Biomedical subjects

E F Dickson

Publications and source records attributed to E F Dickson.

6 recordsLinked to original sources

PubMed2001

An affordable, portable fluorescence imaging device for skin lesion detection using a dual wavelength approach for image contrast enhancement and aminolaevulinic acid-induced protoporphyrin IX. Part I. Design, spectral and spatial characteristics.

Steady-state fluorescence imaging can be used in conjunction with selective exogenous or endogenous fluorescent compounds for the diagnosis of skin lesions, for example cancerous lesions. Depending on the excitation and emission properties of the fluorescent compound used, various excitation and/or emission wavelengths can be chosen in order to allow fluorescence imaging. Unwanted background signals like autofluorescence and scattering can decrease the image quality and hence the diagnosis potential of this imaging method. A method involving two excitation and/or emission wavelengths was used in order to suppress the unwanted background signal and allow contrast enhanced fluorescence imaging. A fluorescence imaging device prototype was assembled using both the two wavelength excitation method and the two wavelength emission method. Additionally, a white light source was included to allow the collection of images as seen with the naked eye. The prototype was designed to be affordable and portable and was laid out towards the diagnosis of skin lesions using aminolaevulinic acid-induced protoporphyrin IX (PpIX). This paper describes the excitation and detection characteristics of a fluorescence imaging device prototype. This includes spectral and spatial characteristics of the various light sources included in the device as well as specifications of the image detector used. Furthermore, the image analysis procedure used for the dual wavelength excitation/emission is described.

Aminolevulinic Acid↗

PubMed2001

An affordable, portable fluorescence imaging device for skin lesion detection using a dual wavelength approach for image contrast enhancement and aminolaevulinic acid-induced protoporphyrin IX. Part II. In vivo testing.

A fluorescence imaging prototype for skin lesion detection and diagnosis using aminolaevulinic acid (ALA) induced protoporphyrin IX (PpIX) was tested in vivo and in the clinic. The prototype was designed as an affordable, portable device to allow contrast enhanced imaging of skin lesions using either the dual excitation wavelength method or the dual emission wavelength method or both. In this study the prototype was tested first on an animal model. Topical application of ALA on defined spots on mouse skin gave PpIX fluorescence after about 3 hours of application. After successful in vivo testing the instrument was tested on basal cell carcinoma patients before ALA-PpIX photodynamic therapy. The patients were topically applied with ALA. After three hours the device was tested (immediately before treatment). The prototype showed good results in terms of contrast enhancement (elimination of unwanted background signals, e.g. autofluorescence) using either contrast enhancement method, both methods achieving similar results. The results achieved in this study, combined with the affordable design of the device, seem to allow cost-effective, contrast-enhanced imaging of skin lesions before or during photodynamic therapy using ALA induced PpIX.

Aminolevulinic Acid↗

PubMed1999

Evaluation of novel nonlaser light source for endometrial ablation using 5-aminolevulinic acid.

BACKGROUND AND OBJECTIVE: This research evaluated the effectiveness of a new nonlaser prototype short-arc lamp to achieve photodynamic ablation of endometrium in a rat. STUDY DESIGN/MATERIALS AND METHODS: Thirty female Sprague-Dawley rats were divided into two groups. 5-Aminolevulinic acid (ALA), the precursor to the photosensitizer protoporphyrin IX, was injected into the left uterine horn and vehicle alone (Hyskon) was injected into the right horn of 23 rats (group 1). An additional seven rats received vehicle only into both uterine horns (group 2). Three hours later, a cylindrical diffusing optical fiber was inserted into the lumen of the uterine horns, and light treatment was delivered from either a laser or a nonlaser light source. Rats in group 1 received either 1 hour (n = 15) or 10 minutes (n = 8) of light treatment into both uterine horns. In rats in group 2, the left horn was exposed to 1 hour of light treatment. Uterine tissues were examined histologically 4 days after light treatment. RESULTS: One hour of light exposure to the uterine horns injected with ALA produced extensive necrosis of the rat uterine wall. No difference in the magnitude of destruction was seen between the groups treated with the laser and nonlaser light sources. Ten minutes of light exposure resulted in endometrial ablation that was comparable in both the laser- and the prototype-treated groups, but the destruction of the deepest layers of the uterine wall was more consistent in the group treated with the nonlaser prototype. One hour of light treatment from either light source did not result in any histological changes in the uterine horns not exposed to ALA. CONCLUSION: The extent of endometrial ablation in the rat uterine horn achieved with the nonlaser prototype was comparable to that achieved with the laser. Thus, the nonlaser prototype may provide a less expensive approach to photodynamic endometrial ablation.

Aminolevulinic Acid↗

PubMed1996

In vitro studies on the potential use of 5-aminolaevulinic acid-mediated photodynamic therapy for gynaecological tumours.

Results are reported on the sensitivity of various gynaecological tumour cell lines to 5-aminolaevulinic acid-induced protoporphyrin IX-sensitised photodynamic therapy (ALA-PDT) in vitro. All cell lines tested accumulated ALA-induced protoporphyrin IX (PpIX) and demonstrated good sensitivity to ALA-PDT. Localisation of PpIX in the mitochondria was demonstrated by fluorescence microscopy. Subcellular damage following ALA-PDT was observed using transmission electron microscopy. This damage was localised initially to the mitochondria, with damage to membranes and the nucleus and complete loss of intracytoplasmic organisation being observed subsequently. There was no apparent difference in ALA-PDT response between a multidrug-resistant ovarian carcinoma cell line and its parent line. These results indicate that ALA-PDT has potential for application to therapy of gynaecological malignancies.

Aminolevulinic Acid↗

PubMed1995

Ultrasensitive bioanalytical assays using time-resolved fluorescence detection.

This article reviews the use of time-resolved fluorimetric detection of lanthanide chelate luminescence as a detection method for ultrasensitive bioanalytical assays. Assay formats and detection methods, and the principle of time-resolved fluorimetric detection, are described. Detection systems, assay formats, reagents, and instrumentation for time-resolved fluorimetric detection are outlined. A review of published and commercially available immunoassays and DNA hybridization assays using time-resolved fluorimetric detection of lanthanide chelate luminescence is given.

Chelating Agents↗

PubMed1995

Time-resolved detection of lanthanide luminescence for ultrasensitive bioanalytical assays.

The principles and practice of the application of time-resolved lanthanide chelate luminescence (or fluorescence) as a detection method for ultrasensitive bioanalytical assays such as immunoassays and nucleic acid hybridization assays are reviewed. The various lanthanide chelate-based detection systems which have been developed for use in heterogeneous and homogeneous assay formats are described, including reagents, assay methods, and instrumentation, along with recent improvements in these methods. Detection systems described include those based on dissociative enhancement of lanthanide ions, direct labeling with luminescent chelates, enzyme-amplified lanthanide luminescence, lanthanide luminescence quenching, and energy transfer.

Animals↗