Imagining of the Thorax

Question 1

What stops X-rays getting through certain tissues?

Answer 1

Atoms with a high atomic number in high concentration

Question 2

What has the lowest e-densities?

Answer 2

Air, then fat then soft tissue

Question 3

What has the highest e-densities?

Answer 3

bone then contrast agents then metal

Question 4

What causes an interface on an x-ray?

Answer 4

Different electron densities between the tissues

Question 5

Why is a CXR done posterior to anterior?

Answer 5

So that the heart is closer to the film to prevent magnification

Question 6

Why is a CXR done on full inspiration?

Answer 6

To fully aerate the lungs to get a good silhouette

Question 7

Why does the patient hug the film in a CXR?

Answer 7

To move the scapula out of the way

Question 8

Why is a CXR done standing?

Answer 8

To see heart failure (by looking at blood flow distribution in the lungs) and to see pleural effusion (fluid will sink)

Question 9

What does it mean if fluid in the lungs has a meniscus?

Answer 9

That the lungs are not open to the atmosphere - if there is no meniscus then the lungs are open to the atmosphere

Question 10

How many ribs can be seen anteriorly on full inspiration?

Answer 10

7

Question 11

How many ribs can be seen posteriorly on full inspiration?

Answer 11

11

Question 12

How can you tell if the heart is enlarged?

Answer 12

The maximum transverse diameter of the heart must be less than 50% of the internal thoracic diameter of the chest (except in children or COPD)

Question 13

What are the areas of a lung on a CXR?

Answer 13

Can’t tell lobes so instead look at zones- upper, middle and lower