Energy-Loss Straggling and Delta-Ray Escape in Solid-State Microdosimeters Used in Ion-Beam Therapy

Abstract

Microdosimetry is increasingly adopted in the characterization of proton and carbon ion beams used in cancer therapy. Spectra and mean values of lineal energy calculated in frequency and dose are seen by many as the tools which, by complementing dosimetric measurements, allow for the most complete characterization of the therapeutic radiation fields. The urgency is now to consolidate the experience and converge to commonly accepted methodologies. In this context, the purpose of this work is to study the effects of the energy-loss straggling and the delta-ray escape, considering slab-sensitive volumes; these are, in fact, the typical shapes of solid-state microdosimeters, which are widely used in investigating light ion therapy beams. The method considers the energy distribution of delta rays resulting from the collision of the impinging ion and, taking into account the escape, convolutes it with itself as many times as the expected number of collisions in the sensitive volume thickness. The resulting distribution is compared to the experimental microdosimetric spectrum showing a substantially good agreement. The extension of the methodology to a wider range of ion energy and detector characteristics is instrumental for a detector-independent microdosimetric assessment of the radiation fields.

Development and Fabrication of Microdosimeter Arrays Based on Single‐Crystal Diamond Schottky Diodes

“…Indeed, the array geometry is characterized by low capacitance improving the noise threshold and by a SV size comparable to a cell improving the accuracy of the delta rays contribution measured. [ 13 ] The possibility to connect and read each single SV individually or in groups would allow for measurement time optimization. At low fluence rate, like those found in the distal part of the Bragg curve or in the out‐of‐field regions of a therapeutic particle beam, the large overall sensitive area helps to reduce measurement time.…”