Characterisation of a Digital Sampling Calorimeter Prototype for Proton Computed Tomography With Electron Beams

Proton CT is a novel imaging modality designed to improve dose planning and treatment monitoring in proton therapy. The precision of the beam of charged particles, like protons, requires accurate diagnostics, to avoid unnecessary irradiation of healthy tissue. CT measurements using photons can be used to determine the range and stopping power of the particles, but with an uncertainty of 2-3% [1]. It is, therefore, preferable to use proton CT, since it provides a more accurate representation of the range of the beam in the patient. Using technology like the ALPIDE (ALICE Pixel Detector) sensor, developed at CERN for high energy physics, a proton CT system is now under development. The ALPIDE is a Monolithic CMOS Active Pixel Sensor with a pixel matrix of 1024 x 512 sensitive pixels, where each pixel measures 29.24 μm x 26.88 μm; giving better resolution and more accurate determination of particle paths. The ALPIDE can also retain a high data rate, resulting in a short scan time. In this thesis, the focus has been on the characterisation of a digital sampling calorimeter prototype. The properties were investigated based on a test beam experiment at DESY using the Electromagnetic Pixel Calorimeter, EPICAL-2, prototype. EPICAL-2 is composed of 48 ALPIDE sensors, consisting of 24 layers, with two ALPIDE sensors and 3 mm of tungsten absorber per layer. This thesis conducts a systematic study of the sensor performance and the shower profiles at various energies for single and multiple electromagnetic showers in one readout frame. The preliminary results of the data analysis show that the prototype performs as a calorimeter should, i.e. the response scales linearly with the energy of the incoming electron.Masteroppgave i fysikkPHYS399MAMN-PHY

Characterisation of a Digital Sampling Calorimeter Prototype for Proton Computed Tomography With Electron Beams

Proton CT is a novel imaging modality designed to improve dose planning and treatment monitoring in proton therapy. The precision of the beam of charged particles, like protons, requires accurate diagnostics, to avoid unnecessary irradiation of healthy tissue. CT measurements using photons can be used to determine the range and stopping power of the particles, but with an uncertainty of 2-3% [1]. It is, therefore, preferable to use proton CT, since it provides a more accurate representation of the range of the beam in the patient. Using technology like the ALPIDE (ALICE Pixel Detector) sensor, developed at CERN for high energy physics, a proton CT system is now under development. The ALPIDE is a Monolithic CMOS Active Pixel Sensor with a pixel matrix of 1024 x 512 sensitive pixels, where each pixel measures 29.24 μm x 26.88 μm; giving better resolution and more accurate determination of particle paths. The ALPIDE can also retain a high data rate, resulting in a short scan time. In this thesis, the focus has been on the characterisation of a digital sampling calorimeter prototype. The properties were investigated based on a test beam experiment at DESY using the Electromagnetic Pixel Calorimeter, EPICAL-2, prototype. EPICAL-2 is composed of 48 ALPIDE sensors, consisting of 24 layers, with two ALPIDE sensors and 3 mm of tungsten absorber per layer. This thesis conducts a systematic study of the sensor performance and the shower profiles at various energies for single and multiple electromagnetic showers in one readout frame. The preliminary results of the data analysis show that the prototype performs as a calorimeter should, i.e. the response scales linearly with the energy of the incoming electron

En sammenlignende studie av prisutvikling på nye og eldre leiligheter i Bergen.

