Introduction to radiology Flashcards
What is attenuation in x-rays?
Absorption of x-ray photons before hitting x-ray plate.
Bone = high attenuation = white.
Soft tissues = intermediate attenuation = shades of grey.
Lungs/air = low attenuation = black.
What is the silhouette sign?
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- this is the silhouette sign
White lungs
What is CT?
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.
CXR vs CT? Pros and cons
Spatial resolution
Contrast resolution
Anatomical superposition
Radiation dose
Spatial resolution is better in CXR than CT. [ability to define separate structures]
Contrast resolution is much better in CT than in CXR.
Anatomical superimposition is a big part of x-ray, but absent in CT so CT better for diagnosis.
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.
At what dose of radiation do you begin to see changes in blood cells?
100mSv.
Remember cumulative dose- each scan adds up
What is the dose of radiation of a chest x-ray?
0.014mSv.
What is the dose of radiation of a CT head?
1.4mSv. [100 x CXR]
What is the dose of radiation of a CT chest?
6.6mSv. [470 x CXR]
What is the dose of radiation of a CT whole spine?
10mSv. [700 x CXR]
What is the annual dose of radiation from living in the UK?
2.7mSv.
What is the annual dose of radiation from living in the US?
6.2mSv.
What is the annual dose of radiation from living in Cornwall?
6.9mSv- higher than other areas of UK
What is the dose of radiation from a transatlantic flight?
0.08mSv.
What is the dose of radiation from eating 100g Brazil nuts?
0.01mSv.
List basic signs in chest imaging
Consolidation.
Ground-glass opacification.
Reticulation.
Honeycombing.
Nodules.
Pulmonary air cysts.
Traction bronchiectasis.
Traction bronchiolectasis.
Cysts.
Halo sign.
Reverse halo.
What is consolidation on chest imaging?
What are the causes?
Areas of increased density/attenuation
Air displaced from airspaces, replacement by fluid/cells.
Ill-defined/ fluffy shadowing.
Confluent.
Loss of vessel pattern.
Air-bronchograms.
Causes:
Infection/inflammation- pneumonia
tumour (lung cancer, lymphoma)
pulmonary oedema
haemorrhage
aspiration
ARDS
What is the ground glass opacification sign on chest imaging?
What are the causes?
Partial displacement of air from lungs.
Increased density- doesn’t obscure airways on CT [lack of obstruction of bronchioles not noticed on CXR]
Causes:
Airspace (haemorrhage)
Interstitial (hypersensitivity pneumonitis)
Both (RBILD).
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
Air has been displaced from the right lower lobe.
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
Significantly higher than from a chest x-ray. Nearly 500x the dose of a chest x-ray.
Types of radiology
Interventional
Non interventional
What part of the heart is seen on right side of CXR?
Right atrium
What part of the heart is seen on left side of CXR?
Left ventricle
What is this?
Azygous vein draining into SCV
What sign can be seen during mediastinal lymph node enlargement?
Loss of Azygo-oesophageal line
Suggests tumour spread
What does consolidation at horizonal fissure indicate?
Consolidation of right upper lobe
When is a circular consolidation in the lungs a nodule or mass?
Nodule <3cm
Mass >3cm
What is this?
Spiculated nodule
Primary lung cancer
NOT normal part of hilum
How are black areas of lung described? What are the causes?
Increased lucency/transradiancy
Causes: pneumothorax, bullae, emphysema
Features of pleural effusion?
Meniscus
Ill defined {and decreasing attenuation of ] superior margin
What causes white out and how to differentiate?
Collapse- trachea towards, rib crowding[closer together]
Pleural effusion= trachea away
What is this?
Cannonball lung mets
