Normal CT scan values

 

Normal CT scan values, measured in Hounsfield Units (HU), vary by tissue type, with some key examples being water (

$0$

HU), air (around

$-1000$

HU), fat (around

$-100$

HU), and cortical bone (above

$\mathrm{+1000}$

HU). Normal values for brain white matter are approximately

$30$

HU, gray matter around

$40$

HU, liver around

$45-50$

HU, and muscle about

$45-50$

HU. 

Examples of normal HU values 

• Air:
  

  $-1000$
  HU
• Fat (subcutaneous):
  

  $-100$
  to
  

  $-115$
  HU
• Water:
  

  $0$
  HU (by definition)
• Cerebrospinal Fluid (CSF): Approximately
  

  $10$
  HU
• Brain (White Matter): Approximately
  

  $30$
  HU
• Brain (Gray Matter): Approximately
  

  $40$
  HU
• Muscle:
  

  $45$
  to
  

  $50$
  HU
• Liver:
  

  $45$
  to
  

  $50$
  HU
• Spleen:
  

  $40$
  to
  

  $45$
  HU
• Kidney Cortex:
  

  $25$
  to
  

  $30$
  HU
• Bone (trabecular):
  

  $300$
  to
  

  $800$
  HU
• Bone (cortical): Greater than
  

  $1000$
  HU