Discrete symmetries tested at 10-4 precision using linear polarization of photons from positronium annihilations.

Discrete symmetries play an important role in particle physics with violation of CP connected to the matter-antimatter imbalance in the Universe. We report the most precise test of P, T and CP invariance in decays of ortho-positronium, performed with methodology involving polarization of photons from these decays. Positronium, the simplest bound state of an electron and positron, is of recent interest with discrepancies reported between measured hyperfine energy structure and theory at the level of 10-4 signaling a need for better understanding of the positronium system at this level. We test discrete symmetries using photon polarizations determined via Compton scattering in the dedicated J-PET tomograph on an event-by-event basis and without the need to control the spin of the positronium with an external magnetic field, in contrast to previous experiments. Our result is consistent with QED expectations at the level of 0.0007 and one standard deviation.

Feasibility of the J-PET to monitor the range of therapeutic proton beams.

PURPOSE: The aim of this work is to investigate the feasibility of the Jagiellonian Positron Emission Tomography (J-PET) scanner for intra-treatment proton beam range monitoring. METHODS: The Monte Carlo simulation studies with GATE and PET image reconstruction with CASToR were performed in order to compare six J-PET scanner geometries. We simulated proton irradiation of a PMMA phantom with a Single Pencil Beam (SPB) and Spread-Out Bragg Peak (SOBP) of various ranges. The sensitivity and precision of each scanner were calculated, and considering the setup's cost-effectiveness, we indicated potentially optimal geometries for the J-PET scanner prototype dedicated to the proton beam range assessment. RESULTS: The investigations indicate that the double-layer cylindrical and triple-layer double-head configurations are the most promising for clinical application. We found that the scanner sensitivity is of the order of 10-5 coincidences per primary proton, while the precision of the range assessment for both SPB and SOBP irradiation plans was found below 1 mm. Among the scanners with the same number of detector modules, the best results are found for the triple-layer dual-head geometry. The results indicate that the double-layer cylindrical and triple-layer double-head configurations are the most promising for the clinical application, CONCLUSIONS:: We performed simulation studies demonstrating that the feasibility of the J-PET detector for PET-based proton beam therapy range monitoring is possible with reasonable sensitivity and precision enabling its pre-clinical tests in the clinical proton therapy environment. Considering the sensitivity, precision and cost-effectiveness, the double-layer cylindrical and triple-layer dual-head J-PET geometry configurations seem promising for future clinical application.

Transformation of PET raw data into images for event classification using convolutional neural networks.

In positron emission tomography (PET) studies, convolutional neural networks (CNNs) may be applied directly to the reconstructed distribution of radioactive tracers injected into the patient's body, as a pattern recognition tool. Nonetheless, unprocessed PET coincidence data exist in tabular format. This paper develops the transformation of tabular data into n-dimensional matrices, as a preparation stage for classification based on CNNs. This method explicitly introduces a nonlinear transformation at the feature engineering stage and then uses principal component analysis to create the images. We apply the proposed methodology to the classification of simulated PET coincidence events originating from NEMA IEC and anthropomorphic XCAT phantom. Comparative studies of neural network architectures, including multilayer perceptron and convolutional networks, were conducted. The developed method increased the initial number of features from 6 to 209 and gave the best precision results (79.8) for all tested neural network architectures; it also showed the smallest decrease when changing the test data to another phantom.

Detection of range shifts in proton beam therapy using the J-PET scanner: a patient simulation study.

OBJECTIVE: The Jagiellonian PET (J-PET) technology, based on plastic scintillators, has been proposed as a cost effective tool for detecting range deviations during proton therapy. This study investigates the feasibility of using J-PET for range monitoring by means of a detailed Monte Carlo simulation study of 95 patients who underwent proton therapy at the Cyclotron Centre Bronowice (CCB) in Krakow, Poland. Approach: Discrepancies between prescribed and delivered treatments were artificially introduced in the simulations by means of shifts in patient positioning and in the Hounsfield unit to the relative proton stopping power calibration curve. A dual-layer, cylindrical J-PET geometry was simulated in an in-room monitoring scenario and a triple-layer, dual-head geometry in an in-beam protocol. The distribution of range shifts in reconstructed PET activity was visualised in the beam's eye view. Linear prediction models were constructed from all patients in the cohort, using the mean shift in reconstructed PET activity as a predictor of the mean proton range deviation. Main results: Maps of deviations in the range of reconstructed PET distributions showed agreement with those of deviations in dose range in most patients. The linear prediction model showed a good fit, with coefficient of determination r^2 = 0.84 (in-room) and 0.75 (in-beam). Residual standard error was below 1 mm: 0.33 mm (in-room) and 0.23 mm (in-beam). Significance: The precision of the proposed prediction models shows the sensitivity of the proposed J-PET scanners to shifts in proton range for a wide range of clinical treatment plans. Furthermore, it motivates the use of such models as a tool for predicting proton range deviations and opens up new prospects for investigations into the use of intra-treatment PET images for predicting clinical metrics that aid in the assessment of the quality of delivered treatment. .

