20071011

Tools for the Physician

In their search for ways to improve the diagnosis and treatment of medical problems, researchers have always been eager to study technological advances. The microscope, X rays, lasers, ultrasonics—these are but a few technologies that quickly found use in the medical community. The many applications of technology to medicine have had enormous benefits, enabling millions of people to enjoy longer, healthier, and more productive lives.

Lasers

A laser is an instrument that produces a narrow, highly concentrated beam of light. All the light in the beam is of the same wavelength and travels in the same direction. The specific wavelength is determined by the material stimulated to emit the light. For example, argon laser energy is quickly absorbed by hemoglobin. This makes it a very effective tool for stopping bleeding from small blood vessels. Energy from a carbon dioxide (CO2) laser can be narrowly localized, making this laser a high-precision surgical knife. Nd:YAG (neodymium–yttrium–aluminum–garnet) laser energy passes through clear liquid, making it a valuable tool for working on the eye and other fluid-filled cavities.

These lasers produce heat energy that destroys tissue by burning it. Although the beam of energy may be very narrow and carefully focused, the risk of heat damage to surrounding tissue is always there. Another type of laser, the excimer laser, emits short bursts of ultraviolet light that are absorbed by molecules with little heating. This light cuts tissue by severing the chemical bonds between molecules.

Advantages.

Even with heat-producing lasers, the light can be targeted so precisely that damage to surrounding tissue is far less than that caused by a scalpel. Most lasers also cauterize as they cut, thereby reducing bleeding and making it easier for the physician to see the surgical field.

During laser surgery, little or no pressure is exerted on the tissues. This is particularly important during brain surgery, where pressure or movement against neighboring tissues can cause irreparable harm.

Many laser operations are noninvasive; that is, the procedures do not require surgical incisions. For example, surgeons can use lasers to perform work in the ears, nose, throat, and other confined areas. Conventional surgery would require additional cutting to open such areas sufficiently for the use of scalpels and other instruments.

Eye Surgery.

The first medical use of lasers came in 1962, when a laser was beamed into the eye of a person suffering from diabetic retinopathy. In this disorder, tiny blood vessels proliferate on the surface of the retina—the layer at the back of the eye that receives images and transmits visual impulses via the optic nerve to the brain. The blood vessels swell and rupture, destroying vision. To correct the problem, a physician beams the laser light at one leaky vessel at a time. The laser energy cauterizes the vessel, which stops it from leaking or proliferating. This technique has become standard for treating what once was a frequent cause of blindness in diabetics.

Leaky blood vessels also are a symptom of macular degeneration, the most common cause of legal blindness after age 60. For unknown reasons, blood vessels behind the retina enlarge and rupture, forming scar tissue on the macula lutea, the area of the retina responsible for head-on vision. Lasers are used to seal the vessels.

Lasers are also used to repair detached retinas. If the retina tears or breaks, it can become separated from the eyeball. As a result, light is no longer focused on the retina, creating serious visual problems. With a laser, the physician "spot-welds" the retina back into place. Tiny spots are burned along the edge of the tear. As the burns heal, scar tissue forms, sealing the tear and holding the retina in place.

Angle-closure glaucoma is a condition in which the fluid inside the eye does not drain. This causes painful pressure to build up behind the iris. If uncorrected, the optic nerve is strangulated, and blindness occurs. The physician uses a laser beam to burn tiny drainage holes in the iris.

In a second form of glaucoma, fluid does not flow properly between the iris and the cornea, resulting in increased pressure on the cornea, the front covering of the eye. Laser treatment helps the majority of people suffering from this condition.

Excimer lasers can be used to reshape the cornea, eliminating the need for glasses in many people with nearsightedness, farsightedness, or astigmatism. The laser light flattens the cornea so that light focuses on the retina.

Other Applications.

Laser treatment is the most successful therapy for a benign skin tumor known as a port-wine stain. This tumor is caused by an abnormal density of blood vessels. The laser energy cauterizes the blood vessels, thereby reducing the redness. Lasers also can be used to remove freckles, moles, and age and liver spots.

Tumors that once were inoperable can be destroyed by laser treatments. Snoring can be eliminated or significantly reduced by using a laser to trim the uvula and reshape the palate. In 1998, the U.S. Food and Drug Administration (FDA) approved a painless, laser-powered drill. Soon after, the agency also cleared lasers for dental applications, including the treatment of tooth decay and both soft and hard tissue surgery.

Fiber Optics

Optical fibers are flexible strands of glass used to carry light. They are very thin—no thicker than a cat's whisker. But light travels through these fibers even when the fibers are twisted or turn a corner.

An endoscope is an instrument that uses fiber optics to enable physicians to look at internal organs. It consists of a slender, usually flexible, tube that contains two bundles of fibers. One bundle carries light to illuminate the area of the body that is being examined. The light reflects off the tissues and is picked up by the second bundle, which carries the image back to the physician's eye. Because the light is propagated by total internal reflection, the light from the external source travels the length of the fiber without losing intensity. The endoscope may have attachments that permit the physician to photograph the tissues or to project the image onto a television monitor so that other medical personnel can also view the tissues.

