STED microscopy visualizes energy deposition of single ions in a solid-state detector beyond diffraction limit

Area of Science:

• Medical physics
• Radiation detection
• Optical microscopy

Background:

• Fluorescent nuclear track detectors (FNTDs) visualize particle traversal in clinical ion beams.
• Confocal microscopy's resolution limit hinders detailed characterization of ion track spots.

Purpose of the Study:

• To enhance the characterization of ion track spots in FNTDs using optical nanoscopy.
• To improve the visualization and analysis of single-particle traversal in clinical ion beams.

Main Methods:

• Readout of FNTDs using stimulated depletion microscopy (STED).
• Visualization of track spots beyond the diffraction limit (80 nm resolution vs. 320 nm confocal).

Main Results:

• Track spots of carbon ions and protons visualized with ~80 nm resolution.
• Discrimination of track spot width based on Linear Energy Transfer (LET) from 2-1016 keV µm⁻¹.
• Track spot width depends on LET, not particle charge, limiting particle type discrimination.

Conclusions:

• Optical nanoscopy significantly improves FNTD readout resolution.
• Enhanced resolution allows refined cross-sectional area determination for energy deposition.
• This technique may enable nanoscopy-based analysis of radiation-induced cellular responses.