Biomedical subjects

Nigel R Munce

Publications and source records attributed to Nigel R Munce.

4 recordsLinked to original sources

PubMed2007

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. We sought to evaluate tissue characterization in arterial (CTOs) by imaging ex vivo peripheral arterial samples with optical coherence tomography (OCT). STUDY DESIGN/MATERIALS AND METHODS: Ex vivo arterial samples were obtained from patients undergoing peripheral limb amputation. Samples were imaged in an enface orientation using an OCT system, enabling sequential acquisition of longitudinal images and volumetric reconstruction of cross-sectional views of the occluded arteries. Histology was performed for comparison. RESULTS: OCT imaging reliably differentiated between the occluded lumen and the underlying arterial wall in peripheral CTOs. OCT correctly identified tissue composition within the CTO, such as the presence of collagen and calcium and was also able to identify intraluminal microchannels. CONCLUSIONS: OCT imaging of CTO anatomy and tissue characteristics may potentially lead to substantial improvements in PCI interventions by providing novel guiding capabilities.

Angiography↗

PubMed2006

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 6.7 microm over an imaging depth of 1mm in water, which improves imaging performance in resolving microspheres in gel samples and Doppler shift estimation precision in a flow phantom. The mirror's small size (1.4 mm x 1 mm) will allow integration with endoscopic MEMS-DOCT for in vivo applications.

Computer Systems↗

PubMed2006

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. Consequently, interstitial Doppler OCT (IS-DOCT) was developed for minimally-invasive in vivo imaging of microvasculature and microstructure at greater depths, providing access to deep-seated solid organs. Using Dunning prostate cancer in a rat xenograft model, this study evaluated the feasibility of IS-DOCT monitoring of microvascular changes deep within a tumor caused by photodynamic therapy (PDT). MATERIALS AND METHODS: The DOCT interstitial probe was constructed using a 22 G (diameter approximately 0.7 mm) needle, with an echogenic surface finish for enhanced ultrasound visualization. The lens of the probe consisted of a gradient-index fiber, fusion spliced to an angle-polished coreless tip to allow side-view scanning. The lens was then fusion spliced to a single-mode optical fiber that was attached to the linear scanner via catheters and driven along the longitudinal axis of the needle to produce a 2D subsurface DOCT image. The resultant IS-DOCT system was used to monitor microvascular changes deep within the tumor mass in response to PDT in the rat xenograft model of Dunning prostate cancer. Surface PDT was delivered at 635 nm with 40 mW of power, for a total light dose of 76 J/cm(2), using 12.5 mg/kg of Photofrin as the photosensitizer dose. RESULTS: IS-DOCT demonstrated its ability to detect microvasculature in vivo and record PDT-induced changes. A reduction of detected vascular cross sectional area during treatment and partial recovery post-treatment were observed. CONCLUSIONS: IS-DOCT is a potentially effective tool for real-time visualization and monitoring of the progress of PDT treatments. This capability may play an important role in elucidating the mechanisms of PDT in tumors, pre-treatment planning, feedback control for treatment optimization, determining treatment endpoints and post-treatment assessments.

Animals↗

PubMed2004

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. Calcein-labeled acute myloid leukemia (AML) cells were selected from an on-chip reservoir and transported by optical tweezers to one of four parallel microfluidic channels. Each channel entrance was manufactured by F2-laser ablation to form a 20- to 10-microm tapered lysis reservoir, creating an injector geometry effective in confining the cellular contents during mechanical shearing of the cell at the 10-microm capillary entrance. The contents of individual cells were simultaneously injected into parallel channels resulting in electrophoretic separation as recorded by laser-induced fluorescence of the labeled cellular contents.

Comet Assay↗