From Ohm

For X-rays the attenuation is proportional

- to the electro density of the material
- (approximately linear proportional)

- to length of the travelled distance
- (inverse exponentially proportional)

Attenuation per distance is expressed via **attenuation coefficient** $\mu$

- Electron density $\approx$ atomic number (in the periodic system of elements)
- → $\mu$ is linear proportional to the atomic number

For water the attenuation coefficient is about $0.15cm^{-1}$.

Example:

- Lead $Pb$ → atomic number 82
- Water $H_2O$ → atomic number ca. 8+1+1
- Thus, lead has a 10 times higher attenuation than water.

Retrieved from http://schorsch.efi.fh-nuernberg.de/roettger/index.php/MedicalVisualization/AttenuationCoefficient

Page last modified on October 14, 2014, at 04:45 PM