Browsing by Author "Meneses, Luis"

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    Analyzing the Spatiotemporal Patterns of Forests Carbon Sink and Sources Between 2000 and 2019
    (2022) Alaniz, Alberto J.; Carvajal, Mario A.; Marquet, Pablo A.; Vergara, Pablo M.; Meneses, Luis; Moreira-Arce, Dario
    Here we present a global time-series of global forest above ground biomass from 2000 to 2019, analyzing spatiotemporal patterns of carbon balance, accounting for losses and gains. We generated a global Above-Ground Biomass (AGB) map for the year 2000 and assessed its correlation with different satellite products. We generated a multi-year analysis of AGB changes at the pixel level was generated, estimating carbon (C) loss and gain. Finally, we estimated the C losses due to forest clearing and wildfires analyzing their trends across biomes and countries. Our results show that the global mean annual loss was 2.88 +/- 0.33 PgC yr(-1), while global mean C gain was 2.95 +/- 0.43 PgC yr(-1), resulting in a neutral to sink behavior of -0.06 +/- 0.58 PgC yr(-1). The mean annual C loss by forest clearing was 1.04 +/- 0.03 PgC yr(-1), with an increasing trend of +0.03 +/- 0.01 PgC yr(-1). Eight biomes and 54 countries showed a significant increasing trend of C loss by forest clearing. Wildfires C losses reached 0.351 +/- 0.02 Pg C yr(-1), representing the 33.71% of forest clearing C losses. Boreal forest presented the highest C losses from wildfires, while significant increasing trends were evidenced in five biomes. We also find increasing trends of wildfire C loss in 20 countries while decreasing trends were identified in 10 countries. Our findings highlight the importance of designing strong policies to halt deforestation as agreed in the recent COP26 and provide information to identify priority areas to start implementing these policies in the short term.
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    Carotid artery dissection: Endovascular treatment. Report of 12 patients
    (WILEY-LISS, 2008) Fava, Mario; Meneses, Luis; Loyola, Soledad; Tevah, Jose; Bertoni, Hernan; Huetel, Isidro; Mellado, Patricio
    Objective: The purpose of this article is to report our experience with endovascular treatment of internal carotid artery (ICA) dissection with the use of stents. Background: Carotid Dissection is an important cause of ischemic stroke in young and middle-aged patients. There are some patients in whom invasive management is recommended. Methods: Twelve patients (eight females, four males), mean age of 50 years (range 3580 years) with ICA dissection, were treated with the endovascular approach during a 24-month period. Patients included in this study underwent magnetic resonance (MR) and digital subtraction angiography (DSA) for diagnosis. Over this time period, 162 patients with ICA dissections were seen at our institution. Indications for endovascular treatment were: recurrent ischemic events despite adequate anticoagulant treatment in seven cases, contraindication to anticoagulation in four cases, and one case with significant mismatch between diffusion and perfusion weighted MR. Eleven dissections were spontaneous and one was traumatic. The follow-up was performed clinically with Doppler ultrasound (US) and MR at 6, 12, and 24 months. Results: Stent deployment was successful in all cases. Acute symptoms were resolved in 66.7% of patients. No patients deteriorated their neurological status. There were no new clinical events, stent stenosis or occlusion on 24 months follow-up. Conclusion: Our results showed an excellent clinical outcome of the treated patients. This suggests promising results with the use of endovascular treatment in selected patients. (c) 2008 Wiley-Liss, Inc.
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    Embolization of spontaneous portosystemic shunts as treatment for refractory hepatic encephalopathy
    (2022) Benitez, Carlos; Munoz, Ana; Poniachik, Jaime; Ramirez, Felipe; Munoz, Claudia; Cermenati, Tomas; Martinez, Nicolas; Diaz, Pia; Meneses, Luis
    Background: Hepatic encephalopathy (HE) is a common complication of cirrhosis associated with a reduced survival. The presence of high-flux spontaneous porto-systemic shunts can induce HE even in patients with preserved liver function. Aim: To evaluate the effect of spontaneous porto-systemic shunt embolization (SPSE) over HE and its long-term evolution. Material and Methods: Retrospective analysis of 11 patients (91% males) with severe HE non-responsive to medical treatment in whom a SPSE was performed. The grade of HE (employing West Haven score), survival, MELD and Child-Pugh score, ammonia levels, degree of disability (employing the modified Rankin scale (mRs)) were evaluated before and at thirty days after procedure. Results: The most common etiology found was non-alcoholic steatohepatitis (63.6%). A reduction of at least two score points of HE was observed in all patients after thirty days. There was a significant reduction on median (IQR) West Haven score from 3 (2-3) at baseline to 1 (0-1) after the procedure (p < 0.01). Twelve months survival was 63.6%. There was a decrease in median ammonia level from 106.5 (79-165) (ug/dL) to 56 (43-61) after SPSE (p = 0.006). The median mRS score before and after the procedure was 3 (3-5) and 1 (1-2.5), respectively (p < 0.01). Conclusions: According to our experience, SPSE is a feasible and effective alternative to improve HE and functionality of patients with refractory EH.
