106 research outputs found
Compressive Sensing of Signals Generated in Plastic Scintillators in a Novel J-PET Instrument
The J-PET scanner, which allows for single bed imaging of the whole human
body, is currently under development at the Jagiellonian University. The dis-
cussed detector offers improvement of the Time of Flight (TOF) resolution due
to the use of fast plastic scintillators and dedicated electronics allowing for
sam- pling in the voltage domain of signals with durations of few nanoseconds.
In this paper we show that recovery of the whole signal, based on only a few
samples, is possible. In order to do that, we incorporate the training signals
into the Tikhonov regularization framework and we perform the Principal
Component Analysis decomposition, which is well known for its compaction
properties. The method yields a simple closed form analytical solution that
does not require iter- ative processing. Moreover, from the Bayes theory the
properties of regularized solution, especially its covariance matrix, may be
easily derived. This is the key to introduce and prove the formula for
calculations of the signal recovery error. In this paper we show that an
average recovery error is approximately inversely proportional to the number of
acquired samples
Application of the Compress Sensing Theory for Improvement of the TOF Resolution in a Novel J-PET Instrument
Nowadays, in Positron Emission Tomography (PET) systems, a Time of Flight
information is used to improve the image reconstruction process. In Time of
Flight PET (TOF-PET), fast detectors are able to measure the difference in the
arrival time of the two gamma rays, with the precision enabling to shorten
significantly a range along the line-of-response (LOR) where the annihilation
occurred. In the new concept, called J-PET scanner, gamma rays are detected in
plastic scintillators. In a single strip of J-PET system, time values are
obtained by probing signals in the amplitude domain. Owing to Compress Sensing
theory, information about the shape and amplitude of the signals is recovered.
In this paper we demonstrate that based on the acquired signals parameters, a
better signal normalization may be provided in order to improve the TOF
resolution. The procedure was tested using large sample of data registered by a
dedicated detection setup enabling sampling of signals with 50 ps intervals.
Experimental setup provided irradiation of a chosen position in the plastic
scintillator strip with annihilation gamma quanta
Novel method for hit-position reconstruction using voltage signals in plastic scintillators and its application to Positron Emission Tomography
Currently inorganic scintillator detectors are used in all commercial Time of
Flight Positron Emission Tomograph (TOF-PET) devices. The J-PET collaboration
investigates a possibility of construction of a PET scanner from plastic
scintillators which would allow for single bed imaging of the whole human body.
This paper describes a novel method of hit-position reconstruction based on
sampled signals and an example of an application of the method for a single
module with a 30 cm long plastic strip, read out on both ends by Hamamatsu
R4998 photomultipliers. The sampling scheme to generate a vector with samples
of a PET event waveform with respect to four user-defined amplitudes is
introduced. The experimental setup provides irradiation of a chosen position in
the plastic scintillator strip with an annihilation gamma quanta of energy
511~keV. The statistical test for a multivariate normal (MVN) distribution of
measured vectors at a given position is developed, and it is shown that signals
sampled at four thresholds in a voltage domain are approximately normally
distributed variables. With the presented method of a vector analysis made out
of waveform samples acquired with four thresholds, we obtain a spatial
resolution of about 1 cm and a timing resolution of about 80 p
Theobald Palm and His Remarkable Observation: How the Sunshine Vitamin Came to Be Recognized
The seminal discovery that sunlight was important in the prevention of nutritional rickets was made in 1890 by Theobald A. Palm, a medical missionary who contrasted the prevalence of rickets in northern European urban areas with similar areas in Japan and other tropical countries. He surmised that exposure to sunlight prevented rickets. Over the next 40 years his observation led to an understanding of ultraviolet irradiation and its role in vitamin D synthesis. This opened a new era of appreciation for the curative powers of the sun and âthe sunshine vitaminâ. While Palmâs observations were in some ways obscure, they had a potent effect on the development of photobiology
The LAGUNA design study- towards giant liquid based underground detectors for neutrino physics and astrophysics and proton decay searches
The feasibility of a next generation neutrino observatory in Europe is being