Ved valg av problemstilling og tematikk ønsket vi å se nærmere på noe som var dagsaktuelt, men som også interesserte oss. Valget falt på eiendomsmarkedet og boligers prisutvikling. Formålet med denne masteroppgaven er å undersøke sammenhengen mellom prisutvikling på eldre og nye leiligheter. Med bakgrunn i dette er det valgt ut ett eldre og ett nyere boligområde, for fire av Bergens bydeler. Dette er boligområder med tilsvarende like kvaliteter, for å kunne undersøke hvordan alder spiller inn på prisutvikling. Følgende hovedproblemstilling og underproblemstillinger undersøkes: Hvordan har prisutviklingen vært på nye leiligheter etter ferdigstillelse sammenlignet med eldre leiligheter? I: I hvilken grad kan prisutvikling indikere hvor lenge en leilighet ansees som ny? II: Hvilke tiltak kan påvirke prisutviklingen på en slik måte at leiligheten ansees for ny i en lengre periode? Oppgaven bygger på metodetriangulering. Ved bruk av kvantitativ metode er det samlet inn data i form av eiendomstransaksjoner fra 2005 til utgangen av 2019. Videre har kvalitativ metode vært viktig for å besvare oppgavens underproblemstillinger. Dette i form av intervjuer av eiendomsmeglere og styreledere i de utvalgte boligområdene. Før studiens start hadde vi noen tanker om hva utfallet av studien ville være, men underveis i oppgaven kunne funnene våre indikere noe annet enn vi først antok. For oss gjorde dette at oppgaven ble mer interessant og spennende. Studien avdekker at det er en forskjell i prisutviklingen på nye og eldre leiligheter, hvor denne er høyere for de eldre leilighetene. Dette forutsatt at de har utført tilstrekkelig vedlikehold og utvikling, i form av å tilpasse seg nye krav og forventninger til en bolig. Videre kan man ut fra oppgavens resultater se en sammenheng ved at leiligheter mister sin status som «ny» etter ni år

Diagnostic accuracy of anti-3-[¹⁸F]-FACBC PET/MRI in gliomas

Purpose - The primary aim was to evaluate whether anti-3-[18F]FACBC PET combined with conventional MRI correlated better with histomolecular diagnosis (reference standard) than MRI alone in glioma diagnostics. The ability of anti-3-[18F]FACBC to differentiate between molecular and histopathological entities in gliomas was also evaluated. Methods - In this prospective study, patients with suspected primary or recurrent gliomas were recruited from two sites in Norway and examined with PET/MRI prior to surgery. Anti-3-[18F]FACBC uptake (TBRpeak) was compared to histomolecular features in 36 patients. PET results were then added to clinical MRI readings (performed by two neuroradiologists, blinded for histomolecular results and PET data) to assess the predicted tumor characteristics with and without PET. Results - Histomolecular analyses revealed two CNS WHO grade 1, nine grade 2, eight grade 3, and 17 grade 4 gliomas. All tumors were visible on MRI FLAIR. The sensitivity of contrast-enhanced MRI and anti-3-[18F]FACBC PET was 61% (95%CI [45, 77]) and 72% (95%CI [58, 87]), respectively, in the detection of gliomas. Median TBRpeak was 7.1 (range: 1.4–19.2) for PET positive tumors. All CNS WHO grade 1 pilocytic astrocytomas/gangliogliomas, grade 3 oligodendrogliomas, and grade 4 glioblastomas/astrocytomas were PET positive, while 25% of grade 2–3 astrocytomas and 56% of grade 2–3 oligodendrogliomas were PET positive. Generally, TBRpeak increased with malignancy grade for diffuse gliomas. A significant difference in PET uptake between CNS WHO grade 2 and 4 gliomas (p peak compared to IDH1/2 mutated gliomas (p 18F]FACBC PET to MRI improved the accuracy of predicted glioma grades, types, and IDH status, and yielded 13.9 and 16.7 percentage point improvement in the overall diagnoses for both readers, respectively. Conclusion - Anti-3-[18F]FACBC PET demonstrated high uptake in the majority of gliomas, especially in IDH wildtype gliomas, and improved the accuracy of preoperatively predicted glioma diagnoses

