Browsing by Author "Andia, Marcelo E."
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- ItemAccelerating three-dimensional molecular cardiovascular MR imaging using compressed sensing(2012) Prieto Vásquez, Claudia; Andia, Marcelo E.; von Bary, Christian; Onthank, David C.; Schaeffter, Tobias; Botnar, René Michael
- ItemArterial spin labeling angiography using a triple inversion recovery prepulse(WILEY-BLACKWELL, 2012) Andia, Marcelo E.; Botnar, Rene M.Arterial spin labeling is a well-known noninvasive angiography technique, which does not necessitate the use of a contrast agent. arterial spin labeling is still clinically underused because of several challenges: (1) long scan times because of the need for two acquisitions (labeled and nonlabeled datasets), (2) sensitivity to spatial misregistration because of the need for image subtraction, and (3) the need for precise planning and choice of an optimal inversion delay for best blood-to-background contrast. In this work, we propose a new arterial spin labeling method based on a triple-inversion-recovery sequence-arterial spin labeling. This approach exploits the ability of two nonselective inversion recovery prepulses to null the background signal over a wide range of T1 values, while maintaining the signal of labeled blood using a third slab selective inversion pulse. This technique therefore allows the acquisition of angiograms with a flexible inversion delay, easier planning procedure and no need for subtraction. Magn Reson Med, 2012. (C) 2011 Wiley Periodicals, Inc.
- ItemAssessment of hepatic fatty acids during non-alcoholic steatohepatitis progression using magnetic resonance spectroscopy(2021) Xavier, Aline; Zacconi, Flavia C. M.; Santana Romo, Fabián Mauricio; Eykyn, Thomas R.; Lavin, Begona; Phinikaridou, Alkystis; Botnar, Rene; Uribe, Sergio; Esteban Oyarzun, Juan; Cabrera, Daniel; Arrese, Marco; Andia, Marcelo E.Abstract: Introduction and objectives: Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver abnormalities including steatosis, steatohepatitis, fibrosis, and cirrhosis. Liver biopsy remains the gold standard method to determine the disease stage in NAFLD but is an invasive and risky procedure. Studies have previously reported that changes in intrahepatic fatty acids (FA) composition are related to the progression of NAFLD, mainly in its early stages. The aim of this study was to characterize the liver FA composition in mice fed a Choline-deficient L-amino-defined (CDAA) diet at different stages of NAFLD using magnetic resonance spectroscopy (MRS). Methods: We used in-vivo MRS to perform a longitudinal characterization of hepatic FA changes in NAFLD mice for 10 weeks. We validated our findings with ex-vivo MRS, gas chromatography-mass spectrometry and histology. Results: In-vivo and ex-vivo results showed that livers from CDAA-fed mice exhibit a significant increase in liver FA content as well as a change in FA composition compared with control mice. After 4 weeks of CDAA diet, a decrease in polyunsaturated and an increase in monounsaturated FA were observed. These changes were associated with the appearance of early stages of steatohepatitis, confirmed by histology (NAFLD Activity Score (NAS) = 4.5). After 10 weeks of CDAA-diet, the liver FA composition remained stable while the NAS increased further to 6 showing a combination of early and late stages of steatohepatitis. Conclusion: Our results suggest that monitoring lipid composition in addition to total water/fat with MRS may yield additional insights that can be translated for non-invasive stratification of high-risk NAFLD patients.
- ItemAutomatic quantification of fat infiltration in paraspinal muscles using T2-weighted images: An OsiriX application(ELSEVIER SCI LTD, 2020) Arrieta, Cristobal; Urrutia, Julio; Besa, Pablo; Montalba, Cristian; Lafont, Nelson; Andia, Marcelo E.; Uribe, SergioFat infiltration of paraspinal muscles has been related with low back pain and quantified using T2w MR images and manual segmentation techniques. This methodology is time consuming and has low reproducibility. Moreover, the accuracy of T2w images to quantify fat has not been validated. This paper presents the development and validation of an OsiriX application to semi-automatically segment infiltrated fat on T2w images. This software was also utilized to validate the quantification of muscle fat infiltration with T2w images, considering Dixon fat images assessments as a gold standard.
