Introduction to Respiratory Radiology Flashcards
What colour (density) is air on a CXR?
Black - least dense
What colour (density) is fat on a CXR?
Grey
What colour (density) is soft tissue/muscle on a CXR?
Grey/white
What colour (density) is bone on a CXR?
White - very dense
What colour (density) is metal on a CXR?
Bright white - densest
(pic)
Label the different densities from least dense to densest
Why is intra-thoracic air not as dense as extra-thoracic air?
Chest wall and blood vessels impair x-ray beams
What is the CT density of air?
-1000
What is the CT density of lungs?
-500
What is the CT density of fat?
-100
What is the CT density of water?
0 (all CT densities are given relative to water - anything less dense than water will be negative and anything denser than water will be positive)
What is the CT density of muscle?
+50
What is the CT density of bone?
+200
What is the CT density of metal?
+1000
(pic)
What does the tiny nodule on the CXR indicate?
Shade of white-grey denser than adjacent ribs - nodule composed of calcium (granuloma)
Are calciferous granulomas worrying?
No, likely to be chronic
What modality other than CXR and CT scans can be used for lung imaging?
Ultrasound
What is ultrasound?
Uses passage of sound waves which bounce off of structures to create image based on speed of return of sound wave
What effect does fluid have on the passage of sound waves?
Allows passage of sound waves - appears black
What effect does soft tissue have on the passage of sound waves?
Allows passage of sound waves - appears bright
What effect does air have on the passage of sound waves?
Blocks passage of sound waves
What complications can fluid in the chest lead to?
Haemothorax - can lead to lung collapse
Fluid - haemothorax
Air - pneumothorax
What is the standard CXR technique?
- Patient stands 2m from the x-ray apparatus, facing the digital cassette
*The shoulders are braced forward so that the scapulae do not obscure the lungs
*The radiograph is taken at full inspiration.
“Breathe in and hold your breath”
*The x-rays pass from Posterior to Anterior producing a ‘PA radiograph’
When is ‘AP’ view taken in CXR?
- When patient cannot stand
What are 3 reasons that AP x-rays are technically inferior to PA views?
- The heart shadow is magnified so heart size cannot be assessed accurately
- The scapulae overlie and partly obscure the lungs
- It can be difficult for the patient to take an adequate inspiration
What are other CXR techniques, aside from AP and PA view?
Lateral view
What are the advantages of lateral view CXR?
Gives additional information - shows structures behind the heart i.e. lung cancer in regions behind heart
What are 3 factors that determine whether a CXR is technically adequate?
The 3 ‘-ations’
- Inspiration
- Rotation
- Penetration (is there enough radiation?)
What is the importance of inspiration and rotation in CXR?
A poorly inspired or rotated CXR can simulate pathology when none is there
How can you tell if a CXR is adequately inspired?
The anterior ends of at least 6 ribs should be visible
How can you tell if a CXR is correctly centred?
The medial ends of the clavicles should be equidistant from the spinous processes of the upper thoracic vertebrae
Why would cardiothoracic ratio change in different images of the same patient’s chest?
Due to inspiration and expiration
What is situs inversus?
Congenital anomaly - large organs are swapped from left to right
Name the mediastinal borders labelled 1-9
pic
1) Aorta
2) Pulmonary artery
3) Left auricle
4) Left ventricle - left heart border
5) Right atrium - right heart border
6) Trachea
7) Hemidiaphragm
8) Horizontal fissure
Why is left hemidiaphragm lower than right hemidiaphragm?
Right hemidiaphragm pushed up by liver
Are lymph nodes visible on CXR?
Only visible when enlarged
What do visible lymph nodes on CXR indicate?
Pathology of the lymph nodes
What are ‘red flags’?
- Weight loss
* Haemoptysis
Label the lateral radiograph of the right lung
pic
1) Oblique fissure
2) Horizontal fissure
3) Posterior costophrenic recess
4) Retrosternal space
How can you tell if an abnormality is if left lower lobe or left upper lobe?
Behind oblique fissure - lef blower lobe
In front of fissure - left upper lobe
What is the only part of the right lung that touches the right heart border?
The right middle lobe
What is the part of the left lung that touches the left heart border?
The lingula
Why is patient history important with regards to CXR?
A tumour would look identical to pneumonia - history of fever (infection) would indicate pneumonia, whereas afebrile may indicate cancer
What are red flags for lung cancer?
- Weight loss
- Loss of appetite
- Haemoptysis
- Dyspnoea
- Cough
