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In this paper, we describe a new single photon emission computed tomography (SPECT) device made up of two detectors (High Resolution System, HRS) integrated into a rotation structure suitable for preclinical imaging applications. The overall objective is to develop an improved scintigraphic system based on our previous detector having high spatial resolution. For this purpose, we have assessed the performance of the new position-sensitive photomultiplier tube (PSPMT) Hamamatsu H13700 with 256 anodes, which replaces the Hamamatsu H9500 model. The adoption of the new PSPMT required the development of a dedicated compact electronics: a new resistive chain readout was optimized and integrated with an ADC system. Moreover, the new detector was engineered from both the mechanical and the electronic point of view. In fact, the entire system was miniaturized in order to reduce the overall dimensions. Alternatively, to the LYSO scintillator used in the previous detector, we have evaluated the CRY018 scintillator crystal, which provides a high light output, a medium density, a short decay time and excellent energy resolution, obtaining high efficiency comparable with the LYSO scintillator. We assessed the detector with the H13700 coupled with LYSO and CRY018 crystals of the same size. The H13700 model shows better quantum efficiency on crystal emission light than the H9500, and besides, the light collection near the edges has improved. Moreover, the use of CRY018 is preferred over the LYSO matrix for issues related to the reduced natural radioactivity of 176Lu. The experimental results were confirmed by an extensive evaluation carried out by GATE/GEANT4 Monte Carlo simulations. Finally, the performance results achieved, pave the way to the development of a Small Animal Imaging SPECT made up by two detectors based on the H13700 coupled with CRY018 crystal array.

Huazhong University of Science and Technology has been developing a proton therapy facility based on a superconducting cyclotron. As an important section of the facility, the gantry beamline has been designed using TRANSPORT code with simplified fringing field model and linear transfer matrix. However, realistic magnetic fringing field and second-order terms of particle motion cannot be precisely described in this approach, which may deviate the actual result from the design value and thereby increase uncertainties for radiation therapy during beam delivery. For this consideration, the specific effects of fringing field and second-order aberrations have been investigated using OPERA code and ODE solvers. For the potential problems of the designed gantry beamline, COSY INFINITY code, which can calculate transfer matrix of any order under the realistic fringing field represented by Enge function, was used to optimize the optics of present gantry beamline. The final results suggest the beam analysis and optimization methods mentioned in this paper are effective and valuable for relevant applications.

Boron neutron capture therapy (BNCT) is an effective cancer therapy that uses neutron irradiation; it is necessary to evaluate the neutron spectrum in the treatment field as precisely as possible. To conduct such evaluations, we developed a new device, called a liquid-moderator-based neutron spectrometer. In the present study, the performance of the developed spectrometer was tested by measuring a mono-energetic neutron field and a fast neutron field generated by a 252Cf neutron source. Finally, we revealed that the response function of the spectrometer could be appropriately calculated and confirmed the capability of the device to measure the neutron energy spectra between 1 keV and 10 MeV.

A collimation system is installed in the Large Hadron Collider to protect its super-conducting magnets and sensitive equipment from potentially dangerous beam halo particles. The collimator settings are determined following an alignment procedure, whereby collimator jaws are moved towards the beam until a suitable spike pattern, consisting of a sharp rise followed by a slow decay, is observed in nearby beam loss monitors. This indicates the collimator jaw is aligned to the beam. The current method for aligning collimators is semi-automated whereby an operator must continuously observe the loss signals to determine whether the jaw has touched the beam, or if some other perturbation in the beam caused the losses. The human element in this procedure can result in errors and is a major bottleneck in automating and speeding up the alignment. This paper proposes to automate the human task of spike detection by using machine learning. A data set was formed from previous alignment campaigns, from which fourteen manually engineered features were extracted and six machine learning models were trained, analysed in-depth and thoroughly tested. The suitability of using machine learning in LHC operation was confirmed during collimator alignments performed in 2018, which significantly benefited from the models trained through machine learning in this study.

Detectors in Positron Emission Tomography (PET) scanners are usually arranged in rings with the specimen lying along the axial direction. This distribution, however, does not maximize the geometrical sensitivity unless the axial extent becomes much longer than the axial Field of View (FOV), a very costly solution. The optimal geometry for a PET scanner is a sphere with the specimen located at the center. The state of the art of scintillator crystals and detectors for γ -rays does not facilitate smooth spherical geometry design. In this work we propose a PET scanner of 4 π steradian coverage for preclinical imaging as a proof of concept. As a first approximation to the ideal spherical topology, the scanner is shaped as an icosahedron. Furthermore we also present the new custom-tailored hexagonal Silicon Photomultiplier (SiPM) and a monolithic laser-engraved LYSO scintillator crystal that tiles the twenty scanner faces. Preliminary results of the scanner performance based on simulations point to enhanced sensitivity. Initial results on the characterization of the hexagonal photodetector by collection of pulses from a 22Na point source show similar performance as conventional square pixels with the benefit of the increased sensitivity and resolution.

Three kinds of MOSFETs with thick oxide layer and long channel were designed to do experiments and analysis on the impact of reactor neutron irradiation on total ionizing dose (TID) degradation in MOSFET. The individual gamma irradiation and the sequential irradiation of reactor neutrons and gamma rays were accomplished on the transistors. The results demonstrate that reactor neutron irradiation enhanced subsequent TID degradation in MOSFET, which was further analysed by Geant4 simulation. Neutron irradiation can also induce total ionizing dose effects rather than displacement effects in MOSFETs. The mechanism of the enhanced degradation under the sequential neutron and gamma irradiation is that ionizing energy loss by incident neutrons also makes ionizing dose accumulation in MOSFET, and neutron-induced and gamma-induced TID degradation are added together, leading to more severe degradation than that under the individual gamma irradiation.

