Assessment of a simulation software for scintillation detector Crespin, S; De Freitas, D; Brette, P ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2004, Letnik:
527, Številka:
1-2
Journal Article
Recenzirano
Aim: A Monte Carlo code based on GEANT 3.21 and Linux platform has been developed and adaptated to simulate gamma detectors dedicated to specific scintigraphic applications. Materials and methods: ...GEANT 3.21 is freely available at the CERN program library. It has been written for simulating the interactions of particles with energy > 10keV. The energy of the gamma rays used in scintigraphic imaging never exceeds 511keV. Interaction cross-sections for energies between 10keV and 10MeV and three media of interest obtained with this program have been compared with data available on the NIST web site. A gamma peroperative hand-held probe has then been simulated. Sensitivity and spatial resolution were evaluated. Results: The high standard deviation for total attenuation coefficient is 4.7% with an uncertainty around 4% given by NIST. The good results obtained have allowed us to go farther in computer programming. In the hope of integrating all the detection lines new routines have been introduced for the simulation of scintillation photons and optical effects. First simulated optical spots have a diameter of 2.5mm (FWHM) for a 6mm NaI(Tl) thickness and gamma rays of 140keV. Conclusion: The code was recently improved with the implementation of a photomultiplier tube and the algorithm for the image reconstruction. In this way, the computed image can be compared with optical image obtained just before the photocathode to improve algorithm. Soon, simulation results will be tested with a mini gamma-camera prototype.
Relevance of a multi-hole collimator for peroperative gamma detection De Freitas, D; Crespin, S; Cachin, F ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2004, Letnik:
527, Številka:
1-2
Journal Article
Recenzirano
Aim: Peroperative detection is usually performed with a gamma probe equipped with a single-hole collimator (SHC). The aim of this study was to compare SHC with a new highly resolutive multi-hole ...collimator (MHC) in situations simulating the in vivo detection of two radioactive sources. Materials and Methods: The probe was composed of a SHC or a MHC, a CsI(Tl) crystal, a photomultiplier tube and a count rate unit. Sensitivity response curves were experimentally obtained with a 57Co source. From these values, the response curve in front of two small sources was simulated with an Excel software. A 30MBq source (A) was placed at 1cm depth and a 300kBq source (B) was placed, successively, at 1, 3 and 5cm. B was then moved towards A by 1mm steps. A threshold background/signal of 50% was used to determine the minimal distance between the sources (Dmin) to remain separately detectable. Results: At 1, 3 and 5cm depth, Dmin was, respectively, 35, 45 and 53mm for SHC and 14, 17 and 20mm for MHC and the count rate in front of B was, respectively, 3060, 480 and 210cps with the SHC and 900, 360 and 150cps with the MHC. Conclusion: When compared with SHC, the loss in sensitivity with the MHC is only moderate for long source–probe distances while the gain in resolution remains important at any distance. MHC is an interesting option for peroperative detection.
This paper discusses hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter (consisting of a lead-liquid argon electromagnetic part and an iron-scintillator hadronic part) ...in the framework of the non-parametrical method. The non-parametrical method utilizes only the known $e/h$ ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to an easy use in a first level trigger. The reconstructed mean values of the hadron energies are within $\pm 1%$ of the true values and the fractional energy resolution is $(58\pm3)% /\sqrt{E}+(2.5\pm0.3)%\oplus (1.7\pm0.2)/E$. The value of the $e/h$ ratio obtained for the electromagnetic compartment of the combined calorimeter is $1.74\pm0.04$ and agrees with the prediction that $e/h > 1.7$ for this electromagnetic calorimeter. Results of a study of the longitudinal hadronic shower development are also presented. The data have been taken in the H8 beam line of the CERN SPS using pions of energies from 10 to 300 GeV.
Monte-Carlo simulation of gamma-cameras using GEANT Berthor, J.; Breton, V.; Brette, P. ...
2000 IEEE Nuclear Science Symposium. Conference Record (Cat. No.00CH37149),
2000, Letnik:
3
Conference Proceeding
Odprti dostop
There is a growing interest among nuclear and particle physicists for the application of the detection techniques used in subatomic physics to medical imaging. As well, the code used to simulate the ...response of these detectors to ionizing particles named GEANT can be applied to simulate medical imaging devices. GEANT allows a complete Monte-Carlo treatment of the attenuation by body parts and of the generation and tracking of optical photons from scintillation inside the crystal. The authors used GEANT to simulate a high resolution gamma camera for small animal imaging. Their study shows a significant correlation between the depth of a source in the body and the energy spectrum of the photons detected in the gamma-camera.
Crude oil is known to disrupt cardiac function in fish embryos. Large oil spills, such as the Deepwater Horizon (DWH) disaster that occurred in 2010 in the Gulf of Mexico, could severely affect fish ...at impacted spawning sites. The physiological mechanisms underlying such potential cardiotoxic effects remain unclear. Here, we show that crude oil samples collected from the DWH spill prolonged the action potential of isolated cardiomyocytes from juvenile bluefin and yellowfin tunas, through the blocking of the delayed rectifier potassium current (IKr). Crude oil exposure also decreased calcium current (ICa) and calcium cycling, which disrupted excitation-contraction coupling in cardiomyocytes. Our findings demonstrate a cardiotoxic mechanism by which crude oil affects the regulation of cellular excitability, with implications for life-threatening arrhythmias in vertebrates.
