Optical Coherence Tomography Catheter Research Articles

Intraluminal crossing of infrainguinal SFA chronic total occlusions may offer patency superiority compared to subintimal crossing.

Patency for chronic total occlusions (CTO) of the superficial femoral artery (SFA) after endovascular interventions traditionally demonstrate a low 1-year patency ranging from 40%-60%. The optical coherence tomography (OCT) catheter (Avinger Inc., Redwood City, CA) uses light-based technology imaging to cross Trans-Atlantic Inter-Society Consensus D (TASC D) lesions intraluminally with direct intra-arterial visualization. Insufficient data exist evaluating intraluminal crossing with OCT imaging compared with traditional subintimal techniques. We evaluated outcomes for TASC D lesions crossed intraluminally. A retrospective analysis of patients with SFA TASC D lesions crossed intra-arterially with the OCT catheter imaging. Descriptive statistics evaluated patient characteristics which included patient demographics, Rutherford scores, ABIs, CTA information, lesion categorization, as well as runoff score. Patency at baseline, 30-day, 6-month, and 1-year outcomes were compared using t-tests. Cumulative patency rates were evaluated using Kaplan-Meier analysis. 101 patients underwent elective intervention for SFA TASC D lesions with the OCT catheter. The crossing rate was 78.2%, mean lesion length was 16.2cm, and runoff at the tibial level was 2.2 patent vessels. Mean age and BMI were 64 years and 29kg/m2, respectively. Patient characteristics are male (57%); Caucasian (90%); ever smoking (85%); hypertension (82%), hyperlipidemia (70%), and diabetes (46%). Pre-operative computed tomography demonstrated SFA lesions were predominantly eccentric (91%) with mild to moderate calcification (90%). All underwent PTA, 87% were stented (mean stent length: 186.1mm), mean crossing time was 13.4 min. Pre-operative, 30-day, 6-month, and 1-year post-operative mean Rutherford-Becker scores were 4, 1, 1, and 1, respectively (p < 0.0001). Mean pre-operative ABI was 0.49, compared to 0.84 at 30 days, 0.64 at 6 months, and 0.67 at 1 year (p < .0001). Duplex demonstrated 6- and 12-month primary patency of 89% and 75%; primary-assisted patency was 94% and 84%. The OCT imaging catheter successfully crossed long chronic total occlusions of the SFA using direct intra-arterial imaging. Compared to subintimal techniques, patients had high 1-year primary patency and prolonged symptom improvement with intraluminal crossing. These data suggest that intraluminal crossing of TASC D lesions may be superior to traditional subintimal crossing techniques.

Longitudinal Stent Deformation at the Proximal Segment of the Left Main Coronary Artery Caused by a Stuck OCT Catheter: Case Report and Review of Literature.

It has been rarely reported that a stuck optical coherence tomography (OCT) catheter can lead to longitudinal stent deformation (LSD). This complication can result in incomplete stent apposition and dissection after stent implantation. In this study, we present a case where a bailout stent was implanted in the distal segment of the left anterior descending artery (LAD) after longitudinal stent deformation caused by a stuck OCT catheter. This approach was taken to prevent acute stent thrombosis, subacute stent thrombosis, in-stent restenosis (ISR), and death. The patients were followed up for one year, and no adverse events were observed.

Direct Comparison of Rotational vs Orbital Atherectomy for Calcified Lesions Guided by Optical Coherence Tomography

BackgroundThere are several retrospective studies comparing rotational atherectomy (RA) and orbital atherectomy (OA), but all percutaneous coronary interventions (PCIs) in those studies were not performed under intracoronary imaging guidance. ObjectivesThis study sought to compare the efficacy and safety of optical coherence tomography (OCT)-guided PCI with RA vs OA. MethodsThe DIRO (To directly compare RA and OA for calcified lesions, a prospective randomized trial) trial was conducted. We enrolled patients with de novo calcified lesions (arc >180°) assessed by OCT or angiographically moderate or severe calcifications if the OCT catheter could not cross the lesion before any intervention. Eligible patients were randomly 1:1 allocated to lesion preparation with RA vs OA. Stent expansion was defined as the minimum stent area divided by the distal reference area multiplied by 100. Tissue modification was assessed using preatherectomy and postatherectomy OCT images. Procedural outcomes including periprocedural myocardial infarctions were evaluated. Furthermore, clinical events and vascular healing evaluated by OCT at 8 months postprocedure were assessed. ResultsThe stent expansion was significantly greater in the RA group vs the OA group (99.5% vs 90.6%; P = 0.02). The maximum atherectomy area was significantly larger in the RA group than in the OA group (1.34 [IQR: 1.02-1.89] mm2 vs 0.83 [IQR: 0.59-1.11] mm2; P = 0.004). The procedural outcomes and clinical events at 8 months did not differ between the groups. The vascular healing was sufficient in both groups. ConclusionsThe prospective randomized DIRO trial revealed that RA could produce a more favorable tissue modification, which may lead to a larger stent expansion than OA in heavily calcified lesions.