To evaluate the biological effect of boron compounds on normal tissues in boron neutron capture therapy, it is necessary to compare the radiation effects of neutron irradiation and gamma ray irradiation on small animals in nonclinical studies. Neutron beams and gamma rays are difficult to collimate; thus, it is impossible to administer a dose on each part of the normal tissues of small animals. Therefore, we have developed a method to compare biological effects by irradiating neutrons and gamma rays after irradiating a proton beam to the point just before the threshold dose at which the biological effects occur. We aim to develop an irradiation field that irradiates proton beams locally using a fixed-field alternating-gradient (FFAG) accelerator and a small ridge filter. An aluminum scatterer, transmission dose monitor, ridge filter, range shifter, collimator , and a proton beam from the FFAG accelerator were used to form an irradiation field with a spread out Bragg peak (SOBP) with a length of 10 mm and a size of 10 mm 2. Dose measurement was performed using a Gafchromic film and an ionization chamber . The irradiation system was simulated using the PHITS Monte Carlo simulation code, and simulation results were compared with experimental results. We succeeded in forming an irradiation field with a dose rate of 14.3 ± 0.24 Gy/min, an SOBP length of 10 mm, and a size of 10 mm2.

Recent studies in BNCT have focused on investigating appropriate neutron sources based on accelerators. One of the common reactions based on accelerators for neutron production is 7Li(p,n)7 Be. In this paper we designed and optimized two-sided Beam Shaping Assembly composed of a moderator, a filter, a reflector and a collimator for the perpendicular neutrons with respect to the direction of the incident beam to provide an appropriate neutron beam in BNCT. Calculations for our design show, using a proton beam of 2.5 MeV with a current of 10 mA, will produce proper epithermal neutron flux in both sides of the system. The final optimized flux for the system was calculated to be 2 . 15 × 1 0 9 n ∕ cm 2 . s for one side of BSA and the epithermal neutron flux on one of two sides has increased by about 32% with respect to the forward direction. All in-air licensed parameters proposed by the International Atomic Energy Agency (IAEA) have been established. The dose evaluation results and depth dose curves were presented for a simulated head phantom and a human phantom including the liver with a typical tumor. The results confirmed that the designed neutron source and BSAs, can potentially be used to treat deep-seated brain and liver tumors in BNCT.

In order to monitor the intense neutron and gamma radiation , multi-element tissue equivalent proportional counters (TEPC) based on the standard gas electron multiplier (GEM) and ceramic thick GEM (THGEM) foils were designed and respectively tested by implanted 55Fe and 241 Am sources which would also be used as calibration sources. The performance testing of GEM-TEPC/THGEM-TEPC detectors at various parameters showed that the detectors could work well. The THGEM-TEPC was also used to measure the linear energy spectra in 241Am–Be and intense (108 ncm−2s−1 ) neutron radiation fields. The results displayed that THGEM-TEPC was available to do microdosimetric research or be a dosimeter in intense neutron/gamma field.

The aim of the work is to describe a new high-performance scintigraphic detector, derived from our previous work based on a Position Sensitive Photomultiplier Tube (PSPMT) with 256 output anodes. This detector is suitable for direct integration into multi-modality imaging systems. Indeed, the detector has been developed in order to be integrated into a pre-clinical system. The detector is based on an H9500 Hamamatsu PSPMT coupled to an LYSO pixelated scintillator and a low-energy tungsten collimator with parallel square holes. In order to limit the overall size of the device, a dedicated compact electronics has been developed. The device design was performed using Monte Carlo transport calculations to aid the development. Our results show a detector performance suitable for application on small animals. The intrinsic spatial resolution was experimentally determined to be about 1.6 mm. The measured energy resolution was ∼ 16% at 140 keV and the maximum recorded sensitivity was ∼ 76 cps/MBq. In addition, the results agree quite well with those of Monte Carlo simulations. We have successfully improved the performance of our previous detector design in order to integrate the new device into a complex system focused on pre-clinical imaging.

The present work describes the GATE/Geant4 simulation of the TOF whole-body scanner constructed with PbF 2 crystals and motivated by the on-going developments of the efficient and fast Cherenkov detector at the IRFU, CEA. We consider different geometrical configurations of the elementary detectors, different options of the optical interface and optimize the scanner construction using TOF-modified noise equivalent count rate calculation.

In proton therapy, the delivered dose should be monitored to a high degree of accuracy to avoid unnecessary exposure to healthy tissues and critical organs. Although positron emission tomography (PET) is most frequently used to verify the proton range, the nuclear reactions between protons and nuclei that generate positrons do not necessarily correspond to the actual proton range. Moreover, such imaging must be conducted after the treatment irradiation, because a PET gantry cannot be used in conjunction with a proton therapy beam. In this paper, we studied one-dimensional (1D) and two-dimensional (2D) distributions of prompt gamma rays of various energies, to determine the most suitable energy window for online monitoring in proton therapy. After an initial simulation study using the particle and heavy ion transport code system (PHITS), we irradiated a poly(methyl methacrylate) (PMMA) phantom with a 70-MeV proton beam to mimic proton range verification in a clinical situation. Using a newly developed Compton camera, we have experimentally confirmed for the first time that 4.4-MeV gamma rays emitted from 12 C and 16 O match the exact position of the Bragg peak in proton range verification.

Thermal powers from radioactive decays (‘decay heat’) within a proton-driven neutron-producing tungsten target on the ISIS Spallation Neutron Source have been measured. Very good agreement is found with calculations using the Monte Carlo code MCNPX.

A Thermal neutron radiography facility based on photoneutrons which produced by an electron linac was studied with the final goal to suggest an attractive alternative to the nuclear research reactors neutron sources which are used for radiographic purposes. The design and the optimization of the facility have been simulated using the MCNPX Monte Carlo code. The relevant with thermal neutron radiography parameters such as the thermal neutron flux, the L/D ratio and the thermal neutron content calculated for an extensive range of values. The results specify that the proposed facility meets all the required values for quality thermal neutron radiographies. The overall evaluation of the unit was also realized through the comparison between the studied facility and some published works.

