Endoscopy Flashcards
What are the four channels contained within a medical endoscope?
Air/water, instrument, illumination and image channel.
What are the advantages of using an endoscope to form a diagnostic image?
Image is true colour, high definition, in real time (moving image) and can be magnified.
What is the standard diameter of an endoscope tube?
13mm
What is the purpose and goals of the tube design?
To protect the optics, prevent light entering fibres from outside sources, and to enable endoscope to easily be inserted into patient.
How is the endoscope inserted?
Usually swallowed by patient; patient may be sedated for comfort reasons.
What is the purpose of the air/water channel?
Injection of air/water keeps face of endoscope clean. Also air suction channel allows cut away material to be extracted.
What are the uses of a surgical endoscope?
Removal of small tissue samples for testing (biopsy) and carrying out small repairs (keyhole surgery).
How may the image formed be viewed?
Through magnifying eyepiece lens or using a CCD camera (and hence projecting image onto screen).
What is the typical diameter range of the optical fibres used?
Between 0.5mm and 3mm.
How many singular optical fibres make up a typical bundle?
Between 5,000 and 40,000.
What is the purpose of the optical fibre bundles?
To transmit light into and out of the body.
What are the main components of a typical optical fibre and what are their relative refractive indexes?
Core-higher refractive index
Cladding-lower refractive index
What is the formula and name of the law used to determine the critical angle of an optical fibre?
Snell’s Law: Sin(C) = n2/n1
where n1>n2
To retain light in the core during bending round small radii what should the critical angle be?
As small as possible
What factor determines an endoscope’s field of view?
The refractive index of the medium from which light enters the end of the fibre.
