Welcome to Classifications and Online Calculators in Radiology

This site was build along with the Atlas of Radiology Images to support your knowledge in radiology.

You will find here:

that are used in radiology and related fields with free access.


  • Some pages are accompanied by illustrations
  • All pages contain tags for easy navigation

The concept

The concept of this website is based on a previous site that was founded in 2008 and is still up and running. The website is composed as a book, where all sources are properly referenced, according to a good practice in scientific publications.

Didn't find a classification?


    Featured page

    Hounsfield units - scale of HU, CT numbers

    The Hounsfield scale of tissue density is based on two values: air as -1000HU (minimum HU value) and water as 0HU. Density of other tissues is related to this range, usually from -1000 to +1000HU (-1024 to 1024 or 3072 depending on the coding of particular vendor). However, the scale by its the definition is open-ended.

    Matter Density (HU)
    Air -1000
    Lung parenchyma (inspirium) -850 to -910
    Fat -50 to -100
    Water 0
    White matter 20 to 30HU
    Kidney 20 to 40HU
    Spleen 35 to 55HU
    Grey matter 37 to 45HU
    Blood 45 to 65HU
    Liver 45 to 65HU
    Hematoma 40 to 90HU
    Bone 700 to 3000


    1. Buzug TM. Computed Tomography: From Photon Statistics to Modern Cone-Beam CT. Springer; 2008:475
    2. Heymsfield S. Human Body Composition. Human Kinetics; 2005
    3. Prokop M. Spiral and Multislice Computed Tomography of the Body. Thieme; 2003.

    See the page
    Syndicate content