The reproduction of neutron fluence derived by the unfolding method was confirmed by simulating an experiment at Cern High energy AcceleRator Mixed field facility (CHARM). Fluences on an NE213 scintillator located at positions surrounded with shields were calculated using PHITS. A neutron light output spectrum and response matrix were calculated according to the calculated fluence. Furthermore, response matrices with simple distributions of neutron incident position and direction on the scintillator were also prepared because a response matrix with guessed distributions is used in measurements. In spite of using response matrices with different distributions, the unfolded fluence agreed with each other, unless the distribution was focused on a position. The agreement of the fluences enables us to measure the fluence at various positions even though the distributions are experimentally unknown. Finally, experimental fluences were obtained under the same conditions, and were compared with the simulation results.

Positron emission tomography (PET) is considered an important and powerful tool for molecular imaging and medical diagnosis with its high sensitivity. Further, single-photon emission CT (SPECT) is another important imaging modality providing different types of information in medical diagnosis. On the other hand, Compton imaging is a promising technique for future molecular imaging with multi-nuclides based on Compton scattering kinetics. In this regard, previously, we have developed gadolinium aluminum gallium garnet (GAGG)-scintillation-based PET systems and GAGG-scintillation-based Compton imaging systems for environmental applications. Here, we propose and develop a novel PET–Compton hybrid simultaneous imager based on a two-layer structure using thin scatterers and thick absorbers for multi-nuclide imaging, for e.g., simultaneous imaging of PET and SPECT tracers such as 18F-FDG and 111In, respectively. For achieving good spatial resolution of the Compton imager, the energy resolution of the utilized scintillators forms one of the most important characteristics. In this regard, GAGG is a promising scintillator because of its high light yield of over 50 000 photon/MeV and excellent energy resolution of 4% with no background radiation and moderate decay time. In this study, we present the development of a simultaneous PET–Compton detector that consists of an 8 × 8 multi-pixel photon counter/SiPM (MPPC) array individually coupled with a 2.5 9-mm Ce:GdGa2.7Al2.3O12 scintillators (absorbers) for proof of concept of simultaneous PET and SPECT imaging. The pixel size of the MPPC is 3 mm 3 mm, and it is operated at 55 V at room temperature. The signals from the MPPC scintillators are individually amplified and converted with a dynamic time over threshold (dTOT) circuit to record the energy and timing information. In image reconstruction, the data acquired with the use of the developed modules are classified into events of either Compton imaging or PET imaging by coincidence detection between scatterer and absorber or between absorber and absorber, respectively. The coincidence events between absorber and absorber are regarded as PET annihilation-gamma events and those between scatterer and absorber are used as Compton imaging events. In our experiment, images of 111In and 18F-FDG, which are used as multi-nuclide tracers, are acquired simultaneously using the developed detector for Compton imaging and PET imaging. We believe that our approach is a significant step forward for medical imaging and related fields.

In this paper, a new radiation sensitive field-effect Transistor (RADFET) dosimeter design based on armchair-edge graphene nanoribbon (AGNR), for high performance low-dose monitoring applications, is proposed through a quantum simulation study. The simulation approach used to investigate the proposed nanoscale RADFET is based on solving the Schrodinger equation using the mode space (MS) non-equilibrium Green’s function (NEGF) formalism coupled self-consistently with a two dimensional (2D) Poisson equation under the ballistic limits. The responsiveness of the proposed RADFET to the modulation of radiation-induced trapped charge densities is reflected via the threshold voltage , which is considered as a sensing parameter. The dosimeter behavior is investigated, and the impact of variation in physical and geometrical parameters on the dosimeter sensitivity is also studied. In comparison to other RADFETs designs, the proposed radiation sensor provides higher sensitivity and better scalability, which are the main requirements for futuristic dosimeters. The obtained results make the suggested RADFET dosimeter as a viable and attractive replacement to silicon-based MOS dosimeters.

The effectiveness of Boron Neutron Capture Therapy (BNCT) treatment depends on the amount of radiation dose deposited locally by the reaction 10B ( n , α ) 7 Li in the tumour; however, the local and real time measurement of this quantity during the neutron irradiation is a big challenge. To evaluate the dose it is necessary to know the spatial distribution of the 10 B concentration and thermal neutron flux in the tissue during the irradiation. One technique to solve this problem relies on the on-line detection of the 478 keV 7 Li de-excitation photons that can be used to map the spatial distribution of the reaction rate of the 10B ( n , α ) 7 Li. The present work has been developed within a project aiming to develop a Single Photon Emission Computed Tomography (SPECT) system based on CdZnTe (CZT) semiconductor detector. This work studied the performances of a 5 × 5 × 20 mm 3 CZT prototype detector focusing on the energy resolution and detection efficiency inside the energy range 200–1400 keV. The energy resolution at 478 keV is ∼ 3% and the detection efficiency is around 6%. These preliminary results confirms the feasibility of a CZT detector as a sensitive unit for a BNCT-SPECT imaging system.

Bozkurt, Ahmet/0000-0002-3163-0131 WOS: 000433206800017 In this study, we have performed the calculations stopping power, depth dose, and range verification for proton beams using dielectric and Bethe-Bloch theories and FLUKA, Geant4 and MCNPX Monte Carlo codes. In the framework, as analytical studies, Drude model was applied for dielectric theory and effective charge approach with Roothaan-Hartree-Fock charge densities was used in Bethe theory. In the simulations different setup parameters were selected to evaluate the performance of three distinct Monte Carlo codes. The lung and breast tissues were investigated are considered to be related to the most common types of cancer throughout the world. The results were compared with each other and the available data in literature. In addition, the obtained results were verified with prompt gamma range data. In both stopping power values and depth-dose distributions, it was found that the Monte Carlo values give better results compared with the analytical ones while the results that agree best with ICRU data in terms of stopping power are those of the effective charge approach between the analytical methods and of the FLUKA code among the MC packages. In the depth dose distributions of the examined tissues, although the Bragg curves for Monte Carlo almost overlap, the analytical ones show significant deviations that become more pronounce with increasing energy. Verifications with the results of prompt gamma photons were attempted for 100-200 MeV protons which are regarded important for proton therapy. The analytical results are within 2%-5% and the Monte Carlo values are within 0%-2% as compared with those of the prompt gammas.

