1,633 research outputs found

    EndoTOFPET-US a Novel Multimodal Tool for Endoscopy and Positron Emission Tomography

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    The EndoTOFPET-US project aims to jointly exploit Time-Of-Flight Positron Emission Tomography (TOFPET) and ultrasound endoscopy with a multi-modal instrument for the development of new biomarkers for pancreas and prostate oncology. The paper outlines the functionality of the proposed instrument and the challenges for its realization. The high level of miniaturization and integration poses strong demands to the fields of scintillating crystallography, ultra-fast photon detection, highly integrated electronics and system integration. Solutions are presented to obtain a coincidence time resolution better than 200 ps and a spatial resolution of ~1 mm with an asymmetric TOFPET detector. A tracking system with better than 1 mm spatial resolution precision enables the online alignment of the system. The detector design, the production and test status of the single detecto

    Influence of X-ray Irradiation on the Properties of the Hamamatsu Silicon Photomultiplier S10362-11-050C

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    We have investigated the effects of X-ray irradiation to doses of 0, 200 Gy, 20 kGy, 2 MGy, and 20 MGy on the Hamamatsu silicon-photomultiplier (SiPM) S10362-11-050C. The SiPMs were irradiated without applied bias voltage. From current-voltage, capacitance/conductance-voltage, -frequency, pulse-shape, and pulse-area measurements, the SiPM characteristics below and above breakdown voltage were determined. Significant changes of some SiPM parameters are observed. Up to a dose of 20 kGy the performance of the SiPMs is hardly affected by X-ray radiation damage. For doses of 2 and 20 MGy the SiPMs operate with hardly any change in gain, but with a significant increase in dark-count rate and cross-talk probability.Comment: 21 pages,30 figure

    SiPM Signal Processing via Multiple Linear Regression

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    This paper presents a novel approach using multiple linear regression to process transient signals from silicon photomultipliers. The method provides excellent noise suppression and pulse detection in scenarios with a high pulse count rate and superimposed pulses. Insights into its implementation and benchmark results are presented. We also show how this approach can be used to automatically detect the pulse shape from a given transient signal, providing good detection for count rates up to 90MHz. Experimental data are used to present an application where this algorithm improves charge spectrum resolution by an order of magnitude

    Radiation Hardness of a Wide Spectral Range SiPM with Quasi-Spherical Junction

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    New pixel geometries are on the rise to achieve high sensitivity in near-infrared wavelengths with silicon photomultipliers (SiPMs). We test prototypes of the tip avalanche photo-diodes, which feature a quasi-spherical p-n junction and a high photodetection efficiency over a wide spectral range, and analyze the performance after neutron irradiation. The observed increase in dark count rate is significantly smaller than for a SiPM with a conventional design, indicating a good radiation hardness of the pixel geometry.Comment: 8 pages, 7 figures. Submitted to NIM Proceedings. This work was presented at the NDIP20 conferenc

    Study of depth-dependent charge collection profiles in irradiated pad diodes

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    In this work, charge collection profiles of non-irradiated and irradiated 150 őľ\mum pp-type pad diodes were measured using a 5.2 GeV electron beam traversing the diode parallel to the readout electrode. Four diodes were irradiated to 1 MeV neutron equivalent fluences of 2, 4, 8, and 12E15 {cm}^{-2} with 23 MeV protons. The Charge Collection Efficiency profiles as a function of depth are extracted by unfolding the data. The results of the measurements are compared to the simulation using three radiation damage models from literature which were tuned to different irradiation types and fluences

    Characterization studies of Silicon Photomultipliers and crystals matrices for a novel time of flight PET detector

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    This paper describes the characterization of crystal matrices and silicon photomultiplier arrays for a novel Positron Emission Tomography (PET) detector, namely the external plate of the EndoTOFPET-US system. The EndoTOFPET-US collaboration aims to integrate Time-Of-Flight PET with ultrasound endoscopy in a novel multimodal device, capable to support the development of new biomarkers for prostate and pancreatic tumors. The detector consists in two parts: a PET head mounted on an ultrasound probe and an external PET plate. The challenging goal of 1 mm spatial resolution for the PET image requires a detector with small crystal size, and therefore high channel density: 4096 LYSO crystals individually readout by Silicon Photomultipliers (SiPM) make up the external plate. The quality and properties of these components must be assessed before the assembly. The dark count rate, gain, breakdown voltage and correlated noise of the SiPMs are measured, while the LYSO crystals are evaluated in terms of light yield and energy resolution. In order to effectively reduce the noise in the PET image, high time resolution for the gamma detection is mandatory. The Coincidence Time Resolution (CTR) of all the SiPMs assembled with crystals is measured, and results show a value close to the demanding goal of 200 ps FWHM. The light output is evaluated for every channel for a preliminary detector calibration, showing an average of about 1800 pixels fired on the SiPM for a 511 keV interaction. Finally, the average energy resolution at 511 keV is about 13 %, enough for effective Compton rejection.Comment: 12 pages, 31 figure

    Investigation of high resistivity p-type FZ silicon diodes after 60Co {\gamma}-irradiation

