Lasers Invention to Application (1987) / Chapter Skim
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Lasers in Medicine
Lasers in Medicine
Pages 101-117
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From page 101... ...
Although the range of laser radiation extends both below and above the visible portion of the electromagnetic spectrum, that radiation is, in a sense, only a special form of light. The use of other forms of light in medicine has a longer history.
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From page 102... ...
In Europe in the late eighteenth and early nineteenth centuries, at the height of the Industrial Revolution, a myriad of factories and industrial plants spewed smoke into the atmosphere, filtering out many of the beneficial components of the sun's rays. Deprivation of ultraviolet radiation contributed to calcium deficiency in the main skeletal bones, leading to the characteristic deformity known as rickets.
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From page 103... ...
Both infrared lasers, the Nd:YAG and particularly the CO2, have found a variety of clinical applications. The CO2 laser has been used to vaporize tissue in almost every specialty, whereas the Nd:YAG laser has been used primarily for tissue coagulation in gastroenterology and urology.
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From page 104... ...
This results in reduced cost, lower morbidity, and less time away from work. Even when MIS techniques are used as an adjunct to more invasive surgical approaches, reduced destruction of tissue frequently leads to quicker recovery with a shortened, lower cost hospitalization.
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From page 105... ...
Thus, each of the surgical laser wavelengths has advantages and disadvantages depending upon the target tissue and the surgical effect desired. It is not completely accurate to generalize about the relative amounts of penetration and scatter of these surgical lasers in tissue, because that is a function of wavelength and the specific absorption characteristics of individual tissues.
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From page 106... ...
The thermal center produced by the Nd:YAG laser is actually beneath the surface of the target tissue, thus making it difficult for the surgeon to judge the ultimate surgical effect. The visible wavelengths have some of the surface heat effect of the CO2 laser, especially once surface vaporization and some penetration into the tissue is initiated.
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From page 107... ...
Coagulation for hemostasis is best effected by using a lower energy density, which is achieved by enlarging the spot size or lowering the absolute power or exposure duration. The surgeon can use this technique, particularly with the visible wavelength lasers and the Nd:YAG laser, for prophylactic hemocoagulation to prevent bleeding in small vessels and vascularized target tissue and to control small vessel hemorrhage if it occurs (Figure 31.
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From page 108... ...
excision. The optimum beam conditions are a large spot size and high power density to achieve a higher rate of tissue removal (Figure 4~.
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From page 109... ...
Coagulating, cutting, and vaporizing are generic surgical effects achieved throughout a procedure by manipulating the beam parameters. When combined with an understanding of 1 111
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From page 110... ...
In the late 1960s, pioneering ophthalmologists first applied the ruby and then the argon laser to prevent and control bleeding from retinal vessels. The visible wavelengths are well suited to this task, since they pass through the cornea, lens, and fluids of the interior of the eye with little absorption until they encounter the hemoglobin pigment within the retinal vessels or the pigment in a layer adjacent to these vessels.
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From page 111... ...
More recently, the KTP/532 laser has also been shown to be effective for these disorders. The visible wavelengths work particularly well in the treatment of skin lesions that involve vascular abnormalities and in the removal of tattoos.
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From page 112... ...
GASTROENTEROLOGY The hemostatic effect of the Nd:YAG and argon lasers has been used to control bleeding from gastric ulcers. However, this application is being superceded by a less expensive resistance heater probe employed in a similar manner through a fiberoptic gastroscope.
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From page 113... ...
Both visible and infrared wavelengths offer increased precision of removal, as well as reduced bleeding and traction on neural structures. These factors reduce patient morbidity and possibly also lower the incidence of certain potential complications.
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From page 114... ...
UROLOGY Clinical application and investigational use of lasers in several urological conditions represent another outstanding example of minimally invasive surgery and the expanding impact of this technology. Bladder tumors that have not penetrated beyond the musculature of the bladder wall are treated with a minimally invasive technique through the natural urinary orifice.
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From page 115... ...
Using an intravascular viewing catheter that holds a fiber-optic waveguide to approach and destroy an obstructive coronary artery lesion is an exciting concept the stuff that dreams are made of. Whether this is feasible by using a laser remains to be seen.
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From page 116... ...
Argon lasers are being used investigationally in attempts to vaporize obstructive lesions directly and to heat probe tips. Excimer lasers are being studied for use in plaque removal, but use of certain ultraviolet wavelengths is encumbered by delivery problems and the longer term mutagenic potential.
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From page 117... ...
Instrumentation derived from combinations of photoelectronics and other core technologies will produce still more alternatives to standard surgical approaches. Exotic and more highly specialized delivery devices will expand the surgeon's ability to achieve precision therapy with low morbidity.
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