chest/thoracic imaging Flashcards
why cant x rays be used all the time
are a form of ionising radiation - can damage tissue, cells and DNA
what does damage to DNA lead to
uncontrolled cell division - cancer
which scans use ionising radiation
X rays
CT scans
which scans dont use ionising radiation
ultrasound
MRI
how do x ray staff protect themselves
they wear lead aprons if they operate in close proximity to x rays
as lead absorbs most x rays
how is safe use of x rays regulated
IRMER
ionising radiation medical exposure regulations
how do dense body parts look on x rays eg bones
white
because dense body parts absorb x rays
how do less dense structures look on x rays eg lungs
darker, almost black
because they do not absorb many x rays
how do soft tissue structures look on x rays
a shade of grey depending on how dense they are
how to view x rays
as if the patient is looking at u
left hand side of image is patients right side
how to differentiate between right and left bronchi on x ray
right main bronchus is wider and more verital
pinpoints of the heart on an x ray
- right atrium on right border
- right ventricle on inferior border
- left ventricle on left border
- left atrium at back
how to assess symmetry of an x ray
using clavicles
why are the anterior aspects of the ribs not easily visible on an x ray
because they are cartilaginous
what are the two ways x rays are directed at a patient
- anterior posterior (AP)
- posterior anterior (PA)
describe anterior posterior (AP) x rays
- 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
describe posterior anterior (PA) x rays
- 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
what does pneumonia cause on x ray image
a patchy opacification in the lung fields
what is a pneumothorax
air in between the parietal (outer) and visceral (inner) pleura
what indicates pneumothorax in x ray
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
why is breathing comprpomised if air gets in the pleural space
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
what is a pleural effusion
a collection of excess fluid in the pleural space
what causes a pleural effusion
infection, cancer or heart failiure
why is it difficult to tell if a unilateral pleural effusion is just pleural fluid or blood on an x ray
because blood and inflammatory/pleural fluid show up as the same colour
