Principles of Practical Radiography

Question 1

Describe the safety features involved in radiography

Answer 1

UK legislation – Ionising Radiation Regulations 2017 & Local Radiation Rules produced by Radiation Protection Advisor
If you do need to be in the room, wear PPE (lead gown, lead gloves, thyroid guard)
Wear your personal dosimeter in the correct place (between the neck and waist and under any PPE)
Record all exposures
Each practice will have at least one Radiation Protection Supervisor
Ensure the radiography equipment is in good working order and routinely checked
Do not perform radiography if you are pregnant

Question 2

What is the purpose of a grid in radiography?

Answer 2

reduces the amount of scatter radiation and improves the contrast of an image.

Question 3

When do we use a grid in radiography?

Answer 3

when the tissue depth of the area we are radiographing is over 10cm

Question 4

What are the 2 types of radiography grid?

Answer 4

Stationary – the grid is placed on top of the cassette on the tabletop (under the patient)
Moving – The cassette is placed in the bucky tray (in landscape), so it is underneath an in-built. Ensure you secure the cassette in the tray and push it all the way under the table.

Question 5

Why is it important to collimate an x-ray correctly?

Answer 5

As the x-ray hits the animal, some is absorbed and some is scattered, so if there is a larger area of animal/plate available for the x-rays to hit, there will be more scatter.Reducing scatter reduces safety risk.

Question 6

What is the effect of changing current (mA) of an x-ray?

Answer 6

controls the number of electrons crossing the tube, affecting the number of x-rays produced. This does not affect contrast but does affect the degree of blackening of the film (radiographic density)

Question 7

What is the effect of changing the voltage (kV) of an x-ray?

Answer 7

controls the number of and speed of the electrons as they cross the tube. This does control contrast.
A higher kV = faster electrons = x-rays with greater energy = greater penetrating ability so better contrast (difference between structures on the image). However, if the kV is excessively high, the contrast may be reduced because the high energy x-rays will pass straight through the patient.

Question 8

What is the appearance of an over and under exposed radiograph?

Answer 8

Over-exposure = black
under-exposure = white