Fully 3D Monte Carlo image reconstruction in SPECT using functional regions

Image reconstruction in Single Photon Emission Computed Tomography (SPECT) is affected by physical effects such as photon attenuation, Compton scatter and detector response. These effects can be compensated for by modeling the corresponding spread of photons in 3D within the system matrix used for tomographic reconstruction. The fully 3D Monte Carlo (F3DMC) reconstruction technique consists in calculating this system matrix using Monte Carlo simulations. The inverse problem of tomographic reconstruction is then solved using conventional iterative algorithms such as maximum likelihood expectation maximization (MLEM). Although F3DMC has already shown promising results, its use is currently limited by two major issues: huge size of the fully 3D system matrix and long computation time required for calculating a robust and accurate system matrix. To address these two issues, we propose to calculate the F3DMC system matrix using a spatial sampling matching the functional regions to be reconstructed. In this approach, different regions of interest can be reconstructed with different spatial sampling. For instance, a single value is reconstructed for a functional region assumed to contain uniform activity. To assess the value of this approach, Monte Carlo simulations have been performed using GATE. Results suggest that F3DMC reconstruction using functional regions improves quantitative accuracy compared to the F3DMC reconstruction method proposed so far. In addition, it considerably reduces disk space requirement and duration of the simulations needed to estimate the system matrix. The concept of functional regions might therefore make F3DMC reconstruction practically feasible.Comment: 6 pages, 3 figures, 3rd International Conference on maging Technologies in Biomedical Sciences : ITBS2005, Milos Island, Greece, 25-28 september 2005, submitted to NIM

Dopaminergic basis for signalling belief updates, but not surprise, and the link to paranoia

Distinguishing between meaningful and meaningless sensory information is fundamental to forming accurate representations of the world. Dopamine is thought to play a central role in processing the meaningful information content of observations, which motivates an agent to update their beliefs about the environment. However, direct evidence for dopamine’s role in human belief updating is lacking. We addressed this question in healthy volunteers who performed a model-based functional magnetic resonance imaging (fMRI) task designed to separate the neural processing of meaningful and meaningless sensory information. We modelled participant behaviour using a normative Bayesian observer model, and used the magnitude of the model-derived belief update following an observation to quantify its meaningful information content. We also acquired positron emission tomography (PET) imaging measures of dopamine function in the same subjects. We show that the magnitude of belief updates about task structure (meaningful information), but not pure sensory surprise (meaningless information), are encoded in midbrain and ventral striatum activity. Using PET we show that the neural encoding of meaningful information is negatively related to dopamine-2/3 receptor availability in the midbrain and dexamphetamine-induced dopamine release capacity in the striatum. Trial-by-trial analysis of task performance indicated that subclinical paranoid ideation is negatively related to behavioural sensitivity to observations carrying meaningful information about the task structure. The findings provide direct evidence implicating dopamine in model-based belief updating in humans, and have implications for understating the pathophysiology of psychotic disorders where dopamine function is disrupted

Thermal imaging is a non-invasive alternative to PET-CT for measurement of brown adipose tissue activity in humans

Background Obesity and its metabolic consequences are a major cause of morbidity and mortality. Brown adipose tissue (BAT) utilises glucose and free fatty acids to produce heat, thereby increasing energy expenditure. Effective evaluation of human BAT stimulators is constrained by current standard BAT assessment methods as positron emission tomography-computed tomography (PET-CT) requires exposure to high doses of ionising radiation. Infrared thermography (IRT) is a potential non-invasive, safe alternative, although direct corroboration with PET-CT has not previously been established. Methods IRT and 18F-fluorodeoxyglucose (¹⁸F-FDG) PET-CT data from 8 healthy male participants subjected to water jacket cooling were directly compared. Thermal images (TIs) were geometrically transformed to overlay PET-CT-derived maximum intensity projection (MIP) images from each subject and the areas of greatest intensity of temperature and glucose-uptake within the supraclavicular regions compared. Relationships between supraclavicular temperatures from IRT (TSCR) and the maximum rate of glucose uptake (MR(gluc)) from PET-CT were determined. Results Glucose uptake on MR(gluc)MIP was positively correlated with change in TSCR relative to a reference region (r² = 0.721; p=0.008). Spatial overlap between areas of maximal MR(gluc)MIP and maximal TSCR was 29.5±5.1%. Prolonged cooling to 60 minutes was associated with further TSCR rise compared with cooling to 10 minutes. Conclusions The supraclavicular hotspot identified on IRT closely corresponds to the area of maximal uptake on PET-CT-derived MR(gluc)MIP images. Greater increases in relative TSCR were associated with raised glucose uptake. IRT should now be considered a suitable method for measuring BAT activation, especially in populations where PET-CT is not feasible, practical or repeatable

