Nanodosimetry: Principle and Current Status

Due to the success of theoretical track structure Monte Carlo simulations, showing that features of ionization patterns on the nanometer level are important for the biological effectiveness of ionizing radiation, several new methods for experimental track structure investigations have been developed in recent years. These methods all use the principle of density scaling in low‐pressure gas to probe track structure in macroscopic dimensions, ideally with single‐ionization resolution. The new field of experimental track structure investigation, which has been called nanodosimetry, can be approached in two ways: (1) the number of ionizations in a defined, ideally wall‐less, sensitive volume is registered per single primary particle and cluster size distributions are obtained, or (2) the full track structure of an ion track segment is “imaged”. Existing nanodosimetric methods are based on the first approach, but a track structure imaging detector is currently under development at Loma Linda University. This contribution will review the principle and existing technical approaches to nanodosimetry and will give an outlook on future developments and applications.