Positron emission tomography (PET) is a nuclear medicine functional imaging technique. It is used in clinical oncology (medical imaging of tumors and the search for metastases), and pre-clinical studies using animals. PET uses small amounts of radioactive materials (radiotracers) and a special photon sensitive camera. Most of these cameras use scintillators with photomultipliers as detectors. However, these detectors have limited energy sensitivity and large pixels. Therefore, the false signal caused by a scattering poses a significant problem. In this work we study properties of position, energy and time sensitive semiconductor detector of Timepix3 type and its applicability for PET measurements. This work presents an initial study and evaluation of two Timepix3 detectors with 2 mm thick CdTe sensors used in simplified geometry for PET imaging. The study is performed on 2 samples — a capillary tube and a cylindrical plexiglass phantom with cavities. Both samples are filled with fluodeoxyglucose (FDG) solution that is used as a radiotracer. The Timepix3 offers better properties compared to conventional detectors — high granularity ( 55 μ m pixel pitch), good energy resolution (1 keV at 60 keV) and sufficient time resolution (1.6 ns). The spectral sensitivity of Timepix3 together with coincidence/anticoincidence technique allows for significant reduction of background signal caused by Compton scattering and internal X-ray fluorescence of Cd and Te.

A large area SiPM array is individually coupled to five different types of scintillators in and each is evaluated for the development of a coded aperture imaging system. In order to readout signals from the 144 pixel array, a resistor network with symmetric charge division circuitry was developed, which successfully provides a significant reduction in the multiplicity of the analog outputs and reduces the size of the accumulated data. Energy resolutions at 662 keV for pixelated arrays of dimensions and material types as follows: 3 × 3 × 20 mm3 CsI(Tl), 4 × 4 × 20 mm3 CsI(Tl), 4 × 4 × 5 mm3 LYSO(Ce), 4 × 4 × 10 mm3 LYSO(Ce), and 2 × 2 × 5 mm3 LaCl3(Ce) have been determined. In addition, sub-millimeter FWHM pixel-identification resolutions were acquired from all of the scintillators tested.

In this research, a spatial electron beam scanning is reported. There are various methods for ion and electron beam scanning. The best known of these methods is the wire scanning wherein the parameters of beam are measured by one or more conductive wires. This article suggests a novel method for e-beam scanning without the previous errors of old wire scanning. In this method, the techniques of atomic physics are applied so that a knife edge has a scanner role and the wires have detector roles. It will determine the 2D e-beam profile readily when the positions of the scanner and detectors are specified.

A PR60020 silicon diode detector (PTW-Freiburg, Germany) was tested at INFN-LNS cyclotron on the scattered proton beamline (62 MeV) dedicated to ocular treatments. For the first time, the detector was also characterized in scanning proton beams accelerated by the CNAO synchrotron (63–229 MeV). The characteristics of the diode detector for proton beam dosimetry were investigated in terms of response stability, linearity with dose and dependence on dose rate and beam quality. Depth–ionization curves were measured for unmodulated, unmodulated range-shifted beams and spread-out Bragg peaks (SOBP); results were compared with reference ones obtained with an ionization chamber. Output Factors of narrow beams used in ocular proton-therapy were measured and compared to those achieved using EBT3 films. The PR60020 diode showed a reproducible response as for short-term precision (0.5%) and medium-term stability (1.5%). Dose and dose rate dependence measurements showed deviations from linearity within ± 1%. The calibration factor (Gy/nC) was constant within ± 1% over the range of proton beam qualities of ocular proton-therapy, while 1.4% maximum variation of diode sensitivity among CNAO energies was found. Output factors agreed with reference ones within 2% down to 5 mm collimator diameter. Bragg peak curves closely matched those acquired with ionization chamber, relative differences being lower than 3% in peak-to-plateau ratios. Very good results were also found for SOBP dose measurements as in scattered and scanned proton beams. In conclusion, diode detector appeared suitable for relative dosimetry and absorbed dose determination in passively scattered and scanning clinical proton beams, particularly for very small fields used for ocular treatments.

Thermal neutron imaging techniques such as radiography or tomography are very useful tool for various scientific investigations and industrial applications. Neutron radiography is complementary to X-ray radiography, as neutrons interact with nucleus as compared to X-ray interaction with orbital electrons. We present here design and development of a neutron imaging beamline at 100 MW Dhruva research reactor for neutron imaging applications such as radiography, tomography and phase contrast imaging. Combinations of sapphire and bismuth single crystals have been used as thermal neutron filter/gamma absorber at the input of a specially designed collimator to maximize thermal neutron to gamma ratio. The maximum beam size of neutrons has been restricted to ∼ 120 mm diameter at the sample position. A cadmium ratio of ∼ 250 with L ∕ D ratio of 160 and thermal neutron flux of ∼ 4 × 10 7 n/cm2 s at the sample position has been measured. In this paper, different aspects of the beamline design such as collimator, shielding, sample manipulator, digital imaging system are described. Nondestructive radiography/tomography experiments on hydrogen concentration in Zr-alloy, aluminium foam, ceramic metal seals etc. are also presented.

Methods are developed for the application of forward biased p–i–n photodiodes to measurements of charged particle fluence beyond 1015 1-MeV-neutron-equivalent/cm2. An order of magnitude extension of the regime where forward voltage can be used to infer fluence is achieved for OSRAM BPW34F devices.

