In CT imaging, the window level (centre) is set to +40 HU for a soft-tissue window. What is the primary effect of changing the window level to +400 HU while keeping the window width constant?

• A The spatial resolution improves
• B The image appears overall brighter
• C Image contrast is lost completely
• D The image appears overall darker ✓

Explanation

The window level sets the centre of the grey scale. D higher window level means that higher attenuation values are mapped to mid-grey, so soft tissue (around +40 HU) falls below the centre and appears darker. Window level controls overall brightness on the displayed image.

Reference: Bushberg, The Essential Physics of Medical Imaging, 3rd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.