•Artificial intelligence is used for assessing response to therapy in rectal cancer.•Textural features extraction from high resolution 3 T MR images.•Artificial intelligence model helps personalize ...therapeutic strategy.•Decisions curves analysis confirm clinical utility.
To develop and validate an Artificial Intelligence (AI) model based on texture analysis of high-resolution T2 weighted MR images able 1) to predict pathologic Complete Response (CR) and 2) to identify non-responders (NR) among patients with locally-advanced rectal cancer (LARC) after receiving neoadjuvant chemoradiotherapy (CRT).
Fifty-five consecutive patients with LARC were retrospectively enrolled in this study. Patients underwent 3 T Magnetic Resonance Imaging (MRI) acquiring T2-weighted images before, during and after CRT. All patients underwent complete surgical resection and histopathology was the gold standard. Textural features were automatically extracted using an open-source software. A sub-set of statistically significant textural features was selected and two AI models were built by training a Random Forest (RF) classifier on 28 patients (training cohort). Model performances were estimated on 27 patients (validation cohort) using a ROC curve and a decision curve analysis.
Sixteen of 55 patients achieved CR. The AI model for CR classification showed good discrimination power with mean area under the receiver operating curve (AUC) of 0.86 (95% CI: 0.70, 0.94) in the validation cohort. The discriminatory power for the NR classification showed a mean AUC of 0.83 (95% CI: 0.71,0.92). Decision curve analysis confirmed higher net patient benefit when using AI models compared to standard-of-care.
AI models based on textural features of MR images of patients with LARC may help to identify patients who will show CR at the end of treatment and those who will not respond to therapy (NR) at an early stage of the treatment.
A novel technique for testing the timing properties of scintillators is presented. The technique is based on transient absorption (TA) induced in a scintillating material by a selective excitation of ...the activator ion. A figure of merit to assess the timing properties of scintillators is suggested. This parameter was estimated for a set of cerium doped lutetium–yttrium oxyorthosilicate (LYSO:Ce) bars, which have been fabricated for Barrel Timing Layer sensor of Compact Muon Solenoid detector (CMS BTL) and exhibited different timing properties, and compared with the results obtained by conventional coincidence time resolution (CTR) measurements. The figure of merit applied for the tested bars shows a strong correlation (Pearson's correlation coefficient R = 0.95) with the CTR. These results suggest that the TA technique could be used as an experimental method to expand in a complementary way the extensive qualification procedure of LYSO:Ce crystals that will be performed for the production of the CMS BTL detector.
•Coincidence time resolution correlates with activator population rise time.•Population rise time can be probed by transient absorption in femtosecond domain.•Transient absorption can be exploited for testing of scintillator timing properties.
Abstract
The barrel section of the novel MIP Timing Detector (MTD)
will be constructed as part of the upgrade of the CMS experiment to
provide a time resolution for single charged tracks in the range ...of
30–60 ps using LYSO:Ce crystal arrays read out with
Silicon Photomultipliers (SiPMs). A major challenge for the
operation of such a detector is the extremely high radiation level,
of about 2 × 10
14
1 MeV(Si) Eqv. n/cm
2
, that will be
integrated over a decade of operation of the High Luminosity Large
Hadron Collider (HL-LHC). Silicon Photomultipliers exposed to
this level of radiation have shown a strong increase in dark count
rate and radiation damage effects that also impact their gain and
photon detection efficiency. For this reason during operations the
whole detector is cooled down to about -35°C. In this
paper we illustrate an innovative and cost-effective solution to
mitigate the impact of radiation damage on the timing performance of
the detector, by integrating small thermo-electric coolers (TECs) on
the back of the SiPM package. This additional feature, fully
integrated as part of the SiPM array, enables a further decrease in
operating temperature down to about -45°C. This leads to a
reduction by a factor of about two in the dark count rate without
requiring additional power budget, since the power required by the
TEC is almost entirely offset by a decrease in the power required
for the SiPM operation due to leakage current. In addition, the
operation of the TECs with reversed polarity during technical stops
of the accelerator can raise the temperature of the SiPMs up to
60°C (about 50°C higher than the rest of the
detector), thus accelerating the annealing of radiation damage
effects and partly recovering the SiPM performance.
