Dense Plasma Focus: physics and applications (radiation material science, single-shot disclosure of hidden illegal objects, radiation biology and medicine, etc.)

The paper presents some outcomes obtained during the year of 2013 of the activity in the frame of the International Atomic Energy Agency Co-ordinated research project "Investigations of Materials under High Repetition and Intense Fusion-Relevant Pulses". The main results are related to the effects created at the interaction of powerful pulses of different types of radiation (soft and hard X-rays, hot plasma and fast ion streams, neutrons, etc. generated in Dense Plasma Focus (DPF) facilities) with various materials including those that are counted as perspective ones for their use in future thermonuclear reactors. Besides we discuss phenomena observed at the irradiation of biological test objects. We examine possible applications of nanosecond powerful pulses of neutrons to the aims of nuclear medicine and for disclosure of hidden illegal objects. Special attention is devoted to discussions of a possibility to create extremely large and enormously diminutive DPF devices and probabilities of their use in energetics, medicine and modern electronics

BNCT AS RADIOSENSITIZER IN HIGH-ENERGY RADIOTHERAPY TREATMENTS

High-energy linear accelerators for radiotherapy produce fast secondary neutrons due to (\u3b3,n) reaction. Considering the moderating effect of human body, an unavoidable and undesired thermal neutron flux is localized in the tumor area. This study proposes the possibility to employ this neutron background to enhance the radiotherapy efficacy: the thermal neutron peak could be exploited for BNCT applications, delivering an additional therapeutic dose to the photon dose concentrated in tumor cells, acting as a localized radiosensitizer

MEASUREMENTS OF THE PARASITIC NEUTRON DOSE AT ORGANS FROM MEDICAL LINACS AT DIFFERENT ENERGIES BY USING BUBBLE DETECTORS

Conventional linear accelerators (LINACs) for radiotherapy produce fast secondary neutrons due to photonuclear processes. The neutron presence is considered as an extra undesired dose during the radiotherapy treatment, which could cause secondary radio-induced tumors and malfunctions to cardiological implantable devices. It is thus important to measure the neutron dose contribution to patients during radiotherapy, not only at high-energy LINACs, but also at lower energies, near the giant dipole resonance reaction threshold. In this work, the full body neutron dose equivalent has been measured during single-field radiotherapy sessions carried out at different LINAC energies (15, 10 and 6 MV) by using a tissue equivalent (for neutrons) anthropomorphic phantom together with bubble dosemeters. Results have shown that some neutron photoproduction is still present also at lower energies. As a consequence, emitted photoneutrons cannot be ignored and represent a risk contribution for patients undergoing radiotherapy

Radiotherapy dose enhancement using BNCT in conventional LINACs high-energy treatment: Simulation and experiment

AimTo employ the thermal neutron background that affects the patient during a traditional high-energy radiotherapy treatment for BNCT (Boron Neutron Capture Therapy) in order to enhance radiotherapy effectiveness.BackgroundConventional high-energy (15–25[[ce:hsp sp="0.25"/]]MV) linear accelerators (LINACs) for radiotherapy produce fast secondary neutrons in the gantry with a mean energy of about 1[[ce:hsp sp="0.25"/]]MeV due to (γ, n) reaction. This neutron flux, isotropically distributed, is considered as an unavoidable undesired dose during the treatment. Considering the moderating effect of human body, a thermal neutron fluence is localized in the tumour area: this neutron background could be employed for BNCT by previously administering 10B-Phenyl-Alanine (10BPA) to the patient.Materials and methodsMonte Carlo simulations (MCNP4B-GN code) were performed to estimate the total amount of neutrons outside and inside human body during a traditional X-ray radiotherapy treatment.Moreover, a simplified tissue equivalent anthropomorphic phantom was used together with bubble detectors for thermal and fast neutron to evaluate the moderation effect of human body.ResultsSimulation and experimental results confirm the thermal neutron background during radiotherapy of 1.55E07[[ce:hsp sp="0.25"/]]cm−2[[ce:hsp sp="0.25"/]]Gy−1.The BNCT equivalent dose delivered at 4[[ce:hsp sp="0.25"/]]cm depth in phantom is 1.5[[ce:hsp sp="0.25"/]]mGy-eq/Gy, that is about 3[[ce:hsp sp="0.25"/]]Gy-eq (4% of X-rays dose) for a 70[[ce:hsp sp="0.25"/]]Gy IMRT treatment.ConclusionsThe thermal neutron component during a traditional high-energy radiotherapy treatment could produce a localized BNCT effect, with a localized therapeutic dose enhancement, corresponding to 4% or more of photon dose, following tumour characteristics. This BNCT additional dose could thus improve radiotherapy, acting as a localized radio-sensitizer

