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Description
Boron Neutron Capture Therapy (BNCT) is a hadron therapy strategy based on low-energy neutron irradiation of a tumor previously loaded with boron-10 atoms. The resulting radiation field is composed of several particles with varying biological effectiveness. Microdosimetry is a valuable tool to monitor this complex field, allowing to distinguish different dose components and providing a physics-based estimation of their biological effectiveness. In the framework of the Next-Generation EU project Anthem, investigations are ongoing to develop microdosimetric detectors suitable for clinical BNCT.
Two miniaturized Tissue-Equivalent Proportional Counters (mini-TEPCs) were designed and constructed, having a cylindrical sensitive cavity only 1 mm in diameter and height. The cathode is made of tissue-equivalent conductive plastic, doped with natural boron in one of the two. The nominal boron-10 concentration is 100 ppm and 0 ppm for the doped and non-doped mini-TEPC, respectively. The detectors are operated with pure propane gas for higher gain and enhanced stability without gas flow, following clinical requirements which prevent the use of gas bottles. Custom low-noise, high-dynamic-range preamplifiers are integrated into the detector case.
The mini-TEPCs were first tested in photon, fast neutron and clinical proton fields, demonstrating identical response in the absence of thermal neutrons. Further measurements were done in the thermal neutron column of the LENA research reactor in Pavia, Italy, under fluxes comparable to clinical conditions. The measured spectra were consistent with previous measurements and showed a clear boron-induced dose enhancement. Finally, microdosimetric measurements were performed at the clinical BNCT center of Xiamen (China), both in-air and in-phantom. The detectors operated without significant pile-up at the clinical beam current, and the boron-doped counter exhibited a distinct BNC spectral component, allowing quantification of the added boron dose contribution.
These results confirm the reliability and clinical suitability of the new mini-TEPCs for microdosimetry-based radiation quality monitoring in BNCT.