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Endoscope with a physician looking down it

Endoscopes

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by Chris Woodford. Last updated: April 16, 2017.

Think back to what medicine was like only a hundred years ago. Suppose you're a 19th-century physician and a patient knocks on your door complaining of acute pains in their abdomen. You can ask them questions and examine their body with your hands. You can prescribe them drugs and watch how they respond over days, weeks, or months. But ultimately, unless you cut their body open and examine it directly, you have no way of knowing with complete confidence what's wrong. So do you take a risk, do nothing, and wait to see how things turn out? Or do you operate immediately, potentially wasting time and money and putting your patient through disruptive and traumatic surgery? Thanks to medical imaging devices such as endoscopes, decisions like this are a thing of the past: physicians can see exactly what's going on inside your body without cutting it open. Let's take a closer look at how they work!

Photo: Endoscopes not only allow physicians to see into your body, they can also be used to carry out delicate, minor surgery. You can see the three key tubes in an endoscope at work here. The big black tube in the middle carries the image of the patient's body into the doctor's eye. The smaller black tube on the right, coming down at an angle, is where light shines into the endoscope from a lamp (not shown) in the operating room. The tube on the upper left at the top (with the silver crown) is where tiny surgical tools can be inserted. The doctor is pressing on a cable that enters the patient's body through this tube to take a tissue sample. Photo by courtesy of National Institutes of Health (NIH).

What is an endoscope?

An endoscope is a bit like a bendy telescope a physician can use for seeing inside one of the body's cavities. Unlike a telescope, which is a very rigid tube, the part of an endoscope that enters a person's body is relatively flexible. It consists of two or three main optical cables, each of which comprises up to 50,000 separate optical fibers (made from optical-quality glass or plastic). One or two of the cables carry light down into the patient's body; another one carries reflected light (the image of the patient's body) back up to the physician's eyepiece (or into a camera, which can display it on a TV monitor), as illustrated in the box below.

The optics of an endoscope are similar to those in a telescope. At the remote (distal) end, there's an objective lens, which links to one or more bendy sections of fiber-optic cable (sometimes called relays) that carry the light back out of the patient's body to a second lens in the eyepiece (or to a monitor or CCD), which can be swiveled from side to side to adjust the focus (much like the eyepieces on binoculars). Typically the lenses and cables are about 0.5cm (1/5 inch) in diameter (sometimes slightly bigger, sometimes slightly smaller).

Endoscope surgery

Most modern endoscopes aren't limited to piping light in and out of a patient's body: they can also be used to carry out small surgical operations and other minor, medical procedures. Typically, the remote end of the endoscope can be moved around by turning knobs or pulling on cables, which swivel and bend it from side to side. A secondary tube attached to the main optical cables can be used for sucking out obstructing material (for example, obstacles that block the bronchial tubes in the lungs) or carrying out biopsies (removing small tissue samples for testing) with tiny forceps. Surgeons can also shine powerful, precision lasers down endoscopes to destroy diseased tissue, make accurate incisions, or heal wounds, all the time watching what they're doing through the eyepiece or on the TV monitor. This type of procedure is called minimally invasive surgery and it's simpler, quicker, less expensive, and far less traumatic than conventional operations. However, it still generally needs the patient to have an anesthetic and it's not always without drawbacks and complications.

How do endoscopes work?

Artwork showing how endoscopy involves light shining into a patient's body cavity and then reflecting back out again

Here's how endoscopy works:

  1. One of the two main endoscope cables carries light from a bright lamp in the operating room into the body, illuminating the cavity where the endoscope has been inserted.
  2. The light bounces along the walls of the cable into the patient's body cavity.
  3. The diseased or injured part of the patient's body is illuminated by the light shining in.
  4. Light reflected off the body part travels back up a separate fiber-optic cable, bouncing off the glass walls as it goes.
  5. The light shines into the physician's eyepiece so he or she can see what's happening inside the patient's body. Sometimes the fiber-optic cable is directed into a video camera (which displays what's happening on a television monitor) or a CCD (which can capture images like a digital camera or feed them into a computer for various kinds of image enhancement).

What are the different kinds of endoscopes?

Image of stomach cancer as seen through an endoscope

Photo: Images of stomach cancer seen through a gastroscope. Photo by courtesy of National Institutes of Health (NIH) Image Bank.

"Endoscope" is the generic name for an instrument used to look inside any part of the body in this way. Endoscopes used for specific forms of examination have the following names:

Endoscopes aren't just used for medical diagnosis: they're incredibly useful for inspecting inaccessible areas of buildings or parts of machines where people can't easily see. Industrial endoscopes used in this way are called borescopes and fiberscopes.

