[Tractography of the uncinate fasciculus and the posterior cingulate fasciculus in patients with mild cognitive impairment and Alzheimer disease]. / Tractografía del fascículo uncinado y el fascículo uncinado posterior en pacientes con deterioro cognitivo leve y enfermedad de Alzheimer.

INTRODUCTION: Brain tractography is a non-invasive medical imaging technique which enables in vivo visualisation and various types of quantitative studies of white matter fibre tracts connecting different parts of the brain. We completed a quantitative study using brain tractography with diffusion tensor imaging in patients with mild cognitive impairment, patients with Alzheimer disease, and normal controls, in order to analyse the reproducibility and validity of the results. SUBJECTS AND METHODS: Fractional anisotropy (FA) and mean diffusivity (MD) were measured across the uncinate fasciculus and the posterior cingulate fasciculus in images, obtained from a database and a research centre, representing 52 subjects distributed among the 3 study groups. Two observers took the measurements twice in order to evaluate intra- and inter-observer reproducibility. RESULTS: Measurements of FA and MD of the uncinate fasciculus delivered an intraclass correlation coefficient above 0.9; ICC was above 0.68 for the posterior cingulate fasciculus. Patients with Alzheimer disease showed lower values of FA and higher MD values in the right uncinate fasciculus in images from the research centre. A comparison of the measurements from the 2 centres revealed significant differences. CONCLUSION: We established a reproducible methodology for performing tractography of the tracts in question. FA and MD indexes may serve as early indicators of Alzheimer disease. The type of equipment and the method used to acquire images must be considered because they may alter results as shown by comparing the 2 data sets in this study.

[Magnetic resonance for evaluating the response to treatment for ovarian hyperstimulation syndrome: comparison of pharmokinetic models.]. / Resonancia magnética en la respuesta al tratamiento del síndrome de hiperestimulación ovárica: comparación de modelos farmacocinéticos.

OBJECTIVE: To evaluate the response to treatment with cabergoline for ovarian hyperstimulation syndrome (OHS) using mono- and bi-compartmental MRI models. MATERIAL AND METHODS: We studied 20 ovum donors with a high risk of developing OHS, divided in two groups (placebo vs. treatment). MRI perfusion studies were performed before and after the beginning of treatment. We compared the monocompartmental model, with the parameters vascular permeability (K(trans)), extraction ratio (k(ep)), and extravascular extracellular space fraction (v(e)), against the bicompartmental model, with the same parameters as in the monocompartmental model and the additional parameter vascular space fraction (v(p)). The differences between groups (placebo vs. treatment) on the two MRI studies and for each pharmacokinetic model were analyzed using t-tests for independent samples. The intraclass correlation coefficient (ICC) was used to assess the variability of the measurements. RESULTS: In the placebo group, a significant increase in K(trans) was observed with both models (p=0.021 for one compartment; and p<0.001 for two compartments). In the treatment group, no statistically significant differences were found for any parameter in either model. Regarding differences between groups, in the bicompartmental model K(trans) increased 168.6%+/-151.9% in the placebo group versus 43.3%+/-54.5% in the treatment group, p=0.04). In the monocompartmental model, no differences were found between groups. In the variability analysis, the ICC was higher than 0.95 for all parameters except v(p) (ICC=0.89). CONCLUSIONS: Capillary permeability calculated with bicompartmental pharmacokinetic models after MRI contrast administration is a biomarker of the treatment effect in OHS patients.

Left orbitofrontal and superior temporal gyrus structural changes associated to suicidal behavior in patients with schizophrenia.

Suicidal attempts are relatively frequent and clinically relevant in patients with schizophrenia. Recent studies have found gray matter differences in suicidal and non-suicidal depressive patients. However, no previous neuroimaging study has investigated possible structural abnormalities associated to suicidal behaviors in patients with schizophrenia. A whole-brain magnetic resonance voxel-based morphometric examination was performed on 37 male patients meeting the DSM-IV criteria for schizophrenia. Thirteen (35.14%) patients had attempted suicide. A non-parametric permutation test was computed to perform the comparability between groups. An analysis of covariance (AnCova) model was constructed with a statistical threshold of p<0.05 corrected for multiple comparisons. After controlling for age and severity of illness, results showed significant gray matter density reduction in left superior temporal lobe (p=0.03) and left orbitofrontal cortex (p=0.04) in patients who had attempted suicide when comparing with non-suicidal patients. Although sample size limitations and potential clinical heterogeneity preclude definitive conclusions, these data point to structural differences in key cerebral areas. Neuroimaging studies are necessary to expand our knowledge of biological mechanisms underlying suicide in schizophrenia.

