Experimental and computational investigation of water-to-air stopping power ratio for ion chamber dosimetry in carbon ion radiotherapy

Particle therapy is an advanced modality of cancer radiotherapy which allows the delivery of a highly conformal dose to the tumour while considerably sparing healthy tissue. This work aims at improving the accuracy of ion chamber dosimetry for particle therapy with carbon ion beams. The readout of air-filled ionization chambers is affected by a number of correction factors, some of which are known only with limited accuracy. This study deals with one of this beam quality correction factors, the stopping power ratio between water and air, or sw,air. On a first step, we planned and carried out experimental measurements to determine the value of water-to-air stopping power ratio in monoenergetic carbon ion beams. Then, we used the Monte Carlo code FLUKA to extend the results of those measurements to realistic treatment beams, and to develop a model to calculate sw,air for any given position in a treatment field. Finally, we tested the developed model in patient cases, to study its possible application in absolute dosimetry and patient plan verification. The obtained results are promising and can, if incorporated in the recommended dosimetry protocols, reduce the uncertainty margins in the determination of absorbed dose for carbon ion beam radiotherapy

Photoacoustic dose monitoring in clinical high-energy photon beams

This work describes all stages of development (setup, optimization, performance, and first experimental measurements) of an acoustic sensor that can be used for range monitoring and dosimetry of clinical radiotherapy beams. The detection device consists of an ultrasonic transducer, a combination of preamplifiers and differential amplifiers with filtered outputs and a digital oscilloscope. Simulations of the experimental setup were carried out to study the optimal measurement geometry and choice of transducer. The dose distributions were calculated with the Monte Carlo code FLUKA, while the acoustic simulations were performed with the analytical wave transport code k-Wave. The temporal profiles of the dose pulses, in the order of mu s, were measured with a scintillating crystal coupled to a photomultiplier and used as input for the acoustic simulation. Measurements were performed in a Cyberknife (TM) radiosurgery beam and a TrueBeam unit. A lead block was submerged in water and placed partially or totally in the irradiation field in order to increase the acoustic signal. Photoacoustic signals were detected with both beams with the expected shape and time-delay, after the frequency response of the detection system was taken into account. The proposed setup can detect photoacoustic signals originating from the penumbra of the treatment fields after being processed with the appropriate image analysis tools

Design of an X-ray irradiator based on a standard imaging X-ray tube with FLASH dose-rate capabilities for preclinical research

This work was funded by Comunidad de Madrid under project B2017/BMD-3888 PRONTO-CM "Protontherapy and nuclear techniques for oncology". Support by the Spanish Government (RTI 2018-098868-B-I00, RTC-2015-3772-1, XPHASE-LASER, CPP 2021-008751 NEW-MBI) , as well as European Regional and Resilience Funds, and the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 793576 (CAP-PERAM) is acknowledged. This is a contribution for the Moncloa Campus of International Excellence, "Grupo de Física Nuclear-UCM", Ref. 910059. Part of the calculations of this work were performed in the "Cluster de Calculo para Técnicas Físicas", funded in part by UCM and in part by EU Regional Funds.We propose a new concept of small animal X-ray irradiator based on a conventional imaging X-ray tube for preclinical research. In this work we assessed its feasibility to deliver FLASH dose rates. Our design puts the imaging X-ray tube into a shielded cabinet, which makes the system affordable and suitable to use without disruption in existing laboratories and with minimum regulatory burden. Two conventional 150 kVp X-ray tubes were characterized with Gafchromic films for dose rates and dose uniformity. Monte Carlo simulations were also performed to model the irradiator, and the efficiencies of the tube and dose rates (with and without additional filtration) were calculated and compared with measurements. The feasibility of achieving ultra-high dose rates was determined from the rating charts provided by the manufacturer and measurements. The small animal irradiator proposed in this work was able to deliver conventional dose rate irradiation (0.5-1 Gy/min) at 150 kVp at 20 cm distance with minimum amount of filtration. FLASH irradiations (a 10 Gy dose delivered at >40 Gy/s) were also possible at the maximum capabilities of the tubes by placing the samples at the closest possible distances from the sources. A first prototype has already been built and characterized.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEComunidad de MadridGobierno de EspañaEuropean Regional and Resilience FundsEuropean Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grantMoncloa Campus of International Excellence, "Grupo de Fisica Nuclear-UCM"Universidad Complutense de Madrid (UCM)EU Regional Fundspu

