chest/thoracic imaging

Question 1

why cant x rays be used all the time

Answer 1

are a form of ionising radiation - can damage tissue, cells and DNA

Question 2

what does damage to DNA lead to

Answer 2

uncontrolled cell division - cancer

Question 3

which scans use ionising radiation

Answer 3

X rays
CT scans

Question 4

which scans dont use ionising radiation

Answer 4

ultrasound
MRI

Question 5

how do x ray staff protect themselves

Answer 5

they wear lead aprons if they operate in close proximity to x rays

as lead absorbs most x rays

Question 6

how is safe use of x rays regulated

Answer 6

IRMER
ionising radiation medical exposure regulations

Question 7

how do dense body parts look on x rays eg bones

Answer 7

white
because dense body parts absorb x rays

Question 8

how do less dense structures look on x rays eg lungs

Answer 8

darker, almost black

because they do not absorb many x rays

Question 9

how do soft tissue structures look on x rays

Answer 9

a shade of grey depending on how dense they are

Question 10

how to view x rays

Answer 10

as if the patient is looking at u
left hand side of image is patients right side

Question 11

how to differentiate between right and left bronchi on x ray

Answer 11

right main bronchus is wider and more verital

Question 12

pinpoints of the heart on an x ray

Answer 12

• right atrium on right border
• right ventricle on inferior border
• left ventricle on left border
• left atrium at back

Question 13

how to assess symmetry of an x ray

Answer 13

using clavicles

Question 14

why are the anterior aspects of the ribs not easily visible on an x ray

Answer 14

because they are cartilaginous

Question 15

what are the two ways x rays are directed at a patient

Answer 15

1. anterior posterior (AP)
2. posterior anterior (PA)

Question 16

describe anterior posterior (AP) x rays

Answer 16

• are from front to back (the detector is behind the patient)
• often performed when patient is v unwell and cannot get into ideal position
• as the heart is at the front of the thorax, the x ray beams diverge after hitting the heart, creating a larger shadow on the detector
• so it appears large and blurry on the image

Question 17

describe posterior anterior (PA) x rays

Answer 17

• x ray is directed at the back of the patient and detected at the front
• heart is closer to the detector so less x ray divergence after hitting it means it produces a more accurate size on the image and less blurry
• also the scapulae can be protected for a PA x ray by having the patient put their arms around the detector, so the scaupulae are not overlying the lung fields

Question 18

what does pneumonia cause on x ray image

Answer 18

a patchy opacification in the lung fields

Question 19

what is a pneumothorax

Answer 19

air in between the parietal (outer) and visceral (inner) pleura

Question 20

what indicates pneumothorax in x ray

Answer 20

you may be able to see where normal lung markings stop and there may be a rim of very clear black around the lung field
- indicating air in the pleural space

Question 21

why is breathing comprpomised if air gets in the pleural space

Answer 21

because normally there is a very small amount of fluid between the pleura to provide surface tension so that they stick together

if air gets in the pleural space the sticky surface tension is lost

so breathing is compromised

Question 22

what is a pleural effusion

Answer 22

a collection of excess fluid in the pleural space

Question 23

what causes a pleural effusion

Answer 23

infection, cancer or heart failiure

Question 24

why is it difficult to tell if a unilateral pleural effusion is just pleural fluid or blood on an x ray

Answer 24

because blood and inflammatory/pleural fluid show up as the same colour

Question 25

can rib fractures be seen on an x ray

Answer 25

yes but are often difficult to see unless displaced

Question 26

what do rib fractures cause

Answer 26

they can damage the pleura and cause a pneumothorax

Question 27

what is useful if there are multiple rib fractures

Answer 27

a CT scan
to better visualise the thorax

Question 28

what features of heart faliure can be seen on chest x ray

Answer 28

• enlarged heart
• small bilateral pleural effusion
• alveolar oedema
• fluid in the lung fissures

Question 29

what do CT scans consist of

Answer 29

many individual x rays directed through the patient from all sides
the data from the x rays detectors is then analysed to produce 3D images

Question 30

do CT scans have more ionising radiation than x rats

Answer 30

yes but they produce more useful 3D images