Radiology of the Thorax 2 Flashcards
When is imaging indicated for pulmonary thromboembolism?
- If CXR normal, do V/Q scan
- If radiation to be avoided/leg swollen consider ultrasound scanning Leg for DVT
- If CXR abnormal/massive PE suspected, do CT pulmonary angiogram
What is the appearance of an abnormal VQ scan?
If blockage in one of the branches, will tend to be a wedge shape downstream from that
What does the abnormal wedge shape in a CTPA result from?
Blood will not be sent to non-ventilated area as blood sent to that area will not be oxygenated - this is called matched V:Q defect
What is mismatched V:Q defect indicative of?
Pulmonary embolism - where a segment of the lung receives ventilation, but the blood flow to that ventilated area is blocked by a blood clot
Is matched ventilation:perfusion indicative of PE?
No, mismatched V:Q is
What is the appearance of a benign pulmonary nodule on a CXR?
- High attenuation indicates calcification
* Mass is also very well defined (sharp)
What are the characteristics of a hamartoma on CT?
- Mass resembles popcorn
* Benign
What are the clinical features and pathology of lung cancer?
- 15-20% are asymptomatic - especially peripheral tumours
- Symptoms: cough, wheeze, haemoptysis, recurrent pneumonia, hypercalcemia
- Weight loss, hoarseness, finger clubbing, persistent supra-clavicle nodes
What is the prevalence of haemoptyisis and the likelihood of someone with haemoptysis having lung cancer?
- 20% of lung cancer sufferers have haemoptysis
* People with haemoptysis 13 times more likely to have lung cancer
Why is it difficult to screen for lung cancer?
- Cough is prevalent (65%) in lung cancer suffers - however, a cough can be indicative of many things (those with a cough are only 2 times more likely to have lung cancer)
- People with haemoptysis are 13 times more likely to have lung cancer - however, only 20% of lung cancer sufferers present with haemoptysis
What are predisposing conditions to lung cancer?
- Inhalation of carcinogens e.g. cigarette smoke, asbestos, radon gas
- Bronchioalveolar adenoma
- Lipoid pneumonia
- Interstitial pulmonary fibrosis
- Previous lung cancer (tumours can be synchronous and metachronous)
What are synchronous tumours?
More than 1 tumour at the same time
What are metachronous tumours?
Second tumour at a later time
What is the appearance of asbestosis on a HRCT scan?
- Sub-pleural nodulation
* Large chunks of white – calcification is hallmark of previous asbestos exposure
What is the most common cause of interstitial fibrosis?
Usual interstitial pneumonia
What is the appearance of pulmonary fibrosis on a HRCT?
- Honeycombing
- Peripheral disease
- Towards bases
What are peripheral tumours?
Tumours arising beyond the hilum
What are central tumours?
Tumours arising at or close to the hilum
What are features of peripheral tumours?
- Rarely visible on chest X-ray if < 1cm diameter
- Usually spherical or oval
- Volume doubling time varies between 40 and 400 days (for solid tumours)
Why is it significant that the volume doubling time for solid peripheral tumours varies between 40 and 400 days?
If see somehting on CXR that has doubled in size in less than 40 days, more likely to be infection, fluid (etc) rather than cancer
What percentage of bronchial cancers are peripheral tumours?
40% bronchial cancers rise beyond segmental bronchi
What are cardinal signs of central tumours?
- Hilar enlargement
- Distal collapse/consolidation
- Much harder to spot
What is the appearance of a central mass in the left lung on CXR?
- Elevation of left hemi-diaphragm and loss of outline
- Triangular-shaped opacity behind heart
- Left lower lobe collapse
(pic)
What abnormalities are seen on this CT? (pic)
- Calcification in wall of aorta
- Lobulated mass at left hilum
- Left lower lobe collapse