Colecistectomía Laparoscópica (Colelap) en Paciente Femenina con Múltiples Comorbilidades ASA II. Reporte de Caso

Laparoscopic cholecystectomy is the accepted treatment for symptomatic biliary disease and remains one of the most common surgical procedures today. Indications include, but are not limited to symptomatic cholelithiasis, biliary dyskinesia, acute cholecystitis, complications related to gallstones, and gallbladder polyps. It should be added that it has become the treatment of choice for patients with symptomatic cholelithiasis, as it is a safe procedure compared to open cholecystectomy, with multiple benefits for the patient such as smaller scars, reduced pain, shorter hospitalization and a return faster to normal daily activities and work. Acute cholecystitis is undoubtedly one of the most common pathologies in the world; It is considered the second cause of acute abdomen after appendicitis. A case of a female patient with multiple comorbidities plus cholelithiasis diagnosed 6 months ago without treatment is reported. She came reporting abdominal pain located in the epigastrium that radiated to the right hypochondrium for 8 hours, Eva 10/10.La colecistectomía laparoscópica es el tratamiento aceptado para la enfermedad biliar sintomática y sigue siendo uno de los procedimientos quirúrgicos más frecuentes en la actualidad. Las indicaciones incluyen, pero no se limitan a colelitiasis sintomática, disquinesia biliar, colecistitis aguda, complicaciones relacionadas con cálculos biliares y pólipos en la vesícula biliar. Se debe agregar que se ha convertido en el tratamiento de elección para pacientes con colelitiasis sintomática, al ser un procedimiento seguro en comparación con la colecistectomía abierta, con múltiples beneficios para el paciente como cicatrices más pequeñas, dolor reducido, hospitalización más corta y un retorno más rápido a las actividades diarias normales y al trabajo. La colecistitis aguda es sin duda una de las patologías más comunes en el mundo; se considera la segunda causa de abdomen agudo después de la apendicitis. Se Reporta un caso de paciente femenina con múltiples comorbilidades más colelitiasis diagnosticada hace 6 meses sin tratamiento, acude por referir desde hace 8 horas dolor abdominal localizado en epigastrio que se irradia a hipocondrio derecho, Eva 10/10

Clinical quantification of the integrin αvβ6 by [18F]FB-A20FMDV2 positron emission tomography in healthy and fibrotic human lung (PETAL Study)

