Imaging the normal and abnormal lung Flashcards
What are the strengths of radiography?
Great spatial resolution- especially bone
Cheap & available
Easy interpretation
What are the weaknesses of radiography?
Projectional
Ionising radiation
Very limited soft tissue visualisation
What are the 4 tissues you can differentiate on radiography?
Air / gas
Fat
Water / soft tissue - all body fluids and tissues except fat and bone
High atomic number calcium iodine barium metals
Can you see blood vessels in a lung?
Can you see airways in a lung?
Yes
No
What are the strengths of CT?
Cross-sectional
Spatial resolution
Widely available
Weaknesses
Why is CT better than x-ray of the lungs?
Shows greater detail
Resolve small structures
Resolve small differences in attenuation
What are the weaknesses of CT?
Ionising radiation
Limited soft tissue contrast
How can HRCT be generated?
High resolution CT -
Slice thickness
Resolution
Thin section (1mm) is the optimal technique for demonstrating lung
CT thorax 5mm slice thickness
What imaging technique is this?
HRCT
What imaging technique is this?
HRCT
Label the diagram.
There is a tumour as one of the labels
Intravenous contrast white in superior vena cava (1)and grey in ascending 2 and descening 3 aorta and the pulmonary arteries4.. There is a tumour 5 of soft tissue density
Label the lobes
Superior
Middle
Inferior
What does this show?
Right upper lobe collapse
Normally horizontal fissure runs horizontally to the hilum but the upper right lobe has collapsed
Has lost volume so collapsed upwards and medially towards spine - pulled horizontal fissure up with it
The primary pulmonary lobule and acinus ______mm
Secondary pulmonary lobule _______mm diam is the functional unit of the lung.
______ alveoli per adult – total area 143m2
6-10
5-20
300 million
What is a secondary pulmonary lobule?
A secondary pulmonary lobule is the functional unit of the lung which is surrounded by a connective tissue septum (CTS).
What does this picture show?
A secondary pulmonary lobule
What does this show?
This patient has some fibrosis of the connective tissue septum surrounded by red arrows.
Pathology of secondary pulmonary lobule
Secondary pulmonary lobules cannot be seen on CT.
True or false?
False
Can see secondary pulmonary lobules on CT scanning, particularly when there is a pathology that causes thickening/fibrosis of the connective tissue septum.
What are the 4 functions of the lungs?
Gas exchange
Ventilation - move air in and out
Perfusion - move blood in and out
Diffusion - moves gases between alveoli and blood
How could we obtain a picture of the distribution of ventilation in the lungs?
Radioactive gas - Xenon-133, Krypton-81m
Radioactive aerosol - Tc99m-DTPA,
Radioactive dry carbon particles 20nm (0.02 microns) 50micrograms Tc99m
Which imaging technique is 2 orders of magnitude below 24 hour permitted atmospheric pollution?
Radioactive dry carbon particles 20nm (0.02 microns) 50micrograms Tc99m
What does this show?
Normal scan
How could we produce a steady state image of lung blood flow?
Inject nuclear isotope into blood stream
- 2-500,000 intravenous particles
- 16-90 micron diameter
- Macroaggregated human serum albumen
- Occlude <1% of pulmonary circulation
What patient posture would achieve the most uniform distribution of particles throughout the lungs?
Lying flat on back
What type of scan is this?
Ventilation/Perfusion scan
V/Q scan
What has happened to the right lung
No vessels in right lung field – the lung has collapsed adjacent to the heart and the pleural cavity is full of air - pneumothorax
What is this showing?
Pleural effusion – liquid in the pleural cavity – typical appearance in the outer bottom corner of the lung field
Why this liquid shape facing towards the hilum why not a horixontal line at the top of the liquid
Fluid looks like its creeping up at lateral edges because it forms meniscus
High temperature & cough
Diagnosis?
Shadow limited by horizontal fissure ie it’s in the upper lobe
Can’t always tell what a shadow on a CXR is due to.
Water = blood = pus on radiograph but the radiograph and the symptoms add up to lobar pneumonia
What does air space shadowing (consolidation) look like on a chest x-ray?
Fluffy blobs
About 1cm dia
Tending to confluence
+/- air bronchogram
What could consolidation be on a chest x-ray?
Could be oedema /transudate / exudate / pus / blood
Diagnosis?
How is the patient breathing?
What might her blood gases be like?
Smoke inhalation has caused water in the alveoli due to inflammation. She has a tracheostomy. Her blood oxygen concentration will be reduced.
Is this shadow at the front or the back?
Diagnosis
Sorry about stripes – ignore. The right heart border has disappeared therefore the shadowing is next to the heart therefore at the front therefore in the middle lobe
Middle lobe pneumonia
Is this shadow at the front or the back ?
Heart border still visible
Shadowing is at the back in the lower lobe
Whats the diagnosis?
Many dots in the airspaces – can still make out vessels just about. TB granulomas miliary – blood borne spread – actually all over the body but easy to see in the lungs
Whats the diagnosis
Intravenous contrast medium shows blood vessels white but grey clot in the pulmonary artery X – pulmonary embolism
What is the diagnosis?
Ventilation scan at top pretty much normal but defects in perfusion images lower row due to pulmonary emboli blocking pulmonary arteries.
