Diagnostic Imaging Techniques

Question 1

What is an endoscope?

Answer 1

An endoscope is a flexible tube that allows you to look inside the body, in many cases there is no need to perform surgery and in other cases only a small incision is required

Question 2

What is endoscopes designed to do?

Answer 2

To provide a direct view of an internal part of the body

Possibly remove samples from body

Question 3

What are some areas that you can get images of?

Answer 3

Oesophagus 
Stomach
Intestines
Heart
Lungs

Question 4

What happens when waves go from a dense medium to a less dense medium?

Answer 4

They speed up at the boundary, this causes light rays to bend, this is kmow an as refraction

Question 5

What is total internal reflection?

Answer 5

When it goes beyond a certain angle, called the critical angle, all the waves reflect back into the glass

Question 6

When is the only time total internal reflection occurs?

Answer 6

When a ray of light is going from a high to a low refractive index

Question 7

What is an optical fibre?

Answer 7

An optical fibre is a thin rod of high-quality glass

Question 8

What happens in optical fibres?

Answer 8

Very little light is absorbed by the glass, light getting in at one end undergoes repeated total internal reflection even when the fibre is bent, and emerges at the other end

Question 9

What is a coherent bundle?

Answer 9

A coherent bundle is when a bundle of fibres is placed together in an orderly manner along its length, with the posititions remaining unchanged, this allows actual images to be transmitted along the fibres

Question 10

Why can coherent bundles transmit images?

Answer 10

It transmits light independently of its neighbour fibres

Question 11

What doe coherent bundles consist of?

Answer 11

Fibres of a very small diameter, about 10mm.

The ends of each bundle are cut square and polished smooth to prevent distortions.

Question 12

What does each fibre transmit in an optical fibre?

Answer 12

Each fibre transmits a small element of the image which is seen at the other end as a mosaic

Question 13

How are incoherent bundles arranged?

Answer 13

This is when the bundle of fibres are arranged at random (or sometimes a light guide)

Question 14

What is incoherent suitable for transmission of?

Answer 14

Only night, not images

Question 15

What size are the fibres in a incoherant bundle?

Answer 15

Relatively large, 50-100mm

Question 16

How is an image formed using an endoscope?

Answer 16

Light is shone down the incoherant bundle so that the site under examination is illuminated. Clear images can then be transmitted back to the eyepiece using a coherent bundle

Question 17

What happens if the fibres in a endoscope touch?

Answer 17

The light leaks from one fibre to another

Question 18

What is used to prevent light leaking from one fibre to another in endoscopes?

Answer 18

The fibres are coated with a second layer of glass of slightly lower refractive index

Question 19

Why do u use cladding in endoscopes?

Answer 19

This increases the critical angle at the edge of the fibre

It also serves to protect the core from the surface scratches, this would lead to loss of light

Question 20

What is the long flexible shaft of the endoscope usually made of?

Answer 20

A crush resistant covering of bronze or steel spiral.

Question 21

What are some applications of endoscopy?

Answer 21

Visual evidence of upsets, tumours and intestinal bleeding
Remove foreign bodies from the oesophagus
Carry out biopsies

Question 22

Is ultrasound ionising?

Answer 22

No

Question 23

How does ultrasound work?

Answer 23

Low intensity ultrasonic waves pass through tissues without causing them harm. They are reflected at the boundaries between biological structures. These reflections are then created by and ultrasound scanner