Nuclear fragmentation produced in 12C ion therapeutic beams contributes significantly to the Relative Biological Effectiveness (RBE)—weighted dose in the distal edge of the Spread out Bragg Peak (SOBP) and surrounding tissues in out-of-field. Complex mixed radiation field originated by the therapeutic 12C ion beam in a phantom is difficult to measure. This study presents a new method to characterise the radiation field produced in a 12C ion beam using a monolithic Δ E-E telescope which provides the capability to identify the particle components of the mixed radiation field as well as the microdosimetric spectra that allows derivation of the RBE based on a radiobiological model. The response of the monolithic Δ E-E telescope to a 290 MeV/u 12C ion beam at defined positions along the pristine Bragg Peak was studied using the Geant4 Monte Carlo toolkit. The microdosimetric spectra derived from the Δ E stage and the two-dimensional scatter plots of energy deposition in Δ E and E stages of the device in coincidence are presented, as calculated in-field and out-of-field. Partial dose weighted contribution to the microdosimetric spectra from nuclear fragments and recoils, such as 1H, 4He, 3He, 7Li, 9Be and 11B, have been analysed for each position. Comparison of simulation and experimental results are presented and demonstrates that the microdosimetric spectra changes dramatically within 0.5 mm depth increments close to and at the distal edge of the Bragg Peak which is impossible to identify using conventional Tissue Equivalent Proportional Counter (TEPC).

The reverse current of irradiated silicon sensors leads to self heating of the sensor and degrades the signal to noise ratio of a detector. Precise knowledge of the expected reverse current during detector operation is crucial for planning and running experiments in High Energy Physics. The dependence of the reverse current on sensor temperature and irradiation fluence is parametrized by the effective energy and the current related damage rate, respectively. In this study 18 n-in-p mini silicon strip sensors from companies Hamamatsu Photonics and Micron Semiconductor Ltd. were deployed. Measurements of the reverse current for different bias voltages were performed at temperatures of −32 ° C, −27 ° C and −23 ° C. The sensors were irradiated with reactor neutrons in Ljubljana to fluences ranging from 2 × 1 0 14 n eq ∕ cm 2 to 2 × 1 0 16 n eq ∕ cm 2 . The measurements were performed directly after irradiation and after 10 and 30 days of room temperature annealing. The aim of the study presented in this paper is to investigate the reverse current of silicon sensors for high fluences of up to 2 × 1 0 16 n eq ∕ cm 2 and compare the measurements to the parametrization models.

Nuclear fragmentation produced in 12C ion therapeutic beams contributes significantly to the Relative Biological Effectiveness (RBE)—weighted dose in the distal edge of the Spread out Bragg Peak (SOBP) and surrounding tissues in out-of-field. Complex mixed radiation field originated by the therapeutic 12C ion beam in a phantom is difficult to measure. This study presents a new method to characterise the radiation field produced in a 12C ion beam using a monolithic E-E telescope which provides the capability to identify the particle components of the mixed radiation field as well as the microdosimetric spectra that allows derivation of the RBE based on a radiobiological model. The response of the monolithic E-E telescope to a 290 MeV/u 12C ion beam at defined positions along the pristine Bragg Peak was studied using the Geant4 Monte Carlo toolkit. The microdosimetric spectra derived from the E stage and the two-dimensional scatter plots of energy deposition in E and E stages of the device in coincidence are presented, as calculated in-field and out-of-field. Partial dose weighted contribution to the microdosimetric spectra from nuclear fragments and recoils, such as 1H, 4He, 3He, 7Li, 9Be and 11B, have been analysed for each position. Comparison of simulation and experimental results are presented and demonstrates that the microdosimetric spectra changes dramatically within 0.5 mm depth increments close to and at the distal edge of the Bragg Peak which is impossible to identify using conventional Tissue Equivalent Proportional Counter (TEPC).

Proton therapy causes less damage to healthy tissue compared to other radiation therapies ; however, the possible damage caused by secondary, fast neutrons is almost unknown. In some simulations, neutron dose amounts to 10% of the proton dose; therefore, a real-time visualization of the neutron dose is needed. We have developed a neutron camera that can visualize the direction and intensity of fast neutron sources . The camera consists of eight units of a plastic scintillator (EJ-299-34) coupled with a compact PMT (R9880U). We demonstrate that a 252Cf neutron source is correctly imaged with an angular resolution of 15.5 deg (FWHM). In addition, fast neutrons emitted from the brass block irradiated by 70 MeV were successfully monitored in real time. Finally, we present our prospects for future clinical applications.

Proton therapy is a widely used and effective treatment for cancer. A high-dose concentration of proton beam reduces damage to normal tissues. However, it also requires a high accuracy of irradiation. PET is generally used to verify the proton range after irradiation, but, the distributions of positrons and the energy deposited by protons are not similar to each other. Recently, prompt gamma-ray imaging has attracted attention as a new, online imaging technique. In particular, 4.4 MeV gamma rays emitted from 12 C* is one of the best probes to monitor the proton dose, however imaging techniques are far from established. We have developed a novel, 3-D position sensitive Compton camera based on Ce:GAGG scintillators coupled with multi-pixel photon counter (MPPC) arrays, thus making it optimized for imaging in the 1–10 MeV range. The angular resolution is 5 degrees (FWHM) at 4.4 MeV. We have established various methods to discriminate multiple-Compton and escape events, both of which can be critical backgrounds for precise imaging of prompt gamma rays. By irradiating a 70 MeV proton beam on the PMMA phantom, we demonstrated that 4.4 MeV gamma ray image is sharply concentrated on the Bragg peak, as was expected from the PHITS simulation.

We designed a neutron spectrometer to measure low-energy neutron beam for boron neutron capture therapy (BNCT) without exchanging thicknesses of neutron moderator. The spectrometer consists of a boron carbide block as a neutron moderator and nine thin neutron silicon sensors with variable detection efficiency. Using the Monte Carlo technique, we simulated the spectrometer’s neutron energy response functions. It represented sharp rise in the response functions with various lower limits of neutron energies distributed over a wide range of neutron energy from a thermal energy to a few 100 keV. The lower limit of neutron energy was dependent on a depth in the boron carbide block. By applying thicker enriched 6LiF neutron converter and covering the deep positioned neutron sensors with polyethylene plates, neutron detection efficiencies were increased to be able to measure the BNCT neutron beam in a short time.

