[Show abstract][Hide abstract]ABSTRACT: Patients who have had one oral cancer are at increased risk of developing a further malignant tumour, the detection of which is made difficult (and is often delayed) by the innocuous appearance of the early oral lesion. A technique that could reliably detect early cancers would be useful to both oral and dental health specialists. We describe a pilot study in which we used a compact spectroscopic instrument designed to excite and measure fluorescence in the oral cavity. The data were processed using principal components analysis, and the results suggest that the technique might be valuable for detecting early oral cancers. Further work should be performed to investigate some unusual characteristics observed within our data to ascertain if these are significant, simply due to errors made due data collection, or are due to other lifestyle factors. Such work could also verify that the data are due to detection of ALA metabolite in cancer and not some other systemic effect.
Full-text available · Article · Feb 2008 · British Journal of Oral and Maxillofacial Surgery
[Show abstract][Hide abstract]ABSTRACT: Topical photodynamic therapy (PDT) is increasingly being used to treat skin cancers. Knowledge of the detailed characteristics of 5-aminolaevulinic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence in diseased and normal skin is incomplete. Understanding the characteristics of PpIX fluorescence in normal skin may facilitate optimization of PDT regimes while minimizing side effects in the surrounding normal skin. We investigated the characteristics of ALA-induced PpIX fluorescence in normal skin.
ALA was applied to the arm, back and leg skin of 21 healthy volunteers for 1-6 h, and PpIX fluorescence was measured for up to 24 h after ALA application using a fluorescent spectrometer. The effect of tape stripping on fluorescence was also examined.
Considerable inter-subject variation was observed in the time to reach peak PpIX fluorescence. Intra-subject variation in the time to peak fluorescence was dependent on ALA application time. Six hours after ALA application, no significant difference was observed in the degree of fluorescence achieved irrespective of ALA application times ranging between 1 and 6 h. PpIX fluorescence was reduced on the leg and increased by tape stripping.
Marked inter- and intra-subject variation in ALA-induced PpIX fluorescence occurs in normal human skin. ALA application time, body site and the state of the stratum corneum are all determinants of PpIX fluorescence within subjects and these factors need to be taken into account in optimization of PDT regimes.
Full-text available · Article · May 2006 · Photodermatology Photoimmunology and Photomedicine
[Show abstract][Hide abstract]ABSTRACT: Patients who have had one oral cancer are at increased risk of developing a semi-malignant tumour. The detecting of oral cancer is made difficult (and is often delayed) by the unknown appearance of the early oral lesion. A technique that could reliably detect early cancers would be useful to the oral and dental health specialist. One possible technique is the use of a photosensitiser that may be preferentially taken up by cancerous cells. 5-aminolaevulinic acid (ALA) is one such drug that is converted to Protoporphyrin IX (PpIX) and fluoresces at 636nm when illuminated with light of wavelength 405nm. It has been hypothesized that cell inclined towards malignant change would have a higher metabolic rate, and thus convert more ALA into its metabolite PpIX. These drugs can then be detected using a technique called Photodynamic detection, through the analysis of their fluorescence spectra. We describe a pilot study that used a compact spectroscopic instrument designed to excite and measure fluorescence in the oral cavity. Some Inter-subject variation in PpIX time course characteristics may be evident in our volunteers, as has been reported by other researchers. The obtained data would suggest that this instrument may be a valuable tool for detecting early oral cancers. However, further studies are required, not least to ensure that these data are due to detection of ALA metabolite in cancer and not some other systemic effect.
Full-text available · Article · Mar 2005 · Proceedings of SPIE - The International Society for Optical Engineering
[Show abstract][Hide abstract]ABSTRACT: Topical photodynamic therapy (PDT) is increasingly accepted and used
as a highly effective treatment for superficial non-melanoma skin cancer and dysplasia.
We describe the developments in topical PDT for the treatment of skin diseases
in our own PDT Centre in Dundee, both clinically and from a research base. Improvements
in PDT could be achieved by optimisation of photosensitiser and light
delivery, and these goals underpin the aims of our centre. We hope to facilitate the
dissemination of use of PDT in dermatology throughout Scotland and outline some
of the progress in these areas.
