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Optical Techniques and Biomedical Applications, IEE Colloquium on

Date 14 Jun 1991

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Displaying Results 1 - 15 of 15
  • Allergy testing using photon counting techniques

    Page(s): 17/1 - 17/3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    A simple photon counting system capable of detecting the chemiluminescent emission levels from each thread of the MAST test chamber has been demonstrated. This has been used in the determination of allergen specific IgE in serum samples. The results obtained using this system agree with those obtained using the photographic system. The system is capable of measuring emission levels up to 20 hours after initiation of the enzymatic reaction. The new system is much faster and easier to use than the photographic system, and can be made into a one stage, compact system View full abstract»

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  • A novel processing scheme for a fibre optical low coherence laser Doppler anemometer system [for blood flow measurement]

    Page(s): 9/1 - 9/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    A system has been assembled for measuring the Doppler frequency shift of scattered light in order to determine velocity. The signal recovery scheme utilises a novel adaptation of a Michelson interferometer to give two output signals in quadrature. Simple signal processing of the output signals then allows determination of velocity rather than speed, in a system which uses simple inexpensive optical components. The system also utilises a low coherence light source. This suppresses unwanted signals and allows the measurement region to be projected ahead of the fibre probe. The instrument is currently being tested in the measurement of fluid flow velocities View full abstract»

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  • Laser angioplasty delivery systems and tip configurations

    Page(s): 3/1 - 3/6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    Laser energy has the potential to vaporize atherosclerotic arterial disease by photo-thermal and photo-ablative effects. Atraumatic delivery devices have been developed which are capable of efficient energy transfer to the target tissue. Recanalisation of totally occluded arteries is possible using both CW and pulsed lasers but perforation and dissection, at rates of up to 30%, remain a problem. Further developments in the field of steerability and imaging are likely to have the largest impact in improving the success rate of laser recanalisation. It would probably be beneficial if the next generation of delivery devices were able to achieve sufficient removal of occluding atheroma to create a lumen which does not require adjunctive balloon dilatation. Restenosis remains a significant cause of failure during long-term follow up View full abstract»

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  • A hollow glass waveguide for CO2 laser power delivery

    Page(s): 12/1 - 12/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    Hollow glass waveguides utilising the anomalous dispersion effect (i.e. η<1) could be used in medical applications requiring CO2 laser power delivery. Certain benefits are possible with this type of waveguide when compared with alternative developments. These include the launching of high power densities with minimal coupling losses. The use of glass material formed from essentially nontoxic constituents could lead to the manufacture of a comparatively cheap waveguide with the application of conventional fibre drawing techniques. The hollow glass waveguide discussed has introduced a degree of flexibility, although attainment of low losses around curvatures of a few centimetres requires further development. Nevertheless, the flexibility achieved may be suitable for delivery systems involving straight and bent rigid endoscopes such as those employed in laparoscopy and bronchoscopy View full abstract»

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  • IEE Colloquium on `Optical Techniques and Biomedical Applications' (Digest No.128)

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (12 KB)  

    The following topics were dealt with: optical generation of thermoelastic waves in tissue; photodynamic dosimetry; laser angioplasty delivery systems; lasers in ophthalmology; gas and solid-state lasers for medical use; optical noncontact measurements during anaesthesia; quantitative fluorescence microscopy of photosensitisers fibre delivery systems for laser hyperthermia; noninvasive measurements using infrared spectroscopy; minimally invasive fibre optic sensors; evanescent fluorescence immunosensor; allergy testing using photon counting View full abstract»

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  • Non-invasive measurement of tissue oxygenation using near infrared (NIR) spectroscopy

    Page(s): 14/1 - 14/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    Non-invasive optical spectroscopy across many centimetres of living tissue is possible at wavelengths between 650 nm and 1100 nm. The short wavelength cut-off wavelength is caused by absorption of light by haemoglobin and the long wavelength cut-off by water absorption. Typical NIR attenuation coefficients are one optical density loss for each centimetre of tissue travelled. Haemoglobin is present in the circulation, and in its oxygenated (HbO2) and deoxygenated (Hb) forms acts as an indicator of blood oxygenation while cytochrome c oxidase (Cyt) in its oxidised and reduced forms is present in the tissue and acts as an indicator of intracellular oxygenation. Problems of multiple scattering in tissue spectroscopy are examined and a method proposed for determining the differential pathlength. Possibilities of adapting the technique to bedside monitoring are also discussed View full abstract»

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  • Quantitative fluorescence microscopy of photosensitisers: aluminium sulphonated phthalocyanine (AlSPc)