© 2019, The Author(s). Purpose: The RGD-integrin, αvβ6, plays a role in the pathogenesis of pulmonary fibrosis through activation of transforming growth factor beta (TGFβ). This study sought to quantify expression of αvβ6 in the lungs of healthy humans and subjects with pulmonary fibrosis using the αvβ6-selective [18F]FB-A20FMDV2 PET ligand. Methods: [18F]FB-A20FMDV2 PET/CT scans were performed in healthy subjects and those with fibrotic lung disease. Standard uptake values (SUV) and volume of distribution (VT) were used to quantify αvβ6 expression. In subjects with fibrotic lung disease, qualitative assessment of the relationship between αvβ6 expression and the distribution of fibrosis on high resolution computed tomography was conducted. Results: A total of 15 participants (6 healthy, 7 with idiopathic pulmonary fibrosis (IPF) and 2 with connective tissue disease (CTD) associated PF) were enrolled. VT and SUV of [18F]FB-A20FMDV2 were increased in the lungs of subjects with pulmonary fibrosis (PF) compared with healthy subjects. Geometric mean VT (95% CI) was 0.88 (0.60, 1.29) mL/cm3 for healthy subjects, and 1.40 (1.22, 1.61) mL/cm3 for subjects with IPF; and SUV was 0.54 (0.36, 0.81) g/mL for healthy subjects and 1.03 (0.86, 1.22) g/mL for subjects with IPF. The IPF/healthy VT ratio (geometric mean, (95% CI of ratio)) was 1.59 (1.09, 2.32) (probability ratio > 1 = 0.988)) and the SUV ratio was 1.91 (1.27, 2.87) (probability ratio > 1 = 0.996). Increased uptake of [18F]FB-A20FMDV2 in PF was predominantly confined to fibrotic areas. [18F]FB-A20FMDV2 measurements were reproducible at an interval of 2 weeks. [18F]FB-A20FMDV2 was safe and well tolerated. Conclusions: Lung uptake of [18F]FB-A20FMDV2, a measure of expression of the integrin αvβ6, was markedly increased in subjects with PF compared with healthy subjects

Qualitative Evidence Synthesis (QES) for Guidelines: Paper 1 – Using qualitative evidence synthesis to inform guideline scope and develop qualitative findings statements

Background: WHO has recognised the need to ensure that guideline processes are transparent and evidence based, and that the resulting recommendations are relevant and applicable. Along with decision-making criteria that require findings from effectiveness reviews, WHO is increasingly using evidence derived from qualitative evidence syntheses (QES) to inform the values, acceptability, equity and feasibility implications of its recommendations. This is the first in a series of three papers examining the use of QES in developing clinical and health systems guidelines. Methods: WHO convened a group of methodologists involved in developing recent (2010–2018) guidelines that were informed by QES. Using a pragmatic and iterative approach that included feedback from WHO staff and other stakeholders, the group reflected on, discussed and identified key methods and research implications from designing QES and using the resulting findings in guideline development. Our aim in this paper is to (1) describe and discuss how the findings of QES can inform the scope of a guideline and (2) develop findings for key guideline decision-making criteria. Results: QES resulted in the addition of new outcomes that are directly relevant to service users, a stronger evidence base for decisions about how much effective interventions and related outcomes are valued by stakeholders in a range of contexts, and a more complete database of summary evidence for guideline panels to consider, linked to decisions about values, acceptability, feasibility and equity. Conclusions: Rigorously conducted QES can be a powerful means of improving the relevance of guidelines, and of ensuring that the concerns of stakeholders, at all levels of the healthcare system and from a wide range of settings, are taken into account at all stages of the process

Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at root s=13 TeV

A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 137 fb(-1) collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on themodel, the combined result excludes a top squarkmass up to 1325 GeV for amassless neutralino, and a neutralinomass up to 700 GeV for a top squarkmass of 1150 GeV. Top squarks with masses from 145 to 295 GeV, for neutralino masses from 0 to 100 GeV, with a mass difference between the top squark and the neutralino in a window of 30 GeV around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 GeV

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

Observation of tW production in the single-lepton channel in pp collisions at root s=13 TeV

A measurement of the cross section of the associated production of a single top quark and a W boson in final states with a muon or electron and jets in proton-proton collisions at root s = 13 TeV is presented. The data correspond to an integrated luminosity of 36 fb(-1) collected with the CMS detector at the CERN LHC in 2016. A boosted decision tree is used to separate the tW signal from the dominant t (t) over bar background, whilst the subleading W+jets and multijet backgrounds are constrained using data-based estimates. This result is the first observation of the tW process in final states containing a muon or electron and jets, with a significance exceeding 5 standard deviations. The cross section is determined to be 89 +/- 4 (stat) +/- 12 (syst) pb, consistent with the standard model.Peer reviewe

Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at root s=13 TeV

Peer reviewe