Schwann-cell cylinders grown inside hyaluronic-acid tubular scaffolds with gradient porosity.

Cell transplantation therapies in the nervous system are frequently hampered by glial scarring and cell drain from the damaged site, among others. To improve this situation, new biomaterials may be of help. Here, novel single-channel tubular conduits based on hyaluronic acid (HA) with and without poly-l-lactide acid fibers in their lumen were fabricated. Rat Schwann cells were seeded within the conduits and cultured for 10days. The conduits possessed a three-layered porous structure that impeded the leakage of the cells seeded in their interior and made them impervious to cell invasion from the exterior, while allowing free transport of nutrients and other molecules needed for cell survival. The channel's surface acted as a template for the formation of a cylindrical sheath-like tapestry of Schwann cells continuously spanning the whole length of the lumen. Schwann-cell tubes having a diameter of around 0.5mm and variable lengths can thus be generated. This structure is not found in nature and represents a truly engineered tissue, the outcome of the specific cell-material interactions. The conduits might be useful to sustain and protect cells for transplantation, and the biohybrids here described, together with neuronal precursors, might be of help in building bridges across significant distances in the central and peripheral nervous system. STATEMENT OF SIGNIFICANCE: The paper entitled "Schwann-cell cylinders grown inside hyaluronic-acid tubular scaffolds with gradient porosity" reports on the development of a novel tubular scaffold and on how this scaffold acts on Schwann cells seeded in its interior as a template to produce macroscopic hollow continuous cylinders of tightly joined Schwann cells. This cellular structure is not found in nature and represents a truly engineered novel tissue, which obtains as a consequence of the specific cell-material interactions within the scaffold.

Fibronectin-matrix sandwich-like microenvironments to manipulate cell fate.

Conventional 2D substrates fail to represent the natural environment of cells surrounded by the 3D extracellular matrix (ECM). We have proposed sandwich-like microenvironments as a versatile tool to study cell behaviour under quasi-3D conditions. This is a system that provides a broad range of dorsal and ventral independent spatio-temporal stimuli. Here, we use this sandwich technology to address the role of dorsal stimuli in cell adhesion, cell proliferation and ECM reorganisation. Under certain conditions, dorsal stimuli within sandwich microenvironments prevent the formation of focal plaques as well as the development of the actin cytoskeleton, whereas α5versusαv integrin expression is increased compared to the corresponding 2D controls. Cell signaling is similarly enhanced after dorsal stimuli (measured by the pFAK/FAK level) for cells sandwiched after 3 h of 2D ventral adhesion, but not when sandwiched immediately after cell seeding (similar levels to the 2D control). Cell proliferation, studied by the 5-bromo-2-deoxyuridine (BrdU) incorporation assay, was significantly reduced within sandwich conditions as compared to 2D substrates. In addition, these results were found to depend on the ability of cells to reorganise the dorsal layer of proteins at the material interface, which could be tuned by adsorbing FN on material surfaces that results in a qualitatively different conformation and distribution of FN. Overall, sandwich-like microenvironments switch cell behaviour (cell adhesion, morphology and proliferation) towards 3D-like patterns, demonstrating the importance of this versatile, simple and robust approach to mimic cell microenvironments in vivo.

Fibronectin adsorption and cell response on electroactive poly(vinylidene fluoride) films.

Due to the large potential of electroactive materials in novel tissue engineering strategies, the aim of this work is to determine if the crystalline phase and/or the surface electrical charge of electroactive poly(vinylidene fluoride), PVDF, have influence on the biological response in monolayer cell culture. Non-polar α-PVDF and electroactive ß-PVDF were prepared. The ß-PVDF films were poled by corona discharge to show negative or positive electrical surface charge density. It has been concluded that hydrophilicity of the PVDF substrates depends significantly on crystalline phase and polarity. Furthermore, by means of atomic force microscopy and an enzyme-linked immunosorbent assay test, it has been shown that positive or negative poling strongly influences the behavior of ß-PVDF supports with respect to fibronectin (FN) adsorption, varying the exhibition of adhesion ligands of adsorbed FN. Culture of MC3T3-E1 pre-osteoeblasts proved that cell proliferation depends on surface polarity as well. These results open the viability of cell culture stimulation by mechanical deformation of a piezoelectric substrate that results in varying electrical charge densities on the substrate surface.