Full-text available · Article · Nov 2004 · Photodiagnosis and Photodynamic Therapy
[Show abstract][Hide abstract]ABSTRACT: In recent years, 5-aminolaevulinic acid (ALA) has become an increasingly popular photosensitizing drug for use in both photodynamic therapy (PDT) and photodetection (PD) of cancers. ALA metabolizes within tissue to form the photosensitizer protoporphyrin IX (PpIX). Like most photosensitizers, PpIX is fluorescent, and this fluorescence progressively decreases during PDT. This phenomenon is referred to as photobleaching.
Our aim in carrying out this experiment was twofold: firstly, to compare the relative capacity of red and blue light to cause photobleaching; and secondly, to compare the capacity of a fixed light dose to cause photobleaching, when delivered at different intensities.
In this paper, we describe the implementation of a compact fluorescence spectrometer in monitoring the photobleaching of ALA-induced PpIX in vivo on the skin of healthy volunteers.
We have been able to show that blue light causes more rapid photobleaching than red light, and that under illumination with red or blue light, delivery of a fixed light dose at a lower intensity results in more photobleaching.
Comparison of the photobleaching rates suggests that a blue light intensity of 5 mW/cm(2) gives the same rate of photobleaching as the typical red light PDT intensity of 100 mW/cm(2). Further investigation of the correlation between PpIX photobleaching and PDT effect would be beneficial in interpreting the clinical significance of our findings.
Full-text available · Article · Sep 2004 · Photodermatology Photoimmunology and Photomedicine
[Show abstract][Hide abstract]ABSTRACT: We describe a differential fluorescence detection system that consists of a 405 nm diode laser for fluorescence excitation, a bifurcated fibre for delivery of light to and collection of light from tissue, birefringent prisms and a tilted filter. This instrument is optimized for the selective detection of protoporphyrin IX fluorescence and autofluorescence from tissue, and its effectiveness demonstrated using low excitation light levels (0.7 mW cm/sup -2/).
Full-text available · Article · Aug 2003 · Journal of Physics D Applied Physics
[Show abstract][Hide abstract]ABSTRACT: We present a compact, portable, and mechanically robust instrument for measuring optical wavelength based on an arrangement of four Wollaston prisms that forms spatially localised fringes in a plane perpendicular to the optic axis. The wavelength is determined from the fringe period. After calibration, the instrument had an accuracy of c. 1 of 106, and was immune to fluctuations in output intensity of a light source of up to 10 dB.
[Show abstract][Hide abstract]ABSTRACT:  Sulphur speciation in volcanic gases acts as a major redox buffer, and H2S/SO2 ratios represent a valuable indicator of magmatic conditions and interactions between magmatic and hydrothermal fluids. However, measurement of H2S/SO2 even by direct sampling techniques, is not straightforward. We7 report here on application of a small ultraviolet spectrometer for real-time field measurement of H2S and SO2 concentrations, using open-path and extractive configurations. The device was tested at fumaroles on Solfatara and Vulcano, Italy, in November 2002. H2S concentrations of up to 220 ppmm (400 ppmv) were measured directly above the Bocca Grande fumarole at Solfatara, and H2S/SO2 molar ratios of 2 and 2.4, respectively, were determined for the ‘F11’ and ‘F0’ fumaroles at Vulcano. In comparison with other optical techniques capable of multiple volcanic gas measurements, such as laser and FTIR spectroscopy, this approach is considerably simpler and cheaper, with the potential for autonomous, sustained high-time resolution operation.
Full-text available · Article · Jun 2003 · Geophysical Research Letters
[Show abstract][Hide abstract]ABSTRACT: We present a device designed to measure laser output wavelength and based on Wollaston prisms and barium borate (BBO) crystal polarizers. The arrangement generates a localized fringe plane perpendicular to the optic axis at which a CCD array is placed; consequently, good spatial coherence of the light is not a critical requirement for effective operation of the device. The interferogram is recorded with a digital camera allowing complete pixel registration, which results in improved accuracy. After calibration of the arrangement, the wavelength can then be measured with a precision of better than 1 part in 10/sup 5/, and has been shown to track changes in the output wavelength of the laser sources used. In addition, the calibrated wavelength meter was found to be able to measure the absolute value of a series of defined laser lines to an accuracy of 0.18 % (+or-0.86 nm).
Full-text available · Article · Jun 2002 · Proceedings of SPIE - The International Society for Optical Engineering