L22 – Cardiothoracic Imaging: Principles, Physiology and Mechanics Flashcards
(24 cards)
How does X-ray show negative image?
X-ray beam traverses body parts > create superimposition of shadows, planar images (2D) of body parts
What happens to X-ray as it leaves point source?
diverge
What are 2 advantages and disadvantages of X-ray?
Advantage: cheap, easily available
Problem: No depth, A lot of information lost
Where is point source in PA and AP?
PA = X-ray from posterior to anterior aspect of patient, Face against plate
AP = X-ray from anterior to posterior aspect of patient,
AP or PA higher quality? which one usually preferred?
PA
When is AP used?
when PA is not possible (e.g. ill, immobile)
AP or PA used in heart X-ray?
PA = More accurately assess heart size (less enlargement ,preferred method)
PA or AP is point source closer to patient?
AP
Chest X-ray = CXR
What is checked first on a CXR?
Check name, date, label
How to assess whether inflation of lungs is adequate?
Lung boundaries should bisect hemidiaphragm at either:
10th posterior rib, or
6th anterior rib
Underinflated lungs may indicate what?
Inadequate inspiration or
Injury limiting inspiration
How to assess CXR rotation?
Ideal = centered: medial end of clavicles on both sides = equi-distance
from spinous process
What can be seen if penetration of chest is adequate?
If well-penetrated can see:
- Retrocardiac region (right behind the heart)
- T-spine outline
What does penetration depend on ?
Need right amount of exposure (depends on size of patient)
Very white CXR means what for penetration?
If underpenetrated = very white, no contrast
What could accumulate in pleural space?
Fluid accumulation = pleural effusion
Air accumulation = pneumothorax
What is the distribution of pleural pressures?
Not uniform:
Lowest (most negative) in superior pleural space
Highest (least negative) in inferior pleural space
What does lack of lung markings (line) or abnormal dark space between edge of lung and thoracic cage point to?
Pneumothorax
What is seen on CXR during end expiration on a pneumothorax patient?
EEP- Chest wall recoils out/bulges out more than normal
What region of lungs is most affected by pneumothorax causing abnormal pleural pressure?
Upper region: lowest pressure = affected most
How does pneumothroax lead to reduced cardiac output?
Pressure in pleural cavity want to expand:
- Ribcage cannot move
out a lot
- Thus pressure goes
medially to mediastinum, heart
- Compress low pressure
vascular compartments (SVC, IVC) = decreased venous return to right atrium - decreased cardiac output
What is tension pneumothorax caused by?
Caused by valve effect during respiration, Pleural air accumulates and exerts positive pressure on mediastinal and intrathoracic structures
What 2 things are seen on CXR of patient with tension pneumothorax?
Shift in mediastinum
(Ipsilateral lung collapses > further pressure on mediastinum )
Increase in rib spaces
( Ipsilateral ribs spaced further apart due to pressure)
What is done to patient with tension pneumothorax?
chest drain insertion > help
to inflate the lung
emergency situation