Enhanced 3D visualization of human fallopian tube morphology using a miniature optical coherence tomography catheter.

We demonstrate the use of our miniature optical coherence tomography catheter to acquire three-dimensional human fallopian tube images. Images of the fallopian tube's tissue morphology, vasculature, and tissue heterogeneity distribution are enhanced by adaptive thresholding, masking, and intensity inverting, making it easier to differentiate malignant tissue from normal tissue. The results show that normal fallopian tubes tend to have rich vasculature accompanied by a patterned tissue scattering background, features that do not appear in malignant cases. This finding suggests that miniature OCT catheters may have great potential for fast optical biopsy of the fallopian tube.

Predictors of coronary artery injury after orbital atherectomy as assessed by optical coherence tomography

Purpose: The association between the extent of the wire and device bias as assessed by optical coherence tomography (OCT) in the healthy portion of the vessel and the risk of coronary artery injury after orbital atherectomy (OA) has not been fully elucidated. Thus, purpose of this study is to investigate the association between pre-OA OCT findings and post-OA coronary artery injury by OCT. Methods: We enrolled 148 de novo lesions having calcified lesion required OA (max Ca angle > 90°) in 135 patients who underwent both pre- and post-OA OCT. In pre-OA OCT, OCT catheter contact angle and the presence or absences of guide-wire (GW) contact with the normal vessel intima were assessed. Also, in post-OA OCT, we assessed there was post-OA coronary artery injury (OA injury), defined as disappearance of both of intima and medial wall of normal vessel, or not. Results: OA injury was found in 19 lesions (13%). Pre-PCI OCT catheter contact angle with the normal coronary artery was significantly larger (median 137°; inter quartile range [IQR] 113–169 vs. median 0°; IQR 0–0, P < 0.001) and more GW contact with the normal vessel was found (63% vs. 8%, P < 0.001). Pre-PCI OCT catheter contact angle > 92° and GW contact with the normal vessel intima were associated with post-OA vascular injury (Both: 92% (11/12), Either: 32% (8/25), Neither: 0% (0/111), P < 0.001). Conclusion: Pre-PCI OCT findings, such as catheter contact angle > 92° and guide-wire contact to the normal coronary artery, were associated with post-OA coronary artery injury.

Abstract No. 171 Benchtop Testing with Procedural Feasibility and Safety Evaluation of an Ultrahigh-Resolution Optical Coherence Tomography Catheter for Assessment of the Biliary Tree

Abstract No. 171 Benchtop Testing with Procedural Feasibility and Safety Evaluation of an Ultrahigh-Resolution Optical Coherence Tomography Catheter for Assessment of the Biliary Tree

Automatic intraluminal scanning with a steerable endoscopic optical coherence tomography catheter for gastroenterology applications

SignificanceEndoscopic optical coherence tomography (OCT) enables real-time optical biopsy of human organs. Endoscopic probes require miniaturization of optics, which in turn limits field of view. When larger imaging areas are needed such as in the gastrointestinal tract, the operator must manually scan the probe over the tissue to extend the field of view, often resulting in an imperfect scanning pattern and increased risk of missing lesions. Automatic scanning has the potential to extend the field of view of OCT, allowing the user to focus on image interpretation during real-time observations.AimThis work proposes an automatic scanning using a steerable OCT catheter integrated with a robotized interventional flexible endoscope. The aim is to extend the field of view of a low-profile OCT probe while improving scanning accuracy and maintaining a stable endoscope’s position during minimally invasive treatment of colorectal lesions.ApproachA geometrical model of the steerable OCT catheter was developed for estimating the volume of the accessible workspace. Experimental validation was done using electromagnetic tracking of the catheter’s positions. An exemplary scanning path was then selected within the available workspace to evaluate motion performance with the robotized steerable OCT catheter. Automatic scanning is compared to a teleoperated one and a manual scanning with a nonrobotized flexible endoscope. Spectral arc length, scanning area, spacing between scan trajectories, and time are metrics used to quantify performance.ResultsThe available scanning workspace was experimentally estimated to be 255 cm3. The automatic scanning mode provided the highest accuracy and smoothness of motion with spectral arc length of −3.18, covered area of 10.11 cm2, 1.54 mm spacing between 15 sweep trajectories, maximum translation of 27.99 mm, and time to finish of 3.11s.ConclusionsAutomatic modality improved the accuracy of scanning within a large workspace. The robotic capability provided better control to the user to define spacing resolution of scanning patterns.

