CT exam Flashcards
Purpose of bow tie filter
Counteract beam hardening
Typical CT kVp
125
80-140
Typical CT ma
100-400
Which collimators help determine slice thickness ?
Post patient collimators
Will a thicker slice increase or decrease SNR?
Increase
What determines slice thickness in a multi slice CT
Beam thickness
Why can’t top hat be achieved ?
FSS
Patient movement
Collimating / penumbra
What determines longitudinal spatial in spiral CT?
Slice thickness
Table move per rotation
Reconstruction algorithm
What can Dey instability cause ?
Ring artifcart
What do solid-state scintilators imprive ?
QDE
What will cross talk reduce ?
Spatial and contrast
What is another name for anisotropic multi slice det
Adaptive
What do multi - slice dets also determine?
Slice thickness
What’s DAS??
Converting a measured radiation to a computer signal
What are the 4 data types ?
Measurement
Raw
Convolved
Image reconstruction
Which data type corrects scatter, faulty dets and beam hardening ?
Measurement data
Which data type resolves Star artifacr through filtered back projection?
Convolved
Which is the iterative algorithm ??
The box number thingies
Name 4 basic reconstruction principles
Fourier
Convultation
Interpolation
Iterative
What’s a Wide window range ?
400-2000
What’s a narrow window range?
50-350
What will a large FOV cause ?
SNR
What is photon flux ?
Number of photons
What will narrow collimation cause ?
Reduce scatter and improve contrast but thicker slices inprove SNR
