Performance improvement of Compton imaging of astatine-211 by optimising coincidence time windows

Astatine-211 is one of the promising radioisotopes for targeted alpha therapy. Optimising treatment strategies as well as determining the suitability of a given agent for a particular patient requires to image the time-dependent distribution of the targeted radiotherapeutic agent both in tumours and in normal tissues. Since the biodistribution of astatine is different from that of iodine, imaging astatine-211 directly is essential. In the previous study of astatine-211 Compton imaging, random coincidence events due to polonium K-shell X-rays were dominant and seemed to cause saturation of counts. Thus optimisation of the coincidence time windows is important to reduce random coincidence events. In this study, we have optimised the coincidence time windows of a Compton camera and improved the sensitivity, noise and spatial resolution of astatine-211 imaging.

Global non-random abundance of short tandem repeats in rodents and primates.

Background: While of predominant abundance across vertebrate genomes and significant biological implications, the relevance of short tandem repeat (STR) abundance to speciation remains largely elusive and attributed to random coincidence for the most part. In a model study, here we collected whole-genome abundance of mono-, di-, and trinucleotide STRs in nine species, encompassing rodents and primates, including rat, mouse, olive baboon, gelada, macaque, gorilla, chimpanzee, bonobo, and human. The obtained unnormalized and normalized data were used to analyze hierarchical clustering of the STR abundances in the selected species. Results: We found massive differential abundances between the rodent and primate orders. In addition, while numerous STRs had random abundance across the nine selected species, the global abundance conformed to three consistent <clusters>, as follows: <rat, mouse>, <gelada, macaque, olive baboon>, <gorilla, chimpanzee, bonobo, human>, which coincided with the phylogenetic distances of the selected species (p< 4E-05). Exceptionally, in the trinucleotide STR compartment, human was significantly distant from all other species. Conclusion: We propose that the global abundance of STRs is non-random in rodents and primates, and probably had a determining impact on the speciation of the two orders. We also propose the STRs and STR lengths which specifically coincided with the phylogeny of the selected species.

Optimizing reconstruction parameters for quantitative 124I-PET in the presence of therapeutic doses of 131I

Purpose To determine the accuracy of quantitative 124I PET imaging in the presence of therapeutic levels of 131I.Material and Methods Multiple PET images were acquired using a NEMA IEC phantom with spheres containing 0.4 MBq/cc of 124I and increasing amount of 131I activity in the phantom background (0 to 3.76 GBq). Acquisitions were performed on a GE Discovery 710 PET/CT scanner. At each 131I activity level two scans were acquired, one with the phantom at the center of the field of view (FOV) and one 11 cm off-center. Images were reconstructed with an ordered subset expectation maximization (OSEM) algorithm using between 1 and 25 iterations of 16 subsets. Results were evaluated visually and by comparing the 124I activity relative to the baseline PET performed in the absence of 131I.Results The presence of 131I within the PET FOV added to the random coincidence rate, to dead-time and to pile-up within the PET detectors. Using our standard clinical reconstruction parameters, the image quality and quantitative accuracy suffered at 131I background activities above 1.4 GBq. However, increasing the number of iterations resulted in dramatic improvements in image quality and quantitative accuracy. Projection space measurements suggest that the dead time corrections implemented on the scanner perform well even at the highest singles count rate tested (52 Mcps).Conclusion This study shows that 124I quantitative PET is feasible in the presence of large amounts of 131I on a GE D710. The high random coincidence fraction slows the reconstruction convergence rate, therefore iterations equivalent to at least 8x16 are recommended.

Reliability of water fittings in operating conditions

Water fittings are an integral part of the internal water supply system. The reliability of their work under operating conditions largely influence on the continuity of water supply to the population. The reliability indicators of sanitary fittings allow the services responsible for the technical condition of the indoor water supply of houses to pay priority attention to the factors that determine the uninterrupted water supply of the population and reduce the loss of drinking water. In this study, the results of indicators of operational reliability of faucets for sinks in kitchens and washbasins in toilet rooms of apartments of multi-store residential buildings in a residential neighborhood are presented. The study was performed based on the analysis of records in the logs of data on valve failures for 2016-2018. The main malfunctions are established, the random coincidence of which leads to failures. The reliability of sanitary fittings is affected not only by their structure and the characteristics of the materials, as well as by the exploitation conditions. The probability of failure-free operation of sanitary fittings in exploitation conditions for a time not exceeding the duration of the reduction of water supply to consumers in residential buildings is the basic parameter of its reliability.

PSX-30 Late-Breaking Abstract: Genotypes database of pedigree cattle population in Kazakhstan and the introduction of a calculating mechanism for livestock parentage verification

A significant increase in pedigree cattle in Kazakhstan has led to scientific work on the conservation of breed genotypes in Kazakhstan and the development of imported breeds. Aim of work: creation a national database and collection of genotyped DNA samples of cattle in Kazakhstan and the introduction of an automated statistical and mathematical calculation of the local pedigree cattle parentage verification. The methodology of work has been the selection of biological samples and registration of data on the animal. DNA and STR locus testing have been performed at the University of Queensland’s Animal Genetics Laboratory (Australia). DNA genotyping was carried out using 21 polymorphic dinucleotide microsatellite loci. The database of DNA genotypes of breeding animals has been written and introduced into the database of breeding livestock in Kazakhstan (www.plem.kz). The method of determining kinship and confirming the origin of the animal was implemented by calculating the probability of random coincidence of genetic markers, taking into account their distribution in the population according to the “product rule.” The frequency distribution of homozygous alleles for 12 microsatellite loci (table 1) recommended by ICAR and 21 DNA loci (table 2) in the context of breeds was calculated, which indicates an increase in reliability when calculating the origin of livestock, with an increase in the number of microsatellite loci studied to 21 markers. The lower probability threshold is established, with 95% statistical significance confirms the relationship between the compared animals (table 3). A database of genotyped DNA samples of beef and dairy cattle breeds in Kazakhstan has been created and is currently used in pedigree beef cattle breeding. Access to the DNA database is provided to Kazakhstan genetic laboratories, and an automated calculation of the mathematical probability of parentage verification for a breeding animal and the generation of a genetic certificate was introduced on the website www.plem.kz

Evaluation of the Impact of Out-of-Axial FOV Scattering Medium on Random Coincidence Rates on Discovery 690 PET/CT Scanner: A Simulation Study

Purpose: Positron Emission Tomography (PET) imaging is a nuclear medicine imaging technique based on the recording of two photons as coincidence created by positron annihilation. Materials and Methods: PET coincidence events include true and unwanted coincidences (random, scattered, multiple coincidences). We modeled the Discovery 690 (D-690) PET scanner using the GATE simulation tool and estimated the effect of the diameter of the scattering medium out of the Axial Field Of View (AFOV) on the random coincidence rates. Results: The validation results indicated that the average difference between simulated and measured data for sensitivity and scatter fraction tests are 5% and 3%, respectively. Moreover, the results revealed that the increasing diameter of the scattering medium out of the AFOV has a direct effect on the random coincidence rates within the Field Of View (FOV). Conclusion: The study concluded that the presence of a scattering medium near the FOV increases the rate of random coincidences.