How are fiber-optic cables different in endoscopes?

You might be wondering what's the difference between fiber-optic cables used in endoscopes and those used for carrying telephone calls, cable TV, and Internet data. Telecommunications cables are designed to carry data in digital form over very long distances; by contrast, the cables used in endoscopes carry pictures over much shorter distances and in analog form. In other words, while telecoms cables carry binary data (long strings of zeros and ones) that represent everything from MP3 music tracks to digital photos of rock stars, endoscope cables carry the actual pictures of someone's insides!

Who invented endoscopes?

Labelled patent artwork showing the 1961 fiber-optic gastroscope designed by Hirschowitz, Curtiss, and Peters.

Artwork: The highly flexible fiber-optic gastroscope designed by Hirschowitz et al in the 1950s. The right-hand end is inserted into the patient; the left-hand end is the bit the doctor looks into. Some of the key bits include 1) Light source (interestingly, still positioned inside the patient); 2) Prism; 3) Focusing lenses; 4) Gear-driven focusing mechanism (shown in more detail in the pullout illustration); 5) Optical fibers surrounded by protective waterproof and air-proof membrane; 6) Metal shell that transmits forces down the tube, allowing it to be manipulated along its entire length by twisting and turning; 7) Air tube allows the body cavity to be inflated; 8) Eyepiece lenses. Original artwork courtesy of US Patent and Trademark Office (with colors and new numbering added for explanatory purposes). For more details, please see US Patent 3,010,357: Flexible light-transmitting tube.

Attempts to see inside the body with crude endoscopes go back to the late 19th century; the earliest US patent I've found using the term is dated 1911. These early medical endoscopes were crude and bulky by modern standards, because they placed the light source itself inside the body cavity that needed to be examined. Typically, that meant using tiny bulbs, which produced little light and burned out quite quickly (because they had to be turned up so brightly). They also produced quite a lot of heat, which meant they risked burning or drying out the body tissue under examination. In the early 1950s, Max Fourestier and colleagues at the Centre National de la Recherche Scientifique in Paris, France developed an endoscope using rods made of quartz or Plexiglas, which enabled light from a source outside the patient's body to be shone down inside a body cavity. It was an important breakthrough—and a major stepping stone to the fiber-optic endoscope.

The basic technology behind the modern endoscope was developed in the early 1950s by English physicist Harold Hopkins (1918–1994) and his Indian-born student Narinder Kapany (1927–), who'd been asked for help by a group of surgeons. After a great deal of research, Hopkins and Kapany developed a way of making flexible pieces of glass that became known as optical fibers—thicker versions of modern fiber-optic cables that are now so widely used in telecommunications.

By the mid-1950s, three University of Michigan scientists (Basil Hirschowitz, Lawrence Curtiss, and C. Wilbur Peters) had used optical-fiber technology (which they neatly defined as "long, thin, highly flexible, rope-like tube for use in transmitting light") to build an instrument called a gastroscope that could be used to see inside a patient's stomach. The same technology was later used to study other body cavities.

Pill cam: the endoscope of the future?

Artwork showing parts inside a miniaturized endoscope pill camera.

Endoscopes are brilliant inventions, but no-one really enjoys having a camera tube stuffed inside them!

What's the alternative? In the future, doctors hope to shrink endoscopes to the size of a tiny pill you can swallow. Inside the pill, a miniature camera will pick up images of your insides and a radio transmitter will beam them out to a monitor nearby.

The top part of the artwork shows how much technology is packed in a pill-cam. Does it sound impossible? Not really! LEDs are smaller than pills and have lenses built into them. CCDs are not much thinner than a piece of card. Watch and calculator batteries are pretty tiny too. And even complex electronic circuits can be made very small and thin. So the whole thing sounds feasible.

And here's how it works:

  1. You swallow the pill-cam and it tumbles through your body, taking pictures of damaged or diseased tissue.
  2. The LEDs at the front of the pill-cam fire out enough light to generate an image.
  3. The CCD chip picks up the reflected light and generates a digital image.
  4. The radio transmitter sends digital images to a computer outside your body.
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Text copyright © Chris Woodford 2008, 2015. All rights reserved. Full copyright notice and terms of use.

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Woodford, Chris. (2008/2015) Endoscopes. Retrieved from http://www.explainthatstuff.com/endoscopes.html. [Accessed (Insert date here)]

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