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• Formal definition of the therapeutic potential and versatility of a BNCT beam. • Derivation of a head and neck cancer TCP model for non-uniform doses. • Introduction of a novel model of uncomplicated tumor control probability in BNCT. • Demonstration of the usefulness of the models to assess the performance of a beam. • Introduction of a practical and essential aid to guide treatment decisions. Boron Neutron Capture Therapy (BNCT) is a treatment modality that uses an external neutron beam to selectively inactive boron10-loaded tumor cells. This work presents the development and innovative use of radiobiological probability models to adequately evaluate and compare the therapeutic potential and versatility of beams presenting different neutron energy spectra. Aforementioned characteristics, collectively refer to as the performance of a beam, were defined on the basis of radiobiological probability models for the first time in BNCT. A model of uncomplicated tumor control probability (UTCP) for HN cancer was introduced. This model considers a NTCP able to predict severe mucositis and a TCP for non-uniform doses derived herein. A systematic study comprising a simplified HN cancer model is presented as a practical application of the introduced radiobiological figures of merit (FOM) for assessing and comparing the performance of different clinical beams. Applications involving treated HN cancer patients were also analyzed. The maximum UTCP proved suitable and sensitive to assess the performance of a beam, revealing particularities of the studied sources that the physical FOMs do not highlight. The radiobiological FOMs evaluated in patients showed to be useful tools both for retrospective analysis of the BNCT treatments, and for prospective studies of beam optimization and feasibility. The presented developments and applications demonstrated that it is possible to assess and compare performances of completely different beams fairly and adequately by assessing the radiobiological FOM UTCP. Thus, this figure would be a practical and essential aid to guide treatment decisions. [ABSTRACT FROM AUTHOR]

A monolithic silicon telescope, consisting of a thin ΔE stage (of ~2 µm in thickness) coupled to a residual-energy stage E (thickness 500 µm), was studied and tested for measuring the boron concentration in biological samples for boron neutron capture therapy (BNCT). At the Laboratorio di Energia Nucleare Applicata BNCT facility, Pavia, Italy, this information is derived by placing the tissue sample in front of a surface barrier diode and by irradiating the system with neutrons generated in the thermal column of the TRIGA Mark H reactor. The boron concentration is estimated through the measurement of the energy deposited in the detector by the products of the 10B(n,α)7Li reaction. However, the low-energy part of the measured spectra is typically distorted by secondary electrons produced by photon background and by protons generated via the 14N(n,p)14C reaction in tissue. This work discusses the possibility of using a different silicon device, namely, the monolithic silicon telescope, for improving the accuracy of the method by exploiting its particle discrimination capabilities. A device with a sensitive area of 1 mm² was irradiated (in vacuo) bare, faced both with a certified boron implanted silicon wafer and with a thin sample of rat lung loaded with boron. The preliminary results showed that (a) alpha particles and lithium ions produced by neutron capture on boron are well identified, (b) the events due to protons generated in tissue by neutron capture on nitrogen can be well discriminated, and (c) the presence of nitrogen inside the detector dead layer gives rise to an additional contribution of protons from neutron absorption. These preliminary studies gave confidence about the possibility of improving the accuracy for the assessment of the 10B concentration in biological samples for BNCT. [ABSTRACT FROM AUTHOR]

Boron Neutron Capture Therapy (BNCT) is an experimental radiotherapy that uses the combination of neutron irradiation and 10 B to treat neoplasms. By means of this technique, many clinical trials were performed worldwide with promising results [1] using research nuclear reactors as neutron sources. Anyhow, these machines have several problems that hinder the development of dedicated BNCT hospitals. This issue can now be overcome by using intense-current proton accelerators, which coupled with beryllium or lithium targets yield more than 10 14 neutron per second. This can be a boost to BNCT because accelerators are more compact and can be installed within hospitals. The Italian National Institute of Nuclear Physics (INFN) designed and manufactured a Radiofrequency Quadrupole proton accelerator (RFQ) [2] , which delivers 5 MeV protons with 30 mA current in a Continuous Wave (CW) mode and it is coupled to a beryllium target. This accelerator could be installed at Centro Nazionale di Adroterapia Oncologica (CNAO) in Pavia. In this work we present the MC calculations for the tailoring of a BNCT neutron beam obtained by the described RFQ. Firstly, we show that MC transport codes such as MCNP and PHITS are not able to simulate the correct neutron spectra from 5 MeV protons interacting on beryllium. Therefore, the neutron double differential source implemented in MCNP was extracted from the measurements performed by Agosteo et al. [3] . As the energy range goes up to 3.5 MeV, neutrons need to be moderated and collimated by a Beam Shaping Assembly (BSA), because BNCT requires a spectrum peaked between 1 and 10 keV. Differently from the past, where the optimal configuration was chosen according to physical characteristics of the beam, in this case the results were evaluated on the basis of the dosimetry obtained in a real clinical case by treatment planning simulation. What emerges, is that the classical figures of merit employed for the tailoring of a clinical BNCT [4] should be taken as a first guideline, while the dosimetric assessment on realistic clinical scenarios is the most appropriate criterion for beam evaluations. [ABSTRACT FROM AUTHOR]