Technical note: Measurement of the bunch structure of a clinical proton beam using a SiPM coupled to a plastic scintillator with an optical fiber

This work was funded by Comunidad de Madrid under project B2017/BMD-3888 PRONTO-CM “Protontherapy and nuclear techniques for oncology” and by the Spanish Government and EU Regional Funds (RTI2018-098868-B-I00, RTC-2015-3772-1). A. Espinosa Rodríguez has been funded by a FPU predoctoral fellowship of the Spanish Ministerio de Educación, Cultura y Deporte (FPU18/02551). This is a contribution for the Moncloa Campus of International Excellence, “Grupo de Física Nuclear-UCM”, Ref. 910059. Part of the calculations of this work were performed in the “Clúster de Cálculo para Técnicas Físicas”, funded in part by Universidad Complutense de Madrid and in part by EU Regional Funds.BackgroundRecent proposals of high dose rate plans in protontherapy as well as very short proton bunches may pose problems to current beam monitor systems. There is an increasing demand for real-time proton beam monitoring with high temporal resolution, extended dynamic range and radiation hardness. Plastic scintillators coupled to optical fiber sensors have great potential in this context to become a practical solution towards clinical implementation. PurposeIn this work, we evaluate the capabilities of a very compact fast plastic scintillator with an optical fiber readout by a SiPM and electronics sensor which has been used to provide information on the time structure at the nanosecond level of a clinical proton beam. Materials and methodsA 3 x 3 x 3 mm(3) plastic scintillator (EJ-232Q Eljen Technology) coupled to a 3 x 3 mm(2) SiPM (MicroFJ-SMA-30035, Onsemi) has been characterized with a 70 MeV clinical proton beam accelerated in a Proteus One synchrocyclotron. The signal was read out by a high sampling rate oscilloscope (5 GS/s). By exposing the sensor directly to the proton beam, the time beam profile of individual spots was recorded. ResultsMeasurements of detector signal have been obtained with a time sampling period of 0.8 ns. Proton bunch period (16 ns), spot (10 mu s) and interspot (1 ms) time structures could be observed in the time profile of the detector signal amplitude. From this, the RF frequency of the accelerator has been extracted, which is found to be 64 MHz. ConclusionsThe proposed system was able to measure the fine time structure of a clinical proton accelerator online and with ns time resolution.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEComunidad de MadridGobierno de EspañaEU Regional FundsMinisterio de Educación, Cultura y Deportepu

Characterization of the proton pulsed beam at CMAM

In this paper, the technicalities performed to obtain a pulsed beam at the CMAM facility will be explained. The pulsed beam has been characterized with an 8 MeV proton beam, using an existing equipment at CMAM: two pairs of electrostatic plates (RASTER) that deflect the beam, commonly used for homogeneous irradiation of large areas. A pulsed beam is used in many areas such as nuclear physics, material science and, in particular, for proton-therapy medical studies. Rectangular and pyramidal functions have been used to generate different pulses and characterize the response of the RASTER. The results point out that the pulses obtained are suitable for preclinical proton-therapy studies in the FLASH regime, which consists on fractionating the dose in time with short and intense pulses. The set-up for the characterization has been a function generator and a Si-PM outside the chamber

Computación interactiva en la nube con JupyterHub y Kubernetes

El proyecto investiga el posible uso de Kubernetes para desplegar la plataforma de cuadernos de Python JupyterHu

Detailed spectroscopy of doubly magic Sn-132

The structure of the doubly magic Sn-132(50)82 has been investigated at the ISOLDE facility at CERN, populated both by the beta(-) decay of In-132 and beta(-)-delayed neutron emission of In-133. The level scheme of Sn-13(2) is greatly expanded with the addition of 68 gamma transitions and 17 levels observed for the first time in the beta decay. The information on the excited structure is completed by new gamma transitions and states populated in the beta-n decay of In-133. Improved delayed neutron emission probabilities are obtained both for In-132 and In-133. Level lifetimes are measured via the advanced time-delayed beta gamma gamma(t) fast-timing method. An interpretation of the level structure is given based on the experimental findings and the particle-hole configurations arising from core excitations both from the N = 82 and Z = 50 shells, leading to positive- and negative-parity particle-hole multiplets. The experimental information provides new data to challenge the theoretical description of Sn-132