Studio di una schermatura per neutroni prodotti mediante acceleratori radioterapici ospedalieri

Lo studio di schermature per neutroni si rivela essenziale in svariate applicazioni scientifiche e mediche. Tali particelle sono difatti utilizzate in radioterapie per cattura neutronica, e.g. Boron Neutron Capture Therapy (BNCT), e causano danneggiamenti di dispositivi elettronici, in particolare dei Dispositivi Cardiaci Impiantabili quali Pacemaker e Defibrillatori. Inoltre, applicazioni radioprotezionistiche richiedono la valutazione e la riduzione della dose conferita dai neutroni in caso di viaggi aerei e missioni spaziali. I fasci neutronici sono oggetto di interessanti studi poich\ue9 la capacit\ue0 di trasferire una dose a un tessuto varia sensibilmente con l\u2019energia. Inoltre, tali particelle sono in grado di attivare diversi materiali con la necessit\ue0 di valutare eventuali dosi da particelle secondarie. Considerando tali peculiarit\ue0 si \ue8 studiato uno schermo per neutroni, il \u201cQuick Boron\u201d (QB), che si presenta in due versioni: rigida e flessibile. Tale materiale, testato sia sperimentalmente sia attraverso simulazioni Monte Carlo, deve le sue qualit\ue0 schermanti alla presenza del boro-10, isotopo con un\u2019elevata sezione d\u2019urto di cattura neutronica per la zona a energie termiche ( = 3840 a E=0.025 eV). Inoltre, nello studio si \ue8 valutato l\u2019accoppiamento del QB con un materiale termalizzante al fine di costituire uno schermo eterogeneo sensibile a un pi\uf9 ampio range energetico

Radiotherapy dose enhancement using {BNCT} in conventional {LINACs} high-energy treatment: Simulation and experiment

AbstractAim To employ the thermal neutron background that affects the patient during a traditional high-energy radiotherapy treatment for {BNCT} (Boron Neutron Capture Therapy) in order to enhance radiotherapy effectiveness. Background Conventional high-energy (15–25 MV) linear accelerators (LINACs) for radiotherapy produce fast secondary neutrons in the gantry with a mean energy of about 1 MeV due to (γ, n) reaction. This neutron flux, isotropically distributed, is considered as an unavoidable undesired dose during the treatment. Considering the moderating effect of human body, a thermal neutron fluence is localized in the tumour area: this neutron background could be employed for {BNCT} by previously administering 10B-Phenyl-Alanine (10BPA) to the patient. Materials and methods Monte Carlo simulations (MCNP4B-GN code) were performed to estimate the total amount of neutrons outside and inside human body during a traditional X-ray radiotherapy treatment. Moreover, a simplified tissue equivalent anthropomorphic phantom was used together with bubble detectors for thermal and fast neutron to evaluate the moderation effect of human body. Results Simulation and experimental results confirm the thermal neutron background during radiotherapy of 1.55E07 cm−2 Gy−1. The {BNCT} equivalent dose delivered at 4 cm depth in phantom is 1.5 mGy-eq/Gy, that is about 3 Gy-eq (4 of X-rays dose) for a 70 Gy {IMRT} treatment. Conclusions The thermal neutron component during a traditional high-energy radiotherapy treatment could produce a localized {BNCT} effect, with a localized therapeutic dose enhancement, corresponding to 4 or more of photon dose, following tumour characteristics. This {BNCT} additional dose could thus improve radiotherapy, acting as a localized radio-sensitizer

