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Positron emission mammography (PEM) studies of high precision diagnostic quality require not only to quantify the fraction of the 511 keV annihilation photons that are attenuated and scattered in the breast, but also to implement correction methods for these effects. This work presents a Monte Carlo (MC) simulation of a PEM system to quantify a) attenuation and scattering effects and b) spatial resolution anisotropy as a function of both the position in the PEM's field of view (FOV) and the amount of attenuating material. For a 6 cm thick phantom and an energy window of [350,750] keV, the PEM simulation study predicts large contributions of scattered events (33%) and an important loss of true coincidences (58%) due to attenuation. The simulation results were compared with experimental data using sealed 22Na point sources showing differences lower than 5% at the center and up to 19% in the corners of the system FOV. [ABSTRACT FROM AUTHOR]

In this work we investigate the effects due to photon attenuation and scattering in a Positron Emission Mammography (PEM) study using the GATE (Geant4 Application for Tomographic Emission) Monte Carlo (MC) code. Breast phantoms with different shapes and volumes placed within a scanner geometry similar to IFUNAM's PEM prototype under development were considered. The results show that attenuation and scatter effects for 511 keV photons depend strongly on the breast phantom volume (and thus, breast thickness). For breast volumes between 200 and 950 ml, scatter contributions vary from 24% to 58%, while the attenuation of primary photons are significant, within 36% and 73%. Our results indicate, overall, that the larger the breast volume, the larger these effects. This implies that for a clinical study to provide precise and quantitative information, complex corrections pre- or post- image reconstruction must necessarily be implemented. [ABSTRACT FROM AUTHOR]

The parallax error introduced by incorrectly assigning the lines-of-response defined by the annihilation photon pairs, limits the attainable spatial resolution in positron emission imaging. Knowledge of the exact position of interaction (x, y, z) inside the scintillation crystal, including the depth of interaction z of the 511 keV photons, reduces this error. In this work, the depth of interaction (DOI) was determined in two different scintillator materials: EJ-232 plastic and LYSO scintillation crystals. These were coupled to an 8×8 silicon photomultiplier (SiPM) array. An analysis of the light distributions produced inside the crystals enabled the determination of the DOI position, allowing the correction for parallax errors. This method is expected to be used in a Positron Emission Mammography (PEM) prototype under development. [ABSTRACT FROM AUTHOR]

Scintillator crystals are widely used as ionizing radiation detectors in nuclear medicine imaging equipment. In many detectors, arrays of small scintillator elements (pixels), optically isolated from each other by a reflective material, are used to provide information on the interaction position of photons in the crystal. The attainable spatial resolution is related to the pixel size. The technique of subsurface laser engraving has been proposed as a low-cost alternative to scintillation crystals arrays to pixelate monolithic crystals. In this work, the first results of the implementation of the laser engraving technique to pixelate cerium doped lutetium yttrium oxyorthosilicate (LYSO:Ce) scintillation crystals in the new Laser Engraving Laboratory at the UNAM Institute of Physics are presented. We characterized the shape and size of the induced microfractures with a Nd:YAG pulsed laser in LYSO crystal, and with this information, we optimized the engraving parameters to produce semi-transparent barriers that optically isolate one pixel from another, thus producing a 6×6 pixelated crystal array with pixel pitch of 1.67 mm. [ABSTRACT FROM AUTHOR]

The Gamma-Ray Computed Tomography was used to detect the amount of resin in the Agarwood trees. In order to get the acquired result, scanning was done by placing the equipment around the trunk of the tree and only on the cross-sections of the trees will be scanned. The results were imagesconsistingof the density profile of the tree trunk. It can easily detect the gross amount of the valuable resin in the trees. The sampleswill be brought to the laboratory and be scanned with different types of Gamma Ray and X-ray Computed Tomography. The image comparisons will determine the exact amount of resins in the tree samples. [ABSTRACT FROM AUTHOR]

In the course of this study, 57 extracted teeth and a dried mandible with metal structures were scanned using multislice, cone beam and microfocus cone beam computed tomography devices. Comparative evaluation of three- dimensional and two-dimensional tomographic reconstructions was performed. Sharpness and clarity of small low- density details as well as suppression of artifacts from metal objects and tooth enamel were the highest on microfocus reconstructions compared to the other techniques. [ABSTRACT FROM AUTHOR]