[Estimating intracranial fluid dynamics using quantitative analyses of phase contrast magnetic resonance images]. / Estimación de la dinámica de líquidos intracraneales mediante análisis cuantitativo de imágenes de resonancia magnética de contraste de fase.

OBJECTIVE: To estimate the dynamic relations between cerebrospinal fluid (CSF) and blood in the cerebral and spinal subarachnoid spaces and in the ventricles by quantifying phase contrast magnetic resonance imaging (MRI). MATERIAL AND METHODS: We analyzed 15 healthy volunteers during the same time of day and using the same magnetic field strength (3T). Each study consisted of four phase contrast sequences: two to calculate the CSF (aqueduct of Sylvius and the C2-C3 perimedullary space) and two to calculate the blood flow (internal carotid and vertebral arteries, superior sagittal sinus, and straight sinus). We calculated the amplitude parameters (systolic volume, mean flow, pulsatility and compliance indexes, absolute pressure gradient, and ratio of CSF volume per cycle) and temporal parameters (delays respect to arterial flow). RESULTS: With respect to the input of arterial blood, the displacement of venous blood (22% and 38% of the cardiac cycle in the straight sinus and superior sagittal sinus, respectively) and of CSF (12% and 25% of the cardiac cycle in the C2-C3 perimedullary space and in the aqueduct of Sylvius, respectively) show the distribution of the pulsatility of the intracranial fluids. We calculated the indexes of compliance of the encephalic and medullary compartments in normal subjects. CONCLUSIONS: It is possible to quantitatively describe the dynamic relations between intracranial fluids and infer the elastic behavior of the brain and spinal canal by using flow velocity maps obtained with phase contrast MRI.

[European Directive 2004/40/EC on workers' exposure to electromagnetic fields from MRI]. / Acerca de la exposición a los campos electromagnéticos presentes en resonancia magnética. Directiva Europea 2004/40/EC.

This article reviews the regulations in force about the exposure of workers to the electromagnetic fields generated by magnetic resonance imaging (MRI) and evaluates the impact of European Directive 2004/40/EC on the daily use of MRI. We provide a detailed review of the safety criteria stipulated in the International Commission on Non-Ionizing Radiation Protection, in Spanish Royal Decree 1066/2001, and in European Directive 2004/40/EC about exposure to electromagnetic fields. In the case of European Directive 2004/40/EC, the European Union (EU) has introduced a law without adequately evaluating its repercussions. In response to alarms sounded by the radiological and general medical communities, the EU has decided to delay implementation of the Directive. Although the implementation of Directive 2004/40/ EC has been postponed until April 30, 2012, it remains in force. There remains the hope that the Directive will be reconsidered during this interval and that MRI workers will be exempt.

Tractografía del fascículo uncinado y el fascículo uncinado posterior en pacientes con deterioro cognitivo leve y enfermedad de Alzheimer / Tractography of the uncinate fasciculus and the posterior cingulate fasciculus in patients with mild cognitive impairment and Alzheimer disease

