Cross-sectional Imaging Flashcards
What are some difficulties in 3D interpretation?
Impossible to distinguish between a sphere and a tube
Need to scroll and track structures
What absorb X-rays well?
- High atomic number
- High density
How much do bone, soft tissue and airways absorb?
Bone-absorb very well
Soft tissue-absorb some
Airways-pass through
What colour are high and low opacities
High opacity-black
Low opacity-White
Why does bone show up white?
Absorb and attenuate x-rays no silver deposited on the detector allowing light to shine through.
What are high and poor attenuators?
Bone/metal-good
Fat/lung air-poor
What is the window level?
Centre of window width
What is the window width?
Range of grey scale
Why is soft tissue hard to distinguish?
Similar CT numbers
Why can fat be helpful in imaging?
Can help distinguish between soft tissue
What happens if there is too much fat in an image?
Requires a higher kV and reduces contrast
What is the ideal CT patient
FAT and stored between organs
What is a tricky CT patient?
Minimal body fat
Fat stored on Periphery
What is a natural contrast?
Air
What is the purpose of contrast?
Highlights detail of structures
High atomic number
What is the purpose of IV contrast?
Highlights cardiovascular structures
When does the arterial and Venous phase happen?
Quickly
Venous phase-60-70seconds
What is the purpose of Oral contrast?
Highlights digestive structures
Identify LNs
How does slice thickness affect image quality?
Sections can include bone and soft tissue (Average)
-Overestimate structures
Smaller slices better
Where is air and gas situated?
Air above diaphragm
Gas-below diaphragm
