128 research outputs found
An analytic model to calculate Voxel S-Values for Lu
Objective: Lu is one of the most employed isotopes in targeted
radionuclide therapies and theranostics, and 3D internal dosimetry for such
procedures has great importance. Voxel S-Values (VSVs) approach is widely used
for this purpose, but VSVs are available for a limited number of voxel
dimensions. The aim of this work is to develop an analytic model for the
calculation of Lu-VSVs in any cubic voxelized geometry of practical
interest. Approach: Monte Carlo (MC) simulations were implemented with the
toolkit GAMOS to evaluate VSVs in voxelized geometries of soft tissue from a
source of Lu homogeneously distributed in the central voxel. Nine
geometric setups, containing 15x15x15 cubic voxels of sides l ranging from 2 mm
to 6 mm, in steps of 0.5 mm, were considered. For each l, the VSVs computed as
a function of the "normalized radius", Rn = R/l (with R = distance from the
center of the source voxel), were fitted with a parametric function. The
dependencies of the parameters as a function of l were then fitted with
appropriate functions, in order to implement the model for deducing
Lu-VSVs for any l within the aforementioned range. Main results: The
MC-derived VSVs were satisfactorily compared with literature data for
validation, and the VSVs computed with the analytic model agree with the MC
ones within 2\% for Rn 2 and within 6\% for Rn > 2. Significance: The
proposed model enables the easy and fast calculation, with a simple
spreadsheet, of Lu-VSVs in any cubic voxelized geometry of practical
interest, avoiding the necessity of implementing ad-hoc MC simulations to
estimate VSVs for specific voxel dimensions not available in literature data.Comment: 16 pages, 7 figures, first round review in "Biomedical Physics &
Engineering Express
F-PSMA-1007 salivary gland dosimetry: Comparison between different methods for dose calculation and assessment of inter- and intra-patient variability
Dosimetry of salivary glands (SGs) is usually implemented using simplified
calculation approaches and approximated geometries. Our aims were to compare
different dosimetry methods to calculate SGs absorbed doses (ADs) following
18F-PSMA-1007 injection, and to assess the AD variation across patients and
single SG components. Five patients with prostate cancer recurrence underwent
PET/CT acquisitions of the head and neck, 0.5, 2 and 4 hours after
18F-PSMA-1007 injection. Parotid and submandibular glands were segmented on CT
to derive SGs volumes and masses, while PETs were used to derive
Time-Integrated Activity Coefficients. Average ADs to single SG components or
total SG (tSG) were calculated with the following methods: i) direct Monte
Carlo (MC) simulation with GATE/GEANT4; ii) spherical model (SM) of OLINDA/EXM
2.1, adopting either patient-specific or standard ICRP89 organ masses (SMstd);
iii) ellipsoidal model (EM); iv) MIRD approach with organ S-factors from
OLINDA/EXM 2.1 and OpenDose collaboration, with or without contribution from
cross irradiation originating outside the SGs. The maximum percent AD
difference across SG components ({\delta}max) and across patients ({\Delta}max)
were calculated. Compared to MC, ADs to single SG components were significantly
underestimated by all methods (average relative differences between -14.5% and
-30.4%). Using MC, SM and EM, {\delta}max were never below 25% (up to 113%).
{\delta}max up to 702% were obtained with SMstd. Concerning tSG, results within
10% of the MC were obtained only if cross irradiation from the remainder of the
body or from the remainder of the head was accounted for. The {\Delta}max
ranged between 58% and 78% across patients. Specific masses of single SG
components should always be considered given their large intra- and inter-
patient variability.Comment: 33 pages, 3 figures, sumbitted to "Physics in Medicine & Biology
Rh/CeO2 thin catalytic layer deposition on alumina foams: Catalytic performance and controlling regimes in biogas reforming processes
: The application of ceramic foams as structured catalyst supports is clearly expanding due to faster mass/heat transfer and higher contact efficiency than honeycomb monoliths and, mainly, packed beds. In this paper, alumina open-cell foams (OCFs) with different pore density (20, 30 and 40 ppi) were coated with Rh/CeO2 catalyst via a two steps synthesis method involving: (i) the solution combustion synthesis (SCS) to in-situ deposit the CeO2 carrier and (ii) the wet impregnation (WI) of the Rh active phase. The catalytic coatings were characterized in terms of morphology and adhesion properties by SEM/EDX analysis and ultrasounds test. Permeability and form coefficient were derived from pressure drop data. Catalytic performance was evaluated towards biogas Steam Reforming (SR) and Oxy-Steam Reforming (OSR) processes at atmospheric pressure by varying temperature (800–900 °C) and space velocity (35,000–140,000 NmL·g−1·h−1). Characteristics time analysis and dimensionless numbers were calculated to identify the controlling regime. Stability tests were performed for both SR and OSR over 200 h of time-on-stream (TOS) through consecutive start-up and shut-down cycles. As a result, homogenous, thin and high-resistance catalytic layers were in situ deposited on foam struts. All structured catalysts showed high activity, following the order 20 ppi < 30 ppi ≈ 40 ppi. External interphase (gas-solid) and external diffusion can be improved by reducing the pore diameter of the OCF structures. Anderson criterion revealed the absence of internal heat transfer resistances, as well as Damköhler and Weisz-Prater numbers excluded any internal mass transfer controlling regime, mainly due to thin coating thickness provided by the SCS method. Good stability was observed over 200 h of TOS for both SR and OSR processes