There are a variety of endoscopes, each designed to examine a specific organ. Among these are the bronchoscope (to examine the bronchial tubes), esophagoscope (esophagus), gastroscope (stomach), cystoscope (bladder), proctoscope (rectum), and colonoscope (colon).

Many endoscopes have a channel through which probes and other instruments can be inserted. This allows a physician to remove cells from the tissues for analysis. Often a laser is combined with an endoscope. The physician uses the endoscope to look at a problem, such as a tumor or a bleeding ulcer, then sends bursts of laser light to correct the problem.

Angioplasty

A new medical tool may incorporate more than one innovative technology. This is well illustrated by recent developments in angioplasty, surgery performed on blood vessels. The term angioplasty comes from Greek words meaning "shaping of blood vessels."

The major cause of cardiovascular disease is atherosclerosis. In atherosclerosis, fats, cholesterol, cellular wastes, and other substances collect on the inner walls of the arteries, forming plaque that builds up until it blocks the vessels and obstructs the flow of blood. If one of the coronary arteries that carry blood to the heart muscles is blocked, a heart attack may occur. Before angioplasty, the only way to treat this problem was through coronary bypass surgery. In this surgery, physicians remove a vein from the patient's leg and use it to construct a detour for blood around the blocked artery.

A technique called laser angioplasty, approved by the U.S. Food and Drug Administration (FDA) in 1992, uses a catheter encasing optical fibers. The catheter is inserted into the femoral artery in the groin and guided through blood vessels until it reaches the area blocked with plaque. The tip of the optical-fiber bundle is pointed at the blockage and an excimer laser is fired in extremely short pulses ranging from 10 billionths of a second to 200 billionths of a second. The laser's energy loosens the biochemical bonds that hold the plaque together, breaking it down into carbon dioxide, hydrogen, and other molecules. It cleans out clogged arteries without surgery.

Balloon angioplasty.

Another nonsurgical technique for treating blocked arteries is called balloon angioplasty. This technique does not remove plaque. Rather, it uses a balloon to push open the artery so that blood can flow through unimpeded.

The patient is given a local anesthetic, and a small incision is made in the groin or arm. A thin plastic tube is inserted into an artery and snaked to the blocked vessel. Then a thinner catheter is threaded through the tube until it reaches the blockage.

Packed tightly in the tip of the catheter is a small, tough balloon. When the balloon is inflated, it pushes the plaque against and into the arterial wall. The vessel's interior diameter is widened by 50 percent or more, allowing blood to flow more freely through the artery. Usually, a balloon is inserted after an excimer laser has vaporized some of the plaque on the artery's wall.

Balloons also are being used to widen the mitral and aortic valves in the heart, which may become so stiff that blood cannot freely flow through them. After angioplasty, a small mesh tube known as a stent may be installed to prevent the collapse of a weakened artery. About one of every three angioplasty procedures will give rise to restenosis or scarring, leading to blockages. To overcome such blockages, cardiologists resort to various methods, including drugs, lasers, and radiation therapy. Another option is to install drug-eluting stents.

Sound Waves

Sound waves with frequencies above the audible range are called ultrasonic waves. The rapid vibrations of these sound waves create tremendous power; this power has found many applications in medicine. Some ultrasonic waves can be focused into narrow beams, making them suitable substitutes for scalpels in delicate neurological surgery. Dentists use ultrasonic drills to cut painlessly into hard tooth material and ultrasonic scalers to remove hard deposits from the surface of teeth.

Lithotripsy.

Kidney stones—solidified deposits of various substances that form in the kidney—are a fairly common, and very painful, problem. Smaller stones pass out of the kidneys and are eliminated in urine. Until the 1980s, surgical removal was the only way to deal with larger stones that became impacted in the kidney, ureter, or bladder. Now many of these stones can be destroyed with an ultrasonic technique called lithotripsy, from the Greek words lithos, for "stone," and triptis, meaning "to crush." The technique is noninvasive; only a local anesthetic is used, and the patient is conscious during the procedure.

The patient is placed in a tub filled with water. Water conducts shock waves at approximately the same rate as does human tissue. X-ray machines locate the kidney stone. The patient is then positioned so that the stone is at the focal point of a shock-wave generator. The shock wave passes harmlessly through body tissue, hitting the stone. The wave lasts only one-half billionth of a second. At every resting point in the patient's heartbeat, another wave is produced. After several hundred waves, the brittle kidney stone begins to break up. Up to 1,500 shock waves may be needed to break a stone into pieces small enough to be eliminated in the urine.

In a newer but similar procedure, lithotripsy is used to break down gallstones.

Microelectronics

The many exciting advancements in microelectronics, including the development of ever-more-powerful computers, are being applied to medicine in numerous ways. Telemetry—sending data via radio signals—is used to monitor the health of astronauts in space. The data are sent to Earth in digitized form, then converted by a computer into easy-to-read graphics. Telemetry also allows hospital nurses sitting at central stations to monitor heart rates, blood pressure, temperature, and other vital functions of intensive-care patients. And it enables doctors to test and adjust pacemakers over the telephone, eliminating the need for patients to travel to medical facilities for such checkups.