A High-Granularity Digital Tracking Calorimeter Optimized for Proton CT

A typical proton CT (pCT) detector comprises a tracking system, used to measure the proton position before and after the imaged object, and an energy/range detector to measure the residual proton range after crossing the object. The Bergen pCT collaboration was established to design and build a prototype pCT scanner with a high granularity digital tracking calorimeter used as both tracking and energy/range detector. In this work the conceptual design and the layout of the mechanical and electronics implementation, along with Monte Carlo simulations of the new pCT system are reported. The digital tracking calorimeter is a multilayer structure with a lateral aperture of 27 cm × 16.6 cm, made of 41 detector/absorber sandwich layers (calorimeter), with aluminum (3.5 mm) used both as absorber and carrier, and two additional layers used as tracking system (rear trackers) positioned downstream of the imaged object; no tracking upstream the object is included. The rear tracker’s structure only differs from the calorimeter layers for the carrier made of ∼200 μm carbon fleece and carbon paper (carbon-epoxy sandwich), to minimize scattering. Each sensitive layer consists of 108 ALICE pixel detector (ALPIDE) chip sensors (developed for ALICE, CERN) bonded on a polyimide flex and subsequently bonded to a larger flexible printed circuit board. Beam tests tailored to the pCT operation have been performed using high-energetic (50–220 MeV/u) proton and ion beams at the Heidelberg Ion-Beam Therapy Center (HIT) in Germany. These tests proved the ALPIDE response independent of occupancy and proportional to the particle energy deposition, making the distinction of different ion tracks possible. The read-out electronics is able to handle enough data to acquire a single 2D image in few seconds making the system fast enough to be used in a clinical environment. For the reconstructed images in the modeled Monte Carlo simulation, the water equivalent path length error is lower than 2 mm, and the relative stopping power accuracy is better than 0.4%. Thanks to its ability to detect different types of radiation and its specific design, the pCT scanner can be employed for additional online applications during the treatment, such as in-situ proton range verification

A high-granularity digital tracking calorimeter optimized for proton CT

A typical proton CT (pCT) detector comprises a tracking system, used to measure the proton position before and after the imaged object, and an energy/range detector to measure the residual proton range after crossing the object. The Bergen pCT collaboration was established to design and build a prototype pCT scanner with a high granularity digital tracking calorimeter used as both tracking and energy/range detector. In this work the conceptual design and the layout of the mechanical and electronics implementation, along with Monte Carlo simulations of the new pCT system are reported. The digital tracking calorimeter is a multilayer structure with a lateral aperture of 27 cm × 16.6 cm, made of 41 detector/absorber sandwich layers (calorimeter), with aluminum (3.5 mm) used both as absorber and carrier, and two additional layers used as tracking system (rear trackers) positioned downstream of the imaged object; no tracking upstream the object is included. The rear tracker’s structure only differs from the calorimeter layers for the carrier made of ∼200 μm carbon fleece and carbon paper (carbon-epoxy sandwich), to minimize scattering. Each sensitive layer consists of 108 ALICE pixel detector (ALPIDE) chip sensors (developed for ALICE, CERN) bonded on a polyimide flex and subsequently bonded to a larger flexible printed circuit board. Beam tests tailored to the pCT operation have been performed using high-energetic (50–220 MeV/u) proton and ion beams at the Heidelberg Ion-Beam Therapy Center (HIT) in Germany. These tests proved the ALPIDE response independent of occupancy and proportional to the particle energy deposition, making the distinction of different ion tracks possible. The read-out electronics is able to handle enough data to acquire a single 2D image in few seconds making the system fast enough to be used in a clinical environment. For the reconstructed images in the modeled Monte Carlo simulation, the water equivalent path length error is lower than 2 mm, and the relative stopping power accuracy is better than 0.4%. Thanks to its ability to detect different types of radiation and its specific design, the pCT scanner can be employed for additional online applications during the treatment, such as in-situ proton range verification