Review of intraluminal optical coherence tomography imaging for cerebral aneurysms

Cerebral aneurysms are an abnormal ballooning of blood vessels which have the potential to rupture and cause hemorrhagic stroke. The diagnosis, treatment, and monitoring of cerebral aneurysms is highly dependant on high resolution imaging. As an imaging modality capable of cross-sectional resolution down to 10 μm, intraluminal optical coherence tomography (OCT) has great potential in improving care for cerebral aneurysms. The ability to assess the blood vessel microanatomy in vivo may be able to predict aneurysm growth and rupture. During treatment, intraluminal OCT may aid in assessment of treatment efficacy and complication avoidance, such as via visualization of in-stent thrombosis, stent wall apposition, and the fate of covered branch vessels. This technology can also be used in post-treatment monitoring, to assess for aneurysmal remnants or for endothelialisation and healing over the diseased segments. The goal of this clinically focused narrative review is to provide an overview of the previous applications of intraluminal OCT in cerebral aneurysms and future prospects of applying this technology to improve care in patients with cerebral aneurysms, including a specific neurovascular OCT catheter, doppler OCT for high resolution blood flow assessment, and further research endeavors.

Inside Cover

We describe a miniaturized optical coherence tomography (OCT) catheter and a residual neural network (ResNet)‐based deep learning model to perform human colorectal tissue classification. An area under the receiver operating characteristic (ROC) curve (AUC) of 0.975 is achieved to distinguish between normal and cancerous colorectal tissue images.Further details can be found in the article by Hongbo Luo, Shuying Li, Yifeng Zeng, Hassam Cheema, Ebunoluwa Otegbeye, Safee Ahmed, William C. Chapman Jr, Matthew Mutch, Chao Zhou, and Quing Zhu (e202100349)image

Human colorectal cancer tissue assessment using optical coherence tomography catheter and deep learning.

Optical coherence tomography (OCT) can differentiate normal colonic mucosa from neoplasia, potentially offering a new mechanism of endoscopic tissue assessment and biopsy targeting, with a high optical resolution and an imaging depth of ~1 mm. Recent advances in convolutional neural networks (CNN) have enabled application in ophthalmology, cardiology, and gastroenterology malignancy detection with high sensitivity and specificity. Here, we describe a miniaturized OCT catheter and a residual neural network (ResNet)-based deep learning model manufactured and trained to perform automatic image processing and real-time diagnosis of the OCT images. The OCT catheter has an outer diameter of 3.8 mm, a lateral resolution of ~7μm, and an axial resolution of ~6μm. A customized ResNet is utilized to classify OCT catheter colorectal images. An area under the receiver operating characteristic (ROC) curve (AUC) of 0.975 is achieved to distinguish between normal and cancerous colorectal tissue images.

Stuck OCT Catheter: An Unanticipated Complication.

During an optical coherence tomography (OCT)-guided percutaneous coronary intervention (PCI) of a calcified left anterior descending artery (LAD), the distal tip of the OCT catheter got stuck, and forceful tugging on the catheter by the operator led to LAD stent deformation proximally across the overlap between the proximal and middle stents. The purpose of these images is to make the readers aware of the very real and serious risk of a stuck OCT catheter, especially while imaging distal coronary arteries and overlapping stents. Increasing the length of the over-the-wire segment and hydrophilic coating of the OCT catheter may also be explored with manufacturers to prevent this complication.

