  Biological effectiveness of a certain absorbed dose of ionizing radiation
depends on the radiation quality, i. e. the spectrum of ionizing particles and
their energy distribution. As has been shown in several studies, the biological
effectiveness is related to the pattern of energy deposits on the microscopic
scale, the so-called track structure. Clusters of lesions in the DNA molecule
within site sizes of few nanometers play a particular role in this context.
This work presents a brief overview of nanodosimetric approaches to relate
biological effects with track structure derived quantities and experimental
techniques to derive such quantities.
