1,813 research outputs found
EndoTOFPET-US a Novel Multimodal Tool for Endoscopy and Positron Emission Tomography
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
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
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
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
In this work, charge collection profiles of non-irradiated and irradiated 150
m -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
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
In this work, the effects of Co -ray irradiation on high
resistivity -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 (--,
--) and microscopic (Thermally Stimulated Current~(TSC)) measurements
were conducted to characterize the radiation-induced changes. The investigated
diodes were manufactured on high resistivity -type Float Zone (FZ) silicon
and were further classified into two types based on the isolation technique
between the pad and guard ring: -stop and -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 (BO) complex, the carbon interstitial
and oxygen interstitial CO defect, the H40K, and the
so-called I. 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 -
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
This study focuses on the properties of the BO
(interstitial Boron~-~interstitial Oxygen) and CO
(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~cm 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 BO
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 profile as well as the occupation of the
BO defect during the electric field dependent electron
emission, are simulated as a function of temperature. The macroscopic
properties (leakage current and ) 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
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 mg Q6W or nivolumab 480 mg Q4W) after switching from canonical interval dosing (CD; pembrolizumab 200 mg Q3W or nivolumab 240 mg 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 = .047), whereas no difference for G3 or G4 events was noted (aOR = 1.55, 95% CI = 0.81 to 2.94; P = .18). Among patients who started upfront with ED (n = 232, 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 = .004 after switching; aHR = 0.57, 95% CI = 0.35 to 0.93; P = .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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