New techniques in laser therapyBMJ 1998; 316 doi: https://doi.org/10.1136/bmj.316.7133.754 (Published 07 March 1998) Cite this as: BMJ 1998;316:754
- Stephen G Bown, professor of laser medicine and surgery
- National Medical Laser Centre, Department of Surgery, University College London Medical School, London W1P 7LD
From a medical point of view, lasers are a convenient but sophisticated source of light in the visible, ultraviolet, and infrared parts of the spectrum. They are easy to control, and the light beam (of a single colour) can be focused to a small spot and in many cases can be transmitted via thin flexible fibres, making internal delivery of light feasible. The range of clinical applications is enormous, from the simple carbon dioxide laser, used as a non-contact scalpel or for superficial tissue ablation, to the precision of the excimer laser, used for reshaping corneas, and the flash lamp pumped dye laser, used to close the small blood vessels of disfiguring port wine birthmarks. This review looks at how the precision of light delivery and the predictability of biological response possible with laser therapy is starting to be exploited for the in situ destruction of diseased tissue and how these techniques might be developed in the future.
The first requirement for successful clinical use of lasers is to understand how light at the wavelength used can interact with living tissue. Most of the simple applications are thermal, but the effect produced depends on how much heat is delivered, how fast it is delivered, and the volume of tissue in which it is absorbed. Increasingly, however, the new technique of photodynamic therapy (non-thermal effects from combining laser light and a photosensitising drug) is attracting interest. This review considers particularly the effects of low power thermal treatment and photodynamic therapy (see table).
Thermal laser therapy
The carbon dioxide laser (wavelength 10 600 nm in the far infrared) is well established as a non-contact scalpel in relatively inaccessible areas like the brain and upper airways and for ablating small lesions as on the skin. However, the beam cannot be transmitted via flexible fibres and can …