Browsing by Author "Uribe, Sergio"

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    A 3D trajectory for undersampling k-space in MRSI applications
    (ELSEVIER SCIENCE INC, 2007) Uribe, Sergio; Guesalaga, Andres; Mir, Roberto; Guarini, Marcelo; Irarrazaval, Pablo
    Magnetic resonance spectroscopic imaging (MRSI) is a noninvasive technique for producing spatially localized spectra. MRSI presents the important challenge of reducing the scan time while maintaining the spatial resolution. The preferred approach for this is to use time-varying readout gradients to collect the spatial and chemical-shift information. Fast, three-dimensional (3D) spatial encoded methods also reduce the scan time. Despite the existence of several new and faster 3D encoded methods, or k-space trajectories, for magnetic resonance imaging (MRI), only stack of spirals and echo planar have been studied in 3D MRSI. A novel formulation for designing fast, 3D k-space trajectory applicable to 3D MRSI is presented. This approach is simple and consists of rays expanding from the origin of k-space into a revolving sphere, collecting spectral data of all 3D spatial k-space at different times in the same scan. This article describes this new method and presents some results of its application to 3D MRSI. This technique allows some degree of undersampling; hence, it is possible to reconstruct high-quality undersampled spectroscopic imaging in order to recognize different compounds in short scan times. Additionally, the method is tested in regular 3D MRI. This proposed method can also be used for dynamic undersampled imaging. (c) 2007 Elsevier Inc. All rights reserved.
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    A Spatial Off-Resonance Correction in Spirals for Magnetic Resonance Fingerprinting
    (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2021) Coronado, Ronal; Cruz, Gastao; Castillo Passi, Carlos; Tejos, Cristian; Uribe, Sergio; Prieto, Claudia; Irarrazaval, Pablo
    In MR Fingerprinting (MRF), balanced Steady-State Free Precession (bSSFP) has advantages over unbalanced SSFP because it retains the spin history achieving a higher signal-to-noise ratio (SNR) and scan efficiency. However, bSSFP-MRF is not frequently used because it is sensitive to off-resonance, producing artifacts and blurring, and affecting the parametric map quality. Here we propose a novel Spatial Off-resonance Correction (SOC) approach for reducing these artifacts in bSSFP-MRF with spiral trajectories. SOC-MRF uses each pixel's Point Spread Function to create system matrices that encode both off-resonance and gridding effects. We iteratively compute the inverse of these matrices to reduce the artifacts. We evaluated the proposed method using brain simulations and actual MRF acquisitions of a standardized T1/T2 phantom and five healthy subjects. The results show that the off-resonance distortions in T1/T2 maps were considerably reduced using SOC-MRF. For T2, the Normalized Root Mean Square Error (NRMSE) was reduced from 17.3 to 8.3% (simulations) and from 35.1 to 14.9% (phantom). For T1, the NRMS was reduced from 14.7 to 7.7% (simulations) and from 17.7 to 6.7% (phantom). For in-vivo, the mean and standard deviation in different ROI in white and gray matter were significantly improved. For example, SOC-MRF estimated an average T2 for white matter of 77ms (the ground truth was 74ms) versus 50 ms of MRF. For the same example the standard deviation was reduced from 18 ms to 6ms. The corrections achieved with the proposed SOC-MRF may expand the potential applications of bSSFP-MRF, taking advantage of its better SNR property.
