Laser spectroscopy applied to environmental and ecological research
Prof Sune Svanberg, Lund University, Sweden and South China Normal University, Guangzhou, China
Laser spectroscopy has been shown to be a valuable tool both in the detection and the therapy of human malignancies. The most important prognostic factor for cancer patients is early tumour discovery. If malignant tumours are detected during the non-invasive stage, most tumours show a high cure rate of more than 90 %. Even though there are many conventional diagnostic modalities, very early tumours may be difficult to discover. Laser-induced fluorescence (LIF) for tissue characterisation is a technique that can be used for monitoring the biomolecular changes in tissue under transformation from normal to dysplastic and cancer tissue before structural tissue changes are seen at a later stage. The technique is based on UV or near-UV illumination for fluorescence excitation. The fluorescence from endogenous chromophores in the tissue alone, or enhanced by exogenously administered tumour seeking substances can be utilised. The technique is non-invasive and gives the results in real-time. LIF can be applied for point monitoring or in an imaging mode for larger areas, such as the vocal cords or the portio of the cervical area.
Photodynamic therapy is a selctive treatment technique for human malignancies. To overcome the limited light penetration in superficial illumination interstitial delivery (IPDT) with the light transmitted to the tumour via optical fibres has been developed. Interactive feed-back dosimetry is of importance for optimising this modality and such a concept has been developed. The technique has special interest for tumours where there are no other options, such as for recurrent prostate cancer after ionising radiation. For correct dosimetry it is important to assess the optical properties of tissue; this can be done by time resolving propagation techniques.
Another technique which has been developed for medical application is based on gas in scattering media absorption spectroscopy (GASMAS). The technique is used to detect free gas (e.g., oxygen and water vapour) in hollow organs in the human body and has been applied to the detection of the human sinus cavities in the facial skeleton. The GASMAS technique might also be used for the surveillance of prematurely born infants. As the organs are not fully developed there is a risk of morbidities. In particular, the lung function is limited and the babies may develop respiratory distress syndrome resulting in decreased oxygen saturation affecting risk organs, such as the brain. GASMAS may also be developed for detection of other diseases, such as middle ear infection in small kids. A certain proportion of these infections are viral induced and in these cases no antibiotics should be prescribed. GASMAS has a potential to discriminate the origin of the disease and thus guide in the decision of appropriate therapy, trying to fight the global problem of antibiotic resistance. Many of these techniques can also be applied to study other organic materials, e.g., food.
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