Positron Annihilation Lifetime Spectroscopy (PALS) allows examining structure of materials in nano and sub-nanometer scale. This technique is based on the lifetime and intensity of ortho-positronium atoms in free volumes of given structures. It is mostly used for studies in material sciences, but it can also be used for in vivo imaging of the cell morphology as proposed in [1], [2]. Cancer cells are characterized by an altered macro structure in comparison to normal cells, thus the main objective of these studies is to compare if these differences can be detected on sub-nanometer level with PALS technique. First studies on standard PAL spectrometers conducted by Jean [3], [4] and J-PET collaboration [5], [6], give promising results showing differences between normal and cancer tissues. This perspective will allow for simultaneous determination of early and advanced stages of carcinogenesis, by observing changes in biomechanical parameters between normal and tumour cells, and standard PET examination, which can be performed with the Jagiellonian Positron Emission Tomograph (J-PET), a multi-purpose detector used for investigations with positronium atoms in life-sciences as well as for development of medical diagnostics. Results of first PALS measurement of cardiac myxoma, with J-PET detector is presented in this paper. Obtained o-Ps lifetime for tumor tissue is equal to 2:03(01)[ns] and its intensity 25:7(1)%. [ABSTRACT FROM AUTHOR]

Positronium is a unique laboratory to study fundamental symmetries in the Standard Model, reflection in space (P), reversal in time (T), charge conjugation (C) and their combinations. The experimental limits on the C, CP and CPT symmetries violation in the decays of positronium are still several orders of magnitude higher than the expectations. The newly constructed Jagiellonian Positron Emission Tomograph (J-PET) was optimized for the registration of photons from the electron-positron annihilations. It enables tests of discrete symmetries in decays of positronium atoms via the determination of the expectation values of the discrete-symmetries-odd operators. In this article we present the capabilities of the J-PET detector in improving the current precision of discrete symmetries tests and report on the progress of analysis data from the first data-taking runs. [ABSTRACT FROM AUTHOR]

A resonant laser-assisted process of the electron-positron pairs annihilation and production is studied theoretically. The second order in fine structure constant process in the laser field transforms into two consistent processes of first order in the fine structure constant: laser-assisted annihilation of initial electron-positron pair into intermediate photon and laser-assisted production of final electron-positron pair by intermediate photon under resonant conditions when virtual photon becomes real. It is demonstrated that the resonant conditions for initial pair include the excess of certain combination of the electron and positron energies over threshold energy and narrow angle between momenta of electron and positron. The same holds true for the final pair. Also, final positron emission angle can vary from zero to some maximum value. It is shown that energies of the final particles depend on this angle and can take from one to two values. A resonant differential cross section of the studied process is obtained. It is shown that the resonant differential cross section can significantly exceed the corresponding cross section without an external field (Bhabha cross section). The project calculations may be experimentally verified by the scientific facilities of pulsed laser radiation (SLAC, FAIR, XFEL, ELI, XCELS). [ABSTRACT FROM AUTHOR]

An experiment to search for double beta processes in 106Cd is in progress with the help of 106CdWO4 crystal scintillator (enriched in 106Cd to 66%) in coincidence with two large volume CdWO4 crystal scintillators in close geometry at the Gran Sasso Underground Laboratory. The time resolution of the set-up was analyzed, and the methods of pulse-shape discrimination of α and γ(β) events was applied to estimate the radioactive contamination of the crystal and to reduce the background counting rate. The possible double beta decay processes and the background components have been simulated by a Monte Carlo method with GEANT4. The experimental sensitivity is approaching the theoretical predictions for the two-neutrino electron capture with positron emission in 106Cd: lim T1/2≥4×1021 yr at 90% C.L. (the best previous limit was established in the previous stage of the experiment as T1/2≥1.1× 1021 yr, while the theoretical predictions are in the region of T1/2∼1021−1022 yr). [ABSTRACT FROM AUTHOR]

We present a scheme for positron beam acceleration in CEBAF antiparallel to the normal electron path, requiring no change in polarity of the magnet systems. This feature is essential to the principal benefit: enabling extremely simple configuration changes between conventional (clockwise) e- acceleration and counter clockwise e+ acceleration. Additionally, it appears possible to configure the accelerating cavity phases to support concurrent acceleration of the electron and positron beams. The last mode also may enable use of the higher peak current electron beam for system diagnostics. The inherent penalty of the concurrent mode in acceleration efficiency and increased energy spread may render this a commissioning-only diagnostic option, but the possibility appears worthy of consideration. [ABSTRACT FROM AUTHOR]