Introducción: La tractografía cerebral es una técnica que permite visualizar los fascículos de sustancia blanca que conectan distintas partes del cerebro y realizar estudios cuantitativos de diversa índole sobre ellos. En este trabajo de investigación se realizó un estudio cuantitativo por tractografía cerebral mediante imágenes de resonancia magnética potenciadas en difusión en pacientes con deterioro cognitivo leve, enfermedad de Alzheimer y controlesnormales, con el fin de analizar la reproducibilidad y validez de los resultados. Sujetos y métodos: Se realizaron mediciones de anisotropía fraccional (FA) y difusividad media (MD) en el fascículo uncinado y el fascículo cingulado posterior, en imágenes obtenidas de una base de datos y de un centro de investigación, en 52 sujetos distribuidos en los 3 grupos de interés. Dos observadores realizaron las mediciones 2 veces para evaluar la reproducibilidad intra- e interobservador. Resultados: En el estudio de reproducibilidad se obtuvieron coeficientes de correlación intraclase superior a 0,9 para las medidas de FA y MD del fascículo uncinado, y mayor de 0,68 para las del fascículo cingulado posterior. Los pacientes con enfermedad de Alzheimer mostraron menores valores de FA y mayores valores de MD para el fascículo uncinado derecho correspondiente al centro de investigación. Existieron diferencias significativas en la comparación entre los datos de la base de datos y los del centro de investigación. Conclusiones: Se estableció una metodología reproducible para realizar tractografía en los fascículos estudiados. Los índices de FA y MD podrían ser indicadores tempranos de la enfermedad de Alzheimer, siendo necesario considerar el equipo y el método de adquisición de imágenes ya que pueden influir en los resultados como se comprobó en la comparación entre los 2 conjuntos de datos empleados

Introduction: Brain tractography is a non-invasive medical imaging technique which enables in vivo visualisation and various types of quantitative studies of white matter fibre tracts connecting different parts of the brain. We completed a quantitative study using brain tractography with diffusion tensor imaging in patients with mild cognitive impairment, patients with Alzheimer disease, and normal controls, in order to analyse the reproducibility and validity of the results. Subjects and methods: Fractional anisotropy (FA) and mean diffusivity (MD) were measured across the uncinate fasciculus and the posterior cingulate fasciculus in images, obtained from a database and a research centre, representing 52 subjects distributed among the 3 study groups. Two observers took the measurements twice in order to evaluate intra- and inter-observer reproducibility. Results: Measurements of FA and MD of the uncinate fasciculus delivered an intraclass correlation coefficient above 0.9; ICC was above 0.68 for the posterior cingulate fasciculus. Patients with Alzheimer disease showed lower values of FA and higher MD values in the right uncinate fasciculus in images from the research centre. A comparison of the measurements from the 2 centres revealed significant differences. Conclusion: We established a reproducible methodology for performing tractography of the tracts in question. FA and MD indexes may serve as early indicators of Alzheimer disease. The type of equipment and the method used to acquire images must be considered because they may alter results as shown by comparing the 2 data sets in this study

[Normal values for cerebrospinal fluid flow dynamics in the aqueduct of Sylvius through optimized analysis of phase-contrast MR images]. / Valores de normalidad de la dinámica del flujo de líquido cefalorraquídeo en el acueducto de Silvio mediante análisis optimizado de imágenes de contraste de fase en resonancia magnética.

OBJECTIVE: To establish normal values for the different parameters that characterize the cerebrospinal fluid (CSF) flow dynamics in the aqueduct of Sylvius (velocity, flow, volume per cycle, and CSF production) obtained from phase-contrast MR images using a reliable and reproducible post-processing method. The optimized semiautomatic method eliminates interobserver variability and corrects errors due to low amplitude movements, aliasing, and the partial volume effect. MATERIAL AND METHODS: We studied 42 healthy subjects without neurological or cerebrovascular disease or disturbances in CSF dynamics. Images were acquired on a 1.5 T MR scanner using a phase-contrast sequence. All images were acquired during the same time frame (14:00 to 18:00) to avoid circadian influences. RESULTS: we obtained normal values for each of the parameters that characterize CSF dynamics in the aqueduct (maximum diastolic and systolic velocity, mean velocity, maximum diastolic and systolic flow, mean flow, production rate, and stroke volume). Although trends were noted, neither sex nor age (< 25, 26-50, >51 years old) had a statistically significant effect on any parameter (p> or =0.05). DISCUSSION: Although measurements of CSF flow dynamics parameter are sensitive to various factors (temporal and spatial resolutions of the MR sequence, circadian rhythms, age, sex, and MR equipment manufacturer), an optimized post-processing method enables reliable and reproducible values and ranges for normal subjects to be established.

[Magnetic resonance imaging of the left ventricle in healthy subjects: normal values for morphology, function, perfusion, and viability]. / Resonancia magnética del ventrículo izquierdo en sujetos sanos: valores normales de morfología, función, perfusión y viabilidad.

