Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering ...process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming γ energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of detection, from the beam particle entering a phantom to the event classification, is simulated using FLUKA. The range determination is later estimated from the reconstructed image obtained from a two and three-event algorithm based on Maximum Likelihood Expectation Maximization. The neutron background and random coincidences due to a therapeutic-like time structure are analyzed for mono-energetic proton beams. The time structure of the beam is included in the simulations, which will affect the rate of particles entering the detector.
We present seven new cases of patients with Crohn disease who developed lesions clinically compatible with amicrobial pustulosis of the flexures during their treatment with anti‐tumour necrosis ...factor therapy.
A first prototype of a Compton camera based on continuous scintillator crystals coupled to silicon photomultiplier (SiPM) arrays has been successfully developed and operated. The prototype is made of ...two detector planes. The first detector is made of a continuous 16×18×5mm3 LaBr3 crystal coupled to a 16-elements SiPM array. The elements have a size of 3×3mm 3 in a 4.5×4.05mm2 pitch. The second detector, selected by availability, consists of a continuous 16×18×5mm3 LYSO crystal coupled to a similar SiPM array. The SPIROC1 ASIC is employed in the readout electronics. Data have been taken with a 22Na source placed at different positions and images have been reconstructed with the simulated one-pass list-mode (SOPL) algorithm.
Detector development for the construction of a second prototype with three detector planes is underway. LaBr3 crystals of 32×36mm2 size and 5/10mm thickness have been acquired and tested with a PMT. The resolution obtained is 3.5% FWHM at 511keV. Each crystal will be coupled to four MPPC arrays. Different options are being tested for the prototype readout.
The ATLAS community is facing the last stages prior to the production of the upgraded silicon strip Inner Tracker for the High-Luminosity Large Hadron Collider. An extensive Market Survey was carried ...out in order to evaluate the capability of different foundries to fabricate large area silicon strip sensors, satisfying the ATLAS specifications. The semiconductor manufacturing company, Infineon Technologies AG, was one of the two foundries, along with Hamamatsu Photonics K.K., that reached the last stage of the evaluation for the production of the new devices. The full prototype wafer layout for the participation of Infineon, called ATLAS17LS-IFX, was designed using a newly developed Python-based Automatic Layout Generation Tool, able to rapidly design sensors with different characteristics and dimensions based on a few geometrical and technological input parameters. This work presents the layout design process and the results obtained from the evaluation of the new Infineon large area sensors before and after proton and neutron irradiations, up to fluences expected in the inner layers of the future ATLAS detector.
. Background events are one of the most relevant contributions to image degradation in Compton camera imaging for hadron therapy treatment monitoring. A study of the background and its contribution ...to image degradation is important to define future strategies to reduce the background in the system.
. In this simulation study, the percentage of different kinds of events and their contribution to the reconstructed image in a two-layer Compton camera have been evaluated. To this end, GATE v8.2 simulations of a proton beam impinging on a PMMA phantom have been carried out, for different proton beam energies and at different beam intensities.
. For a simulated Compton camera made of Lanthanum (III) Bromide monolithic crystals, coincidences caused by neutrons arriving from the phantom are the most common type of background produced by secondary radiations in the Compton camera, causing between 13% and 33% of the detected coincidences, depending on the beam energy. Results also show that random coincidences are a significant cause of image degradation at high beam intensities, and their influence in the reconstructed images is studied for values of the time coincidence windows from 500 ps to 100 ns.
. Results indicate the timing capabilities required to retrieve the fall-off position with good precision. Still, the noise observed in the image when no randoms are considered make us consider further background rejection methods.
The IRIS group at IFIC Valencia is developing a three-layer Compton camera for treatment monitoring in proton therapy. The system is composed of three detector planes, each made of a Formula: see ...text monolithic crystal coupled to a SiPM array. Having obtained successful results with the first prototype (MACACO) that demonstrated the feasibility of the proposed technology, a second prototype (MACACO II) with improved performance has been developed, and is the subject of this work. The new system has an enhanced detector energy resolution which translates into a higher spatial resolution of the telescope. The image reconstruction method has also been improved with an accurate model of the sensitivity matrix. The device has been tested with high energy photons at the National Accelerator Centre (CNA, Seville). The tests involved a proton beam of 18 MeV impinging on a graphite target, to produce 4.4 MeV photons. Data were taken at different system positions of the telescope with the first detector at 65 and 160 mm from the target, and at different beam intensities. The measurements allowed successful reconstruction of the photon emission distribution at two target positions separated by 5 mm in different telescope configurations. This result was obtained both with data recorded in the first and second telescope planes (two interaction events) and, for the first time in beam experiments, with data recorded in the three planes (three interaction events).
