Weefselgewichtsfactor

Weefselgewichtsfactor (WGF) is a term used primarily in the fields of medical physics, radiology and dosimetry to describe a dimensionless coefficient that relates the mass density of a specific tissue to a reference tissue, most often water. The factor is employed in the calculation of attenuation, scattering and energy deposition of ionising radiation within the human body, allowing the conversion of measured quantities in a phantom to equivalent values in patient tissues.

The factor is defined as the ratio ρt/ρw, where ρt is the mass density of the tissue of interest and ρw is the density of water (approximately 1 g·cm⁻³ at 4 °C). Values typically range from 0.9 for adipose tissue to 1.1–1.2 for bone and higher‑density organs. In practice, the weefselgewichtsfactor is combined with photon interaction cross‑section data to generate tissue‑specific dose conversion coefficients.

In clinical dosimetry, the WGF is used to adjust monitor unit calculations for external beam radiotherapy and to refine organ dose estimates in nuclear medicine. It also appears in Monte‑Carlo simulation packages as an input parameter for voxel‑based anatomical models. Because it simplifies the representation of heterogeneous anatomy, the factor aids in achieving more accurate treatment planning while keeping computational requirements manageable. The concept is closely related to the mass attenuation coefficient and electron density, which together define the radiological properties of tissues.