Data Stream Stabilization for Optical Coherence Tomography Volumetric Scanning

Optical Coherence Tomography (OCT) is an emerging medical imaging modality for luminal organ diagnosis. The non-constant rotation speed of optical components in the OCT catheter tip causes rotational distortion in OCT volumetric scanning. By improving the scanning process, this instability can be partially reduced. To further correct the rotational distortion in the OCT image, a volumetric data stabilization algorithm is proposed. The algorithm first estimates the Non-Uniform Rotational Distortion (NURD) for each B-scan by using a Convolutional Neural Network (CNN). A correlation map between two successive B-scans is computed and provided as input to the CNN. To solve the problem of accumulative error in iterative frame stream processing, we deploy an overall rotation estimation between reference orientation and actual OCT image orientation. We train the network with synthetic OCT videos by intentionally adding rotational distortion into real OCT images. As part of this article we discuss the proposed method in two different scanning modes: the first is a conventional pullback mode where the optical components move along the protection sheath, and the second is a self-designed scanning mode where the catheter is globally translated by using an external actuator. The efficiency and robustness of the proposed method are evaluated with synthetic scans as well as real scans under two scanning modes.

Small airway dilation measured by endoscopic optical coherence tomography correlates with chronic lung allograft dysfunction.

.Significance: Chronic lung allograft dysfunction (CLAD) is the leading cause of death in transplant patients who survive past the first year post-transplant. Current diagnosis is based on sustained decline in lung function; there is a need for tools that can identify CLAD onset.Aim: Endoscopic optical coherence tomography (OCT) can visualize structural changes in the small airways, which are of interest in CLAD progression. We aim to identify OCT features in the small airways of lung allografts that correlate with CLAD status.Approach: Imaging was conducted with an endoscopic rotary pullback OCT catheter during routine bronchoscopy procedures (), collecting volumetric scans of three segmental airways per patient. Six features of interest were identified, and four blinded raters scored the dataset on the presence and intensity of each feature.Results: Airway dilation (AD) was the only feature found to significantly () correlate with CLAD diagnosis ( to 0.61). AD could also be fairly consistently scored between raters (, ). There is a stronger relationship between AD and the combined obstructive and restrictive (BOS + RAS) phenotypes than the obstructive-only (BOS) phenotype for two raters ().Conclusions: OCT examination of small AD shows potential as a diagnostic indicator for CLAD and CLAD phenotype and merits further exploration.

Complete Coronary Stent Removal After Optical Coherence Tomography Performance 8 Months Later for Device Entrapment: A Scary Challenge.

We describe an uncommon and potentially life-threatening complication during stent assessment by optical coherence tomography (OCT) with entrapment and complete stent removal. Possible mechanisms for OCT-catheter entrapment include malapposed stent struts, catheter deformation, and loss of guidewire position. In this case, the OCT catheter was advanced over the guidewire, which was probably passed through a proximal malapposed stent strut. Tips to avoid potential complications during OCT performance are provided.

Minimally invasive intrathecal spinal cord imaging with optical coherence tomography.

.Significance: Imaging of the spinal cord is challenging due to the surrounding bony anatomy, physiologic motion, and the small diameter of the spinal cord. This precludes the use of non-invasive imaging techniques in assessing structural changes related to trauma and evaluating residual function.Aim: The purpose of our research was to apply endovascular technology and techniques and construct a preclinical animal model of intrathecal spinal cord imaging using optical coherence tomography (OCT).Approach: Five animals (2 Yorkshire Swine and 3 New Zealand Rabbits) were utilized. Intrathecal access was gained using a 16-guage Tuohy, and an OCT catheter was advanced under roadmap technique into the cervical canal. The OCT catheter has a motorized pullback, and a total length of 54 mm of the spinal canal is imaged.Results: Image acquisition was successful for all animals. There were no instances of difficult catheter navigation, enabling OCT imaging rostrally to C2. The thecal sac provided excellent thoroughfare for the OCT catheter. The clear cerebrospinal fluid also provided an excellent medium for image acquisition, with no detectable artifact from the contents of the cerebrospinal fluid. The anatomical space of the spinal canal could be readily appreciated including: dural lining of the thecal sac, epidural veins, pial lining of the spinal cord, arachnoid bands, dentate ligaments, and nerve rootlets/roots.Conclusion: Minimally invasive intrathecal imaging using endovascular OCT was feasible in this preclinical animal study. The repurposing of an endovascular device for spinal imaging comes with limitations, and a spine-specific device is necessary.

