Density of tissue (attenuation) seen on computed tomography (CT) scans are expressed in Hounsfield units.
|
Tissue
|
Hounsfield Units
|
|
metal
|
1,000
|
|
dense cortical bone
|
near to 1,000
|
|
calcium
|
100 to 1,000
|
|
blood
|
80 to 85
|
|
cerebral gray mater
|
35 to 40
|
|
cerebral white matter
|
25 to 30
|
|
water
|
0
|
|
CSF
|
0
|
|
fat
|
(-100)
|
|
soft tissue
|
(-100) to (-300)
|
|
air or vacuum
|
(-1,000)
|
where:
• Bushberg et al state that the maximum reading is 3,000 rather than 1,000.
