The characterization of high intensity charged particle beams at medical accelerators poses several challenges. In this work, we investigate the use of a highly segmented CMOS Image Sensors (CIS), an ...MT9T031 from Aptina, as a way to study the spatial homogeneity and the time stability of the beam. The approach relies on the possibility to define many adjacent small regions that perform the radiation flux measurement with sufficient precision (below 1%) to extract the spatial structure of the beam. The device has been exposed to a 10 MeV therapeutic electron beam at Santa Maria Hospital (Terni, Italy) to measure the electron flux at a distance of 140 cm. The whole sensor, using a non-linear calibration, has measured the value of the flux, then the segmentation approach has been applied to study the spatial structure of the beam. Concerning the variation in time, the current limitation of a rolling shutter CIS limits the capability to disentangle the time structure of the beam. However, in light of the possibility to obtain some CIS with the new global shutter architecture, having integration time of the order of a few tens of microseconds, the measurement procedure has been implemented and tested using ∼1Hz frequency frame-rate, to study its limits. Uncertainty of the order of 0.5% has been reached for measurement of both spatial and time beam homogeneity.
•CIS devices could be used as spatially very precise ionizing radiation detectors.•Non-linear calibration could be used to keep uncertainty at the 1% level.•The intrinsic homogeneous response of CIS to ionizing radiation over the whole surface open the way for uncertainty disentangling procedures.
Radioguided surgery (RGS) is a medical practice which thanks to a radiopharmaceutical tracer and a probe allows the surgeon to identify tumor residuals up to a millimetric resolution in real-time. ...The employment of β− emitters, instead of γ or β+, reduces background from healthy tissues, administered activity to the patient, and medical exposure. In a previous work the possibility of using a CMOS Imager (Aptina MT9V011), initially designed for visible light imaging, to detect β− from 90Y or 90Sr sources has been established. Because of its possible application as counting probe in RGS, the performances of MT9V011 in clinical-like conditions were studied.11This work financed by Istituto Nazionale Fisica Nucleare, Italy, project CHIR2, and partially supported by Universitá degli Studi di Perugia, Italy , Fondo Ricerca di Base 2017, project SEISIPO.
Through horizontal scans on a collimated 90Sr source of different sizes (1, 3, 5, 7 mm), we have determined relationships between scan fit parameters and the source dimension, namely A quadratic correlation and a linear dependency of, respectively, signal integrated over scan interval, and maximum signal against source diameter, are determined. Horizontal scan measurements on a source, interposing collimators of different size, aim to determine relationships or correlations between scan fit parameters and source dimension. A quadratic correlation and a linear dependency of, respectively, signal integrated over scan interval, and maximum signal against source diameter are determined.
In order to get closer to clinical conditions, agar–agar phantoms containing 90Y with different dimensions and activities were prepared. A 90Y phantom is characterized by a central spot and a ring all around, for simulating both signal (tumor) and background (surrounding healthy tissue). The relationship found between scan maximum and 90Sr source diameter is then exploited to extract the concentration ratio between spot and external ring of the 90Y phantom. This observable, defined as the ratio between the tumor and the nearby healthy tissues uptake simulates the Tumor-to-Non-tumor Ratio (TNR). With the aim of evaluating the sensor’s ability to discriminate signal from background relying on the significance parameter, a further 90Y phantom, featuring a well-known and clinical-like activity will mimic the signal only condition. This result is used to extrapolate to different source sizes, after having estimated the background for various TNR. The obtained significance values suggest that the MT9V011 sensor is capable of distinguishing a signal from an estimated background, depending on the interplay among TNR, acquisition time and tumor diameter.
•A CMOS imager has been used as sensor for beta- emission from isotopes (90Y) of interest in Radioguided surgery.•Using a position scan a correlation between the source dimension and the shape of the response has been found.•The sensitivity of the sensor to tumor detection has been determined by studying the interplay among TNR, acquisition time and tumor diameter.
In medical radiation dosimetry, the use of small photon fields is almost a prerequisite for high precision localized dose delivery to delineated target volumes. The accurate measurement of standard ...dosimetric quantities in such situations depends on the size of the detector with respect to the field dimensions. Polycrystalline diamond devices with 3-dimensional structures are produced by using laser pulses to create graphitic paths in the diamond bulk. By fabricating very narrow and close-by columnar electrodes perpendicular to the detector surface, it is possible to create arrays of 3-D cells (pixels) with a very small sensitive volume. In order to present a solution to the problem of the detector size for small field dosimetry the 3-D technology aims to a new highly segmented larger polycrystalline diamond dosimeter to obtain field profiles in a single measurement, reducing the uncertainty of the delivered dose. To this purpose a 3D all carbon detector with an array of 9 3-D pixels has been produced. Due to the heterogeneous structure of the polycrystalline diamond substrate, it was necessary to study the response of each pixel under a standard field photon beam (10 x 10 cm2). For 6 pixels of the array was demonstrated that they present different sensitivities to the radiation beam, but the response is linear and stable hence different calibration factors can be applied to obtain an overall detector response and reduce the uncertainty of the delivered dose.