OBJECTIVE: To define normal values of MRI parameters related to cardiac morphology, function, perfusion, and delayed enhancement of the left ventricle and to analyze differences based on age and sex. MATERIAL AND METHODS: We used 1.5T and 3T MRI scanners to analyze 18 healthy subjects ranging in age from 15 to 77 years old. Dedicated image processing software (Cardio-MR, View Forum, Philips Medical Systems) was used to evaluate morphological and functional parameters (end-diastolic and end-systolic volume, stroke volume, ejection fraction, cardiac output, wall mass, wall thickness, wall thickening, wall motion), perfusion parameters (relative maximum upslope, relative maximum enhancement), and delayed enhancement (percentage of late hyperenhancement). Student's t-test was used for statistical analyses. RESULTS: Sex differences were observed: end-diastolic and end-systolic volumes, stroke volume, and wall mass were significantly higher in men and the ejection fraction was significantly larger in women. Healthy subjects over 45 years of age had significantly greater wall thickness. CONCLUSION: We report cardiac MRI reference values for morphological, functional, perfusion, and delayed enhancement parameters. Sex and age should be taken into account as important variables related to some of these parameters.

Prognostic and therapeutic implications of dipyridamole stress cardiovascular magnetic resonance on the basis of the ischaemic cascade.

OBJECTIVE: To determine the prognostic and therapeutic implications of stress perfusion cardiovascular magnetic resonance (CMR) on the basis of the ischaemic cascade. SETTING: Single centre study in a teaching hospital in Spain. PATIENTS: Dipyridamole stress CMR was performed on 601 patients with ischaemic chest pain and known or suspected coronary artery disease. On the basis of the ischaemic cascade, patients were categorised in C1 (no evidence of ischaemia, n = 354), C2 (isolated perfusion deficit at stress first-pass perfusion imaging, n = 181) and C3 (simultaneous perfusion deficit and inducible wall motion abnormalities, n = 66). CMR-related revascularisation (n = 102, 17%) was defined as the procedure prompted by the CMR results and carried out within the next three months. RESULTS: During a median follow-up of 553 days, 69 major adverse cardiac events (MACE), including 21 cardiac deaths, 14 non-fatal myocardial infarctions and 34 admissions for unstable angina with documented abnormal angiography were detected. In non-revascularised patients (n = 499), the MACE rate was 4% (14/340) in C1, 20% (26/128) in C2 and 39% (12/31) in C3 (adjusted p value = 0.004 vs C2 and <0.001 vs C1). CMR-related revascularisation had neutral effects in C2 (20% vs 19%, 1.1 (0.5 to 2.4), p = 0.7) but independently reduced the risk of MACE in C3 (39% vs 11%, 0.2 (0.1 to 0.7), p = 0.01). CONCLUSIONS: Dypiridamole stress CMR is able to stratify risk on the basis of the ischaemic cascade. A small group of patients with severe ischaemia-simultaneous perfusion deficit and inducible wall motion abnormalities-are at the highest risk and benefit most from MACE reduction due to revascularisation.

[Morphological characterization of trabecular bone structure using high resolution magnetic resonance imaging]. / Caracterización morfológica de la estructura trabecular ósea mediante resonancia magnética de alta resolución.

OBJECTIVE: The morphological analysis of trabecular bone of the distal epiphysis of the radius and its three-dimensional representation allow an adequate evaluation of bone quality. We analyzed trabecular bone morphology and its three-dimensional modeling with high resolution magnetic resonance imaging (MRI) to determine the parameters that provide useful information about bone condition. MATERIAL AND METHODS: All data were acquired using 3D T1-weighted gradient-echo sequences in a 3-Tesla MRI scanner. The mathematical algorithms required to study trabecular bone structure were developed in a Matlab environment on a personal computer. A total of 16 healthy subjects (10 women and 6 men; aged 23 to 54 years, mean 36+/-10 years) were studied. No significant differences were found between women (mean age 39+/-12, range: 23-54 years) and men (mean age 33+/-6, range: 25-42) (p = 0.285). Healthy subjects were recruited from among normal subjects studied to assess the ligaments of the wrist. The morphological parameters analyzed were trabecular volume, mean trabecular thickness, mean trabecular separation, and trabecular index. RESULTS: The morphological parameters that were useful in the evaluation of bone quality were trabecular volume (women: 23.22+/-1.78%; men: 27.49+/-1.30%), trabecular thickness (women: 0.1901+/-0.0014 mm; men: 0.1935+/-0.0014 mm), trabecular separation (women: 0.8332+/-0.0440 mm; men: 0.7697+/-0.0258 mm), and the number of trabeculae (women: 1.2215+/-0.0920 mm-1; men: 1.4207+/-0.0640 mm-1). Statistically significant differences between men and women were found for all the parameters analyzed; no significant differences were found in relation with age in this series. CONCLUSIONS: High resolution MRI enabled the morphological characterization of the trabecular bone structure; this represents an advance in the detection of biomarkers for disease.