In this work, a Monte Carlo simulation of a positron emission mammography (PEM) prototype under development at the Institute of Physics, UNAM, is presented. The simulated geometry included two parallel detector modules with a 73 mm separation. Each module consisted of 3 detector blocks, each one formed by an array of 38?38 lutetium yttrium orthosilicate crystal elements of 1.96?1.96?10 mm³ at 2 mm pitch. An energy resolution of 26% for 511 keV photons, a 350-650 keV energy window and a 6 ns coincidence window were assumed. Image reconstruction was performed using focal plane tomography. Spatial resolution was assessed through the point spread function at different positions within the field of view (FOV). In addition, image quality was evaluated following the NEMA NU 4-2008 protocol. Different depth-of-interaction (DOI) assumptions were considered. The best spatial resolution (0.75 mm FWHM) was obtained when depth-of-interaction information was used, deteriorating drastically to 2.21 mm when DOI is unknown. The overall sensitivity of the system was 2.50%. [ABSTRACT FROM AUTHOR]

A combined measurement is presented of all inclusive deep inelastic cross sections measured by the H1 and ZEUS collaborations in neutral and charged current unpolarised e±p scattering at HERA. The H1 and ZEUS collaborations collected total integrated luminosities of approximately 500 pb-1 each, divided about equally between e+p and e-p scattering. They include data taken at electron (positron) beam energy of 27.5 GeV and proton beam energies of 920, 820, 575 and 460 GeV corresponding to centre-of-mass energy of 320, 300, 251 and 225 GeV respectively. This enabled the two collaborations to explore a large phase space in Bjorken x and negative four-momentum-transfer squared, Q2. The combination method takes the correlations of the systematic uncertainties into account, resulting in improved accuracy. [ABSTRACT FROM AUTHOR]

The positron-emitting isotopes of arsenic have unique potential for imaging research in medical and environmental applications. The production and purification of radioarsenic from proton-irradiated natural GeO2 targets is reported. The separation procedure utilizes precipitation and anion exchange separation steps. Two anion exchange procedures were investigated. An overall arsenic decay-corrected separation yield of 80% was obtained. [ABSTRACT FROM AUTHOR]

There is worldwide growing interest for the production of long-lived positron emitters for molecular imaging and the development of novel immuno-PET techniques for drugs discovery. The desire to produce solid target isotopes in Australia has significantly increased over the years and several research projects for labelling of peptides, proteins and biomolecules, including labelling of recombinant antibodies has been limited due to the availability of suitable isotopes. This has led to the recent installation and commissioning of a new lab dedicated to fully automated solid target isotope production, including 124I, 64Cu, 89Zr and 86Y. [ABSTRACT FROM AUTHOR]

A semi-automated, in-house external beamline, ≤40 μA at 11.7 MeV for 120 min (degraded from 18 MeV to suppress 88Y & 88Zr co-production) produced 89Zr from 89Y(p,n)89Zr. EOB activity (by HPGe γ-spectr.) of 89Zr in target discs, derived from multiple runs, was 1.42 GBq (±0.45 GBq [SD], n=4) which was 67% (±21%, n=4) of the theoretical activity, with a maximum of 1.84 GBq (87% of theory) achieved. Recovery was 88% (±9%, n=4), radionuclidic purity >99% (n=4) and chemical purity 0.2 ppm Zr (±0.3 ppm, n=3, ICP-MS). The Zr:Y ratio improved from 1:10000 in the pre-filtered solution to 1:10 in the product purified by hydroxamate column. Efficiency of radiolabeling to monoclonal antibody (mAb; trastuzumab) was 100% and purified 89Zr did not bind non-specifically to mAb. Chelator:mAb ratio was 1.3:1. No-carrier-added specific activity of purified 89Zr was 408 MBq/μg (±26 MBq/μg, n=2) via the titration-by-chelator method. Minimum ligand concentration for which 100% labeling occurred was 302 nmol/L. Small animal PET imaging (Philips Mosaic; scan acquisition time 10 min; decay & randoms corrected; image reconstructed using a 3-D RAMLA algorithm) demonstrated marked tumor-specific uptake of 89Zr-labeled mAb but nil 'free' 89Zr (as chloride) tumor uptake. [ABSTRACT FROM AUTHOR]

A positron emitter 86Y and the radiotherapeutic beta emitter, 67Cu are two radionuclides, that require the use of enriched isotopes for their cost effective production. Proton irradiation of monoisotopic 86Sr is conducive to the production of 86Y with less than 2% 87/87mY impurities, while the use of enriched 68Zn results in a 4-5 fold increase in the 67Cu yield compared to natural Zn. Both 86Sr and 68Zn are expensive and therefore their full recovery and re-utilization is critical to reduce production costs. In this paper we describe our experience with recovery and consequent irradiation of the 86Sr and 68Zn. [ABSTRACT FROM AUTHOR]