considered within the LAGUNA design study. To accommodate giant neutrino
detectors and shield them from cosmic rays, a new very large underground
infrastructure is required. Seven potential candidate sites in different parts
of Europe and at several distances from CERN are being studied: Boulby (UK),
Canfranc (Spain), Fr\'ejus (France/Italy), Pyh\"asalmi (Finland),
Polkowice-Sieroszowice (Poland), Slanic (Romania) and Umbria (Italy). The
design study aims at the comprehensive and coordinated technical assessment of
each site, at a coherent cost estimation, and at a prioritization of the sites
within the summer 2010.Comment: 5 pages, contribution to the Workshop "European Strategy for Future
Neutrino Physics", CERN, Oct. 200
A feasibility study of the time reversal violation test based on polarization of annihilation photons from the decay of ortho-Positronium with the J-PET detector
The Jagiellonian Positron Emission Tomograph (J-PET) is a novel de- vice
being developed at Jagiellonian University in Krakow, Poland based on or- ganic
scintillators. J-PET is an axially symmetric and high acceptance scanner that
can be used as a multi-purpose detector system. It is well suited to pur- sue
tests of discrete symmetries in decays of positronium in addition to medical
imaging. J-PET enables the measurement of both momenta and the polarization
vectors of annihilation photons. The latter is a unique feature of the J-PET
detector which allows the study of time reversal symmetry violation operator
which can be constructed solely from the annihilation photons momenta before
and after the scattering in the detector
17Â -Estradiol and Tamoxifen Prevent Gastric Cancer by Modulating Leukocyte Recruitment and Oncogenic Pathways in Helicobacter Pylori-Infected INS-GAS Male Mice
Helicobacter pylori infection promotes male-predominant gastric adenocarcinoma in humans. Estrogens reduce gastric cancer risk and previous studies demonstrated that prophylactic 17ÎČ-estradiol (E2) in INS-GAS mice decreases H. pylori-induced carcinogenesis. We examined the effect of E2 and Tamoxifen, on H. pylori-induced gastric cancer in male and female INS-GAS mice. After confirming robust gastric pathology at 16 weeks post-infection (WPI), mice were implanted with E2, Tamoxifen, both E2 and Tamoxifen, or placebo pellets for 12 weeks. At 28 WPI, gastric histopathology, gene expression and immune cell infiltration were evaluated, and serum inflammatory cytokines measured. After treatment, no gastric cancer was observed in H. pylori-infected males receiving E2 and/or Tamoxifen, while 40% of infected untreated males developed gastric cancer. E2, Tamoxifen and their combination significantly reduced gastric precancerous lesions in infected males compared to infected untreated males (P<0.001, 0.01 and 0.01, respectively). However, Tamoxifen did not alter female pathology regardless of infection status. Differentially expressed genes from males treated with E2 or Tamoxifen (n=363 and n=144, Q<0.05) associated highly with cancer and cellular movement, indicating overlapping pathways in the reduction of gastric lesions. E2 or Tamoxifen deregulated genes associated with metastasis (PLAUR and MMP10) and Wnt inhibition (FZD6 and SFRP2). Compared to controls, E2 decreased gastric mRNA (Q<0.05) and serum levels (P<0.05) of CXCL1, a neutrophil chemokine, leading to decreased neutrophil infiltration (P<0.01). Prevention of H. pylori-induced gastric cancer by E2 and Tamoxifen may be mediated by estrogen signaling and is associated with decreased CXCL1, decreased neutrophil counts and downregulation of oncogenic pathways
Feasibility studies for imaging ee annihilation with modular multi-strip detectors
Studies based on imaging the annihilation of the electron (e) and its
antiparticle positron (e) open up several interesting applications in
nuclear medicine and fundamental research. The annihilation process involves
both the direct conversion of ee into photons and the formation of
their atomically bound state, the positronium atom (Ps), which can be used as a
probe for fundamental studies. With the ability to produce large quantities of
Ps, manipulate them in long-lived Ps states, and image their annihilations
after a free fall or after passing through atomic interferometers, this purely
leptonic antimatter system can be used to perform inertial sensing studies in
view of a direct test of Einstein equivalence principle. It is envisioned that
modular multistrip detectors can be exploited as potential detection units for
this kind of studies. In this work, we report the results of the first
feasibility study performed on a e beamline using two detection modules
to evaluate their reconstruction performance and spatial resolution for imaging
ee annihilations and thus their applicability for gravitational
studies of Ps
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