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    Accelerating dual cardiac phase images using phase encoding trajectories
    (ELSEVIER SCIENCE INC, 2016) Letelier, Karis; Urbina, Jesus; Andia, Marcelo; Tejos, Cristian; Irarrazaval, Pablo; Prieto, Claudia; Uribe, Sergio
    A three-dimensional dual-cardiac-phase (3D-DCP) scan has been proposed to acquire two data sets of the whole heart and great vessels during the end-diastolic and end-systolic cardiac phases in a single free-breathing scan. This method has shown accurate assessment of cardiac anatomy and function but is limited by long acquisition times. This work proposes to accelerate the acquisition and reconstruction of 3D-DCP scans by exploiting redundant information of the outer k-space regions of both cardiac phases. This is achieved using a modified radial-phase-encoding trajectory and gridding reconstruction with uniform coil combination. The end-diastolic acquisition trajectory was angularly shifted with respect to the end-systolic phase. Initially, a fully-sampled 3D-DCP scan was acquired to determine the optimal percentage of the outer k-space data that can be combined between cardiac phases. Thereafter, prospectively undersampled data were reconstructed based on this percentage. As gold standard images, the undersampled data were also reconstructed using iterative SENSE. To validate the method, image quality assessments and a cardiac volume analysis were performed. The proposed method was tested in thirteen healthy volunteers (mean age, 30 years). Prospectively undersampled data (R = 4) reconstructed with 50% combination led high quality images. There were no significant differences in the image quality and in the cardiac volume analysis between our method and iterative SENSE. In addition, the proposed approach reduced the reconstruction time from 40 min to 1 min. In conclusion, the proposed method obtains 3D-DCP scans with an image quality comparable to those reconstructed with iterative SENSE, and within a clinically acceptable reconstruction time. (C) 2016 Elsevier Inc. All rights reserved.
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    Assessment 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.
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    Automatic 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, Sergio
    Fat 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.
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    Chemical species separation with simultaneous estimation of field map and T-2* using a k-space formulation
    (WILEY-BLACKWELL, 2012) Luis Honorato, Jose; Parot, Vicente; Tejos, Cristian; Uribe, Sergio; Irarrazaval, Pablo
    Chemical species separation techniques in image space are prone to incorporate several distortions. Some of these are signal accentuation in borders and geometrical warping from field inhomogeneity. These errors come from neglecting intraecho time variations. In this work, we present a new approach for chemical species separation in MRI with simultaneous estimation of field map and T?2* decay, formulated entirely in k-space. In this approach, the time map is used to model the phase accrual from off-resonance precession and also the amplitude decay due to T?2*. Our technique fits the signal model directly in k-space with the acquired data minimizing the l2-norm with an interior-point algorithm. Standard two dimensional gradient echo sequences in the thighs and head were used for demonstrating the technique. With this approach, we were able to obtain excellent estimation for the species, the field inhomogeneity, and T?2* decay images. The results do not suffer from geometric distortions derived from the chemical shift or the field inhomogeneity. Importantly, as the T?2* map is well positioned, the species signal in borders is correctly estimated. Considering intraecho time variations in a complete signal model in k-space for separating species yields superior estimation of the variables of interest when compared to existing methods. Magn Reson Med, 2012. (C) 2011 Wiley Periodicals, Inc.
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    Congenital Heart Disease in Children: Coronary MR Angiography during Systole and Diastole with Dual Cardiac Phase Whole-Heart Imaging
    (RADIOLOGICAL SOC NORTH AMERICA, 2011) Uribe, Sergio; Hussain, Tarique; Valverde, Israel; Tejos, Cristian; Irarrazaval, Pablo; Fava, Mario; Beerbaum, Philipp; Botnar, Rene M.; Razavi, Reza; Schaeffter, Tobias; Greil, Gerald F.
    Purpose: To assess the optimal timing for coronary magnetic resonance (MR) angiography in children with congenital heart disease by using dual cardiac phase whole-heart MR imaging.
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    Functional cardiac MRI in preterm and term newborns
    (B M J PUBLISHING GROUP, 2011) Groves, Alan M.; Chiesa, Gaia; Durighel, Giuliana; Goldring, Stephen T.; Fitzpatrick, Julie A.; Uribe, Sergio; Razavi, Reza; Hajnal, Jo V.; Edwards, A. David
    Objective To use cardiac MRI techniques to assess ventricular function and systemic perfusion in preterm and term newborns, to compare techniques to echocardiographic methods, and to obtain initial reference data.
