the teeth were divided into three groups (n = 10, each), and the root-end cavity was either left unfilled or filled with mineral trioxide aggregate (MTA) or super-EBA. The resected surface was observed with OCT and DM after the root-end resection, ultrasonic root-end preparation, and root-end filling, and the frequency of incomplete and complete cracks were recorded. The observation was repeated after two weeks, one month, and two months, and micro-CT scans after two months were taken as the gold standard.

RESULTS

The DM results show dentinal crack formation in 47% of the samples following root-end resection and in 87% following ultrasonic preparation. After the ultrasonic preparation, no existing crack propagated to a complete crack, but new cracks were formed. MTA and super-EBA had no effect on crack formation. The Spearman correlation coefficient between OCT and DM was 0.186 (very weak correlation; p = 0.015). Sensitivity and specificity in comparison to micro-CT were 0.50 and 0.55 in OCT and 1.00 and 0.35 in DM, respectively. McNemar's test showed a significant difference between OCT and DM (p < 0.05).

CONCLUSION

Apical resection and ultrasonic preparation could form dentinal cracks. OCT and DM showed different detection frequencies of cracks with very weak correlation. DM showed superior sensitivity compared with OCT.

Optical coherence tomography for serial in vivo imaging of aortic plaque in the rabbit: a preliminary experience

Background

In this pilot feasibility study, we aimed to establish a reproducible means of performing serial optical coherence tomography (OCT) procedures in the abdominal aorta of the cholesterol-fed rabbit.

Methods

Eight cholesterol-fed New Zealand White rabbits were assigned to abdominal aortic balloon injury at baseline (n=6) or as controls (n=2). Three of the balloon injured rabbits received statins from weeks 6 to 12 post balloon injury. OCT of the abdominal aorta in each rabbit was performed at baseline±week 6±week 12 via alternate vascular access points (left or right femoral artery or left carotid artery). OCT sequences were analysed to derive an indexed plaque volume and other OCT measures of plaque complexity, and results were compared between groups. Histopathological correlations with OCT images were made following terminal procedures.

Results

Of the 16 OCT procedures in these rabbits (6 at baseline, 4 at 6 weeks, 6 at 12 weeks), excellent and analysable images were obtained on 15 occasions (94%). Inability to obtain adequate arterial access for the OCT catheter was the major experimental limitation encountered in the early part of our experience. Balloon injured rabbits developed larger volume and more complex plaque than non-balloon injured rabbits on all OCT indices measured (eg, both mean plaque volume and lumen stenosis were approximately double in the balloon injured group, p<0.0001). A significant correlation between 12 week measures of plaque area by OCT and histology was demonstrated (Pearson correlation coefficient: 0.992, p<0.0001).

Conclusions

Our preliminary experience suggests that serial OCT of the abdominal aorta in the New Zealand White rabbit is feasible and a potentially promising means of performing serial studies of aortic atherosclerosis.

Optical Coherence Tomography in the Diagnosis and Management of Spontaneous Coronary Artery Dissection

Spontaneous coronary artery dissection (SCAD) is an infrequent condition that has been underdiagnosed and misdiagnosed. The use of intracoronary imaging with intravascular ultrasound or optical coherence tomography enables the accurate diagnosis of this challenging condition. Diagnostic and management algorithms have been proposed to improve the diagnosis and therapeutic stratification of SCAD. Optical coherence tomography has superior spatial resolution than intravascular ultrasound, and is instrumental in the diagnosis of SCAD cases where angiographic findings are ambiguous for confirming SCAD. Understanding the role and appropriate and careful use of this technology is expected to improve the diagnosis of SCAD, and also improve outcomes with percutaneous coronary intervention, when clinically indicated.

Fundamentals of Optical Coherence Tomography: Image Acquisition and Interpretation

Optical coherence tomography (OCT) is an intravascular imaging modality that enables high-resolution cross-sectional imaging of coronary arteries in vivo. With resolution that is a 10-fold improvement compared with intravascular ultrasonography, OCT can facilitate detailed plaque characterization. This article introduces the basic principles of OCT image acquisition and interpretation. Qualitative analysis entails the evaluation of plaque morphology, including features associated with plaque vulnerability to rupture. Quantitative analysis and recognition of OCT image artifacts are also discussed.

3D assessment of stent cell size and side branch access in intravascular optical coherence tomographic pullback runs

We present a semi-automatic approach to assess the maximum circular unsupported surface area (MCUSA) of selected stent cells and the side branch access through stent cells in intravascular optical coherence tomography (IVOCT) pullback runs. Such 3D information may influence coronary interventions, stent design, blood flow analysis or prognostic evaluation. First, the stent struts are detected automatically and stent cells are reconstructed with users' assistance. Using cylinder fitting, a 2D approximation of the stent cell is generated for MCUSA detection and measurement. Next, a stent surface is reconstructed and stent-covered side branches are detected. Both the stent cell contours and side branch lumen contours are projected onto the stent surface to indicate their areas, and the overlapping regions are measured as the side branch access through these stent cells. The method was evaluated on phantom data sets and the accuracy of the MCUSA and side branch access was found to be 95% and 91%, respectively. The usability of this approach for clinical research was proved on 12 in vivo IVOCT pullback runs.

Inner structure detection by optical tomography technology based on feedback of microchip Nd:YAG lasers

We describe a new optical tomography technology based on feedback of microchip Nd:YAG lasers. In the case of feedback light frequency-shifted, light can be magnified by a fact of 10(6) in the Nd:YAG microchip lasers, which makes it possible to realize optical tomography with a greater depth than current optical tomography. The results of the measuring and imaging of kinds of samples are presented, which demonstrate the feasibility and potential of this approach in the inner structure detection. The system has a lateral resolution of ~1 μm, a vertical resolution of 15 μm and a longitudinal scanning range of over 10mm.