    Page(s): 10/1 - 10/3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    A quantitative technique based on fluorescence microscopic detection has been developed for measurements of AlSPc distributions in frozen sections of tissue and cultured cells. Imaging for AlSPc fluorescence was achieved with negligible interference from AlSPc photodegradation and tissue autofluorescence using laser excitation (at 633 nm) and detection with a highly sensitive CCD (charge-coupled device) camera system. Once the image is recorded the tissue section is stained for confirmation of histology. This has enabled pharmacokinetic studies of AlSPc distributions at the microscopic level: for example, in the case of rat bladder the authors have shown that uptake in the mucosa relative to the muscle layer is highest at 24 hours. Since the level of fluorescence should correlate with the AlSPc photoactivity these results are important in determining the optimal treatment time View full abstract»

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  • Minimally invasive high resolution fibre optic interferometric sensors for temperature and pressure measurements

    Page(s): 15/1 - 15/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    The author discusses the potential of fibre optic interferometric sensors for diagnostic temperature and pressure measurements. Problems in the use of these sensors (signal fading and ambiguity) are found to be overcome by the use of `white light' signal processing View full abstract»

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  • Near infrared solid state lasers for medical applications

    Page(s): 7/1 - 7/6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    There have however been recent advances in crystal growth techniques and laser development which have allowed several new laser systems to be designed. These new solid state lasers, in particular erbium YAG, holmium YAG and titanium sapphire, which all operate in the near infrared at wavelengths ranging from 650 nm to 3 μm, open up the possibility of new and improved surgical techniques because of the particular interaction of these wavelengths with biological tissue and the pulsed nature of these flashlamp pumped laser systems View full abstract»

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  • A novel method to determine and control power delivered during laser angioplasty

    Page(s): 4/1 - 4/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    For accurate measurements the in-line powermeter (ILP) described requires standardising against a bolometer each and every time it is used, since the registered power varies with each fibre placement. However, fibre alignment may be accomplished using the ILP alone. The combination of the laser output powermeter (LOP) and the ILP provides accurate and inexpensive control of laser power during angioplasty. Both dye degradation and damage to the proximal end of delivery devices may be identified. The power delivered can thus be accurately controlled without removing the delivery device from the patient, thereby improving safety and efficiency View full abstract»

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  • An evanescent fluorescence immunosensor based on K+ and Na+-exchanged patterned optical waveguides in glass

    Page(s): 16/1 - 16/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (180 KB)  

    The authors describe, the successful fabrication of K+ and Na+-exchanged patterned waveguides and their application to wash-free immunoassays using evanescent excitation of fluorescence. Experimental results show that the specific binding of a fluorescently labelled antibody to its appropriate antigen could be resolved at the concentration level of 1 μg/ml View full abstract»

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  • Optical non-contact measurement of abdominal volume change during anaesthesia

    Page(s): 8/1 - 8/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    A low cost optic method for chest wall measurement is described. The equipment operates in real time and allows changes in breathing patterns to be tracked. A low power Helium Neon laser beam is used to generate a plane of light that can be positioned rapidly (1 ms) by means of a galvanometer mounted mirror to illuminate the chest wall at a selected position. At each illumination position, a frame of information from a video camera is processed by special purpose electronics, to extract shape information from the illuminated contour and thus reduce the amount of data that requires to be processed. The plane is sequenced through a number of positions to derive 3-D information for the complete chest surface. Information from the hardware is passed to a Personal Computer to process and display the results. Alternate forms of data can be presented to the operator within three minutes of measuring a 108 second breathing episode View full abstract»

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  • The basis for photodynamic dosimetry and consequences for light delivery systems

    Page(s): 13/1 - 13/4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    The author discusses the need to make physical measurements of the space irradiance in tissue in order to establish effective and repeatable treatment of patients using photodynamic therapy. Work on the development of fibre based detectors, which can be used to monitor the space irradiance, is examined. Implications for light delivery are also discussed View full abstract»

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  • A comparison of CO and CO2 lasers for medical applications

    Page(s): 6/1 - 618
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (364 KB)  

    The authors investigation of the interaction of CO laser light with tissue was motivated mainly by the possibility of fibre delivery of the 5 micron wavelength. If the CO laser has a similar tissue interaction to CO2, then there could be a major market for such medical laser systems. The fibre delivery would open new potential treatments in fields such as angioplasty, laserthermia and other procedures possible only by fibre delivery View full abstract»

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  • Lasers in ophthalmology: new lasers, new optics, new frontiers

    Page(s): 5/1 - 5/2
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (100 KB)  

    The authors discuss progress of lasers in ophthalmology on five fronts, diagnostic and surgical. Previously, diagnostic techniques, utilising lasers have been limited and esoteric; however, the emergence of the laser scanning ophthalmoscope holds much promise. On the surgical front, the application of newer lasers for new procedures to relieve glaucoma and more sophisticated controls such as short bursts of femtosecond or picosecond pulses in order to restrict the damage zones promise better treatments for sight threatening diseases View full abstract»

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