Temperature distribution produced by a cylindrical etched fibre tip in laser treatment of tumours by local hyperthermia
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A mathematical model is described for the temperature distribution produced when the optical fibre used in laser treatment of tumours has an etched cylindrical tip. Exact solutions are quoted for the equilibrium temperature distribution, of a form easily evaluated with minimal computing facilities. A number of special cases are worked out to illustrate the shape and size of the region treated for different lengths of the tip and different applied powers. Strongly scattering combinations of tissue and wavelength are considered, as well as an example in which absorption is dominant, and an intermediate case. These calculations can be used to estimate the power necessary, alignment of the fibre, and exposure necessary to treat a given tumour. It is clear from them that an etched fibre has many advantages over a conventional tip, especially the greatly reduced risk of charting of the tissue as the maximum temperature reached for a given power is much lower. Consequently, a larger region can be treated than would be possible with a normal tip. Information obtained in this way can be used to supplement the surgeon's experience when deciding on the appropriate form of treatment.
Key wordsLaser surgery Hyperthermia Tumours Etched fibre Thermal diffusion
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