Introduction to radiology

Question 1

What is attenuation in x-rays?

Answer 1

Absorption of x-ray photons before hitting x-ray plate.
Bone = high attenuation = white.
Soft tissues = intermediate attenuation = shades of grey.
Lungs = low attenuation = black.

Question 2

What is the silhouette sign?

Answer 2

Different tissues absorb different amounts of x-ray. If vessels can’t be seen, or diaphragm, or heart, then something is going on in the lungs.

Question 3

What is CT?

Answer 3

Rotation of x-ray tube and bank of detectors (not film) around patient. Attenuation information directly entered into computer.
Multislice CT is quicker, modern version, can map anatomy really well.

Question 4

CXR vs CT.

Answer 4

Spatial resolution is better in CXR than CT.
Contrast resolution is much better in CT than in CXR.
Anatomical superimposition is a big part of x-ray, but absent in CT.
Dose of ionising radiation is 100x higher in CT head than CXR, CT chest is 470x higher than CXR, CT whole spine is 715x higher than CXR.

Question 5

At what dose of radiation do you begin to see changes in blood cells?

Answer 5

100mSv.

Question 6

What is the dose of radiation of a chest x-ray?

Answer 6

0.014mSv.

Question 7

What is the dose of radiation of a CT head?

Answer 7

1.4mSv.

Question 8

What is the dose of radiation of a CT chest?

Answer 8

6.6mSv.

Question 9

What is the dose of radiation of a CT whole spine?

Answer 9

10mSv.

Question 10

What is the annual dose of radiation from living in the UK?

Answer 10

2.7mSv.

Question 11

What is the annual dose of radiation from living in the US?

Answer 11

6.2mSv.

Question 12

What is the annual dose of radiation from living in Cornwall?

Answer 12

6.9mSv.

Question 13

What is the dose of radiation from a transatlantic flight?

Answer 13

0.08mSv.

Question 14

What is the dose of radiation from eating 100g Brazil nuts?

Answer 14

0.01mSv.

Question 15

List basic signs in chest imaging.

Answer 15

Consolidation.
Ground-glass opacification.
Reticulation.
Honeycombing.
Nodules.
Pulmonary air cysts.
Traction bronchiectasis.
Traction bronchiolectasis.
Halo sign.
Reverse halo.

Question 16

What is consolidation on chest imaging?

Answer 16

Air displaced from airspaces.
Infection/inflammation; tumour (lung cancer, lymphoma); blood, etc.
Replacement of airspaces by fluid or cells without volume loss.
Ill-defined/ fluffy shadowing.
Confluent.
Loss of vessel pattern.
Air-bronchograms.
Causes: pneumonia, oedema, haemorrhage, aspiration.

Question 17

What is the ground glass opacification sign on chest imaging?

Answer 17

Partial displacement of air from lungs.

Airspace (haemorrhage), interstitial (hypersensitivity, pneumonitis), or both (RBILD).

Question 18

A chest x-ray report describes ‘consolidation in the right lower lobe’. This means:

a) there is infection in the right lower lobe
b) the most likely diagnosis is lung cancer
c) there is blood in the airspaces
d) air has been displaced from the right lower lobe
e) the most likely diagnosis is tuberculosis

Answer 18

Air has been displaced from the right lower lobe.

Question 19

The radiation dose from a CT chest is:

a) significantly higher than from a chest x-ray
b) significantly lower than form a chest x-ray
c) nearly 500x the dose of a chest x-ray
d) equivalent to the dose from a thoracic MRI examination
e) nearly 700x the dose from a chest x-ray

Answer 19

Significantly higher than from a chest x-ray.

Nearly 500x the dose of a chest x-ray.