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328 Optical Fiber Techniques for Medical Applications

include optical fibers for diagnostic purposes, and the A. Gastroenterology
distal end of these fibers might even include transducers
One of the first uses of the fiberoptic laser endoscope was
(optodes). A third channel would include a power fiber,
in treating bleeding ulcers. The laser light could photo-
for laser power delivery. A fourth channel could be used
coagulate blood and therefore cause hemostasis (cessa-
for injecting liquids such as drugs, dyes, or saline solution.
tion of bleeding). Among the three important lasers (CO 2 ,
This (or another) channel could be used for pumping out
Nd:YAG, and Ar), some physicians prefer the Nd:YAG
liquids or for the aspiration of gases.
laser because it penetrates deep into tissue and its ef-
Some of these systems incorporate novel devices
fects are not localized at the surface. Others have used the
such as miniature ultrasound devices that provide three-
Ar ion laser for controlling gastric hemorrhage (bleed-
dimensional (3D) imaging. This is particularly useful in
ing). In both cases, the laser beam is sent through thin
cardiology for 3D imaging inside blood vessels. Laser en-
silica “power”fibers. These procedures have been per-
doscopes have reached the stage where they are being used
formed on patients with bleeding ulcers in the stomach,
clinically in several medical disciplines such as otolaryn-
the esophagus, or the colon, and the results have been very
gology, gynecology, gastroenterology, and brain surgery.
good.
Some examples are mentioned in Section VII.
B. Urology
D. Robotic Systems
An Nd:YAG laser beam, sent through the power fiber of
Incorporating complex computer controls, which make
a laser endoscope, is used for destroying small tumors
it a robotic system, could enhance the effectiveness and
in the urinary bladder. In other cases, larger tumors are
safety of surgical endoscopic systems. In a simple ver-
electroresected (using the endoscopic snare described ear-
sion of the system, the thin articulated arms of a robot are
lier), and Nd:YAG radiation is then used for coagulation.
equipped with surgical tools. These are inserted into the
Again, the deep penetration of Nd:YAG in tissue may be
body through a small incision. The physician does not di-
advantageous.
rectly operate the surgical instruments. Instead, the physi-
Laser catheters based on dye lasers and Nd:YAG lasers
cian operates joysticks at the robot’s computer control,
have been used for laser lithotripsy, the shattering of stones
which is located near the patient. These joysticks, in turn,
inside the body. In this case, the catheter is inserted into
control the placing and the operation of the surgical instru-
the body and the distal tip of the power fiber is brought in
ments using the sophisticated electronics and software of contact with the stone. Dye laser, Ho:YAG, or frequency-
the system. A thin endoscope is also inserted into the body. doubled Nd:YAG laser pulses sent through these quartz
This endoscope could be a flexible or rigid fiberoptic en- fibers are absorbed in the stone surface and generate hot
doscope, with two imaging bundles, or it could incorporate plasma. The resulting shock waves rapidly shatter the
two tiny CCDs. In both cases, it would be possible to gen- stone. This procedure is particularly useful in cases where
erate a 3D image of the treated site, which is important other methods such as shock wave lithotripsy cannot be
for the control of the surgical tools inside the body. The applied. Laser lithotripsy has been successfully applied
accuracy of the operation of such a robotic system can, in on patients for the removal of urinary stones or biliary
principle, be very high. In the future, the articulated arms
stones. (Comment: an identical procedure has been used
of the robot could be replaced by optical fibers, which will
in otolaryngology for salivary gland calculi.)
provide both diagnosis and therapy (or surgery), and the
With aging, the prostate of the human male enlarges
whole system will be endoscopic.
and presses on the bladder or the urethra. This condition,
called benign prostatic hyperplasia, results in poor urine
flow and large residual urine volume. The prostate can
VII. LASER–FIBEROPTIC SYSTEMS AND be resected surgically using a cauterizing tool inserted
THEIR CLINICAL APPLICATIONS through the urethra. This transurethral resection of the
prostate (TURP) is a very common surgical procedure, but
An increasing number of physicians are using integrated has many undesirable side effects. Alternatively, a laser
laser–fiberoptic systems, such as laser catheters or laser catheter could be inserted through the urethra, and placed
endoscopes, in a clinical setting. A few examples illus- inside the prostate. A visible laser beam sent through the
trate the use of laser catheters and endoscopes for clinical power fiber can then be used to ablate the prostate, in a
applications. The sections on cardiology and on cancer procedure called visual laser prostatectomy (VLAP). Al-
diagnosis and therapy illustrate the enormous potential of ternatively, laser-induced laser therapy can be used for the
laser–fiberoptic techniques. treatment of the prostate gland. A beam of Nd:YAG laser