The full overview of fiber optic bundles applied in medicine

A fiber optic bundle is an element of a fiber cable that is a very thin quartz thread with a diameter of 0.1 mm. This optical fiber is used for transmitting electromagnetic radiation. The operating principle of the fiber bundle is based on the use of such processes as reflection, as well as refraction of the wave at the boundary of the shell and the thread itself, which have different properties, which, in turn, depend on the refractive index. 

Due to the fact that the value of laser beam light attenuation in the optical fiber is quite small, fiber optic bundles are often used to transmit an optical signal over long distances. The optical signal is not subject to interference in fiber bundles, and this property is widely applied in the development of fiber optic sensors. Fiber optic bundles make it possible to transmit light like an electric current.

The fiber bundle is considered to be the main element of a fiber optic cable. The optical fiber of which consists of a core, one or more shells, and one or more protective coatings. The core is the central part of the optical fiber, through which the main part of the signal power is transmitted. If the core is employed to transmit electromagnetic energy, then the shell is used for creating better reflection conditions at the core-shell interface, protecting the fiber core from mechanical damage, as well as protecting it from energy radiation to the surrounding space and absorbing unwanted radiation from outside.

Fiber optic bundles are divided into two groups: multimode and single-mode.

The operating principle of the fiber bundle is based on fiber optic technology – a technology for transmitting laser beam light through a fiber optic bundle of optical fibers that are very thin, flexible glass or plastic. A good fiber bundle will transmit the entire spectrum of visible light without loss. These fiber optic cables have a very high-quality optical transmission.

Fiber optic bundles can have different shells, up to metal, but this option is not recommended for use in medicine since it is very difficult to clean. The disadvantage of this fiber bundle is regarded as its fragility. As you use fiber optic bundles, some optical fibers break down. The loss of optical fibers can be seen if one end of the fiber cable is viewed in daylight. The broken fibers are visible as black dots.

To avoid damage to these fibers, it is necessary to take into account the radius of the curvature of the bundle. The fiber may also be damaged if the cooling system of the light source does not work properly. In this case, the optical fibers of the bundle are burned (melted), which dramatically reduces the light intensity. If low-quality fibers or glue are used, the fiber optic bundle may burn out after several months of use.

Fiber bundles are widely used in optical communication systems, in sensors of various types, etc. At the same time, fiber optic bundles have played a huge role in the development of communication, they have a revolutionizing influence on the methods of observation, diagnosis, and treatment in medicine. 

These ultra-thin flexible optical fibers “opened a window into the living tissue of the human body”. By inserting fiber optic bundles into natural holes or small incisions and passing them through channels in the human body, doctors can carefully examine the bronchi of the lungs, intestinal folds, heart chambers, and many other internal organs that were previously unavailable for such careful observation. 

By placing fiber optic sensors in the bloodstream, doctors can perform rapid and reliable biochemical analyses directly at the patient’s bedside, in the exam room, or in the operating room. All other methods of blood analysis require a certain amount of blood for subsequent laboratory tests. 

By directing laser beam radiation through the fiber bundle, doctors can even perform surgical operations inside the human body, which sometimes avoids the usual surgical procedure involving cutting healthy tissue to have access to the focus of the disease.

By transmitting laser radiation through fiber optic bundles, gastroenterologists, for example, cauterize blood vessels to stop bleeding in the intestines, cardiologists have begun to destroy plaques and blood clots in the peripheral arteries, and neurosurgeons will soon be able to restore nerve fibers in the brain and spinal cord. 

Fiber optic systems can help combine diagnosis and treatment, for example, by combining the means of detecting cancer cells with ways to destroy them without damaging neighboring healthy tissues. Many diagnostic and therapeutic procedures using fiber optic bundles do not require pain relief and can be performed reliably and without risk to health in the doctor’s office; therefore, further development of fiber optic technology should reduce the risk and cost of medical care. 

It is possible that the use of fiber optic systems will make medical care more reliable in cases where conventional surgical operations are dangerous or even impossible, for example, in young children or in elderly people.

The application of fiber bundles in medicine began with the use of image transmission systems called fiberscopes in diagnostic practice. The first fiberscope designed to examine the stomach and esophagus was developed in 1957. Since then, such fiber optic systems have been significantly improved, and now they can be used to examine almost all human organs. 