Mud volcanoes and methane seeps in Romania: main features and gas flux
Romania is one of the European countries with the most vigorous natural seepage of methane, uprising from
pressurised natural gas and petroleum reservoirs through deep faults. The largest seepage zone is represented by
large mud volcanoes, with CH4 >80% v/v, occurring on the Berca-Arbanasi hydrocarbon-bearing faulted anticline,
in the Carpathian Foredeep. Smaller mud volcanoes have been identified in other areas of the Carpathian
Foredeep, in the Transylvanian Depression and on the Moldavian Platform. New surveys carried out in Transylvania
allowed us to discover the richest N2 mud volcano zone in the world (N2>90% v/v), with a remarkably
high He content and a helium isotopic signature which highlights a contribution of mantle-derived source. The
large mud volcanoes are generally quiescent, with rare explosive episodes and provide a methane flux in the order
of 102-103 t km?2 y?1. Independently from mud volcanism, a remarkable dry macroseepage, however, has been
found, with a degassing rate up to three orders of magnitude higher than that of mud volcanoes (i.e. 103-105 t
km?2 y?1). The total gas flux from all investigated macroseepage zones in Romania is estimated in the range of
1500-2500 t y?1. The emission from microseepage, pervasively occurring throughout the hydrocarbon-prone
basins, has yet to be assessed and added to the total gas output to the atmosphere
Stanja Jπ = 2+ i 0+, T = 0 8Be na energijama pobuđenja oko 20 MeV
The 7Li(d, αα)n reaction induced by deuterons of an incident energy of 7 MeV has been used to excite the 8Be nucleus in the region of excitation energy Ex of about 20 MeV. Each of the obtained αα coincidence spectra was fitted by an incoherent sum of the Jπ=2+ and 0+, T=0 8Be levels at Ex=20.1 and 20.2 MeV, respectively. The results show that the experimental data are well fitted when the G values deduced for these levels are 0.90 and 0.70 MeV, respectively.Reakcija 7Li (d, αα) n inducirana deuteronima energije 7 MeV je iskorištena za proučavanje jezgre 8Be na energijama pobuđenja Ex oko 20 MeV. Koincidentni αα spektri poravnani su nekoherentnim zbrojem stanja Jπ = 2 + na Ex = 20, 1 MeV i Jπ = 0+ na Ex = 20,2 MeV. Rezultati pokazuju da su eksperimentalni podaci najbolje opisani ako se za širine navedenih stanja uzmu vrijednosti 0,90 MeV odnosno 0, 70 Me V
Stanja Jπ = 2+ i 0+, T = 0 8Be na energijama pobuđenja oko 20 MeV
The 7Li(d, αα)n reaction induced by deuterons of an incident energy of 7 MeV has been used to excite the 8Be nucleus in the region of excitation energy Ex of about 20 MeV. Each of the obtained αα coincidence spectra was fitted by an incoherent sum of the Jπ=2+ and 0+, T=0 8Be levels at Ex=20.1 and 20.2 MeV, respectively. The results show that the experimental data are well fitted when the G values deduced for these levels are 0.90 and 0.70 MeV, respectively.Reakcija 7Li (d, αα) n inducirana deuteronima energije 7 MeV je iskorištena za proučavanje jezgre 8Be na energijama pobuđenja Ex oko 20 MeV. Koincidentni αα spektri poravnani su nekoherentnim zbrojem stanja Jπ = 2 + na Ex = 20, 1 MeV i Jπ = 0+ na Ex = 20,2 MeV. Rezultati pokazuju da su eksperimentalni podaci najbolje opisani ako se za širine navedenih stanja uzmu vrijednosti 0,90 MeV odnosno 0, 70 Me V
Long-term geochemical monitoring and extensive/compressive phenomena: case study of the Umbria Region (Central Apennines, Italy)
Long-term geochemical monitoring performed in the seismic area of the Umbria-Marche region of Italy (i.e. Central
Apennines) has allowed us to create a model of the circulation of fluids and interpret the temporal chemical
and isotopic variations of both the thermal springs as well as the gas vents. Coincident with the last seismic crisis,
which struck the region in 1997-1998, an enhanced CO2 degassing on a regional scale caused a pH-drop in
all the thermal waters as a consequence of CO2 dissolution. Furthermore, much higher 3He/4He isotope ratios
pointed to a slight mantle-derived contribution. Radon activity increased to well above the ±2 sinterval of the earlier
seismic period, after which it abruptly decreased to very low levels a few days before the occurrence of the
single deep-located shock (March 26, 1998, 51 km deep). The anomalous CO2 discharge was closely related to
the extensional movement of the normal faults responsible for the Mw 5.7, 6.0 and 5.6 main shocks that characterized
the earlier seismic phase. In contrast, a clear compressive sign is recognizable in the transient disappearance
of the deep-originating components related to the Mw 5.3, 51 km-deep event that occurred on March 26,
1998. Anomalies were detected concomitantly with the seismicity, although they also occurred after the seismic