The ATLAS collaboration is designing the all-silicon Inner Tracker (ITk) that will operate in the HL-LHC replacing the current design. The silicon microstrip sensors for the barrel and the endcap ...regions in the ITk are fabricated in 6 inch, p-type, float-zone wafers, where large-area strip sensor designs are laid out together with a number of miniature sensors. The radiation tolerance and specific system issues like the need for slim edge of 450 μm have been tested with square shaped sensors intended for the barrel part of the tracker. This work presents the design of the first full size silicon microstrip sensor for the endcap region with a slim edge of 450 μm. The strip endcaps will consist of several wheels with two layers of silicon strip sensors each. The strips have to lie along the azimuthal direction, apart from a small stereo angle rotation (20 mrad on each side, giving 40 mrad total) for measuring the second coordinate of tracks. This stereo angle is built into the strip layout of the sensor and, in order to avoid orphan strips, the sensor edges are inclined by the stereo angle. On top of this, the top and bottom edges are designed as arcs to have equal length strips. Together with the design of this new Stereo Annulus sensor, we will report on the initial measurements of the leakage current as a function of bias voltage, after dicing, and the depletion voltage.
The Quality Control (QC) of pre-production strip sensors for the Inner Tracker (ITk) of the ATLAS Inner Detector upgrade has finished, and the collaboration has embarked on the QC test programme for ...production sensors. This programme will last more than 3 years and comprises the evaluation of approximately 22000 sensors. 8 Types of sensors, 2 barrel and 6 endcap, will be measured at many different collaborating institutes. The sustained throughput requirement of the combined QC processes is around 500 sensors per month in total. Measurement protocols have been established and acceptance criteria have been defined in accordance with the terms agreed with the supplier. For effective monitoring of test results, common data file formats have been agreed upon across the collaboration. To enable evaluation of test results produced by many different test setups at the various collaboration institutes, common algorithms have been developed to collate, evaluate, plot and upload measurement data. This allows for objective application of pass/fail criteria and compilation of corresponding yield data. These scripts have been used to process the data of more than 3000 sensors so far, and have been instrumental for identification of faulty sensors and monitoring of QC testing progress.
The characterization of a PET detector head based on continuous LYSO crystals and silicon photomultiplier (SiPM) arrays as photodetectors has been carried out for its use in the development of a ...small animal PET prototype. The detector heads are composed of a continuous crystal and a SiPM matrix with 64 pixels in a common substrate, fabricated specifically for this project. Three crystals of 12 mm × 12 mm × 5 mm size with different types of painting have been tested: white, black and black on the sides but white on the back of the crystal. The best energy resolution, obtained with the white crystal, is 16% FWHM. The detector response is linear up to 1275 keV. Tests with different position determination algorithms have been carried out with the three crystals. The spatial resolution obtained with the center of gravity algorithm is around 0.9 mm FWHM for the three crystals. As expected, the use of this algorithm results in the displacement of the reconstructed position toward the center of the crystal, more pronounced in the case of the white crystal. A maximum likelihood algorithm has been tested that can reconstruct correctly the interaction position of the photons also in the case of the white crystal.
► Organic system was more energetically efficient than conventional or conservation. ► Cereal monoculture was an energetically unviable practice, especially in dry seasons. ► Chemical fertilization ...was low efficient in arid and semi-arid environments. ► Crop rotations, mainly those including leguminous crops, increased energy efficiency.
This study was conducted to determine how energy balances of crop production are affected by three farming systems (conventional, conservation with no tillage, and organic) and four barley-based crop rotations (barley followed by fallow B–F, barley in rotation with vetch B–V or sunflower B–S, and barley monoculture B–B), under the semi-arid conditions of central Spain over a 15-year period (1993/94–2007/08). As inputs, the factors supplied and controlled by farmers were considered. The energy balance variables considered were net energy produced (energy output minus energy input), the energy output/input ratio, and energy productivity (crop yield per unit energy input). The total energy inputs were 3.0–3.5 times greater in the conservation (10.4
GJ
ha
−1
year
−1) and conventional (11.7
GJ
ha
−1
year
−1) systems than in the organic system (3.41
GJ
ha
−1
year
−1). With respect to the crop rotations, the total energy inputs varied from 6.19
GJ
ha
−1
year
−1 for B–F to 11.7
GJ
ha
−1
year
−1 for B–B. The lowest energy use corresponded to B–F in the organic system (2.56
GJ
ha
−1
year
−1), and the highest to B–B in the conventional and conservation systems (16.3 and 14.9
GJ
ha
−1
year
−1, respectively). Energy output was lowest in the organic system (17.9
GJ
ha
−1
year
−1), a consequence of the lower barley grain and vetch hay yields. With respect to the crop rotation, the order followed B–B (19.1
GJ
ha
−1
year
−1)
≈
B–F
<
B–S
<
B–V (29.3
GJ
ha
−1
year
−1, 53% higher). All the energy efficiency variables analysed had the highest values for the organic system (net energy of 14.5
GJ
ha
−1
year
−1, output/input ratio of 5.36 and energy productivity of 400
kg
GJ
−1). No differences were recorded between the conventional and conservation managements. This indicates that, in terms of energy efficiency, the viability of organic systems (low-input practices) under semi-arid conditions, compared to farming systems requiring agrochemicals (conventional and conservation), would appear more recommendable. Cereal monoculture (B–B), independent of the crop management employed, is an energetically unfavourable practice, especially in the driest seasons. However, crop rotations, especially those including a leguminous plant, increase energy efficiency.
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