artefact

Question 1

Define spatial resolution 2

Answer 1

the ability to differentiate densities. this is the number of pixels and matrix size 512 512 or 1024 by 1024

Question 2

define contrast resolution

Answer 2

the ability to differentiate small changes in tissue contrast

Question 3

what factors influence spatial resolution

Answer 3

focal spot and detector width size
sample frequency so the number of projections/ helical or multislice
slice thickness
increasing pixel matrix
detector efficiency
reduce helical pitch

Question 4

what factors influence contrast resolution

Answer 4

kvp and mas
increase slice thickness
smaller patient size
sensitivity of detector
soft recon algorith,
smaller matrix size

Question 5

what effects noise

Answer 5

mas
slice thickness
helical pitch
pixel size

Question 6

slice thickness

Answer 6

higher msa for thinner slices

thinner slices means sharper images

Question 7

misregistration artefact

Answer 7

movement artefact from one slice to another
respiratory gating
patient cooperation
thicker slices low pitch

Question 8

beam hardening

Answer 8

occures between bone tissue bone
low energy photons are absorbed hence the ct numbers of certain structures are changed
FIXED 
thinner slices
software correction mars
or iterative

Question 9

metalic artefact

Answer 9

change gantry angle
mars
increase hu range

Question 10

partial volume effect

Answer 10

thicke slices with overlaping data hence a low pitch

Question 11

volume averaging

Answer 11

two structures going through one slice appear as one

match a suitable slice width