crisis had terminated. We argue that the observed geochemical anomalies were driven by rock permeability
changes induced by crustal deformations, and we describe how, in the absence of any release of elastic energy, the
detection of anomalies reveals that a seismogenic process is developing. Indeed, comprehensive, long-term geochemical
monitoring can provide new tools allowing us to better understand the development of seismogenesis
Nota histórica sobre caso importado de loíase no Rio de Janeiro, Brasil, 1964
Loiasis is a filarial disease transmitted by the Chrysops spp. tabanid flies in West and Central Africa. It is most commonly diagnosed by the clinical manifestations of Calabar swellings (transient localized inflammatory edema) or, most dramatically, by the appearance of a migrating worm through the conjunctival tissues or the bridge of the nose. We report the case of a 35-year-old resident in the city of Rio de Janeiro who displayed a moving Loa loa in the bulbar conjunctival tissue two years after returning from a six-month trip to Uganda. Surgical removal of the worm was performed.A loaíase é uma filaríase transmitida por tabanídeos (mutucas) do gênero Chrysops na África central e ocidental, comumente diagnosticada pela apresentação clínica de edema de Calabar (edema inflamatório transitório e localizado) ou, mais dramaticamente, pela migração de um verme adulto pelo tecido conjuntival ou asa do nariz. Descrevemos o caso clínico de um paciente do sexo masculino, 35 anos, residente no Rio de Janeiro, que se apresentou com um verme adulto de Loa loa migrando sobre o tecido conjuntival bulbar dois anos após retornar de uma viagem de seis meses de duração a Uganda. Procedeu-se a remoção cirúrgica do verme
Fisiopatología, perfil epidemiológico y manejo terapéutico en el síndrome coronario agudo
Las enfermedades cardiovasculares siguen siendo ampliamente la primera causa de muerte en el mundo actual. La cardiopatía isquémica conlleva a una importante carga de gastos de Salud Pública, por lo cual es importante conocer la prevalencia, epidemiología, fisiopatología y el manejo diagnóstico y terapéutico adecuado del síndrome coronario agudo (SCA). Los hallazgos recientes indican que los primeros pasos en la aterosclerosis son esencialmente inflamatorios. Una respuesta inflamatoria sistémica a menudo acompaña al SCA, y la documentación de su presencia ha sido ampliamente reconocida como un indicador de eventos coronarios a repetición. La medicina basada en la evidencia sugiere fuertemente la importancia de la etiología inflamatoria en el SCA. Los factores tradicionales de riesgo coronario terminan en un pasaje final común que desarrolla un proceso inflamatorio en la pared arterial. El entendimiento mejorado y la comprensión adecuada de la influencia de los procesos inflamatorios en el SCA pueden llevar no solo a una mejor utilización de la terapéutica actualmente disponible sino también al desarrollo de nuevas herramientas terapéuticas. Sin duda alguna los refinamientos constantes en las diferentes estrategias terapéuticas del SCA, sumados a la combinación del entendimiento científico en el uso adecuado de los marcadores inflamatorios, los nuevos agentes farmacológicos y las nuevas técnicas de intervención coronaria percutánea con los nuevos stents y otros dispositivos intracoronarios van a aclarar nuestras dudas y mejorar nuestro manejo diagnóstico y terapéutico del síndrome coronario agudo basado en la evidencia científica
Active degassing across the Maltese Islands (Mediterranean Sea) and implications for its neotectonics
The Maltese Islands, located in the central Mediterranean Sea, are intersected by two normal fault systems associated with continental rifting to the south. Due to a lack of evidence for offshore displacement and insignificant historical seismicity, the systems are thought to be inactive and the rift-related deformation is believed to have ceased. In this study we integrate aerial, marine and onshore geological, geophysical and geochemical data from the Maltese Islands to demonstrate that the majority of faults offshore the archipelago underwent extensional to transtensional deformation during the last 20 ka. We also document an active fluid flow system responsible for degassing of CH4 and CO2. The gases migrate through carbonate bedrock and overlying sedimentary layers via focused pathways, such as faults and pipe structures, and possibly via diffuse pathways, such as fractures. Where the gases seep offshore, they form pockmarks and rise through the water column into the atmosphere. Gas migration and seepage implies that the onshore and offshore faults systems are permeable and that they were active recently and simultaneously. The latter can be explained by a transtensional system involving two right-stepping, right-lateral NW-SE trending faults, either binding a pull-apart basin between the islands of Malta and Gozo or associated with minor connecting antitethic structures. Such a configuration may be responsible for the generation or reactivation of faults onshore and offshore the Maltese Islands, and fits into the modern divergent strain-stress regime inferred from geodetic data
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