55Co is a positron emitting isotope that is of interest to the nuclear medicine imaging community. 55Co was produced by the 58Ni(p,α)55Co reaction and purified by chromatography. Our method has produced 55Co in millicurie quantities with a final recovery of 78% and an effective specific activity of 28μCi/μmol. The only radioactive impurity recovered with 55Co is 57Co(271.8d) and is at a concentration of ∼0.182% that of 55Co. [ABSTRACT FROM AUTHOR]

Do Positron emission particle tracking (PEPT) has been used to track the motion of a single radioactively labeled tracer particle within a bed of similar particles. In this paper, the effect of the original event fraction on the results precise in two experiments has been reviewed. Results showed that the algorithm can no longer distinguish some corrupt trajectories, in addition to; further iteration reduces the statistical significance of the sample without improving its quality. Results show that the optimum value of trajectories depends on the type of experiment. [ABSTRACT FROM AUTHOR]

In this communication we study in detail the relations between the smoothness of f and [formula] in the case when the smoothness of the univariate non-negative functions f is measured via Besov and Triebel-Lizorkin space scales. The results obtained can be considered also as embedding theorems for usual Besov and Triebel-Lizorkin spaces and their analogues in Hellinger metric. These results can be used in constrained approximation using wavelets, with applications to probability density estimation in speech recognition, non-negative non-parametric regression-function estimation in positron-emission tomography (PET) imaging, shape/order-preserving and/or one-sided approximation and many others. [ABSTRACT FROM AUTHOR]

We study the characteristics of the Outer Crust of neutron stars, that is the region of neutron stars characterized by a mass density less than the “neutron drip” density and composed by white dwarf—like material (fully ionized nuclei and free electrons). In particular, we calculate its mass and its thickness (Mcrust and ΔRcrust respectively) with a general relativistic model, finding that the Outer Crust is smaller in mass and in radial extension for more compact objects. We also propose a correlation with the Fireshell Model of GRBs, that assumes that GRBs originates from the gravitational collapse to a black hole. One of the parameters used in this model is the baryon loading B of the electron—positron plasma, related to the mass of the baryonic remnant of the star progenitor MB. We propose that B originates from the Outer Crust of neutron stars and compare Mcrust with the values of MB used to reproduce the observational data of several GRBs, finding that they are compatible. [ABSTRACT FROM AUTHOR]

The in-pile positron source of NEPOMUC at the neutron source Heinz Maier-Leibnitz (FRM II) provides at the experimental site an intense beam of monoenergetic positrons with selectable energy between 15 eV and 3 keV. The principle of the source is based on neutron capture gamma rays produced by cadmium in a beam tube tip close to the reactor core. The gamma ray absorption in platinum produces positrons which are moderated and formed to the beam. An unprecedented beam intensity of 9.108 e+/s is achieved (1 keV). The performance and applications of the facility are presented. [ABSTRACT FROM AUTHOR]

This paper shows the significance of the Positron Emission Tomography (PET) in the veterinary medication through a case study of a cat brain tumor. A castrated male cat with bilateral mydriasis and blindness arrived at the veterinary clinic. After physical, laboratory and neurological investigations other sickness was ruled out and the inkling of the intracranial lesion had come to light. Brain tumor seemed the most likely to cause the illness because other symptoms appeared (for example: anorexia, depression) and they progrediated fast. PET examination, using 18F-FDG isotope, was performed to confirm the possible causes of the cat’s symptoms [ABSTRACT FROM AUTHOR]

PET at the highest level is an inverse problem: reconstruct the location of the emission (which localize biological function) from detected photons. Ideally, one would like to directly measure an annihilation photon's incident direction on the detector. In the developed algorithm, Bayesian Estimation for Angle Recovery (BEAR), we utilized the increased information gathered from localizing photon interactions in the detector and developed a Bayesian estimator for a photon's incident direction. Probability distribution functions (PDFs) were filled using an interaction energy weighted mean or center of mass (COM) reference space, which had the following computational advantages: (1) a significant reduction in the size of the data in measurement space, making further manipulation and searches faster (2) the construction of COM space does not depend on measurement location, it takes advantage of measurement symmetries, and data can be added to the training set without knowledge and recalculation of prior training data, (3) calculation of posterior probability map is fully parallelizable, it can scale to any number of processors. These PDFs were used to estimate the point spread function (PSF) in incident angle space for (i) algorithm assessment and (ii) to provide probability selection criteria for classification. The algorithm calculates both the incident θ and [lowercase_phi_synonym] angle, with ∼16 degrees RMS in both angles, limiting the incoming direction to a narrow cone. Feature size did not improve using the BEAR algorithm as an angle filter, but the contrast ratio improved 40% on average. [ABSTRACT FROM AUTHOR]

