The Professional Development Service for Teachers is funded by the Department of Education and Science under the National Development Plan Endoscopy

Endoscopy This unit is about endoscopy and how doctors use this method to look inside patients bodies

Objectives By the end of this unit you should be able to Understand Total Internal Reflection and how endoscopes rely on this Understand how an endoscope works Understand when doctors choose to use endoscopes Have the basic knowledge needed for expert group tasks

WHAT IS ENDOSCOPY? The word endoscopy is derived from the Greek words "Endo" meaning "inside" and "skopeein" meaning "to see". It is a word used in medicine to describe the procedure used see inside various parts of the body. Historically, it was known that it is possible to insert tubes into body orifices, but to see clearly a method was needed to illuminate the inside of the organ to be seen. The earliest crude attempts used oil lamps, which were later replaced by small electric filament bulbs. These were not very bright and tended to produce a lot of heat.

Science of Endoscopy Medical endoscopy really came into its own after the invention and application of fibre-optic technology to endoscopy. Fibre-optic endoscopes use bundles of thin glass fibres to transmit light to and from the organ being viewed. These fibres use the principle of total internal reflection to transmit almost 100 % of the light entering one end to the other end.

Student Activity You can observe Total Internal Reflection in the lab using the apparatus shown Fill the bottle with water Pierce a hole in the side Shine the laser through the hole Observe!! You should see the laser light trapped inside the stream of water Play video intrefl_low.aviintrefl_low.avi

Investigating total internal reflection Shine rays of light onto the curved surface of a semicircular perspex block as shown Observe what happens To the refracted ray The angle of incidence is the angle between the incident ray and the normal Ray 1: The angle of incidence is < 42º Ray 2: The angle of incidence = 42º Ray 3: The angle of incidence >42º

42º is called the critical angle for perspex Use your observations to help you complete the sentences When the angle of incidence is< critical angle then………………….. When the angle of incidence is= critical angle then………………. When the angle of incidence is>critical angle then………………….

Fibre optics An important application of total internal reflection is in fibre optics. Light is shone along a thin glass fibre and as it hits the glass-air boundary at more than the critical angle it reflects along inside the fibre. The bundles are often called light pipes but you must realize that they are not really a pipe – there is no hollow tube down the centre, each fibre is solid glass and the light is simply “trapped” inside the glass Figure 1

The effect of cladding the fibres with another glass of slightly lower refractive index is shown in the following two diagrams Core (n = 1.55) Cladding (n = 1.45) Figure 3 Figure 2 n is the refractive index of the glass this determines how much the light is “bent” Without cladding some light may escape from the glass into the air

An Endoscope Fibre-optic endoscopes are delicate and expensive items. The fibres have to be made of special glass.

“Endoscopy" is a general term. There are specific words for viewing specific parts and organs of the body. Endoscopy done through existing body openings can usually be done under local anaesthesia, but other types that require a small puncture to see an "internal cavity" may need hospital admission and a general anaesthetic. In each type small pieces of tissue can be removed for tests and some other procedures can be done.

List of the major types of endoscopy GASTROSCOPY: To see the gullet, stomach and upper small intestine. COLONOSCOPY: To see the large intestine. LAPAROSCOPY: To see the "stomach cavity" and the organs therein. PROCTOSCOPY: This is used to check for piles and other conditions of the anus and rectum. The picture on the right illustrates this. CYSTOSCOPY: To see the urinary bladder. BRONCHOSCOPY: To see the air passages to the lungs. LARYNGOSCOPY: To see the larynx or voice box. NASOPHARYNGOSCOPY: To see the nose and related cavities. ARTHROSCOPY: To see inside joints such as the knee joint. THORACOSCOPY: To see inside the chest cavity.

Limitations of Endoscopy Compared with other parts of the digestive tract, the small intestine is difficult for doctors to access. While a camera-tipped tube slipped down the throat can get images of the stomach and a tube inserted at the other end of the tract reveals the large intestine, no such device reaches into most of the small intestine. So, doctors rely on externally generated images

Capsule endoscopy Scientists recently devised a disposable flash camera only slightly larger than a vitamin pill. In a procedure called capsule endoscopy, the patient swallows the minicam, which then takes pictures inside the small intestine. On its journey through the digestive tract, the tiny tumbling camera transmits images that are stored in a recorder that the person wears around the waist. After 8 hours, the camera's battery runs out, and the capsule is eliminated in the faeces. Scientists then download the recorder's images into a computer.

An Endoscopic Image of the Colon Click on image to play