Abstract
Cerium-doped Lutetium-Yttrium Oxyorthosilicate (LYSO:Ce) is
one of the most widely used Cerium-doped Lutetium based
scintillation crystals. Initially developed for medical detectors it
...rapidly became attractive for High Energy Particle Physics (HEP)
applications, especially in the frame of high luminosity particle
colliders.
In this paper, a comprehensive and systematic study of LYSO:Ce
(Lu
(1-
x
)
Y
x
2
SiO
5
:Ce) crystals
is presented. It involves for the first time a large number of
crystal samples (180) of the same size from a dozen of producers.
The study consists of a comparative characterization of LYSO:Ce
crystal products available on the market by mechanical, optical and
scintillation measurements and aims specifically, to investigate key
parameters of timing applications for HEP.
Hundreds of concurrent collisions per bunch crossing are expected at future hadron colliders. Precision timing calorimetry has been advocated as a way to mitigate the pileup effects and, thanks to ...their excellent time resolution, microchannel plates (MCPs) are good candidate detectors for this goal. We report on the response of MCPs, used as secondary emission detectors, to single relativistic particles and to electromagnetic showers. Several prototypes, with different geometries and characteristics, were exposed to particle beams at the INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency are measured for single particles and as a function of the multiplicity of particles. Efficiencies between 50% and 90% to single relativistic particles are reached, and up to 100% in presence of a large number of particles. Time resolutions between 20 ps and 30 ps are obtained.
The CMS scintillating lead-tungstate calorimeter was designed to operate for at least ten years at the LHC, assuming an instantaneous luminosity of 1034 cm−2 s−1. The measurements obtained with data ...collected in LHC Run1 (2010–2012) show that the detector has performed according to design specifications and will survive with excellent performance through the lifetime of the LHC. However, plans for an upgrade of the LHC (the High Luminosity LHC, HL-LHC, project) aim at accumulating a much higher integrated luminosity, up to 3000 fb−1 in ten years. This will expose the detector to a total irradiation about six times higher with respect to the design specifications.
An intense campaign of activities has started to define the improvements needed to survive such an increase in irradiation levels. The activities carried out include irradiation studies, simulations, design, realisation and test of prototypes of new detectors that may substitute the present one in the endcap regions.
The options currently under study and the results obtained so far on the subjects outlined above will be presented.
A prototype for a sampling calorimeter made out of cerium fluoride crystals interleaved with tungsten plates, and read out by wavelength-shifting fibres, has been exposed to beams of electrons with ...energies between 20 and 150GeV, produced by the CERN Super Proton Synchrotron accelerator complex. The performance of the prototype is presented and compared to that of a Geant4 simulation of the apparatus. Particular emphasis is given to the response uniformity across the channel front face, and to the prototype׳s energy resolution.
At the high luminosity LHC (HL-LHC) about 200 concurrent interactions are expected, with a spread between the interaction vertices of few centimeters in the beam direction and 200 ps in the collision ...time. A time of flight resolution of the order of 30 ps would be able to reduce neutral particles pile-up contamination at the calorimeter level of about one order of magnitude, restoring pile-up conditions similar to what is routinely sustained in the current run of the LHC . Micro-channel plates have been used in PMT configuration as fast charged particles detector (resolution of better than 20 ps have been achieved with commercial devices), however they are not particularly radiation tolerant, mostly due to the ion feedback on the photocathode. The possibility of using micro-channel plates without a photocathode (i-MCP) has been studied in several test beams. Different MCP geometries are compared with the goal to identify the optimal configuration. Efficiency of more then 70% with a time resolution of better than 40 ps are achieved for single charged particles, leading to an efficiency close to 100% for EM shower after few radiation lengths. This open the possibility to use i-MCPs as a timing layer in a sampling calorimeter or to use it in a pre-shower device independent from the calorimeter technology.
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