imaging the thorax theme 3

Question 1

how do we take a chest x-ray?

Answer 1

• x-ray source 2 metres behind the patient with the heart closer to the plate to prevent enlargement

Question 2

how can we image the lungs? 3

Answer 2

• chest x-ray
• CT
• ventilation and perfusion imaging

Question 3

how should we assess a chest x-ray? 3

what are the review areas? 5

Answer 3

• rotation
• exposure
• coverage
• apices
• costo-phrenic angle
• behind the heart
• hila
• peripheries

Question 4

how do we assess the size of the heart? 2

Answer 4

• cardio thoracic ratio

- widest diameter of the heart/ total intrathoracic diaphragm width, should be less than 0.5

Question 5

why do we use CT scans of the lungs? 3

Answer 5

• shower greater detail
• resolve small structures
• resolve small differences in attenuation

Question 6

what parts of the lung structure are particularly important in scans? 2

Answer 6

• the primary pulmonary lobule and acinus 6-10mm

- the secondary pulmonary lobule 5-20mm in diameter and is the functional unit of the lung

Question 7

how can we image the function of the lung? 3

Answer 7

• ventilation= more air in and out
• perfusion= move blood in and out
• diffusion= move gases between alveoli and blood

Question 8

how do we obtain a picture of the distribution of ventilation in the lungs?

Answer 8

• breathe in radioactive gas or aerosol of dry carbon particles

Question 9

how do we produce a steady state image of the lung blood flow? 4

Answer 9

• use radio isotope
• 2-500,000 intravenous particles
• only occlude <1% of pulmonary circulation
• always take scan with patient lying on back

Question 10

describe air space shadowing in a lung scan? 4

Answer 10

• fluffy blobs
• 1cm in diameter
• tending to confluence
• could be oedema, transudate, pus, blood