A test version of a prompt-gamma single photon emission computed tomography (PG-SPECT) system for boron neutron capture therapy (BNCT) using a CdZnTe (CZT) semiconductor detector with a secondary BGO anti-Compton suppression detector has been designed. A phantom with healthy tissue region of pure water, and 2 tumor regions of 5 wt% borated polyethylene was irradiated to a fluence of 1.3 × 10 9 n/cm 2 . The number of 478 keV foreground, background, and net counts were measured for each detector position and angle. Using only experimentally measured net counts, an image of the 478 keV production from the 10 B ( n , α ) 7 Li * reaction was reconstructed. Using Monte Carlo simulation and the experimentally measured background counts, the reliability of the system under clinically accurate parameters was extrapolated. After extrapolation, it was found that the value of the maximum-value pixel in the reconstructed 478 keV γ -ray production image overestimates the simulated production by an average of 9.2%, and that the standard deviation associated with the same value is 11.4%.

Measurements of dose distribution are important for high energy X-ray beam from linear accelerators (LINAC) for quality assessment (QA) of the system. Although ionization chambers are commonly used for this purpose, measurements need relatively long time to obtain the data especially for the two- or three-dimensional dose distributions. To solve the problem, we conducted optical imaging of water during irradiations of high energy X-ray beam from a LINAC. We placed a water phantom set on a table with a LINAC system, and optical images of water were measured with a high-sensitivity cooled charge coupled device (CCD) camera during X-ray beam irradiations to the water phantom from the upper side. Measurements were made for different energies and doses of X-ray beams. We also measured dynamic images while moving the multi-leaf collimators of the LINAC system to evaluate the performance for more practical condition. Then we measured the light spectra of the optical images of water for X-ray beam by changing the optical filters. In all irradiations of different energies and doses of X-ray beam, we could obtain clear optical images in water. The lateral profiles of the images were almost identical to those calculated by planning system. However the depth profiles were slightly smaller at the deeper area. We obtained dynamic images while moving the multi-leaf collimators. The light spectrum of the image during X-ray beam irradiation was similar to that of the Cerenkov-light. There was not a significant difference in the depth profiles between different wave lengths of light. Optical imaging of water during irradiations of X-ray beam has a potential to be used for the lateral profile of the beams. Also it might be useful to estimate the depth profiles with slight under estimations at deeper areas. Dynamic optical imaging while moving the multi-leaf collimators during irradiation of X-ray were possible.

There have been many studies on Depth Of Interaction (DOI) identification for high resolution Positron Emission Tomography (PET) systems, including those on phoswich detectors, double-sided readout, light sharing methods, and wavelength discrimination. The wavelength discrimination method utilizes the difference in wavelength of stacked scintillators and requires a color sensitive photodetector. Here, a new silicon photomultiplier (SiPM) coupled to a color filter (colorSiPM) was designed and fabricated for DOI detection. The fabricated colorSiPM has two anode readouts that are sensitive to blue and green color. The colorSiPM's response and DOI identification capability for stacked GAGG and LYSO crystals are characterized. The fabricated colorSiPM is sensitive enough to detect a peak of 662 keV from a 137 Cs source.

We characterized and calibrated a triple Gas Electron Multiplier (triple-GEM) detector, and studied its possible applications in medical dosimetry . The response to various sources of radiation was analyzed, and its gain, energy resolution, and time resolution were calculated. Then, radiation doses from an Iron-55 source and a medical portable X-ray machine were measured, obtaining the calibration factor for the GEM detector by comparison with reference values. We found an energy resolution of 19.5%, a time resolution of 40 ns, and a maximum gain of 5 × 1 0 6 . The detector’s response to dose measurements was linear, with a calibration coefficient of 1 . 13 × 1 0 4 for different sources of radiation. It was concluded that GEM detectors can be reliably used as dosimeters in nuclear medicine and radiology .

Silicon photomultipliers are a novel technology for the detection of photons in near ultraviolet, visible, and near-infrared spectral ranges. Their application is rapidly growing and extending to many fields in physics, replacing traditional PMTs and APDs. In this study a large-size CsI(Tl) crystal coupled to small-area SiPM ( 3 × 3 mm 2 ) was used to detect α -particles and low energy protons. In particular, the detector was irradiated with proton beams accelerated by the Tandem Van-der-Graff of the INFN-Laboratori Nazionali del Sud (LNS), at incident energies between 2.5 MeV and 24 MeV. The detector performance was studied in terms of light yield, linearity and energy resolution. In addition, we investigated the dependence of the detector response on the impact point of the particles.

Proton therapy is now recognized as one of the most effective radiation therapy methods for cancers. A proton therapy facility with multiple gantry treatment rooms is under development in HUST (Huazhong University of Science and Technology), which is based on isochronous superconducting cyclotron scheme. In the beam line, the scanning system spreads out the proton beam on the target according to the complex tumour shape by two scanning magnets for horizontal and vertical scanning independently. Since these two magnets are excited by alternating currents and the maximum repetition frequency is up to 100 Hz, eddy currents and losses are expected to be significant. Slits are proven to be an effective way to reduce the eddy currents. To evaluate the heat distribution due to eddy losses in the pole end of the scanning magnet, the transient electromagnetic analysis and steady-state thermal analysis are performed. This paper describes design considerations of the scanning system and mainly analyses the eddy current effect of the scanning magnets. Different coil shapes and slit arrangements are simulated and compared to obtain the optimal configuration. The maximum temperatures of two magnets are optimized below 70 °C. In addition, the lag effect due to eddy currents is also discussed.