Numerous antihydrogen atoms are created at CERN, by ATRAP and ATHENA experiments, by bringing together positrons and antiprotons in a magnetic Penning trap. Most of these atoms are created in exotic, highly excited states, such that the magnetic forces on positrons are greater than the Coulomb attraction of antiprotons. This paper presents an overview of the recent progress made toward theoretical understanding of the complicated dynamics which leads to the formation and detection of antihydrogen atoms. There is no formal difference between the plasmas described here and normal, electron-proton, matter plasmas, except the reversed sign of electrical charges. The next generation of experiments need to bring the antihydrogen atoms to the ground state and to cool them to sub-milliKelvin temperature. Only then, high resolution spectroscopy can expose differences between matter and antimatter due to CPT violations. Suggestions are made for possible pathways toward this goal. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The problem of production and study of superheavy elements is discussed in the talk. Different nuclear reactions leading to formation of superheavy nuclei are analyzed. Collisions of transactinide nuclei are investigated as an alternative way for production of neutron-rich superheavy elements. In many events lifetime of the composite giant nuclear system consisting of two touching nuclei turns out to be rather long (>= 10-20 s); sufficient for observing line structure in spontaneous positron emission from super-strong electric fields, a fundamental QED process. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

A new method for generating positrons has been proposed that uses betatron X-rays emitted by an electron beam in a high-K plasma wiggler. The plasma wiggler is an ion column produced by the head of the beam when the peak beam density exceeds the plasma density. The radial electric field of the beam blows out the plasma electrons transversely, creating an ion column. The focusing electric field of the ion column causes the beam electrons to execute betatron oscillations about the ion column axis. If the beam energy and the plasma density are high enough, these oscillations lead to synchrotron radiation in the 1–50 MeV range. A significant amount of electron energy can be lost to these radiated X-ray photons. These photons strike a thin (.5Xo), high-Z target and create e+/e- pairs. The experiment was performed at the Stanford Linear Accelerator Center (SLAC) where a 28.5 GeV electron beam with σr ≈ 10μm and σz ≈ 25μm was propagated through a neutral Lithium vapor (Li). The radial electric field of the dense beam was large enough to field ionize the Li vapor to form a plasma. The positron yield was measured as a function of plasma density, ion column length and electron beam pulse length. A computational model was written to match the experimental data with theory. The measured positron spectra are in excellent agreement with those expected from the calculated X-ray spectral yield from the plasma wiggler. After matching the model with the experimental results, it was used to design a more efficient positron source, giving positron yields of 0.44 e+/e-, a number that is close to the target goal of 1–2 e+/e- for future positron sources. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT), two nuclear medicine imaging modalities broadly used in clinics and research, share many common instrumentation, detector, and electronics technology platforms with calorimetry in high-energy physics, astronomy, and other physics sciences. Historically, advances made in calorimetry had played major roles in the development of novel approaches and critical technologies essential to the evolution of PET and SPECT. There have also been examples in which PET/SPECT developments had led to new techniques in calorimetry for other application areas. In recent years, several innovations have propelled advances in both calorimetry in general and PET/SPECT in particular. Examples include time-of-flight (TOF) measurements, silicon photomultipliers (SiPMs), etc. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Positron annihilation radiation from the Galaxy has been observed by the OSSE, SMM and TGRS instruments. Improved spectral modeling of OSSE observations has allowed studies of the distribution of both positron annihilation radiation components, the narrow line emission at 511 keV and the positronium continuum emission. The results derived for each individual annihilation component are then compared with each other. These comparisons reveal approximate agreement between the distribution of these two emissions. In certain regions of the sky (notably in the vicinity of the previously reported positive latitude enhancement), the distribution of the emissions differ. We discuss these differences and the methods currently being employed to understand whether the differences are physical or a systematic error in the present analysis. [ABSTRACT FROM AUTHOR]

The present form of the Standard Model (SM) describes weak process in terms of vector and axial-vector type interaction, with fully left handed massless neutrinos. Any experimental deviation from the SM predictions will in special cases reveal the need for extensions to the SM. The longitudinal polarization of the positron emitted from polarized muon present a simple and sensitive case. We present hereafter the status of a longitudinal polarization measurement of these positrons. [ABSTRACT FROM AUTHOR]