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    In this work, the effects of 60^\text{60}Co ő≥\gamma-ray irradiation on high resistivity pp-type diodes have been investigated. The diodes were exposed to dose values of 0.1, 0.2, 1, and \SI{2}{\mega Gy}. Both macroscopic (II--VV, CC--VV) and microscopic (Thermally Stimulated Current~(TSC)) measurements were conducted to characterize the radiation-induced changes. The investigated diodes were manufactured on high resistivity pp-type Float Zone (FZ) silicon and were further classified into two types based on the isolation technique between the pad and guard ring: pp-stop and pp-spray. After irradiation, the macroscopic results of current-voltage and capacitance-voltage measurements were obtained and compared with existing literature data. Additionally, the microscopic measurements focused on the development of the concentration of different radiation-induced defects, including the boron interstitial and oxygen interstitial (Bi_\text{i}Oi_\text{i}) complex, the carbon interstitial and oxygen interstitial Ci_\text{i}Oi_\text{i} defect, the H40K, and the so-called IP‚ąó_\text{P}^*. To investigate the thermal stability of induced defects in the bulk, isochronal annealing studies were performed in the temperature range of \SI{80}{\celsius} to \SI{300}{\celsius}. These annealing processes were carried out on diodes irradiated with doses of 1 and \SI{2}{\mega Gy} and the corresponding TSC spectra were analysed. Furthermore, in order to investigate the unexpected results observed in the CC-VV measurements after irradiation with high dose values, the surface conductance between the pad and guard ring was measured as a function of both dose and annealing temperature

    Investigation of the Boron removal effect induced by 5.5 MeV electrons on highly doped EPI- and Cz-silicon

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    This study focuses on the properties of the Bi_\text{i}Oi_\text{i} (interstitial Boron~-~interstitial Oxygen) and Ci_\text{i}Oi_\text{i} (interstitial Carbon~-~interstitial Oxygen) defect complexes by \SI{5.5}{\mega\electronvolt} electrons in low resistivity silicon. Two different types of diodes manufactured on p-type epitaxial and Czochralski silicon with a resistivity of about 10~ő©‚čÖ\Omega\cdotcm were irradiated with fluence values between \SI{1e15}{\per\square\centi\meter} and \SI{6e15}{\per\square\centi\meter}. Such diodes cannot be fully depleted and thus the accurate evaluation of defect concentrations and properties (activation energy, capture cross-section, concentration) from Thermally Stimulated Currents (TSC) experiments alone is not possible. In this study we demonstrate that by performing Thermally Stimulated Capacitance (TS-Cap) experiments in similar conditions to TSC measurements and developing theoretical models for simulating both types of Bi_\text{i}Oi_\text{i} signals generated in TSC and TS-Cap measurements, accurate evaluations can be performed. The changes of the position-dependent electric field, the effective space charge density NeffN_\text{eff} profile as well as the occupation of the Bi_\text{i}Oi_\text{i} defect during the electric field dependent electron emission, are simulated as a function of temperature. The macroscopic properties (leakage current and NeffN_\text{eff}) extracted from current-voltage and capacitance-voltage measurements at \SI{20}{\celsius} are also presented and discusse

    Safety of extended interval dosing immune checkpoint inhibitors:a multicenter cohort study

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    BACKGROUND: Real-life spectrum and survival implications of immune-related adverse events (irAEs) in patients treated with extended interval dosing (ED) immune checkpoint inhibitors (ICIs) are unknown. METHODS: Characteristics of 812 consecutive solid cancer patients who received at least 1 cycle of ED monotherapy (pembrolizumab 400‚ÄČmg Q6W or nivolumab 480‚ÄČmg Q4W) after switching from canonical interval dosing (CD; pembrolizumab 200‚ÄČmg Q3W or nivolumab 240‚ÄČmg Q2W) or treated upfront with ED were retrieved. The primary objective was to compare irAEs patterns within the same population (before and after switch to ED). irAEs spectrum in patients treated upfront with ED and association between irAEs and overall survival were also described. RESULTS: A total of 550 (68%) patients started ICIs with CD and switched to ED. During CD, 225 (41%) patients developed any grade and 17 (3%) G3 or G4 irAEs; after switching to ED, any grade and G3 or G4 irAEs were experienced by 155 (36%) and 20 (5%) patients. Switching to ED was associated with a lower probability of any grade irAEs (adjusted odds ratio [aOR] = 0.83, 95% confidence interval [CI] = 0.64 to 0.99; P‚ÄČ=‚ÄČ.047), whereas no difference for G3 or G4 events was noted (aOR = 1.55, 95% CI = 0.81 to 2.94; P‚ÄČ=‚ÄČ.18). Among patients who started upfront with ED (n‚ÄČ=‚ÄČ232, 32%), 107 (41%) developed any grade and 14 (5%) G3 or G4 irAEs during ED. Patients with irAEs during ED had improved overall survival (adjusted hazard ratio [aHR] = 0.53, 95% CI = 0.34 to 0.82; P‚ÄČ=‚ÄČ.004 after switching; aHR = 0.57, 95% CI = 0.35 to 0.93; P‚ÄČ=‚ÄČ.025 upfront). CONCLUSIONS: Switching ICI treatment from CD and ED did not increase the incidence of irAEs and represents a safe option also outside clinical trials.</p
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