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    Identification of hemodynamic biomarkers for bicuspid aortic valve induced aortic dilation using machine learning
    (2022) Franco, Pamela; Sotelo, Julio; Guala, Andrea; Dux-Santoy, Lydia; Evangelista, Arturo; Rodriguez-Palomares, Jose; Mery Quiroz, Domingo Arturo; Salas, Rodrigo; Uribe, Sergio
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    Intake of red wine grape pomace decreased atherosclerosis, attenuated myocardial damage and increased survival in a murine model of lethal coronary heart disease
    (MDPI, 2019) Salas Perez, Francisca Lorena; Rivera Vega, Katherine Solange; Echeverria, Guadalupe; Urquiaga, Ines; Dicenta, Sara; Perez, Druso; Andia, Marcelo; Uribe, Sergio; Tejos, Cristian; Busso, Dolores; Irarrazaval Mena, Pablo; Rigotti, Attilio
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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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    New Respiratory Gating Technique for Whole Heart Cine Imaging: Integration of a Navigator Slice in Steady State Free Precession Sequences
    (WILEY-BLACKWELL, 2011) Uribe, Sergio; Tejos, Cristian; Razavi, Reza; Schaeffter, Tobias
    Purpose: To evaluate the performance of a slice navigator sequence integrated into a b-SSFP sequence for obtaining real time respiratory self-gated whole heart cine imaging.
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    Prevalence of Advanced Liver Fibrosis and Nonalcoholic Steato-hepatitis Diagnosed by Noninvasive Methods in Chilean Type 2 Diabetic Patients
    (2014) Gallego, Consuelo; Valderas, Juan P.; Uribe, Sergio; Tejos, Cristian; Serrano, Cristobal; Huete, Alvaro; Barrera, Francisco; Liberona, Jessica; Labbe, Pilar; Quiroga, Teresa; Irarrazabal, Pablo; Arrese, Marco
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    Quantification of visceral adipose tissue using magnetic resonance imaging compared with anthropometry, in type 2 diabetic patients
    (SOC MEDICA SANTIAGO, 2012) Serrano Garcia, Cristobal; Barrera, Francisco; Labbe, Pilar; Liberona, Jessica; Arrese, Marco; Irarrazaval, Pablo; Tejos, Cristian; Uribe, Sergio
    Background: Visceral fat accumulation is associated with the development of metabolic diseases. Anthropometry is one of the methods used to quantify it. aim: to evaluate the relationship between visceral adipose tissue volume (VAT), measured with magnetic resonance imaging (MRI), and anthropometric indexes, such as body mass index (BMI) and waist circumference (WC), in type 2 diabetic patients (DM2). Patients and Methods: Twenty four type 2 diabetic patients aged 55 to 78 years (15 females) and weighting 61.5 to 97 kg, were included. The patients underwent MRI examination on a Philips Intera (R) 1.5T MR scanner. The MRI protocol included a spectral excitation sequence centered at the fat peak. The field of view included from L4-L5 to the diaphragmatic border. VAT was measured using the software Image J (R). Weight, height, BMI, WC and body fat percentage (BF%), derived from the measurement of four skinfolds with the equation of Durnin and Womersley, were also measured. The association between MRI VAT measurement and anthropometry was evaluated using the Pearson's correlation coefficient. Results: Mean VAT was 2478 +/- 758 ml, mean BMI 29.5 +/- 4.7 kg/m(2), and mean WC was 100 +/- 9.7 cm. There was a poor correlation between VAT, BMI (r = 0.18) and WC (r = 0.56). Conclusions: BMI and WC are inaccurate predictors of VAT volume in type 2 diabetic patients. (Rev Med Chile 2012; 140: 1535-1543).
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    Single Breath-Hold Assessment of Ventricular Volumes Using 32-Channel Coil Technology and an Extracellular Contrast Agent
    (JOHN WILEY & SONS INC, 2010) Parish, Victoria; Hussain, Tarique; Beerbaum, Philip; Greil, Gerald; Nagel, Eike; Razavi, Reza; Schaeffter, Tobias; Uribe, Sergio
    Purpose: To evaluate the feasibility of a single breath-hold 3D eine balanced steady-state free precession (b-SSFP) sequence after gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) injection for volumetric cardiac assessment.
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    Soluble Free, Esterified and Insoluble-Bound Phenolic Antioxidants from Chickpeas Prevent Cytotoxicity in Human Hepatoma HuH-7 Cells Induced by Peroxyl Radicals
    (2022) Costa de Camargo, Adriano; Alvarez, Alina Concepción ; Arias-Santé, María Fernanda; Oyarzún, Juan Esteban; Andia, Marcelo E.; Uribe, Sergio; Nunez-Pizarro, Paula; Bustos, Simón M.; Schwember, Andrés R. ; Shahidi, Fereidoon ; Bridi, Raquel