Indeed, a new area of medicine called telemedicine has emerged to help treat patients in rural areas and other remote locations. Often, people in such places need the services of specialists, but are unable to travel to the urban medical centers where specialists typically work. Now, they can visit their local general practitioner, who sets up a teleconference with a specialist. Using special tools that transmit data over phone lines, the local doctor conducts an examination. The specialist sees what the local doctor sees, analyzes the data, and prescribes treatment. During the Persian Gulf War, doctors in the war zone used telemedicine to consult with experts in Washington, D.C. Yellowstone National Park uses telemedicine to send X rays of hikers with possible fractures to a hospital.

Computers can be used to analyze blood and other laboratory samples, analyze the results of electrocardiograms, evaluate pulmonary-function tests, and yield findings for many other tests in a matter of minutes, sometimes even seconds.

It is impossible for any one physician to keep abreast of the many developments constantly occurring in medicine. Medical databases provide timely information on diseases and their treatment. One such database contains data on approximately 100 types of cancer, including prognosis, survival rates, stages of the cancer, spread of the cancer, and treatment options.

Both physicians and pharmacists are using computers to cross-check prescriptions against other medicines that a patient is taking. This helps avoid adverse drug interactions, which can range from nausea and headaches to internal bleeding and, death. Computer programs also can indicate interactions between the chemicals in a drug and a patient's allergies and diet.

Many additional medical uses of the computer are in existence or are being tested for future application. In the near future, for instance, each person may have all of his or her vital statistics and medical history encoded on cards no larger than a credit card. The data can include X rays, electrocardiograms, a facsimile of the person's signature, lists of medicines being taken, and a host of other vital medical information. A laser is used to burn this information onto the card in digital form. A physician can then plug the card into a computer and have a laser scanning device read the data. The data are then displayed on the computer monitor.

Centrifuges

Centrifuges are devices that use centrifugal force to separate one material from another. They have long been used in medicine. For example, centrifuges are used to separate blood cells from plasma (the liquid portion of the blood). This is one of the steps in LDL-phoresis, a procedure that removes particles called low-density lipoproteins (LDLs) from the blood.

LDLs are particles that consist primarily of cholesterol and fatty acids. They are normally suspended in the plasma. But if the LDL level is too high, excess particles build up on the inner walls of the arteries, forming plaque. Eventually this can cause atherosclerosis.

Some people have a genetic disorder that causes extremely high levels of LDLs to accumulate in the blood. This results in the formation of fatty nodules under the skin, and life-threatening heart disease. LDL-phoresis is enabling these people to live longer, healthier lives.

The patient is attached to the machine by two tubes. From a tube connected to a vein in one arm, blood flows to a centrifuge, which separates the LDL-rich plasma from the blood cells. The plasma flows through a jar filled with porous beads coated with a custom-made antibody that traps the LDL. Each protein molecule can bind to an LDL particle and remove it from the plasma. The cleansed plasma is remixed with the blood cells, brought back to body temperature, and returned to the patient via a tube connected to a vein in his or her other arm.

The three-hour procedure can remove as much as 80 percent of the LDL in the plasma. The cleansing is temporary, however. The LDL level gradually rises, requiring repeat treatments. But researchers have found that weekly treatments can reduce a patient's average LDL level by 50 percent or more.

Zoom-Lens Microscopes

Technological miniaturization has not been limited to electronics. Today, there are scalpels, forceps, and other surgical tools smaller than your little finger. There are monofilament nylon or polyethylene sutures so fine they can barely be seen by the unaided eye. These are important tools in the development of microsurgery—surgery done under a microscope.

Microsurgery enables surgeons not only to reattach fingers, hands, arms, and legs that have been amputated in accidents, but also to restore function and sensation to the parts. The microscope allows surgeons to see and work on tiny parts of the body, such as nerves and minute blood vessels. Surgeons can reconnect two ends of a severed blood vessel so that blood will once again flow through the vessel; they can reconnect two ends of a nerve to restore feeling and movement.

Microsurgery also allows surgeons to operate on the retina and other parts of the eye; reshape the bones in the middle ear to overcome a patient's deafness; remove tumors from the brain or spinal cord; restore fertility to women by reopening diseased fallopian tubes; and much more.

The technique involves working under a special zoom-lens microscope capable of magnifying the operating field from 4 to 25 times. The surgeon controls the zoom system with a foot pedal, keeping the hands free for the operating procedure.

The microscope provides binocular, stereoscopic vision for the surgeon. Some models have two binocular viewing pieces, permitting two surgeons to work simultaneously. A beam splitter intercepts the light path to one eye of the surgeon so that an assistant can view the procedure, albeit in two rather than three dimensions. A beam splitter intercepting the light path to the surgeon's second eye supplies an image for a television system for medical observers to view the surgical procedure.

The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies.

Copyright Information: Public domain information with acknowledgement given to the U.S. National Library of Medicine.

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