Imaging the Thorax

Question 1

Assessing a CXR

Answer 1

Rotation, Exposure, Coverage, Review areas
- apices, costo-phrenic angle, behind the heart, hila, peripheries
Heart Size: cardiothoracic ratio: <0.5 (C+T < 0.5)

Question 2

CT scans of lung

Answer 2

Shows greater detail
Small structures resolved
Resolve small differences in attenuation
Strengths: cross sectional, spatial resolution, available
Weaknesses: ionising radiation, limited soft tissue contrast

Question 3

CT of Thorax & HRCT Lung

Answer 3

Slice thickness
Resolution
This section (1mm) is optimal technique for demonstrating the lung
30 million alveoli/adult - total area 143m^2

Question 4

Lung

Answer 4

2-500 000 intravenous particles, 16-90um diameter
Macroaggregated human serum albumin
Occlude <1% of pulmonary circulation
Ventilation can be seen using radioactive gas/aerosol/dry carbon particles

Question 5

Air space shadowing

Answer 5

Fluffy blobs, 1 cm diameter
Tend to confluence
Could be oedema/transudate/exudate/pus/blood
+/- air bronchogram

Question 6

Radiography

Answer 6

Strengths: great spatial resolution (esp bone), cheap and available, easy interpretation
Weaknesses: projectional, ionising radiation, limited soft tissue visualisation.
Air/gas; fat; water/soft tissue; and things with a high atomic number (Ca/I/Ba metals)