Creep Behavior of CLT Beams with Finite Thickness Layers of Flexible Adhesives.

Creep behavior of Cross-Laminated-Timber (CLT) beams with a finite-thickness layer of flexible adhesives is investigated. Creep tests were carried out for all component materials as well as for the composite structure itself. Three-point bending creep tests were performed for spruce planks and for CLT beams, and uniaxial compression creep tests were performed for two flexible polyurethane adhesives: Sika® PS and Sika® PMM. All materials are characterized with the use of the three-element Generalized Maxwell Model. The results of creep tests for component materials were used in elaboration of the Finite Element (FE) model. The problem of linear theory of viscoelasticity was solved numerically with the use of the Abaqus software. Obtained results of Finite Element Analysis (FEA) are compared with experimental results.

ProTheRaMon - a GATE simulation framework for proton therapy range monitoring using PET imaging.

OBJECTIVE: This paper reports on the implementation and shows examples of the use of the ProTheRaMon framework for simulating the delivery of proton therapy treatment plans and range monitoring using positron emission tomography (PET). ProTheRaMon offers complete processing of proton therapy treatment plans, patient CT geometries, and intra-treatment PET imaging, taking into account therapy and imaging coordinate systems and activity decay during the PET imaging protocol specific to a given proton therapy facility. We present the ProTheRaMon framework and illustrate its potential use case and data processing steps for a patient treated at the Cyclotron Centre Bronowice (CCB) proton therapy center in Krakow, Poland. APPROACH: The ProTheRaMon framework is based on GATE Monte Carlo software, the CASToR reconstruction package and in-house developed Python and bash scripts. The framework consists of five separated simulation and data processing steps, that can be further optimized according to the user's needs and specific settings of a given proton therapy facility and PET scanner design. MAIN RESULTS: ProTheRaMon is presented using example data from a patient treated at CCB and the J-PET scanner to demonstrate the application of the framework for proton therapy range monitoring. The output of each simulation and data processing stage is described and visualized. SIGNIFICANCE: We demonstrate that the ProTheRaMon simulation platform is a high-performance tool, capable of running on a computational cluster and suitable for multi-parameter studies, with databases consisting of large number of patients, as well as different PET scanner geometries and settings for range monitoring in a clinical environment. Due to its modular structure, the ProTheRaMon framework can be adjusted for different proton therapy centers and/or different PET detector geometries. It is available to the community via github.

Positronium imaging with the novel multiphoton PET scanner.

In vivo assessment of cancer and precise location of altered tissues at initial stages of molecular disorders are important diagnostic challenges. Positronium is copiously formed in the free molecular spaces in the patient's body during positron emission tomography (PET). The positronium properties vary according to the size of inter- and intramolecular voids and the concentration of molecules in them such as, e.g., molecular oxygen, O2; therefore, positronium imaging may provide information about disease progression during the initial stages of molecular alterations. Current PET systems do not allow acquisition of positronium images. This study presents a new method that enables positronium imaging by simultaneous registration of annihilation photons and deexcitation photons from pharmaceuticals labeled with radionuclides. The first positronium imaging of a phantom built from cardiac myxoma and adipose tissue is demonstrated. It is anticipated that positronium imaging will substantially enhance the specificity of PET diagnostics.

Signals of diagnostic ions in the product ion spectra of [M - H]- ions of methoxylated flavonoids.

RATIONALE: The main feature of the fragmentation of [M - H]- ions of methoxylated flavonoids is the loss of methyl radical (formation of the [M - H - CH3 ]-• product ion). Subsequent decomposition of [M - H - CH3 ]-• product ions may be useful for identification of a given compound by HPLC/MS. This paper describes how the selected diagnostic fragment ions can be useful during HPLC/MS(-) analysis of methoxylated flavonoids. METHODS: Product ion spectra (ESI-CID-MS/MS spectra) of [M - H]- ions of 17 methoxylated flavonoids (flavones, isoflavones and flavonols) were obtained with a Q-TOF mass spectrometer. Full scan mass spectra (ESI-MS) were obtained with a single quadrupole type of instrument. RESULTS: A number of product ions were recognized as useful from the point of view of structural elucidation. In most cases they were diagnostic product ions, formed as a result of C ring breaking. CONCLUSIONS: The most important conclusions drawn from this study are: the product ion at m/z 132 indicates that the analysed compound is an isoflavone; the product ion at m/z 117 indicates the presence of one hydroxy group at ring B or at the 3-position; biochanin A and prunetin can be differentiated by their 'in-source' fragmentation, by the relative abundances of product ions at m/z 195, 183 and 167; loss of mass 102 from the [M - H - CH3 ]-• ion indicates that ring B is not substituted and there is no hydroxy group at the 3-position; and rhamnetin can be detected using three diagnostic product ions, namely at m/z 121, 165 and 193.

