Therapeutic angiogenesis with VEGF164 for facilitation of guidewire crossing in experimental arterial chronic total occlusions.

Aims: Percutaneous revascularisation of chronic total occlusions (CTO) is limited by failure of guidewire crossing. Neovascularisation within the proximal CTO segment may be important for guidewire crossing and dramatically declines in CTO beyond six weeks of age. The aims of the current study were to determine whether local delivery of a pro-angiogenic growth factor increases neovascularisation in mature CTO and facilitates guidewire crossings.

Intraoperative handheld optical coherence tomography forward-viewing probe: physical performance and preliminary animal imaging.

A prototype intraoperative hand-held optical coherence tomography (OCT) imaging probe was developed to provide micron resolution cross-sectional images of subsurface tissue during open surgery. This new ergonomic probe was designed based on electrostatically driven optical fibers, and packaged into a catheter probe in the form factor of clinically accepted Bayonet shaped neurosurgical probes. Optical properties of the probe were measured to have a ~20 μm spot size, 5 mm working distance and 4 mm field of view.

Hybrid intravascular ultrasound and optical coherence tomography catheter for imaging of coronary atherosclerosis.

Objective: To demonstrate the feasibility of imaging human coronary atherosclerosis using a novel hybrid intravascular ultrasound (IVUS) and optical coherence tomography (OCT) imaging catheter.

Background: IVUS and OCT have synergistic advantages and recent studies involving both modalities suggest the use of a hybrid imaging catheter may offer improved guidance of coronary interventions and plaque characterization.

Methods: A 1.

Characterisation of a novel porcine coronary artery CTO model.

Aims: To create a large animal coronary chronic total occlusion (CTO) model. Presence of microvessels within the CTO lumen facilitates guidewire crossing. The patterns and time profiles of matrix changes and microvessel formation during coronary CTO maturation are unknown.

Intravascular and extravascular microvessel formation in chronic total occlusions a micro-CT imaging study.

Objectives: The purpose of this study was to characterize the 3-dimensional structure of intravascular and extravascular microvessels during chronic total occlusion (CTO) maturation in a rabbit model.

Background: Intravascular microchannels are an important component of a CTO and may predict guidewire crossability. However, temporal changes in the structure and geographic localization of these microvessels are poorly understood.

Doppler optical coherence tomography for interventional cardiovascular guidance: in vivo feasibility and forward-viewing probe flow phantom demonstration.

We demonstrate the potential of a forward-looking Doppler optical coherence tomography (OCT) probe for color flow imaging in several commonly seen narrowed artery morphologies. As a proof of concept, we present imaging results of a surgically exposed thrombotic occlusion model that was imaged superficially to demonstrate that Doppler OCT can identify flow within the recanalization channels of a blocked artery. We present Doppler OCT images in which the flow is nearly antiparallel to the imaging direction.

In vivo endoscopic multi-beam optical coherence tomography.

A multichannel optical coherence tomography (multi-beam OCT) system and an in vivo endoscopic imaging probe were developed using a swept-source OCT system. The distal optics were micro-machined to produce a high numerical aperture, multi-focus fibre optic array. This combination resulted in a transverse design resolution of <10 microm full width half maximum (FWHM) throughout the entire imaging range, while also increasing the signal intensity within the focus of the individual channels.

High-power wavelength-swept laser in Littman telescope-less polygon filter and dual-amplifier configuration for multichannel optical coherence tomography.

We report a high-power wavelength-swept laser source for multichannel optical coherence tomography (OCT) imaging. Wavelength tuning is performed by a compact telescope-less polygon-based filter in Littman arrangement. High output power is achieved by incorporating two serial semiconductor optical amplifiers in the laser cavity in Fourier domain mode-locked configuration.

Natural history of experimental arterial chronic total occlusions.

Objectives: We sought to perform the first systematic study of the natural history of chronic total arterial occlusions (CTOs) in an experimental model.

