Imaging

Question 1

What is the range of wavelengths of x-rays?

Answer 1

0.1 to 10 nanometres

Question 2

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

Answer 2

Produce stream of electrons

Thermionic emission at 2200 centigrade

Tungsten

Question 3

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

Answer 3

Rotate the target plate

Question 4

Energy from the electron stream is converted into what?

Answer 4

Mainly heat

1% photons of x-rays

Question 5

What is attenuation?

Answer 5

Absorption of the x-rays

Question 6

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

Bone 
Muscle
Air 
Contrasts / metal implants 
Fat

Answer 6

Air
Fat
Muscle
Bone
Contrasts

Question 7

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

Answer 7

Thickness
Density
Atomic number

Question 8

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

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

Answer 8

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

Question 9

Why is barium useful in imaging?

Answer 9

Hefty high attenuation coefficient ∴ contrasting agent

Question 10

Barium studies are useful for viewing what?

Answer 10

Hollow structures

Intestines, stomach, oesophagus etc

Question 11

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

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

Answer 11

Ionising radiation

Question 12

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

Answer 12

Repair
Death
Transformation - bad - cancer

Question 13

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

Answer 13

Sieverts

milli sieverts is most commonly used