PHYSICS

treatment of inflammatory, degenerative and dystrophic diseases,
such as trophic and indolent wounds, burns, injuries to tendons
and bones, arthritis, and gastric ulcers. The effects of red radiation
on the inflammatory processes, neuro-endocrine and nervous
systems, metabolism, bioelectric activity of organism, hematologic
parameters, and bone regeneration are excellent
examples of the use of laser phototherapy in animals. However, it
is necessary to note that specific parameters of laser radiation
(coherence, monochromaticity, polarization) do not appear to
be important. As a consequence, red light phototherapy can be
considered as usual photobiological phenomenon.
Laser Photochemotherapy. This photomedical technique is based
on the ability of the photosensitizer to accumulate and be selectively
retained in malignant tissue to a greater degree than in normal
tissue. As a consequence, laser irradiation can be used to preferentially
destroy tumors. Laser photochemotherapy involves the
injection of a photosensitizer and after an appropriate incubation
period, illumination of the malignant tissue with laser radiation
(48 - 72 hours). The photosensitizer absorbs sufficient light energy
to shift the molecule from the singlet to a tri plet state. The
excited triplet state photosensitizer then produces either free
radicals or singlet oxygen that oxidatively disrupt the cells in malignant
tissue causing necrosis and death. Photosensitizers commonly
employed in the laser photochemotherapy of the malignant
tumors are hematoporphyrin derivatives (HpD). Secondary
effects of HpD include edema and sunburn of the skin if the
patient is exposed to excessive sunlight. The development of new
photosensitizers without adverse side-effects represents an important
research topic.
Laser Acupuncture. The ability of laser radiation to penetrate
tissues allows it to be used for acupuncture - a medical procedure
that involves the stimulation of biologically active points on
the surface of the body. An example of the positioning of the
acupoints on an animal is presented in fig. 23.4. The advantages
lasers confer to acupuncture are that it is non-invasive, rapid,
aseptic, and painless. Typical acupuncture parameters for laser
radiation are a 1 - 2 mm diameter laser beam and a radiation intensity
of about 1 - 5 mw/cm". Usually an optical system (laser
and fiber) is used in conjunction with an electrical system that
Fig. 23.4. The typical picture of acupoints of the animal
monitors skin resistance to indicate the appropriate positions for
the acupoints. Changes in resistance are indicated by a sound or
light signal. The duration of the laser radiation treatment is for a
relatively precise time interval. Treatment effects on animals include
increased phagocytosis, tissue granulation, stimulated collagen
synthesis, vascularisation, acetylcholine release, production
of T- and fj-lymphocytes, increased serotonin synthesis, inhibition
of prostaglandin effects in the tissue, stimulation and release
of fj-endorphins, and increased synthesis of ketosteroids and hydroxycorticosteroids.
The adoption of laser acupuncture remains a subject of debate
with the advantages of the procedure being touted by supporters
and the deficiencies by opponents.
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