Carbon ion dosimetry on a fluorescent nuclear track detector using widefield microscopy

Fluorescent nuclear track detectors (FNTD) are solid-state dosimeters used in a wide range of dosimetric and biomedical applications in research worldwide. FNTDs are a core but currently underutilized dosimetry tool in the field of radiation biology which are inherently capable of visualizing the tracks of ions used in hadron therapy. The ions that traverse the FNTD deposit their energy according to their linear energy transfer (LET) and transform colour centres to form trackspots around their trajectory. These trackspots are the fingerprints of the ions which have fluorescent properties (620 nm peak excitation and 750 nm emission). These properties enable an analysis of the trackspots in the FNTD using fluorescence microscopy enables a well-defined dosimetric readout with a spatial component indicating the trajectory of individual ions. The current method used to analyse the FNTDs is laser scanning confocal microscopy (LSM). This imaging technique enables a precise localization and imaging of track spots in x, y and z however due to the scanning of a single laser spot across the sample requires a lot of time for large samples. This body of work conclusively shows for the first time that the readout of the trackspots present after irradiation (0.5 Gy carbon ions) in the FNTD can be captured with a widefield microscope (WF). This method was developed to optimize the readout of the Cell-FIT-HD biomedical sensor based on a Landauer Al2O3:C,Mg FNTD which is used for biological single cell dosimetry and tracking using widefield microscopy. The cells to be analysed are seeded onto an FNTD and irradiated with carbon ions, then the FNTD and the cells can be imaged using an LSM and the WF microscope respectively. The capture of the two separate readouts, cells and tracks, on two separate microscopes is not only time intensive but also introduces a spatial error between tracks and cells which needs to be corrected. The work in this paper now enables the use of a single widefield microscope to image the cells growing on the FNTD and the tracks in the FNTD. In comparison to the current LSM system the WF readout of the FNTD is a factor ~10 faster, for an area 2.97 times the size making the method nearly a factor 19 faster in track acquisition. This WF setup will replace LSM in the Cell-FIT-HD for FNTD track readout, which will enable a higher throughput of samples as well as a reduced error in the correlation between tracks and cells and enable a high throughput readout of Cell-FIT-HD.