10: CT Scans - Smith

Question 1

2 images taken in CT scan

Answer 1

axial/transverse and coronal/frontal

some computers will make a sagittal from this info

Question 2

“legend”

Answer 2

scout view

Question 3

axail positioning

Answer 3

obtained with feet perpendicular to gantry table

Question 4

coronal positioning

Answer 4

knees flexed with feet flat against the gantry table

Question 5

pixel size

Answer 5

1.3 mm x 1.3 mm

each pixel correlates to the density of the tissue in that pixel

Question 6

pixel attenuation units

Answer 6

hounsfield units HU

Question 7

bone window v. soft tissue window

Answer 7

wide gray scale or window to pick up tissue with high attenuation or hugh HU

narrow gray scale or window to pick up tissue with low attenuation or low HU

Question 8

average radiation exposure for CT exam

Answer 8

2.6 rads for about 20 slices

comparison - 5 convential xras is 0.1 rads

Question 9

how long does a CT exam last?

Answer 9

3-5 sec per slice

about 30 min for whole exam

older machines can take 20 sec per slice

Question 10

gold standard osseous anatomy

Answer 10

CT scan

soft tissue things better seen with MRI