Design and simulation of an optimized e-linac based neutron source for {BNCT} research

Abstract The paper is focused on the study of a novel photo-neutron source for {BNCT} preclinical research based on medical electron Linacs. Previous studies by the authors already demonstrated the possibility to obtain a mixed thermal and epithermal neutron flux of the order of 107 cm−2 s−1. This paper investigates possible Linac’s modifications and a new photo-converter design to rise the neutron flux above 5 107 cm−2 s−1, also reducing the gamma contamination

Malfunction of cardiac devices after radiotherapy without direct exposure to ionizing radiation: Mechanisms and experimental data

AIMS: Malfunctions of cardiac implantable electronical devices (CIED) have been described after high-energy radiation therapy even in the absence of direct exposure to ionizing radiation, due to diffusion of neutrons (n) causing soft errors in inner circuits. The purpose of the study was to analyse the effect of scattered radiation on different types and models of CIED and the possible sources of malfunctions. METHODS AND RESULTS: Fifty-nine explanted CIED were placed on an anthropomorphous phantom of tissue-equivalent material, and a high-energy photon (15 MV) radiotherapy course (total dose = 70 Gy) for prostate treatment was performed. All devices were interrogated before and after radiation. Radiation dose, the electromagnetic field, and neutron fluence at the CIED site were measured. Thirty-four pacemakers (PM) and 25 implantable cardioverter-defibrillators (ICD) were analysed. No malfunctions were detected before radiation. After radiation a software malfunction was evident in 13 (52%) ICD and 6 (18%) PM; no significant electromagnetic field or photon radiations were detected in the thoracic region. Neutron capture was demonstrated by the presence of the (198)Au((197)Au + n) or (192)Ir((191)Ir + n) isotope activation; it was significantly greater in ICD than in PM and non-significantly greater in damaged devices. A greater effect in St Jude PM (2/2 damaged), Boston (9/11), and St Jude ICD (3/6) and in older ICD models was observed; the year of production was not relevant in PM. CONCLUSION: High-energy radiation can cause different malfunctions on CIED, particularly ICD, even without direct exposure to ionizing radiation due to scattered radiation of neutrons produced by the linear accelerator

AIRWATCH: the fast detector

The discovery of the extreme energy cosmic rays (EERC) with energy greater than 10(superscript 20) eV has opened a new research branch of astrophysics on both observational and interpretative point of views. Together with the EECR one has also to consider the neutrino component which, independently on its primary or secondary origin, can reach comparable energies. These particles can be detected through the giant showers (EAS) produced in the Earth atmosphere and the induced fluorescent molecular nitrogen emission. Observing the EECR 'signals' is very difficult; we need forefront technology or new developments. The main reason is that their flux is very weak, typically of the order of a few events/year/1000 km(superscript 2) per EECR of E approximately equals 10(superscript 20) eV. The proposed Airwatch mission, base don a single orbiting telescope which can measure both intensity and direction of the EAS, impose new concepts for the detectors; single photon sensitivity, fast response of the order of few microseconds with sampling times of tenths of nanoseconds, low noise and good S/N ratio, large area, adaptability to a curved surface. Fortunately the spatial resolution requirements are somehow relaxed. The peculiar characteristics of this application are such that no available detectors satisfies completely the requirements. Therefore the final detector has to be the result of a R and D program dedicated to the specific problem. In this paper we survey a number of possible detectors and identify their characteristics versus the Airwatch mission requirements