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Flashcards in Imaging Deck (13)
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1
Q

What is the range of wavelengths of x-rays?

A

0.1 to 10 nanometres

2
Q

What is the purpose of the cathode in an x-ray machine?

A

Produce stream of electrons

Thermionic emission at 2200 centigrade

Tungsten

3
Q

What is the purpose of the stater induction coils in the x-ray machine?

A

Rotate the target plate

4
Q

Energy from the electron stream is converted into what?

A

Mainly heat

1% photons of x-rays

5
Q

What is attenuation?

A

Absorption of the x-rays

6
Q

Rank the following in terms of their attenuation coefficient (low - high) :

Bone 
Muscle
Air 
Contrasts / metal implants 
Fat
A
Air
Fat
Muscle
Bone
Contrasts
7
Q

What factors affect how well an object absorbs x-rays?

A

Thickness
Density
Atomic number

8
Q

Ultrasound scanners range in frequencies from 3 Mega hertz to 100.

Explain the differences in the scans done using high and low frequency.

A

Low frequencies are further penetrating, but give less detailed scans - abdominal on a larger patient for example

High frequencies don’t travel very far, but give very highly detailed scans - scans on eyes use high frequencies

9
Q

Why is barium useful in imaging?

A

Hefty high attenuation coefficient ∴ contrasting agent

10
Q

Barium studies are useful for viewing what?

A

Hollow structures

Intestines, stomach, oesophagus etc

11
Q

Ultrasound scans are most commonly used to look at a baby’s development.

Why would it not be suitable to use a CT scan?

A

Ionising radiation

12
Q

When a cell is hit with ionising radiation, there are 3 possible things that can happen. What are they, and which is dangerous?

A

Repair
Death
Transformation - bad - cancer

13
Q

Absorption of radiation by the body is measured in what unit?

A

Sieverts

milli sieverts is most commonly used