A high-granularity digital tracking calorimeter optimized for proton CT

A typical proton CT (pCT) detector comprises a tracking system, used to measure the proton position before and after the imaged object, and an energy/range detector to measure the residual proton range after crossing the object. The Bergen pCT collaboration was established to design and build a prototype pCT scanner with a high granularity digital tracking calorimeter used as both tracking and energy/range detector. In this work the conceptual design and the layout of the mechanical and electronics implementation, along with Monte Carlo simulations of the new pCT system are reported. The digital tracking calorimeter is a multilayer structure with a lateral aperture of 27 cm × 16.6 cm, made of 41 detector/absorber sandwich layers (calorimeter), with aluminum (3.5 mm) used both as absorber and carrier, and two additional layers used as tracking system (rear trackers) positioned downstream of the imaged object; no tracking upstream the object is included. The rear tracker’s structure only differs from the calorimeter layers for the carrier made of ∼200 μm carbon fleece and carbon paper (carbon-epoxy sandwich), to minimize scattering. Each sensitive layer consists of 108 ALICE pixel detector (ALPIDE) chip sensors (developed for ALICE, CERN) bonded on a polyimide flex and subsequently bonded to a larger flexible printed circuit board. Beam tests tailored to the pCT operation have been performed using high-energetic (50–220 MeV/u) proton and ion beams at the Heidelberg Ion-Beam Therapy Center (HIT) in Germany. These tests proved the ALPIDE response independent of occupancy and proportional to the particle energy deposition, making the distinction of different ion tracks possible. The read-out electronics is able to handle enough data to acquire a single 2D image in few seconds making the system fast enough to be used in a clinical environment. For the reconstructed images in the modeled Monte Carlo simulation, the water equivalent path length error is lower than 2 mm, and the relative stopping power accuracy is better than 0.4%. Thanks to its ability to detect different types of radiation and its specific design, the pCT scanner can be employed for additional online applications during the treatment, such as in-situ proton range verification

Measurement of (anti)alpha production in central Pb-Pb collisions at sNN\sqrt{s_{\rm NN}} = 5.02 TeV

International audienceIn this letter, measurements of (anti)alpha production in central (0$-$10%) Pb$-$Pb collisions at a center-of-mass energy per nucleon$-$nucleon pair of $\sqrt{s_{\rm NN}}$ = 5.02 TeV are presented, including the first measurement of an antialpha transverse-momentum spectrum. Owing to its large mass, (anti)alpha production yields and transverse-momentum spectra are of particular interest because they provide a stringent test of particle production models. The averaged antialpha and alpha spectrum is included into a common blast-wave fit with lighter particles, indicating that the (anti)alpha also participates in the collective expansion of the medium created in the collision. A blast-wave fit including only protons, (anti)alpha, and other light nuclei results in a similar flow velocity as the fit that includes all particles. A similar flow velocity, but a significantly larger kinetic freeze-out temperature is obtained when only protons and light nuclei are included in the fit. The coalescence parameter $B_4$ is well described by calculations from a statistical hadronization model but significantly underestimated by calculations assuming nucleus formation via coalescence of nucleons. Similarly, the (anti)alpha-to-proton ratio is well described by the statistical hadronization model. On the other hand, coalescence calculations including approaches with different implementations of the (anti)alpha substructure tend to underestimate the data

Studying the interaction between charm and light-flavor mesons

International audienceThe two-particle momentum correlation functions between charm mesons ($\mathrm{D^{*\pm}}$ and $\mathrm{D}^\pm$) and charged light-flavor mesons ($\pi^{\pm}$ and K$^{\pm}$) in all charge-combinations are measured for the first time by the ALICE Collaboration in high-multiplicity proton-proton collisions at a center-of-mass energy of $\sqrt{s} =13$ TeV. For $\mathrm{DK}$ and $\mathrm{D^*K}$ pairs, the experimental results are in agreement with theoretical predictions of the residual strong interaction based on quantum chromodynamics calculations on the lattice and chiral effective field theory. In the case of $\mathrm{D}\pi$ and $\mathrm{D^*}\pi$ pairs, tension between the calculations including strong interactions and the measurement is observed. For all particle pairs, the data can be adequately described by Coulomb interaction only, indicating a shallow interaction between charm and light-flavor mesons. Finally, the scattering lengths governing the residual strong interaction of the $\mathrm{D}\pi$ and $\mathrm{D^*}\pi$ systems are determined by fitting the experimental correlation functions with a model that employs a Gaussian potential. The extracted values are small and compatible with zero