Imaging the normal and abnormal lung

Question 1

What are the strengths of radiography?

Answer 1

Great spatial resolution- especially bone

Cheap & available

Easy interpretation

Question 2

What are the weaknesses of radiography?

Answer 2

Projectional

Ionising radiation

Very limited soft tissue visualisation

Question 3

What are the 4 tissues you can differentiate on radiography?

Answer 3

Air / gas

Fat

Water / soft tissue - all body fluids and tissues except fat and bone

High atomic number calcium iodine barium metals

Question 4

Can you see blood vessels in a lung?

Can you see airways in a lung?

Answer 4

Yes

No

Question 5

What are the strengths of CT?

Answer 5

Cross-sectional

Spatial resolution

Widely available

Weaknesses

Question 6

Why is CT better than x-ray of the lungs?

Answer 6

Shows greater detail

Resolve small structures

Resolve small differences in attenuation

Question 7

What are the weaknesses of CT?

Answer 7

Ionising radiation

Limited soft tissue contrast

Question 8

How can HRCT be generated?

Answer 8

High resolution CT -

Slice thickness

Resolution

Thin section (1mm) is the optimal technique for demonstrating lung

CT thorax 5mm slice thickness

Question 9

What imaging technique is this?

Answer 9

HRCT

Question 10

What imaging technique is this?

Answer 10

HRCT

Question 11

Label the diagram.

There is a tumour as one of the labels

Answer 11

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

Question 12

Label the lobes

Answer 12

Superior

Middle

Inferior

Question 13

What does this show?

Answer 13

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

Question 15

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

Answer 15

6-10

5-20

300 million

Question 16

What is a secondary pulmonary lobule?

Answer 16

A secondary pulmonary lobule is the functional unit of the lung which is surrounded by a connective tissue septum (CTS).

Question 17

What does this picture show?

Answer 17

A secondary pulmonary lobule

Question 18

What does this show?

Answer 18

This patient has some fibrosis of the connective tissue septum surrounded by red arrows.

Pathology of secondary pulmonary lobule

Question 19

Secondary pulmonary lobules cannot be seen on CT.

True or false?

Answer 19

False

Can see secondary pulmonary lobules on CT scanning, particularly when there is a pathology that causes thickening/fibrosis of the connective tissue septum.

Question 20

What are the 4 functions of the lungs?

Answer 20

Gas exchange

Ventilation - move air in and out

Perfusion - move blood in and out

Diffusion - moves gases between alveoli and blood

Question 21

How could we obtain a picture of the distribution of ventilation in the lungs?

Answer 21

Radioactive gas - Xenon-133, Krypton-81m

Radioactive aerosol - Tc99m-DTPA,

Radioactive dry carbon particles 20nm (0.02 microns) 50micrograms Tc99m

Question 22

Which imaging technique is 2 orders of magnitude below 24 hour permitted atmospheric pollution?

Answer 22

Radioactive dry carbon particles 20nm (0.02 microns) 50micrograms Tc99m

Question 23

What does this show?

Answer 23

Normal scan

Question 24

How could we produce a steady state image of lung blood flow?

Answer 24

Inject nuclear isotope into blood stream

• 2-500,000 intravenous particles
• 16-90 micron diameter
• Macroaggregated human serum albumen
• Occlude <1% of pulmonary circulation

Question 25

What patient posture would achieve the most uniform distribution of particles throughout the lungs?

Answer 25

Lying flat on back

Question 26

What type of scan is this?

Answer 26

Ventilation/Perfusion scan V/Q scan

Question 27

What has happened to the right lung

Answer 27

No vessels in right lung field – the lung has collapsed adjacent to the heart and the pleural cavity is full of air - pneumothorax

Question 28

What is this showing?

Answer 28

Pleural effusion – liquid in the pleural cavity – typical appearance in the outer bottom corner of the lung field

Question 29

Why this liquid shape facing towards the hilum why not a horixontal line at the top of the liquid

Answer 29

Fluid looks like its creeping up at lateral edges because it forms meniscus

Question 30

High temperature & cough Diagnosis?

Answer 30

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

Question 31

What does air space shadowing (consolidation) look like on a chest x-ray?

Answer 31

Fluffy blobs About 1cm dia Tending to confluence +/- air bronchogram

Question 32

What could consolidation be on a chest x-ray?

Answer 32

Could be oedema /transudate / exudate / pus / blood

Question 33

Diagnosis? How is the patient breathing? What might her blood gases be like?

Answer 33

Smoke inhalation has caused water in the alveoli due to inflammation. She has a tracheostomy. Her blood oxygen concentration will be reduced.

Question 34

Is this shadow at the front or the back? Diagnosis

Answer 34

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

Question 35

Is this shadow at the front or the back ?

Answer 35

Heart border still visible Shadowing is at the back in the lower lobe

Question 36

Whats the diagnosis?

Answer 36

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

Question 37

Whats the diagnosis

Answer 37

Intravenous contrast medium shows blood vessels white but grey clot in the pulmonary artery X – pulmonary embolism

Question 38

What is the diagnosis?

Answer 38

Ventilation scan at top pretty much normal but defects in perfusion images lower row due to pulmonary emboli blocking pulmonary arteries.