Optimization of the tantalum ore production by control the milling process

Tantalum is a strategic metal with multiple applications in the new technologies. Tantalum deposits are scarce in EU. Thus, more efficient extracting processes are necessary to contribute to major European independency on these critical raw materials. Tantalum occurs mainly in pegmatites and leucogranite deposits and its placers. Europe does not produce tantalum; however, several deposits are susceptible of being exploited if technologies of processing are improved. This work is part of the Optimore Project which aims to develop modelling and control technologies, using advanced sensing and advanced industrial control by using artificial intelligence techniques, for the more efficient and flexible tantalum and tungsten processing from crushing to separation process. In this paper, a preliminary study of characterization of tantalum ores from leucogranite and alluvial deposits is presented to be used as a base for design the milling experiments to optimize the tantalum recovering during the processing. In the ore deposits tantalum appears in solid solution with niobium in complex oxides, which forms low grade aggregates which need to be processed by means of a separation process. Tantalum ores characterised here belong to alluvial placers of pegmatitic origin located in the Bolivian Amazon Craton and to leocogranites of Penuota, in Spain. Ta bearing minerals of the Bolivian placers are mainly from the columbite group minerals. In Penouta microlite is abundant and often it has a zoning characterised by a Nb-rich core followed by a Ta-rich rim of several cm in thickness.Peer ReviewedPostprint (published version

Conectando Física y Matemáticas a través de material docente creado por alumnos

Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasFALSEsubmitte

In vivo production of fluorine-18 in a chicken egg tumor model of breast cancer for proton therapy range verification

Range verification of clinical protontherapy systems via positron-emission tomography (PET) is not a mature technology, suffering from two major issues: insufficient signal from low-energy protons in the Bragg peak area and biological washout of PET emitters. The use of contrast agents including O-18, Zn-68 or Cu-63, isotopes with a high cross section for low-energy protons in nuclear reactions producing PET emitters, has been proposed to enhance the PET signal in the last millimeters of the proton path. However, it remains a challenge to achieve sufficient concentrations of these isotopes in the target volume. Here we investigate the possibilities of O-18-enriched water (18-W), a potential contrast agent that could be incorporated in large proportions in live tissues by replacing regular water. We hypothesize that 18-W could also mitigate the problem of biological washout, as PET (F-18) isotopes created inside live cells would remain trapped in the form of fluoride anions (F-), allowing its signal to be detected even hours after irradiation. To test our hypothesis, we designed an experiment with two main goals: first, prove that 18-W can incorporate enough O-18 into a living organism to produce a detectable signal from F-18 after proton irradiation, and second, determine the amount of activity that remains trapped inside the cells. The experiment was performed on a chicken embryo chorioallantoic membrane tumor model of head and neck cancer. Seven eggs with visible tumors were infused with 18-W and irradiated with 8-MeV protons (range in water: 0.74 mm), equivalent to clinical protons at the end of particle range. The activity produced after irradiation was detected and quantified in a small-animal PET-CT scanner, and further studied by placing ex-vivo tumours in a gamma radiation detector. In the acquired images, specific activity of F-18 (originating from 18-W) could be detected in the tumour area of the alive chicken embryo up to 9 h after irradiation, which confirms that low-energy protons can indeed produce a detectable PET signal if a suitable contrast agent is employed. Moreover, dynamic PET studies in two of the eggs evidenced a minimal effect of biological washout, with 68% retained specific F-18 activity at 8 h after irradiation. Furthermore, ex-vivo analysis of 4 irradiated tumours showed that up to 3% of oxygen atoms in the targets were replaced by O-18 from infused 18-W, and evidenced an entrapment of 59% for specific activity of F-18 after washing, supporting our hypothesis that F- ions remain trapped within the cells. An infusion of 18-W can incorporate O-18 in animal tissues by replacing regular water inside cells, producing a PET signal when irradiated with low-energy protons that could be used for range verification in protontherapy. F-18 produced inside cells remains entrapped and suffers from minimal biological washout, allowing for a sharper localization with longer PET acquisitions. Further studies must evaluate the feasibility of this technique in dosimetric conditions closer to clinical practice, in order to define potential protocols for its use in patients