Chest X-ray Interpretation

Question 1

What do the shadows tell you on a CRX?

Answer 1

blackest (rays will pass through) to whitest/opaque (rays will be blocked) - air (least dense) => soft tissues/fluids => bone => metal (most dense)

Question 2

What factors determine the adequacy of a CRX?

Answer 2

projection, inspiration, penetration, rotation

Question 3

How do you assess projection on a CRX?

Answer 3

PA is standard - heart is closer to the imaging surface => gives a truer image of its actual size

Question 4

How do you assess rotation on a CRX?

Answer 4

should be centered - medial ends of clavicles are equidistant from the spinous process

Question 5

How do you assess penetration on a CRX?

Answer 5

vertebral bodies should be just visible through the heart

Question 6

How do you assess inspiration on a CRX?

Answer 6

8-10 posterior ribs should be visible

Question 7

What is the appropriate approach to assessing a CRX?

Answer 7

systematic - inside out: heart, medisatinum/hilum, airways/lungs, thoracic wall

Question 8

What is the size of a normal heart on CRX?

Answer 8

cardiothoracic ratio - the transverse diameter of the heart divided by the diameter of the thoracic cage: < 0.5 is normal (cardiomegaly if > 0.5); should see post pericardial window on cardiac silhouette; should not see enlargement of any chambers

Question 9

How does the normal hila appear on CRX?

Answer 9

finger width branches pointed down

Question 10

How does the normal pulmonary vasculature appear on CRX?

Answer 10

lower lobe vessels are larger in size than upper lobe vessels, and all vessels taper gradually from central to peripheral

Question 11

What does opacity indicate on CRX?

Answer 11

air space disease - pathological process fills alveoli with fluid, pus, blood, or cells (e.g., tumor cells) => distribution may be lobar (pneumonia), diffused (edema), or multifocal (pneumonia or mass)

Question 12

What is the silhouette sign of pneumonia on CRX?

Answer 12

when two objects of equal density touch each other, the edge or margin between them disappears

Question 13

What is the spine sign of pneumonia on CRX?

Answer 13

opacity obscures view of the spine

Question 14

What is the significance of air bronchograms on CRX?

Answer 14

bronchi are not usually visible on CRX - when inflammatory exudate surrounds bronchi (e.g., with pneumonia), bronchi become visible as black tubular structures

Question 15

What does bat wing opacity on CRX suggest?

Answer 15

pulmonary edema

Question 16

What is an opacity?

Answer 16

fluid filled alveolus

Question 17

What is interstitial disease?

Answer 17

abnormal change in supporting structures (alveolar wall) due to inflammation, edema, or fibrosis

Question 18

What are the most common causes of interstitial disease?

Answer 18

interstitial pneumonia, pulmonary congestion, asbestosis, silicosis, idiopathic pulmonary fibrosis

Question 19

What are the patterns of interstitial markings?

Answer 19

reticular (fine lines) or nodular (dots)

Question 20

What is the most common cause of reticular patterns of interstitial lung disease?

Answer 20

pneumonia

Question 21

How does atelectasis (lung volume loss) appear on CRX?

Answer 21

sharply defined opacification, plate-like or fan-like, no air bronchograms, possible displacement of mobile structures (diaphragm and trachea)

Question 22

What are the signs of pleural effusion on CRX?

Answer 22

blunting of costophrenic angles (meniscus sign) and Kerley B lines (accumulation of fluids in interlobular spaces)

Question 23

What are the signs of pneumothorax on CRX?

Answer 23

visceral pleura becomes visible as a thin white line (parallel to the curvature of the chest wall) => absence of lung marking peripheral to the viseral pleural line

Question 24

How does the diaphragm usually appear on CRX?

Answer 24

right hemi-diaphragm is usually higher, with concave shape and sharp costophrenic angle

Question 25

What are the common signs of pneumonia on CRX?

Answer 25

segmental/lobar opacity, silhouette sign, spine sign, bronchograms, pleural effusion (usually unilateral)

Question 26

What are the common signs of pulmonary edema/congestion on CRX?

Answer 26

cardiomegaly, diffused (bilateral) opacities, bronchograms, Kerley B lines, pleural effusion (bilateral)