Background: Angioplasty of CTOs has low success rates. The structural and perfusion changes during CTO maturation, which may adversely affect angioplasty outcome, have not been systematically studied.

Conducting polymer based active catheter for minimally invasive interventions inside arteries.

An active catheter intended for controllable intravascular maneuvers is presented and initial experimental results are shown. A commercial catheter is coated with polypyrrole and laser micromachined into electrodes, which are electrochemically activated, leading to bending of the catheter. The catheter's electro-chemo-mechanical properties are theoretically modeled to design the first prototype device, and used to predict an optimal polypyrrole thickness for the desired degree of bending within approximately 30 seconds.

Interstitial Doppler optical coherence tomography as a local tumor necrosis predictor in photodynamic therapy of prostatic carcinoma: an in vivo study.

We have tested the feasibility of real-time localized blood flow measurements, obtained with interstitial (IS) Doppler optical coherence tomography (DOCT), to predict photodynamic therapy (PDT)-induced tumor necrosis deep within solid Dunning rat prostate tumors. IS-DOCT was used to quantify the PDT-induced microvascular shutdown rate in s.c.

High power wavelength linearly swept mode locked fiber laser for OCT imaging.

We report a long coherence length, high power, and wide tuning range wavelength linearly swept fiber mode-locked laser based on polygon scanning filters. An output power of 52.6 mW with 112 nm wavelength tuning range at 62.

Speckle variance detection of microvasculature using swept-source optical coherence tomography.

We report on imaging of microcirculation by calculating the speckle variance of optical coherence tomography (OCT) structural images acquired using a Fourier domain mode-locked swept-wavelength laser. The algorithm calculates interframe speckle variance in two-dimensional and three-dimensional OCT data sets and shows little dependence to the Doppler angle ranging from 75 degrees to 90 degrees . We demonstrate in vivo detection of blood flow in vessels as small as 25 microm in diameter in a dorsal skinfold window chamber model with direct comparison with intravital fluorescence confocal microscopy.

Electrostatic forward-viewing scanning probe for Doppler optical coherence tomography using a dissipative polymer catheter.

A novel flexible scanning optical probe is constructed with a finely etched optical fiber strung through a platinum coil in the lumen of a dissipative polymer. The packaged probe is 2.2 mm in diameter with a rigid length of 6mm when using a ball lens or 12 mm when scanning the fiber proximal to a gradient-index (GRIN) lens.

Innovations in imaging for chronic total occlusions: a glimpse into the future of angiography's blind-spot.

Chronic total occlusions (CTOs) are a subset of lesions that present a considerable burden to cardiovascular patients. There exists a strong clinical desire to improve non-surgical options for CTO revascularization. While several techniques, devices, and guide wires have been developed and refined for use in CTOs, the inability of angiography to adequately visualize occluded arterial segments makes interventions in this setting technically challenging.

Investigation of micro-ultrasound for microvessel imaging in a model of chronic total occlusion.

The aim of the current study is to investigate the ability of micro-ultrasound (microUS) to identify microvasculature in CTOs in vivo. Results are compared with MRI studies. CTOs were developed in nine porcine superficial femoral arteries (SFA) by percutaneous insertion of a dissolvable polymer plug.

Doppler optical coherence tomography monitoring of microvascular tissue response during photodynamic therapy in an animal model of Barrett's esophagus.

Background: Doppler optical coherence tomography (DOCT) is an imaging modality that allows assessment of the microvascular response during photodynamic therapy (PDT) and may be a powerful tool for treatment monitoring/optimization in conditions such as Barrett's esophagus (BE).

Objective: To assess the technical feasibility of catheter-based intraluminal DOCT for monitoring the microvascular response during endoluminal PDT in an animal model of BE.

Design: Thirteen female Sprague-Dawley rats underwent esophagojejunostomy to induce enteroesophageal reflux for 35 to 42 weeks and the formation of Barrett's mucosa.

Interstitial Doppler optical coherence tomography monitors microvascular changes during photodynamic therapy in a Dunning prostate model under varying treatment conditions.