Utilization potential of intraluminal optical coherence tomography for the Eustachian tube

Imaging the Eustachian tube is challenging because of its complex anatomy and limited accessibility. This study fabricated a fiber-based optical coherence tomography (OCT) catheter and investigated its potential for assessing the Eustachian tube anatomy. A customized OCT system and an imaging catheter, termed the Eustachian OCT, were developed for visualizing the Eustachian tube. Three male swine cadaver heads were used to study OCT image acquisition and for subsequent histologic correlation. The imaging catheter was introduced through the nasopharyngeal opening and reached toward the middle ear. The OCT images were acquired from the superior to the nasopharyngeal opening before and after Eustachian tube balloon dilatation. The histological anatomy of the Eustachian tube was compared with corresponding OCT images, The new, Eustachian OCT catheter was successfully inserted in the tubal lumen without damage. Cross-sectional images of the tube were successfully obtained, and the margins of the anatomical structures including cartilage, mucosa lining, and fat could be successfully delineated. After balloon dilatation, the expansion of the cross-sectional area could be identified from the OCT images. Using the OCT technique to assess the Eustachian tube anatomy was shown to be feasible, and the fabricated OCT image catheter was determined to be suitable for Eustachian tube assessment.

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

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). 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. 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). 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.

Endovascular Cerebral Venous Sinus Imaging with Optical Coherence Tomography.

Imaging of the cerebral venous sinuses has evolved Substantially during the past 2 decades, and most recently intravascular sinus imaging with sonography has shed light on the pathophysiology of sinus thrombosis and intracranial hypertension. Optical coherence tomography is the highest resolution intravascular imaging technique available but has not been previously used in cerebral sinus imaging. The purpose of this study was to develop a preclinical animal model of endovascular optical coherence tomography cerebral venous sinus imaging and compare optical coherence tomography findings with histology. Four consecutive Yorkshire swine were selected. The superior sagittal sinus was first catheterized with a microwire, and the optical coherence tomography catheter was delivered via a monorail technique into the sinus. Luminal blood was cleared with a single arterial injection. After structural and Doppler optical coherence tomography imaging, a craniotomy was performed and the sinus and adjacent dura/veins were resected. Bland-Altman analysis was performed to compare optical coherence tomography and histology. Technically successful optical coherence tomography images were obtained in 3 of 4 swine. The luminal environment and visualization of dural arteries and draining cortical veins were characterized. The average maximum diameters of the sinus, dural arteries, and cortical veins were 3.14 mm, 135 µm, and 260 µm, respectively. Bland-Altman analysis demonstrated good agreement between histology and optical coherence tomography images. Endovascular optical coherence tomography imaging was feasible in this preclinical animal study. Adoption of this imaging technique in the human cerebral venous sinus could aid in the diagnosis, treatment, and understanding of the pathophysiology of various diseases of the sinus. Human safety and feasibility studies are needed.

Stick-slip nonuniform rotation distortion correction in distal scanning optical coherence tomography catheters

We present a robust and fiducial-marker-free algorithm that can identify and correct stick-slip distortion caused by nonuniform rotation (or beam scanning) in distally scanned catheters for endoscopic optical coherence tomography (OCT) images. This algorithm employs spatial frequency analysis to select and remove distortions. We demonstrate the feasibility of this algorithm on images acquired from ex vivo rat colon with a distally scanned DC motor-based endoscope. The proposed algorithm can be applied to general endoscopic OCT images for correcting nonuniform rotation distortion.

Ultrathin monolithic 3D printed optical coherence tomography endoscopy for preclinical and clinical use

Preclinical and clinical diagnostics increasingly rely on techniques to visualize internal organs at high resolution via endoscopes. Miniaturized endoscopic probes are necessary for imaging small luminal or delicate organs without causing trauma to tissue. However, current fabrication methods limit the imaging performance of highly miniaturized probes, restricting their widespread application. To overcome this limitation, we developed a novel ultrathin probe fabrication technique that utilizes 3D microprinting to reliably create side-facing freeform micro-optics (<130 µm diameter) on single-mode fibers. Using this technique, we built a fully functional ultrathin aberration-corrected optical coherence tomography probe. This is the smallest freeform 3D imaging probe yet reported, with a diameter of 0.457 mm, including the catheter sheath. We demonstrated image quality and mechanical flexibility by imaging atherosclerotic human and mouse arteries. The ability to provide microstructural information with the smallest optical coherence tomography catheter opens a gateway for novel minimally invasive applications in disease.