A modern fiberscope consists of two fiber optic bundles: one leads light to the bio tissues, and the other transmits the image to the observer. The fiber bundle is connected to a powerful light source, the light enters the cores of the fiber optic bundle made of high-purity quartz glass. Such an optical fiber is 10,000 times more transparent than window glass and therefore can conduct laser beam light over many kilometers without much loss. 

Individual fiber optic bundles are glued together only at its ends, which provides it with flexibility and at the same time eliminates mixing of individual parts of the transmitted image. The restored image can be viewed through an eyepiece, recorded on videotape, or played back on a display. Since thousands of fiber bundles can be located in a single fiber optic system with a diameter of less than one millimeter, the fiberscope can transmit images with high spatial resolution and almost perfect color reproduction.

The lighting and image-transmitting fiber optic bundles can be easily inserted into a catheter with a diameter of several millimeters resulting in an endoscopic fiber catheter.  Often fiberscopes are considered to be a part of more complex instruments called endoscopes, which have additional auxiliary channels through which the functions of the medical device are expanded. 

For example, it is possible to improve visibility through one of the channels, you can also withdraw fluid from the body or enter water or air to clean the wound from foreign substances or organic residues. Another channel may contain thin wires to rotate the end of the endoscopic fiber catheter. The third channel can have tiny scalpels that can be inserted to cut through the bio tissue and remove polyps, as well as needles for injecting drugs.

Using such fiber optic systems, doctors can examine the internal cavity of the digestive, circulatory, respiratory, and genitourinary systems of a person, take small samples of bio tissues for laboratory tests, and even perform surgical operations. The application of a fiberscope allows doctors to detect polyps in the colon, objects in the lungs, and tumors in the esophagus and then remove them with minimal surgery.

The production of ultra-thin optical fibers developed in recent years has allowed to reduce the diameter of fiberscopes and increase the number of optical fibers in the fiber bundle for observations, which in turn has improved its resolution. The latest endoscopic fiber catheters contain up to 10,000 fiber optic bundles less than one millimeter in diameter. Such a fiber optic system, inserted through an artery on a person’s shoulder, can transmit images of heart valves, as well as blockages in the coronary arteries — the vessels that supply the heart with blood.

In addition to obtaining images using fiber optic technology, you can make direct and rapid biochemical and clinical blood tests and solve other problems of human physiology. The main element of such a system is a fiber optic bundle inserted through a catheter into the human body. 

In many cases, a medical examination using fiber optic systems can be more accurate, reliable, and cost-effective than traditional methods that are based on laboratory analyses of fluids taken from the body.

Fiber bundles eliminate analysis delays and reduce the likelihood of errors. In addition, fiber optic sensors do not interact chemically with the body’s tissues and do not cause a reaction of the immune system. They are more durable, versatile, and potentially safer than microelectronic devices that are also designed to collect data on the functional activity of the body and are inserted inside the human body. 

Fiber bundles also allow directly determining the oxygen content in the blood. The fiber optic sensor can measure pressure in the arteries, bladder, and urethra. In recent years, the most significant application of fiber optic bundles in medicine is considered to be the transfer of laser radiation energy inside the human body for surgical and therapeutic purposes.

Maintenance of fiber bundles

When maintenance of any fiber optic bundles is performed, the following conditions must be observed:

  • Handle the fiber bundles carefully.
  • Avoid twisting them too much.
  • After the operation has been completed, first disconnect the fiber bundle connector from the endoscopic fiber catheter, and then disconnect it from the light source.
  • The end of the bundle should be periodically cleaned with a ball of cotton wool moistened with alcohol.
  • The outer coating of the fiber bundle must be cleaned with a mild cleaning agent or disinfectant.
  • The distal end of a fiber optic bundle should never be placed near a tissue or near a patient when connected to a light source. The heat generated due to the intensity of the light can cause the patient to burn or ignite the tissue.
  • The intensity of the light source is so high that there is a chance of damage to the retina if the light falls directly on the eye. Never try to look directly at a working light source, or at the distal end of the fiber optic bundle when it is connected to such a source.

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