Spatial correlation between traversal and cellular response in ion radiotherapy - Towards single track spectroscopy

► We parameterized the intensity profile of a single ion gained by the FNTD read-out. ► Maximum intensity signal of acquired FNTD images seems to be a surrogate for LET. ► FWHM of intensity profile is a limited measure for the maximum sec. electron range. ► FNTD were read out by STED microscopy with a resolution beyond diffraction limit.