Characterizing radiation quality in radiotherapy is essential for accurately assessing radiobiological effects, yet it remains a significant challenge. Linear Energy Transfer (LET) is a commonly used metric for quantifying radiation quality. However, microdosimetry offers a valuable alternative, by providing a more precise description of the energy deposition at the cellular level. While microdosimetry has a rich history of experiments in different radiation fields, LET measurements—rather than relying on calculations or simulations—is a novel attempt. This study compares radiation quality assessments performed with two silicon-based detectors with distinct geometries: The mushroom silicon-cylinder microdosimeter developed at the University of Wollongong and the hybrid pixel Timepix3 detector equipped with a 300 µm-thick silicon sensor. Both detectors were irradiated with a monoenergetic 149 MeV/u helium-ion beam. LET probability density distributions and lineal energy spectra were recorded at various depths along the Bragg curve using PMMA slabs. Although both detectors are made of silicon, their differing geometries, sensor thicknesses, and detection principles lead to notable variations in their energy deposition spectra. The results are analyzed with a focus on spectral resolution, energy spectrum shape, and low- and high- tail behavior. Experimental data are supported by Monte Carlo simulations performed using the FLUKA code to validate and interpret the measurements. The advantages and limitations of both detection systems are discussed in the context of efforts to standardize radiation quality measurements. Such standardization could facilitate the integration of LET-based dosimetry into treatment planning systems in clinical radiotherapy, thereby improving the precision of radiobiological damage assessments.
Hamad et al. (Thu,) studied this question.