Novel scintillating material 2-(4-styrylphenyl)benzoxazole for the fully digital and MRI compatible J-PET tomograph based on plastic scintillators.

A novel plastic scintillator is developed for the application in the digital positron emission tomography (PET). The novelty of the concept lies in application of the 2-(4-styrylphenyl)benzoxazole as a wavelength shifter. The substance has not been used as scintillator dopant before. A dopant shifts the scintillation spectrum towards longer wavelengths making it more suitable for applications in scintillators of long strips geometry and light detection with digital silicon photomultipliers. These features open perspectives for the construction of the cost-effective and MRI-compatible PET scanner with the large field of view. In this article we present the synthesis method and characterize performance of the elaborated scintillator by determining its light emission spectrum, light emission efficiency, rising and decay time of the scintillation pulses and resulting timing resolution when applied in the positron emission tomography. The optimal concentration of the novel wavelength shifter was established by maximizing the light output and it was found to be 0.05 ‰ for cuboidal scintillator with dimensions of 14 mm x 14 mm x 20 mm.

Complexation of phosphates by 1,3-bis(3-(2-pyridylureido)propyl)-1,1,3,3-tetramethyldisiloxane.

RATIONALE: Compounds containing a urea or thiourea moiety form complexes with anions thanks to the ability to form quite strong hydrogen bonds. We have synthesized 1,3-bis(3-(2-pyridylureido)propyl)-1,1,3,3-tetramethyldisiloxane (1). Compound 1 contains two urea moieties connected by a long flexible linker; thus, it should be able to adopt a structure suitable for formation of quite stable complexes with anions. METHODS: The ability to form complexes of compound 1 with phosphates was tested by electrospray ionization mass spectrometry (ESI-MS). Full scan ESI mass spectra and collision-induced dissociation tandem mass (CID-MS/MS) spectra of the ions of interest were obtained on a quadrupole time-of-flight (QTOF) mass spectrometer. RESULTS: It has been found that compound 1 is not only much more prone to form complexes with the phosphate anion than with other inorganic anions, but it is also able to form complexes with organic phosphates, namely nucleotides and phospholipids. However, compound 1 is not able to form complexes with organic compounds not containing a phosphate group (e.g. nucleosides, sugars, glycerolipids). CONCLUSIONS: Compound 1 can be regarded as selective towards phosphate-containing organic compounds. Formation of such complexes may have some interesting applications for identification of organic phosphates in crude extracts from biological materials.

Biodegradation of poly(propylene glycol)s under the conditions of the OECD screening test.

Two poly(propylene glycol)s (PPGs): PPG 425 and PPG 725 were tested under the conditions of the OECD Screening Test with activated sludge as inoculum. Tested PPG were the sole source of organic carbon in the test. Quantitative determination of the biodegradation progress was performed by the HPLC with fluorescence detection after derivatisation of PPG with naphthyl isocyanate. The liquid chromatography-mass spectrometry technique was used for identification and semiquantitative determination of metabolites. Separation of PPG and metabolites from the water matrix was performed by liquid-liquid extraction with chloroform. It was found that the shorter PPG 425 is biodegraded significantly worse than the longer PPG 725 and that biodegradation occurs without shortening of the PPG chain for both PPG. PPG molecules are oxidised to ketones and/or aldehydes during the aerobic biodegradation process.

Cationization versus surface activity--the effect on electrospray ionization.

Ethoxylated fatty alcohols, C(12)E(1), C(12)E(2), C(18)E(1) and C(18)E(2), were studied by electrospray ionization mass spectrometry (E is the ethoxylene unit OCH(2)CH(2)). For compounds containing two ethoxylene units, which form quite stable adducts with sodium cation, the abundances of [M + Na](+) ions were not affected by alkyl chain, so the hydrophobic effect was not observed. For the compounds containing one ethoxylene unit, forming rather unstable adducts with sodium, the hydrophobic effect was clearly seen since the [C(18)E(1) + Na](+) ion was more abundant than the [C(12)E(1) + Na](+) ion. Two ethoxylene units are not able to form stable adducts with potassium cations, therefore the hydrophobic effect was observed for the [C(12)E(2) + K](+) and [C(18)E(2) + Na](+) ions, the latter being more abundant than the former. For lithium cation adducts with C(12)E(1) and C(18)E(1), the hydrophobic effect was observed, but was less manifested than for sodium cations since lithium adducts are more stable than sodium ones. C(18)E(1) and C(18)E(2) gave more intense signals at higher cone voltage values than C(12)E(1) and C(12)E(2), respectively. However, this is not related to the hydrophobic effect but to the collisions being less effective for the former.