In CT physics, the Hounsfield Unit (HU) of water is defined as 0. Which of the following CT density values is CORRECT for cortical bone?
- A +80 to +130 HU
- B +150 to +200 HU
- C +400 to +1000 HU ✓
- D +50 to +70 HU
Correct answer: C. +400 to +1000 HU
Explanation
Hounsfield units for key tissues: air = −1000 HU, fat = −100 to −50 HU, water = 0 HU, soft tissue/muscle = +40 to +80 HU, calcification = +100 to +400 HU, cortical bone = +400 to +1000 HU. This linear scale allows tissue characterisation. Acute haemorrhage is approximately +50 to +80 HU. Iodine-containing contrast further increases HU. Understanding these values is essential for interpreting CT density of lesions.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.