- ItemCan a smartphone be used for ‘tele-auscultation’?(2023) Godoy Sánchez, Eduardo Javier; Echenique, María Belén; Cádiz, Rodrigo F.; Andia, Marcelo E.Introduction: Telemedicine has become an important way to provide healthcare. However, it lacks a traditional physical examination. This study aims to validate the use of a smartphone as an auscultation device as compared to a digital stethoscope. Methods: Lung and heart sounds were obtained from 50 volunteers. Recordings were made with a smartphone and a commercial digital stethoscope simultaneously, capturing the same respiratory and heart cycles. Sounds were captured by the smartphone using an application of our own, then stored in the cloud and processed in the Julia Language. Clinical validation was performed by ten clinicians in an online survey by comparing the quality of 40 paired recordings against each other, using conventional headphones and without knowing the device used to capture the audios. The recordings included both normal and abnormal lung and heart sounds. Results: Overall, all subjects indicated that the quality of the samples recorded by a smartphone was of equal or superior quality to that of the stethoscope. In our sample of normal lung and heart sounds, the probability to obtain a favourable response for the smartphone was 66% (95%CI 58.9%–72.5%), while in our sample of abnormal sounds, that probability was 87% (95%CI 81.5%–91.3%). Discussion: Our findings suggest that a smartphone is capable of recording lung and heart sounds with enough quality to be interpreted by clinicians by using only its built-in microphone. This, and given their capability to access the internet, would allow for the use of smartphones as tele-auscultation devices.
- ItemDetermination of the Respiratory Compensation Point by Detecting Changes in Intercostal Muscles Oxygenation by Using Near-Infrared Spectroscopy(MDPI, 2022) Contreras Briceño, Felipe; Espinosa Ramírez, Maximiliano; Keim Bagnara, Vicente; Carreño Roman, Matías Ignacio; Rodríguez Villagra, Rafael Alejandro; Villegas Belmar, Fernanda; Viscor, Gines; Gabrielli Nervi, Luigi Arnaldo; Andia, Marcelo E.; Araneda, Oscar F.; Hurtado, Daniel E.This study aimed to evaluate if the changes in oxygen saturation levels at intercostal muscles (SmO2 m.intercostales) assessed by near-infrared spectroscopy (NIRS) using a wearable device could determine the respiratory compensation point (RCP) during exercise. Fifteen healthy competitive triathletes (eight males; 29 +/- 6 years; height 167.6 +/- 25.6 cm; weight 69.2 +/- 9.4 kg; (V) over dotO(2)-max 58.4 +/- 8.1 mL.kg(-1).min(-1)) were evaluated in a cycle ergometer during the maximal oxygen-uptake test ((V) over dotO(2)-max), while lung ventilation ((V) over dotE), power output (watts, W) and SmO2 mantercostales were measured. RCP was determined by visual method (RCPvisual : changes at ventilatory equivalents ((V) over dotE.CO2-1, (V) over dotE.(V) over dotO(2)(-1)) and end-tidal respiratory pressure (PetO(2), PetCO(2)) and NIRS method (RCP NIRS : breakpoint of fall in SmO2 m.intercostales). During exercise, SmO2 m.intercostales decreased continuously showing a higher decrease when (V) over dotE increased abruptly. A good agreement between methods used to determine RCP was found (visual vs NIRS) at %(V) over dotO(2)-max, (V) over dotO(2), (V) over dotE, and W (Bland-Altman test). Correlations were found to each parameters analyzed (r = 0.854; r = 0.865; r = 0.981; and r = 0,968; respectively. p < 0.001 in all variables, Pearson test), with no differences (p < 0.001 in all variables, Student's t-test) between methods used (RCPvisual and RCPNIRS). We concluded that changes at SmO2 m.intercostales measured by NIRS could adequately determine RCP in triathletes.
- ItemEnhancement 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, PabloInstitutional 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
- ItemGeographic variation of gallbladder cancer mortality and risk factors in Chile: A population-based ecologic study(WILEY, 2008) Andia, Marcelo E.; Hsing, Ann W.; Andreotti, Gabriella; Ferreccio, CatterinaChile's gallbladder cancer rates are among the highest in the world, being the leading cause of cancer deaths among Chilean women. To provide insights into the etiology of gallbladder cancer, we conducted an ecologic study examining the geographical variation of gallbladder cancer and several putative risk factors. The relative risk of dying from gallbladder cancer between 1985 and 2003 was estimated for each of the 333 Chilean counties, using a hierarchical Poisson regression model, adjusting for age, sex and geographical location. The risk of gallbladder cancer mortality was analyzed in relation to region, poverty, Amerindian (Mapuche) population, typhoid fever and access to cholecystectomy, using logistic regression analysis. There were 27,183 gallbladder cancer deaths, with age and sex-adjusted county mortality rates ranging from 8.2 to 12.4 per 100,000 inhabitants. Rates were highest in inland and southern regions. Compared to the northern-coast, the northern-inland region had a 10-fold risk (95% of confidence interval (95% CI): 2.4-42.2) and the southern-inland region had a 26-fold risk (95% CI: 6.0-114.2). Independent of region, other risk factors for gallbladder cancer included a high Mapuche population (Odds ratio (011):3.9, 95% CI 1.8-8.7), high typhoid fever incidence (011:2.9, 95% Cl 1.2-6.9), high poverty (011:5.1., 95% CI 1.6-15.9), low access to cholecystectomy (011:3.9, 95% CI 1.5-10.1), low access to hospital care (011:14.2, 95% C1 4.2-48.7) and high urbanization (011:8.0, 95% CI 3.4-18.7). Our results suggest that gallbladder cancer in Chile may be related to both genetic factors and poor living conditions. Future analytic studies are needed to further clarify the role of these factors in gallbladder cancer etiology. Published 2008 Wiley-Liss, Inc.