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    Enhancement of Visual Perception with Use of Dynamic Cues
    (RADIOLOGICAL SOC NORTH AMERICA, 2009) Andia, Marcelo E.; Plett, Johannes; Tejos, Cristian; Guarini, Marcelo W.; Navarro, Maria E.; Razmilic, Dravna; Meneses, Luis; Villalon, Manuel J.; Irarrazaval, Pablo
    Institutional review board approval and signed informed consent were not needed, as medical images included in public databases were used in this study. The purpose of this study was to improve the detection of microcalcifications on mammograms and lung nodules on chest radiographs by using the dynamic cues algorithm and the motion and flickering sensitivity of the human visual system (HVS). Different sets of mammograms from the Mammographic Image Analysis Society database and chest radiographs from the Japanese Society of Radiological Technology database were presented statically, as is standard, and in a video sequence generated with the dynamic cues algorithm. Nine observers were asked to rate the presence of abnormalities with a five-point scale (1, definitely not present; 5, definitely present). The data were analyzed with receiver operating characteristic (ROC) techniques and the Dorfman-Berbaum-Metz method. The video sequence generated with the dynamic cues algorithm increased the rate of detection of microcalcifications by 10.2% (P = .002) compared with that obtained with the standard static method, as measured by the area under the ROC curve. Similar results were obtained for lung nodules, with an increase of 12.3% (P = .0054). The increase in the rate of correct detection did not come just from the image contrast change produced by the algorithm but also from the fact that image frames generated with the dynamic cues algorithm were put together in a video sequence so that the motion sensitivity of the HVS could be used to facilitate the detection of low-contrast objects. (C) RSNA, 2009
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    Myocardial lipids and creatine measured by magnetic resonance spectroscopy among patients with heart failure
    (SOC MEDICA SANTIAGO, 2010) Luis Winter, Jose; Castro, Pablo; Meneses, Luis; Chalhub, Monica; Verdejo, Hugo; Greig, Douglas; Gabrielli, Luigi; Chiong, Mario; Concepcion, Roberto; Mellado, Rosemarie; Hernandez, Claudia; Uribe, Sergio; Lavander, Sergio
    Background: Heart failure (HF) is characterized, among other features, by the development of alterations in myocardial energy metabolism, involving a decrease in glucose utilization and increased free fatty acid uptake by cardiomyocytes, associated with decreased deposits of high-energy phosphates (creatine phosphate/ creatine transporter). Magnetic resonance (MR) imaging allows a direct and noninvasive assessment of myocardial metabolites. Aim: To measure myocardial creatine and lipids by MR spectroscopy among patients with HE Material and Methods: Cardiac MR spectroscopy (1.5 Tesla) with Hydrogen antenna and single voxel acquisition was performed in five patients with non-ischemic heart failure, aged 58 +/- 9.7 years, (60% males) and 5 healthy volunteers matched for age and sex. We analyzed the signals of creatine (Cr), lipids (L) and water (W) in the interventricular septum, establishing the water/lipid (W/L) and water/creatine (W/Cr) index to normalize the values obtained. Results: Among patients, left ventricular ejection fraction was 32 +/- 6.9%, 60% were in functional capacity II, 60% had hypertension and one was diabetic. Spectroscopic curves showed a depletion of total Cr, evidenced by the W/Cr index, among patients with heart failure, when compared with healthy controls (1.46 +/- 1.21 and 5.96 +/- 2.25 respectively, p < 0,05). Differences in myocardial lipid content, measured as the W/L index, were not significant (5.06 +/- 2.66 and 1.80 +/- 1.62 respectively, p = 0.08). Conclusions: Among patients with heart failure of non-ischemic etiology, there is a depletion of creatine levels measured by MR spectroscopy. (Rev Med Chile 2010; 138: 1475-1479).
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    Natriuretic peptide type-B can be a marker of reperfusion in patients with pulmonary thromboembolism subjected to invasive treatment
    (2012) Andresen, Max; Gonzalez, Alejandro; Mercado, Marcelo; Diaz, Orlando; Meneses, Luis; Fava, Mario; Cordova, Samuel; Castro, Ricardo
    This study was intended to investigate changes in cardiac biomarkers and pulmonary hemodynamic effects of invasive treatment in patients with intermediate-risk (hemodynamic stability with evidence of right ventricle dysfunction and/or myocardial injury) pulmonary embolism. Also, to also evaluate if natriuretic peptide type-B (NT-proBNP) plasma levels are associated with right ventricle function and pulmonary arterial pressures. Interventional study: Fourteen normotensive adult patients with acute and radiologically massive pulmonary embolism plus positive biomarkers and evidences of right ventricle dysfunction underwent invasive pulmonary angiography for invasive treatment consisting on mechanical thrombus fragmentation and catheter-directed intrathrombus thrombolysis. Angiography was repeated after 12-24 h to reevaluate perfusion status. Plasma biomarkers were monitored before and 8-h after intervention. Biomarkers were initially elevated in all patients. Eleven patients (78.6%) exhibited significant angiographic reperfusion. NT-proBNP and mean pulmonary arterial pressure decreased significantly in all of them [3693 (1803, 8862) to 1951 (1309, 7918) pg/ml; P = 0.008) and 40.0 (24.0, 46.0) to 22.0 (14.0, 27.0) mmHg; P = 0.003, respectively]. No significant variation was observed in troponin-T levels. In patients with high-risk pulmonary embolism, NT-proBNP plasma levels experience rapid and significant reduction after successful invasive treatment. In pulmonary embolism, serial measurements of NT-proBNP could be useful as a tracking tool to assess the success or failure of the thrombolytic treatment.