Endoscopes

by Chris Woodford. Last updated: June 27, 2011.

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 (distal) 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.

Who invented endoscopes?

Attempts to see inside the body with crude endoscopes date back to the late 19th century, but the modern endoscope is a more recent invention. The basic technology 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 end of the 1950s, three University of Michigan scientists (Lawrence Curtiss, Basil Hirschowitz, and Wilbur Peters) had used optical-fiber technology 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.

How are fiber-optic cables different from 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!

Further reading

On this website

• Fiber optics
• Glass
• Lenses
• Light

Books

• Medical Imaging by Victoria Sherrow. Marshall Cavendish, 2006. A very good school library text for teenage readers that describes the varied advances in imaging over the 20th century, including X rays, endoscopes, MRI scans, and CT scans.
• City of Light: The Story of Fiber Optics by Jeff Hecht. Oxford University Press, 1999. A more general book about how fiber optics has changed our world (mainly in telecommunications).