A prototype multi-element gaseous microdosimetric detector was developed using the Thick Gas Electron Multiplier (THGEM) technique. The detector aims at measuring neutron and gamma-ray dose rates for weak neutron-gamma radiation fields. The multi-element design was employed to increase the neutron detection efficiency. The prototype THGEM multi-element detector consists of three layers of tissue equivalent plastic hexagons and each layer houses a hexagonal array of seven cylindrical gas cavity elements with equal heights and diameters of 17 mm. The final detector structure incorporates 21 gaseous volumes. Owing to the absence of wire electrodes, the THGEM multi-element detector offers flexible and convenient fabrication. The detector responses to neutron and gamma-ray were investigated using the McMaster Tandetron 7 Li(p,n) neutron source. The dosimetric performance of the detector is presented in contrast to the response of a commercial tissue equivalent proportional counter. Compared to the standard TEPC response, the detector gave a consistent microdosimetric response with an average discrepancy of 8 % in measured neutron absorbed dose. An improvement of a factor of 3.0 in neutron detection efficiency has been accomplished with only a small degradation in energy resolution. However, its low energy cut off is about 6 keV/μm, which is not sufficient to measure the gamma-ray dose. This problem will be addressed by increasing the electron multiplication gain using double THGEM layers.

The MEG II experiment is an upgrade of the MEG experiment to search for the charged lepton flavor violating decay of muon, μ + → e + γ . The MEG II experiment is expected to reach a branching ratio sensitivity of 4 × 10 − 14 , which is one order of magnitude better than the sensitivity of the current MEG experiment. The performance of the liquid xenon (LXe) γ -ray detector will be greatly improved with a highly granular scintillation readout realized by replacing 216 photomultiplier tubes (PMTs) on the γ -ray entrance face with 4092 Multi-Pixel Photon Counters (MPPCs). For this purpose, we have developed a new type of MPPC which is sensitive to the LXe scintillation light in vacuum ultraviolet (VUV) range, in collaboration with Hamamatsu Photonics K.K. We have measured the performance of the MPPC in LXe, and an excellent performance has been confirmed including high photon detection efficiency ( > 15 % ) for LXe scintillation light. An excellent performance of the LXe detector has been confirmed by Monte Carlo simulations based on the measured properties of the MPPC. The construction of the detector is in progress, aiming to start physics data taking in 2017.

We propose a time-of-flight (TOF) technique using plastic scintillators which have fast decay time of a few ns for positron emission tomography (PET). While the photoelectric absorption probability of the plastic for 511 keV gamma rays are extremely low due to its small density and effective atomic number, the cross section of Compton scattering is comparable to that of absorption by conventional inorganic scintillators. We thus propose TOF-PET using Compton scattering with plastic scintillators (Compton-PET), and performed fundamental experiments towards exploration of the Compton-PET capability. We demonstrated that the plastic scintillators achieved the better time resolution in comparison to LYSO(Ce) and GAGG(Ce) scintillators. In addition we evaluated the depth-of-interaction resolving capability with the plastic scintillators.

We present recent results on the investigation of the KETEK, ZECOTEK, HAMAMATSU and SENSL SiPM properties after irradiation by the 6–35 MeV neutrons. The typical neutron fluence was about 1012n/cm2. The changing of the internal structure of the irradiated SiPMs was studied by the measuring of the C–V and C–f characteristics. We have observed the strong influence of the SiPM manufacturing technology on their radiation hardness. The application of the obtained results to the development of the readout electronics is discussed.

In recent years the use of hadrons for cancer radiation treatment has grown in importance, and many facilities are currently operational or under construction worldwide. To fully exploit the therapeutic advantages offered by hadron therapy, precise body imaging for accurate beam delivery is decisive. While traditional X-ray Computed Tomography (xCT) fails in providing 3D images with the precision required for hadrons treatment guidance, Proton Computer Tomography (pCT) scanners, currently in their R&D phase, can. A pCT scanner consists of a tracker system, to track protons, and of a calorimeter, to measure their residual energy. In this paper we will present the iMPACT project, which foresees a novel proton tracking detector with higher scanning speed, better spatial resolution and lower material budget with respect to present state-of-the-art detectors, leading to enhanced performances. The tracker will be matched to a fast, highly segmented proton range calorimeter.

Hadrontherapy is a technique for cancer treatment that exploits ion beams (mostly protons and carbons). A critical issue is the accuracy that is achievable when monitoring the dose released by the beam to the tumor and to the surrounding tissues. We present the design of a tracking device, developed in the framework of the INSIDE project [1] , capable of monitoring in real time the longitudinal profile of the dose delivered in the patient. This is possible by detecting the secondary particles produced by the interaction of the beam in the tissues. The position of the Bragg peak can be correlated to the charged particles emission point distribution measurement. The tracking device will be able to provide a fast response on the dose pattern by tracking the secondary charged fragments. The tracks are detected using 6 planes of scintillating fibers, providing the 3D coordinates of the track intersection with each plane. The fibers planes are followed by a plastic scintillator and by a small calorimeter built with a pixelated Lutetium Fine Silicate (LFS) crystal. A complete detector simulation, followed by the event reconstruction, has been performed to determine the achievable monitoring spatial resolution.

The SAFIR development represents a novel Positron Emission Tomography (PET) detector, conceived for preclinical fast acquisitions inside the bore of a Magnetic Resonance Imaging (MRI) scanner. The goal is hybrid and simultaneous PET/MRI dynamic studies at unprecedented temporal resolutions of a few seconds. The detector relies on matrices of scintillating LSO-based crystals coupled one-to-one with SiPM arrays and readout by fast ASICs with excellent timing resolution and high rate capabilities. The paper describes the detector concept and the initial results in terms of simulations and characterisation measurements.