We measure the tumor vascular response to varying irradiance rates during photodynamic therapy (PDT) in a Dunning rat prostate model with interstitial Doppler optical coherence tomography (IS-DOCT). Rats are given a photosensitizer drug, Photofrin, and the tumors are exposed to light (635 nm) with irradiance rates ranging from 8 to 133 mWcm(2) for 25 min, corresponding to total irradiance of 12 to 200 Jcm(2) (measured at surface). The vascular index computed from IS-DOCT results shows the irradiance rate and total irradiance dependent microvascular shutdown in the tumor tissue during PDT.

Doppler optical cardiogram gated 2D color flow imaging at 1000 fps and 4D in vivo visualization of embryonic heart at 45 fps on a swept source OCT system.

We report a Doppler optical cardiogram gating technique for increasing the effective frame rate of Doppler optical coherence tomography (DOCT) when imaging periodic motion as found in the cardiovascular system of embryos. This was accomplished with a Thorlabs swept-source DOCT system that simultaneously acquired and displayed structural and Doppler images at 12 frames per second (fps). The gating technique allowed for ultra-high speed visualization of the blood flow pattern in the developing hearts of African clawed frog embryos (Xenopus laevis) at up to 1000 fps.

Ex vivo imaging of chronic total occlusions using forward-looking optical coherence tomography.

Background And Objectives: Percutaneous coronary interventions (PCI) of chronic total occlusions (CTOs) of arteries are more challenging lesions to treat with angioplasty and stenting than stenotic vessels due primarily to the difficulty in guiding the wire across the lesion. Angiography alone is unable to differentiate between the occluded lumen and the vessel wall and to characterize the content of the occlusion. New technologies to aid in interventional guidance are therefore highly desirable.

Feasibility of interstitial Doppler optical coherence tomography for in vivo detection of microvascular changes during photodynamic therapy.

Introduction: Doppler optical coherence tomography (DOCT) is an emerging imaging modality that provides subsurface microstructural and microvascular tissue images with near histological resolution and sub-mm/second velocity sensitivity. A key drawback of OCT for some applications is its shallow (1-3 mm) penetration depth. This fundamentally limits DOCT imaging to transparent, near-surface, intravascular, or intracavitary anatomical sites.

Doppler optical coherence tomography with a micro-electro-mechanical membrane mirror for high-speed dynamic focus tracking.

An elliptical microelectromechanical system (MEMS) membrane mirror is electrostatically actuated to dynamically adjust the optical beam focus and track the axial scanning of the coherence gate in a Doppler optical coherence tomography (DOCT) system at 8 kHz. The MEMS mirror is designed to maintain a constant numerical aperture of approximately 0.13 and a spot size of approximately 6.

Microvessels in chronic total occlusions: pathways for successful guidewire crossing?

Arterial chronic total occlusions (CTO) are a common and clinically relevant problem in patients with coronary artery disease. Percutaneous coronary intervention (PCI) success rates in a wide range of CTO are low, primarily due to inability of guidewire crossing. The pathophysiology of CTO is poorly understood and limits our ability to introduce innovative therapies.

Interstitial Doppler optical coherence tomography.

Doppler optical coherence tomography (OCT) can image tissue structure and blood flow at micrometer-scale resolution but has limited imaging depth. We report a novel, linear-scanning, needle-based Doppler OCT system using angle-polished gradient-index or ball-lensed fibers. A prototype system with a 19-guage (diameter of approximately 0.

Microfabricated system for parallel single-cell capillary electrophoresis.

Performing single-cell electrophoresis separations using multiple parallel microchannels offers the possibility of both increasing throughput and eliminating cross-contamination between different separations. The instrumentation for such a system requires spatial and temporal control of both single-cell selection and lysis. To address these problems, a compact platform is presented for single-cell capillary electrophoresis in parallel microchannels that combines optical tweezers for cell selection and electromechanical lysis.