- ItemIncidence and survival of stomach cancer in a high-risk population of Chile(BAISHIDENG PUBLISHING GROUP INC, 2009) Heise, Katy; Bertran, Enriqueta; Andia, Marcelo E.; Ferreccio, CatterinaAIM: To study the incidence and survival rate of stomach cancer (SC) and its associated factors in a high risk population in Chile.
- ItemNoninvasive Magnetic Resonance Imaging Evaluation of Endothelial Permeability in Murine Atherosclerosis Using an Albumin-Binding Contrast Agent(LIPPINCOTT WILLIAMS & WILKINS, 2012) Phinikaridou, Alkystis; Andia, Marcelo E.; Protti, Andrea; Indermuchle, Andreas; Shah, Ajay; Smith, Alberto; Warley, Alice; Botnar, Rene M.Backgound-Endothelial dysfunction promotes atherosclerosis and precedes acute cardiovascular events. We investigated wether in vivo magnetic resonance imaging with the use of an albumin-binding contrast agent, gadofosveset, could detect endothelial damage associated with atherosclerosis in apolipoprotein E-deficient (ApoE(-/-)) mice. Furthermore, we tested whether magnetic resonance imaging could noninvasively assess endothelial function by measuring the endothelial-dependent vasolidation in response to acetycholine.
- ItemThe Spectrum from Overt Primary Aldosteronism to Mild Dysregulated Aldosterone Production in Incidentally Discovered Adrenocortical Adenomas(2024) Uslar Nawrath, Thomas Hermann; Olmos, Roberto; Burnier, Alberth; Sanfuentes, Benjamín; Böhm, Pauline; Orellana, Maria Paz; Guarda, Francisco J.; Huete, Alvaro; Mertens, Nicolás; Besa, Cecilia; Andia, Marcelo E.; Majerson, Alejandro; Cartes, Jaime; Fardella, Carlos; Allende, Fidel; Solari, Sandra; Vaidya, Anand; Baudrand Biggs, RenéBackground Incidental adrenocortical adenomas (IA) are common. Current guidelines suggest screening for primary aldosteronism (PA) only in cases of hypertension or hypokalemia. This study aimed to evaluate the spectrum from overt PA to mild dysregulated aldosterone production with a sensitive protocol irrespective of blood pressure (BP) and potassium in patients with IA.Methods 254 consecutive patients (excluding hypercortisolism) were evaluated. The spectrum of PA was defined as a suppressed renin plus the following criteria: 1)Overt PA: aldosterone-to-renin-ratio (ARR) >30 ng/dL-to-ng/mL/hr, plasma aldosterone concentration (PAC) >15ng/dL, and/or 24h urinary aldosterone >10 ug/24h; 2)Moderate PA: ARR 20-30 ng/dL-to-ng/mL/hr, PAC 10-15 ng/dL; 3)Mild dysregulated aldosterone production: ARR <20 ng/dL-to-ng/mL/hr and PAC >5-10 ng/dL.Results 35% (n=89/254) met criteria for PA spectrum, 20% (34/89) were initially normotensive and 94% (84/89) normokalemic. Overt, moderate, and mild groups were 10%, 12%, and 13%. There were trends across groups of clinical severity: systolic BP (153±19, 140±14, 137±14 mmHg, p-trend<0.05), resistant hypertension (50%, 23%, 7% p-trend=<0.001), daily defined dose of antihypertensives (DDD) (3.2±1.6, 1.2±1.5, 0.4±0.6 p-trend=0.001), and lower eGFR (75.5±30.8, 97.8±38.5, 101±25.5, p-trend<0.01). At follow-up (mean 28±15 months), 87% had treatment with MR antagonists or surgery with decreased systolic BP relative to clinical severity, −31.3 ±23, −12.7 ±19, and −11.4 ±19 mmHg, (p-trend<0.001). Similar trends were observed for DDD, with significant increase in renin.Conclusions There is a prevalent spectrum of clinically-relevant PA and dysregulated aldosterone production in IA, irrespective of BP or potassium, usually undetected. Aldosterone-directed treatment improved BP and normalized renin even in milder cases.