Medical procedures where real-time X-ray imaging is needed have rapidly increased in number in the past decades. Consequently, the personnel dosimetry for medical staff has become more important, ...also in light of the revision of worker safety regulations. Detailed knowledge of the dose-rate is needed to reduce the total absorbed dose during a single procedure. Real-time monitoring through wearable active devices would greatly facilitate this task. In this work, we will present the characterization of the RAPID wireless device (based on CMOS imager as X-ray sensing detector) in clinical conditions, with PMMA phantoms. The prototype has shown the capability to measure dose-rates with a frequency in the range of few Hz, and an uncertainty smaller than 10%.
In 2012, 14 Italian institutions participating in LHC Experiments won a grant from the Italian Ministry of Research (MIUR), with the aim of optimising analysis activities, and in general the Tier2 ...Tier3 infrastructure. We report on the activities being researched upon, on the considerable improvement in the ease of access to resources by physicists, also those with no specific computing interests. We focused on items like distributed storage federations, access to batch-like facilities, provisioning of user interfaces on demand and cloud systems. R&D on next-generation databases, distributed analysis interfaces, and new computing architectures was also carried on. The project, ending in the first months of 2016, will produce a white paper with recommendations on best practices for data-analysis support by computing centers.
•Radio Guided Surgery (RGS) based on βradiation extends its range of application.•PET radiotracers can be exploited as tumor marker enabling complete resection.•RGS based on β-probe and ...68 Ga-emitters is for neuroendocrine and prostate cancers.
Radio Guided Surgery (RGS) is a technique that helps the surgeon to achieve an as complete as possible tumor resection, thanks to the intraoperative detection of particles emitted by a radio tracer that bounds to tumoral cells.
In the last years, a novel approach to this technique has been proposed that, exploiting β- emitting radio tracers, overtakes some limitations of established γ-RGS.
In this context, a first prototype of an intraoperative β particle detector, based on a high light yield and low density organic scintillator, has been developed and characterised on pure β- emitters, like 90Y. The demonstrated very high efficiency to β- particles, together with the remarkable transparency to photons, suggested the possibility to use this detector also with β+ emitting sources, that have plenty of applications in nuclear medicine. In this paper, we present upgrades and optimisations performed to the detector to reveal such particles.
Laboratory measurement have been performed on liquid Ga68 source, and were used to validate and tune a Monte Carlo simulation.
The upgraded detector has an ~80% efficiency to electrons above ~110keV, reaching a plateau value of ~95%. At the same time, the probe is substantially transparent to photons below ~200keV, reaching a plateau value of ~3%.
The new prototype seems to have promising characteristics to perform RGS also with β+ emitting isotopes.
In a carbon ion treatment the nuclear fragmentation of both target and beam projectiles impacts on the dose released on the tumor and on the surrounding healthy tissues. Carbon ion fragmentation ...occurring inside the patient body has to be studied in order to take into account this contribution. These data are also important for the development of the range monitoring techniques with charged particles. The production of charged fragments generated by carbon ion beams of 115-353 MeV/u kinetic energy impinging on carbon, oxygen, and hydrogen targets has been measured at the CNAO particle therapy center (Pavia, Italy). The use of thin targets of graphite (C), PMMA (C 2 O 5 H 8 ) and polyvinyl-toluene plastic scintillator (PS), <inline-formula> <tex-math notation="LaTeX">{\text{C}}_{b}{\text{H}}_{a} </tex-math></inline-formula> allowed to measure fragments production cross sections, exploiting a time-of-flight (ToF) technique. PS detectors have been used to perform the ToF measurements, while LYSO crystals have been used for the deposited energy measurement and to perform particle identification. Cross sections have been measured at 90° and 60° with respect to the beam direction. The measured proton, deuteron, and triton differential production cross sections on C, O, and H, obtained exploiting the target subtraction strategy, are presented here as a function of the fragment kinetic energy.
Charged Particle Therapy (CPT) is a powerful radiotherapy technique for the treatment of deep-seated tumours characterized by a large dose released in the Bragg peak area (corresponding to the tumour ...region) and a small dose delivered to the surrounding healthy tissues. The precise measurement of the fragments produced in the nuclear interactions of charged particle beams with patient tissues is a crucial task to improve the clinical treatment plans. The FOOT (FragmentatiOn Of Target) experiment is an international project, funded by the Istituto Nazionale di Fisica Nucleare (INFN), aimed to study the dose released by the tissues and particle beams fragmentation. The target (16O, 12C) fragmentation induced by 150-400 MeV/n proton beams will be studied via the inverse kinematic approach, where 16O and 12C therapeutic beams collide on graphite and hydrocarbon target to provide the cross section on Hydrogen. A table-top detector is being developed and it includes a drift chamber as a beam monitor upstream of the target to measure the beam direction, a magnetic spectrometer based on silicon pixel and strip detectors, a scintillating crystal calorimeter able to stop the heavier produced fragments, and a ΔE detector, with TOF capability, for the particle identification. A setup based on the concept of the “Emulsion Cloud Chamber”, coupled with the interaction region of the electronic FOOT setup, will complement the physics program by measuring lighter charged fragments to extend the angular acceptance up to about 70 degrees. In this work, the experimental design and the requirements of the FOOT experiment will be discussed and preliminary results on the emulsion spectrometer tests will be presented.
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