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Leon Goldman first pioneered laser surgery by using lasers to treat cutaneous melanoma, in 1961, in his dermatologic practice. In 1966 he again became the first to use lasers for tumor removal. He went on to become a founder of the American Society for Laser Medicine and Surgery (ASLMS) in 1979.
Surgical Applications
Lasers have made great advances in the field of surgical applications. This is because of its collimated and intense beam which releases high energy in the targeted tissue, but can be adjusted to minimize collateral damage.
The ability to focus the laser beam allows precise cutting or ablation of tissue, instead of using a steel scalpel. Other advantages of using a laser beam for surgery include the reduction in pain and tissue contact, resulting in less pain and shorter recovery times, and excellent control of bleeding. As a result lasers are being used in diverse areas such as:
- Removing tumors in difficult or inaccessible locations with less difficulty and tissue damage
- Treating superficial growths and very early skin tumors
- Removal of tumors in the female pelvic organs
- Cosmetic and dermatologic procedures including scar removal, skin resurfacing, and vascular tumor treatment
- Direct tumor removal
- Debulking or shrinking obstructing growths in the trachea, esophagus, bronchial tree and colon, to relieve symptoms such as dyspnea, dysphagia or obstructed bowel. Lasers are also useful in removing secondary tumors from lung tissue, in place of excising large lung segments surgically, as the latter would require prolonged recovery times and cause greater pain and suffering. Such palliative techniques are important in improving the quality of life in patients who cannot be cured of their cancer.
- Laser treatment of many malignant neoplasms of the head, neck, lungs and airways, and some vocal cord tumors
Increasing the Precision of Laser Surgery
Laser surgery is ever advancing in effectiveness and accuracy. The following factors help achieve spot precision:
Wavelength
Infra-red region lasers such as the CO2 and Nd:YAG lasers are preferred to reduce tumor size or remove tumors. Near- infrared lasers are weakly absorbed by tissues compared to infrared and mid infrared lasers. Increasing the laser power causes more collateral damage, however.
Use of Flexible Optics
They are often used with endoscopes for internal procedures on the stomach or urologic organs. Other lasers can be fitted to flexible fiberoptics to allow surgery in deeper parts of the body without big incisions. Endoscopic visualization allows precise placement of the laser beam.
Spot Size
By adjusting the spot size the precision of laser surgery can be optimized while avoiding collateral tissue damage due to excessive penetration of the laser beam.
Laser Mode
Choosing the right laser mode is essential in achieving the optimal results with good coagulation parameters but minimal tissue damage outside the operating zone. The use of pulsed laser allows greater but more focused power than continuous wave lasers.
Microsurgery
Another way in which lasers improve accuracy is by coupling them with low-power microscopes which magnify the operating area. The use of micromanipulators allows fine movements within as little as 200 microns.
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Constant Improvement
The principle underlying the surgical laser ought to ensure its ability to achieve single-cell resolution and thus help to perform minimally invasive procedures. The problem with this goal has been the thermal and mechanical damage to adjacent tissue.
Early on, continuous wave (CW) lasers were in use. The discovery of the CO2 laser allows laser incisions and tissue excision, while the argon laser is more useful in eye and skin surgery. The Nd:YAG laser is used alone or after passing it through the KTP (potassium titanyl phosphate) crystal for frequency doubling to operate on the eye or for laparoscopic procedures. CW lasers have the unpleasant feature of causing non-selective photothermal tissue-laser interactions with collateral tissue damage. The need for a long period of learning and much experience limited their clinical application to a few centers at first.
Selective Photothermolysis
However, Richard Anderson and John Parrish introduced selective photothermolysis in 1983, using lasers which are absorbed only by cells containing specific pigments for each type of laser used, and short laser pulses. This innovation led to the availability of precisely induced heat injury to treat vascular and pigmented skin lesions without significant scarring, using very short pulses to target only pigmented cells. There is no need for precise focusing of the laser beam upon a particular cell because the selectivity is provided by the optical pigment itself.
The key determinants for accurate treatment in this method are the threshold fluence and the thermal relaxation time. The threshold fluence is taken advantage of to ensure precise and controlled damage zones by adjusting the wavelength, the fluence and the pulse duration. Multiple synchronized pulsing is a technique used to minimize nonspecific epidermal damage due to its high pigment content.
This led to the widespread use of the pulsed yellow dye laser to treat vascular lesions, and later the development of Q-switched lasers at very short pulses for highly targeted treatment of pigmented lesions and tattoos.
Scanning Lasers
In the 1990s scanning technology was coupled with the CO2 and Er:YAG lasers to provide computerized laser control. This resulted in the development of fractionated lasers, splitting the laser into thousands of tiny beams to induce zones of damage in between untreated areas, which promote the rapid regrowth of normal skin to re-epithelialize the treated areas. Dynamic thermal optimization is a technique that tunes the laser beam automatically to match skin heating, thus preventing under- and overtreatment.
Newer Developments
The Picosecond IR Laser (PIRL) is a novel laser concept which transfers energy to the water in the tissue, causing them to vaporize to produce tissue ablation, but avoiding mechanical or ionizing damage. Photochemical and photothermal effects are minimized by the targeted process. The scars are thinner and more collagen is regenerated during early wound healing. Better wound healing means shorter recovery times. Sonoillumination is a very new technique which changes skin properties using an ultrasound generator, coupled with an arrangement that ensures that the laser works only if it is in touch with the skin, protecting the eyes and the skin from unintended exposure.
Sources and Further Reading
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