k-Space tutorial: an MRI educational tool for a better understanding of k-space.

A main difference between Magnetic Resonance (MR) imaging and other medical imaging modalities is the control over the data acquisition and how it can be managed to finally show the adequate reconstructed image. With some basic programming adjustments, the user can modify the spatial resolution, field of view (FOV), image contrast, acquisition velocity, artifacts and so many other parameters that will contribute to form the final image. The main character and agent of all this control is called k-space, which represents the matrix where the MR data will be stored previously to a Fourier transformation to obtain the desired image.This work introduces 'k-Space tutorial', a MATLAB-based educational environment to learn how the image and the k-space are related, and how the image can be affected through k-space modifications. This MR imaging educational environment has learning facilities on the basic acceleration strategies that can be encountered in almost all MR scanners: scan percentage, rectangular FOV and partial Fourier imaging. It also permits one to apply low- and high-pass filtering to the k-space, and to observe how the contrast or the details are selected in the reconstructed image. It also allows one to modify the signal-to-noise ratio of the acquisition and create some artifacts on the image as a simulated movement of the patient - with variable intensity level - and some electromagnetic spikes on k-space occurring during data acquisition.

[Assessment of reliable quantification of the dynamics of cerebrospinal fluid by magnetic resonance imaging in idiopathic normal pressure hydrocephalus]. / Valoración de la cuantificación fiable de la dinámica del líquido cefalorraquídeo en el acueducto de Silvio mediante resonancia magnética en la hidrocefalia normopresiva idiopática.

INTRODUCTION: A combination of good clinical selection with reliable quantification of diverse parameters that characterize the dynamics of cerebrospinal fluid (CSF) flow from phase-contrast magnetic resonance imaging may identify patients with idiopathic normal pressure hydrocephalus (NPH). MATERIAL AND METHODS: We have carried out a quantitative analysis of 38 subjects (19 healthy subjects and 19 patients with suspected idiopathic NPH). The images were acquired using a 1.5 T MR unit with a phase-contrast sequence in an oblique-transversal plane perpendicular to the Sylvius aqueduct codified to 20 cm/s and with 27 observations per cardiac cycle by means of retrospective synchronization. The area was defined to half the height of the peak velocity, to maximize accuracy. Parameters quantified were mean flow, maximum systolic and diastolic flow, maximum systolic and diastolic velocity, mean velocity, CSF production and stroke volume. RESULTS: All the parameters measured showed a significant difference (ANOVA: p

Microvascular perfusion 1 week and 6 months after myocardial infarction by first-pass perfusion cardiovascular magnetic resonance imaging.

OBJECTIVE: To characterise the evolution of myocardial perfusion during the first 6 months after myocardial infarction by first-pass perfusion cardiovascular magnetic resonance imaging (CMR) and determine its significance. DESIGN: Prospective cohort design. SETTING: Single-centre study in a teaching hospital in Spain. PATIENTS: 40 patients with a first ST-elevation myocardial infarction, single-vessel disease and thrombolysis in myocardial infarction (TIMI) grade 3 flow (stent in 33 patients) underwent rest and low-dose dobutamine CMR 7 (SD 1) and 184 (SD 11) days after infarction. Microvascular perfusion was assessed at rest by visual assessment and quantitative analysis of first-pass perfusion CMR. Of the 640 segments, 290 segments subtended by the infarct-related artery (IRA) were focused on. RESULTS: Both 1 week and 6 months after infarction, segments with normal perfusion showed more wall thickening, contractile reserve and wall thickness, and less transmural necrosis, p <0.05 in all cases. Of 76 hypoperfused segments at the first week, 47 (62%) normalised perfusion at the sixth month. However, 42 segments (14% of the whole group) showed chronic abnormal perfusion; these segments showed worse CMR indices in the late phase (p<0.05 in all cases). CONCLUSIONS: In patients with an open IRA, more than half of the segments with abnormal perfusion at the first week are normally perfused after six months. First-pass perfusion CMR shows that in a small percentage of segments, abnormal perfusion may become a chronic phenomenon-these areas have a more severe deterioration of systolic function, wall thickness, contractile reserve and the transmural extent of necrosis.