A superconducting rotating-gantry for carbon-ion radiotherapy was developed. This isocentric gantry can transport carbon ions having kinetic energies of between E =430 and 48 MeV/ u to an isocenter over an angle of ±180°, and is further capable of performing three-dimensional raster-scanning irradiation. Construction of the entire rotating-gantry system was completed by the end of September 2015. Prior to beam commissioning, phase-space distributions of extracted carbon beams from the synchrotron were deduced by using an empirical method. In this method, phase-space distributions at the extraction channel of the synchrotron were modeled with 8 parameters, and the best parameters were determined so as to minimize a difference between the calculated and measured beam profiles by using a simplex method. Based on the phase-space distributions, beam optics through the beam-transport lines as well as the rotating gantry were designed. Since horizontal and vertical beam emittances, as extracted slowly from the synchrotron, generally differ with each other, a horizontal–vertical beam coupling would occur when the gantry rotates. Thus, the size and shape of beam spots at the isocenter should vary depending on the gantry angle. To compensate for the difference in the emittances, we employed a method to utilize multiple Coulomb scattering of the beam particles by a thin scatterer. Having compensated for the emittances and designed beam optics through the rotating gantry, beam commissioning over various combinations of gantry angles and beam energies was performed. By finely tuning the superconducting quadrupoles of the rotating gantry, we could successfully obtain the designed beam quality, which satisfies the requirements of scanning irradiation.

Luminescence imaging of water using X-ray photon irradiation at energy lower than maximum energy of ~200 keV is thought to be impossible because the secondary electrons produced in this energy range do not emit Cerenkov- light. Contrary to this consensus assumption, we show that the luminescence imaging of water can be achieved by X-ray irradiation at energy lower than 120 keV. We placed water phantoms on a table with a conventional X-ray imaging system, and luminescence images of these phantoms were measured with a high-sensitivity, cooled charge coupled device (CCD) camera during X-ray photon irradiation at energy below 120 keV. We also carried out such imaging of an acrylic block and plastic scintillator. The luminescence images of water phantoms taken during X-ray photon irradiation clearly showed X-ray photon distribution. The intensity of the X-ray photon images of the phantom increased almost proportionally to the number of X-ray irradiations. Lower-energy X-ray photon irradiation showed lower-intensity luminescence at the deeper parts of the phantom due to the higher X-ray absorption in the water phantom. Furthermore, lower-intensity luminescence also appeared at the deeper parts of the acrylic phantom due to its higher density than water. The intensity of the luminescence for water was 0.005% of that for plastic scintillator. Luminescence imaging of water during X-ray photon irradiation at energy lower than 120 keV was possible. This luminescence imaging method is promising for dose estimation in X-ray imaging systems.

A device to characterize position-sensitive germanium detectors has been implemented at GSI. The main component of this so called scanning table is a gamma camera that is capable of producing online 2D images of the scanned detector by means of a PET technique. To calibrate the gamma camera Compton imaging is employed. The 2D data can be processed further offline to obtain depth information. Of main interest is the response of the scanned detector in terms of the digitized pulse shapes from the preamplifier. This is an important input for pulse-shape analysis algorithms as they are in use for gamma tracking arrays in gamma spectroscopy. To validate the scanning table, a comparison of its results with a second scanning table implemented at the IPHC Strasbourg is envisaged. For this purpose a pixelated germanium detector has been scanned.

Poly (methyl methacrylate) (PMMA) is widely used in scientific and industrial applications. Because of its favorable properties, it is used in various fields such as optical, medical, and nuclear applications. Effects of ionization radiations on physical properties of PMMA have greatly studied in recent years. However, to the best of our knowledge, there have been no reports on the effects of ionizing radiations, especially the gamma radiation, on the nonlinear optical properties of PMMA. In this paper, for the first time, detection of large and measurable nonlinear refractive index of PMMA after interaction with the gamma radiation is reported. The optical Z-scan technique is used for measuring the nonlinear optical properties of the gamma-irradiated PMMA samples in the 5–300 kGy dose range. It is shown that variation of the induced nonlinear refractive index in this dose range is more or less linear with deposited dose. A new dosimetry method is proposed, which is based on using the Z-scan technique for measuring the nonlinear refractive index of PMMA and obtaining the amount of absorbed dose using this linear response. The name Z-scan dosimetry is coined for this new dosimetry method.

Estimations of the ambient dose equivalent H ∗ 10 and the effective dose (anterior–posterior)​ E A P from prompt gamma intensities are investigated theoretically using Monte Carlo simulations. The system considered consists of a NaI(Tl) gamma detector to measure prompt gamma intensities emitted due to neutron irradiation from a high density polyethylene (HDPE) cylinder embedded in a hollow borated-HDPE cylinder and covered by a layer of lead. A comparative evaluation of different computational techniques of dose estimation, such as, the multiple linear regression method, the detector response-matrix inversion method and the convolution of the unfolded neutron energy distributions with the fluence to dose conversion coefficients (DCC) provided by the International Commission on Radiological Protection (ICRP) is done. The dose estimations are done using the prompt gamma responses (response matrix) obtained for the five distinct gamma peak intensities (boron, hydrogen, carbon and 2 from lead) emitted from the system for incident mono-energetic neutrons ranging from 0.01 eV to 1 GeV. Different workplace neutron spectra are used for the estimation of ambient dose and effective dose to evaluate performances of these three dose estimation methods. The doses ( H ∗ 10 and E A P ) estimated using the convolution of the unfolded neutron spectra with the DCC-ICRP result in satisfactory and accurate agreement with the actual dose, followed by the estimated dose obtained from the regression analysis.

The Frisch-grid CdZnTe detector is a kind of unipolar detector, which can solve the problem of low resolution of planar CdZnTe detectors caused by the poor charge transport of holes. In this paper, high-quality CdZnTe crystals grown by traveling heater method were adopted to develop Frisch-grid CdZnTe detectors. The Geant4 software was adopted to simulate the interaction process of various γ -rays in CdZnTe detectors with different thickness. The Comsol software was used to simulate the structural and material parameters on the weighting potential and energy spectra of Frisch-grid CdZnTe detectors. According to the simulation results, the Frisch-grid CdZnTe detectors were fabricated, and the energy spectra of the detectors under different bias and shaping time were studied experimentally. The 4 × 4 array module of Frisch-grid CdZnTe detectors was designed, whereby the detection efficiency and energy spectra of the array module were studied with the Rena-3 readout ASIC.