Air pollution is associated with detrimental effects on human health, including decreased cardiovascular function. However, the causative mechanisms behind these effects have yet to be fully ...elucidated. Here we review the current epidemiological, clinical and experimental evidence linking pollution with cardiovascular dysfunction. Our focus is on particulate matter (PM) and the associated low molecular weight polycyclic aromatic hydrocarbons (PAHs) as key mediators of cardiotoxicity. We begin by reviewing the growing epidemiological evidence linking air pollution to cardiovascular dysfunction in humans. We next address the pollution‐based cardiotoxic mechanisms first identified in fish following the release of large quantities of PAHs into the marine environment from point oil spills (e.g. Deepwater Horizon). We finish by discussing the current state of mechanistic knowledge linking PM and PAH exposure to mammalian cardiovascular patho‐physiologies such as atherosclerosis, cardiac hypertrophy, arrhythmias, contractile dysfunction and the underlying alterations in gene regulation. Our aim is to show conservation of toxicant pathways and cellular targets across vertebrate hearts to allow a broad framework of the global problem of cardiotoxic pollution to be established. AhR; Aryl hydrocarbon receptor. Dark lines indicate topics discussed in this review. Grey lines indicate topics reviewed elsewhere.
Polycyclic aromatic hydrocarbons are common in both air and aquatic pollution. Exposure to these pollutants can lead to PAH accumulation in the body and cause cardiovascular dysfunction via a number of direct and indirect mechanisms. PAH exposure is associated with arrhythmias, hypertrophy, atherosclerosis and developmental toxicity (among others). This review discusses current evidence linking PAH‐based pollution and cardiovascular disease in vertebrates.
•AIS/axon locations within neurons are highly variable.•AIS and soma are coupled resistively.•Resistive coupling impacts synaptic integration and action potentials.•Heterogeneity of axon location may ...expand synaptic integration in circuits.
The axon initial segment (AIS) is a unique domain of the proximal axon serving critical electrical and structural roles including the initiation of action potentials and maintenance of cellular polarity. Recent experimental and theoretical advances demonstrate that the anatomical site for initiation is remarkably diverse. The AIS location varies not only axially, along the axon, but axons also emerge variably from either the soma or proximal dendrites. Here, we review the evidence that the diversity of AIS and axon location has a substantial impact on the electrical properties and speculate that the anatomical heterogeneity of axon locations expands synaptic integration within cell types and improves information processing in neural circuits.
We describe an overgrowth condition associated with X-linked copy number variation. Three brothers displayed an overgrowth pattern at birth that continued postnatally. Clinical findings included ...macrocephaly, distinctive facial features, developmental delay and variable clubfoot. Normal fetal growth was noted until the third trimester by Hadlock standards, revealing a late gestational overgrowth pattern. Microarray analysis in the family showed a maternally inherited 680 kb copy number duplication at Xq26.1-q26.2 in all three brothers. Molecular sequencing for known overgrowth conditions including GPC3, Sotos 1 (NSD1), Malan (NFIX), Perlman (DIS3L2), Weaver (EZH2), Opitz-Kaveggia (MED12) loci were negative. BWS IC1 and IC2 methylation and CDKN1C testing was also negative. Normal IGF1 levels excluded X-linked acrogiantism. The duplicated region Xq26.1-q26.2 contained IGSF1 and at least part of the lncRNA FIRRE. IGSF1, a highly expressed pituitary immunoglobulin superfamily gene, was recently implicated in a genome-wide association study of canine size. IGSF1 variants were associated with large canine breeds compared to smaller breeds. Our findings support the hypothesis that an X-linked variant encompassing the IGSF1 region may be associated with body size. Although IGSF1 loss has been noted in human hypothyroidism, this is the first reported phenotype in a family with copy number duplication in the region. Our findings suggest that prenatal evaluation, cross-species evaluation, Mendelian, and GWAS studies may describe a distinctive familial condition and its corresponding phenotypic features.
The Deepwater Horizon disaster drew global attention to the toxicity of crude oil and the potential for adverse health effects amongst marine life and spill responders in the northern Gulf of Mexico. ...The blowout released complex mixtures of polycyclic aromatic hydrocarbons (PAHs) into critical pelagic spawning habitats for tunas, billfishes, and other ecologically important top predators. Crude oil disrupts cardiac function and has been associated with heart malformations in developing fish. However, the precise identity of cardiotoxic PAHs, and the mechanisms underlying contractile dysfunction are not known. Here we show that phenanthrene, a PAH with a benzene 3-ring structure, is the key moiety disrupting the physiology of heart muscle cells. Phenanthrene is a ubiquitous pollutant in water and air, and the cellular targets for this compound are highly conserved across vertebrates. Our findings therefore suggest that phenanthrene may be a major worldwide cause of vertebrate cardiac dysfunction.
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