Segmentación deiimágenes de resonancia magnétic en contraste de fase para el eestudio de la dinámica del líquido cefalorraquídeo perimedular / Segmentation of Phase Contrast Magnetic Resonance Imaging to Study the Dynamic of Perimedullary Cerebrospinal Fluid

La imagen de resonancia magnética en contraste de fase permite estudiar la dinámica del líquido cefalorraquídeo (LCR) perimedular de manera cuantitativa. Sin embargo la anatomía propia del espacio subaracnoideo dificulta la segmentación del LCR debido a la presencia de estructuras vasculares y nervios raquídeos. El objetivo de este trabajo es describir un método de segmentación semiautomático para el estudio de la dinámica del LCR perimedular. El proceso se inicializa con un punto semilla dentro de la región a analizar. El algoritmo crea un mapa de correlación, calcula un valor de umbral y clasifica píxeles de LCR combinando diversas características temporales del comportamiento del flujo como atributos de entrada a un algoritmo k-medias. Un observador llevó a cabo diez veces la segmentación en cinco sujetos sanos y se calculó el volumen por ciclo y el área en el espacio perimedular C2C3. Las variaciones de las medidas fueron evaluadas como una estimación de la reproducibilidad del método. Para esto se calculó el coeficiente de variación. La variabilidad de las medidas fue menor del 5%. El método facilita la cuantificación del LCR perimedular. En 16 sujetos sanos se cuantificó el volumen por ciclo de LCR y el área en el espacio C2C3 y cisterna prepontina.

Phase contrast magnetic resonance imaging allows studying quantitatively the perimedullary cerebrospinal fluid (CSF) dynamics. However, the anatomy of the subarachnoid space difficults the segmentation of CSF due to the presence of vascular structures and spinal nerves. The aim of this paper is to describe a semiautomatic segmentation method for the study of the perimedullary CSF dynamics. The process is started with a seed point within the region to analyze. The algorithm creates a correlation map, calculates a threshold value and classifies pixels of CSF combining different temporal characteristics of flow behavior as input attributes to a k-means algorithm. One observer carried out ten times the segmentation of the cervical images in 5 healthy subjects; stroke volume and area were calculated. The variability of the obtained measurements was evaluated as an estimation of the reproducibility of the method. For this the coefficient of variation was calculated. The variability of the measurements was less than 5%. The method facilitates the quantification of perimedullary CSF. Stroke volume and the area at C2C3 space and prepontine cistern were measured in 16 healthy subjects.

Estimación de la dinámica de líquidos intracraneales mediante análisis cuantitativo de imágenes de resonancia magnética de contraste de fase / Estimating intracranial fluid dynamics using quantitative analyses of phase contrast magnetic resonance images

ObjetivoEstimar las relaciones dinámicas entre los fluidos craneoespinales (líquido cefalorraquídeo [LCR] y sangre) en el espacio ventricular, subaracnoideo cerebral y subaracnoideo espinal mediante la cuantificación de imágenes de resonancia magnética (RM) en contraste de fase.Material y métodosSe analizaron 15 sujetos voluntarios sanos en la misma franja horaria y bajo la misma intensidad de campo (3T). Para cada estudio se realizaron 4 exploraciones en contraste de fase: 2 secuencias para el cálculo de LCR (acueducto de Silvio y espacio perimedular C2-C3) y 2 para el cálculo del flujo sanguíneo (arterias carótidas internas y vertebrales, seno sagital superior y recto). En todos los sujetos se calcularon los parámetros de amplitud (volumen sistólico, flujo promedio, índices de pulsatibilidad y distensibilidad, amplitud del gradiente de presión absoluta y relación de volumen de fluido de LCR por ciclo) y temporales (retrasos frente a la entrada de flujo arterial).ResultadosRespecto a la entrada de sangre arterial, el desplazamiento de sangre venosa (al 22 y 38% del ciclo cardíaco en los senos recto y sagital superior, respectivamente) y del LCR (al 12 y 25% de ciclo cardíaco en el espacio perimedular C2-C3 y el acueducto de Silvio, respectivamente) describen la distribución de la pulsatibilidad de los fluidos intracraneales. Se obtienen índices de distensibilidad para los compartimientos encefálico y medular en una población normal.ConclusionesMediante los mapas de velocidad de flujo obtenidos con RM es posible describir de manera cuantitativa las relaciones dinámicas de los fluidos intracraneales e inferir el comportamiento elástico encefálico y medular (AU)

ObjectiveTo estimate the dynamic relations between cerebrospinal fluid (CSF) and blood in the cerebral and spinal subarachnoid spaces and in the ventricles by quantifying phase contrast magnetic resonance imaging (MRI).Material and methodsWe analyzed 15 healthy volunteers during the same time of day and using the same magnetic field strength (3T). Each study consisted of four phase contrast sequences: two to calculate the CSF (aqueduct of Sylvius and the C2-C3 perimedullary space) and two to calculate the blood flow (internal carotid and vertebral arteries, superior sagittal sinus, and straight sinus). We calculated the amplitude parameters (systolic volume, mean flow, pulsatility and compliance indexes, absolute pressure gradient, and ratio of CSF volume per cycle) and temporal parameters (delays respect to arterial flow).ResultsWith respect to the input of arterial blood, the displacement of venous blood (22% and 38% of the cardiac cycle in the straight sinus and superior sagittal sinus, respectively) and of CSF (12% and 25% of the cardiac cycle in the C2-C3 perimedullary space and in the aqueduct of Sylvius, respectively) show the distribution of the pulsatility of the intracranial fluids. We calculated the indexes of compliance of the encephalic and medullary compartments in normal subjects.ConclusionsIt is possible to quantitatively describe the dynamic relations between intracranial fluids and infer the elastic behavior of the brain and spinal canal by using flow velocity maps obtained with phase contrast MRI (AU)

Acerca de la exposición a los campos electromagnéticos presentes en resonancia magnética. Directiva Europea 2004/40/EC / European Directive 2004/40/EC on workers' exposure to electromagnetic fields from MRI

En este trabajo se revisa la normativa vigente acerca de la exposición de los trabajadores a los campos electromagnéticos presentes en resonancia magnética (RM) y se evalúa el impacto de la Directiva Europea 2004/40/EC acerca del uso diario en la RM. Para ello se revisan en detalle los criterios de seguridad de la International Commission on Non-Ionizing Radiation Protection, el Real Decreto español 1066/2001 y la Directiva Europea 2004/40/EC referentes a la exposición a los campos electromagnéticos. Con la Directiva 2004/40/EC la Unión Europea (UE) introducía una ley sin valorar adecuadamente sus repercusiones. La UE ha decidido su aplazamiento puntual respondiendo a las alertas aportadas por la comunidad radiológica y médica en general. Aunque la normativa Directiva 2004/40/EC se ha pospuesto hasta el 30 de abril de 2012, ésta sigue vigente. Se espera que el replanteamiento de esta normativa produzca una exención del efecto en el ámbito de la RM (AU)

This article reviews the regulations in force about the exposure of workers to the electromagnetic fields generated by magnetic resonance imaging (MRI) and evaluates the impact of European Directive 2004/40/EC on the daily use of MRI. We provide a detailed review of the safety criteria stipulated in the International Commission on Non-Ionizing Radiation Protection, in Spanish Royal Decree 1066/2001, and in European Directive 2004/40/EC about exposure to electromagnetic fields. In the case of European Directive 2004/40/EC, the European Union (EU) has introduced a law without adequately evaluating its repercussions. In response to alarms sounded by the radiological and general medical communities, the EU has decided to delay implementation of the Directive. Although the implementation of Directive 2004/40/ EC has been postponed until April 30, 2012, it remains in force. There remains the hope that the Directive will be reconsidered during this interval and that MRI workers will be exempt (AU)