Effect of water T2 shortening in the quantification of in-vitro proton MR spectroscopy

Short communication[Abstract] PURPOSE. This work studies the relationship between in-vitro Proton Magnetic Resonance Spectroscopy metabolite quantification and water T2 decay. MATERIALS AND METHODS. An in-vitro correspondence is established between the iron accumulation and the shortening of water T2 relaxation times using seven spherical phantoms, 6 of them were doped with an increasing concentration of iron metal nanoparticles solution. This is later proposed as a source of error during the LCModel metabolite quantification of either absolute concentrations or ratios. RESULTS. The Pearson's correlation coefficient between water T2 values against absolute metabolite concentrations was on average [r] = 0.97 and on average [r] = 0.85 for metabolite ratios. CONCLUSION. These results suggest that the shortening of T2 values should be taken into account when performing metabolite quantification. Also, the need of demonstrated similar results in in-vivo studies, since the presence of iron deposits or other factors affecting the water T2 decay measurements could explain part of the inter-subject variability in the metabolite concentration and ratio quantification

The partial volume effect in the quantification of 1H magnetic resonance spectroscopy in Alzheimer's disease and aging

[Abstract] 1H-MRS variability increases due to normal aging and also as a result of atrophy in grey and white matter caused by neurodegeneration. In this work, an automatic process was developed to integrate data from spectra and high-resolution anatomical images to quantify metabolites, taking into account tissue partial volumes within the voxel of interest avoiding additional spectra acquisitions required for partial volume correction. To evaluate this method, we use a cohort of 135 subjects (47 male and 88 female, aged between 57 and 99 years) classified into 4 groups: 38 healthy participants, 20 amnesic mild cognitive impairment patients, 22 multi-domain mild cognitive impairment patients, and 55 Alzheimer's disease patients. Our findings suggest that knowing the voxel composition of white and grey matter and cerebrospinal fluid is necessary to avoid partial volume variations in a single-voxel study and to decrease part of the variability found in metabolites quantification, particularly in those studies involving elder patients and neurodegenerative diseases. The proposed method facilitates the use of 1H-MRS techniques in statistical studies in Alzheimer's disease, because it provides more accurate quantitative measurements, reduces the inter-subject variability, and improves statistical results when performing group comparisons

Classification of mild cognitive impairment and Alzheimer’s Disease with machine-learning techniques using 1H Magnetic Resonance Spectroscopy data

[Abstract] Several magnetic resonance techniques have been proposed as non-invasive imaging biomarkers for the evaluation of disease progression and early diagnosis of Alzheimer’s Disease (AD). This work is the first application of the Proton Magnetic Resonance Spectroscopy 1H-MRS data and machine-learning techniques to the classification of AD. A gender-matched cohort of 260 subjects aged between 57 and 99 years from the Alzheimer’s Disease Research Unit, of the Fundación CIEN-Fundación Reina Sofía has been used. A single-layer perceptron was found for AD prediction with only two spectroscopic voxel volumes (Tvol and CSFvol) in the left hippocampus, with an AUROC value of 0.866 (with TPR 0.812 and FPR 0.204) in a filter feature selection approach. These results suggest that knowing the composition of white and grey matter and cerebrospinal fluid of the spectroscopic voxel is essential in a 1H-MRS study to improve the accuracy of the quantifications and classifications, particularly in those studies involving elder patients and neurodegenerative diseases.Instituto de Salud Carlos III; PI13/0028

In vivo neurometabolic profiling in orthostatic tremor

The pathogenesis of orthostatic tremor (OT) remains unclear, although some evidence points to dysfunction in the brainstem or cerebellum. We used single voxel proton magnetic resonance spectroscopy (1H-MRS) (3 T) to investigate whether neurochemical changes underlie abnormal cerebellar or cortical function in OT. Fourteen OT patients and 14 healthy controls underwent 1H-MRS studies with voxels placed in midparietal gray matter and cerebellum (vermis and central white matter). Spectral analysis was analyzed using the software package LCModel (version 6.3). The absolute metabolite concentrations and ratios of total N-acetylaspartate + N-acetylaspartyl glutamate (NAA), choline-containing compounds, myoinositol, and glutamate + glutamine to creatine were calculated. In midparietal gray matter spectra, we found a significant decrease in the absolute concentration of NAA in OT patients versus healthy controls (7.76 ± 0.25 vs 8.11 ± 0.45, P = 0.017). A similar decrease in NAA was seen in the cerebellar vermis (7.33 ± 0.61 vs 8.55 ± 1.54, P = 0.014) and cerebellar white matter (8.54 ± 0.79 vs 9.95 ± 1.57, P = 0.010). No differences in the other metabolites or their ratios were observed. Reductions in both cerebral cortical and cerebellar NAA suggest that there is neuronal damage or loss in OT, raising the intriguing question as to whether OT is a neurodegenerative disease. Along with clinical history and electrophysio0logical examination, 1H-MRS could serve as a useful diagnostic aid for OT

Management of medical images through the Web

En los últimos años, el uso de imágenes digitales para investigación y diagnóstico médico ha aumentado considerablemente. Debido a esto, es necesario desarrollar nuevas y mejores aplicaciones para gestionar grandes cantidades de información médica de forma eficiente. Los formatos más utilizados para codificar las imágenes médicas son DICOM y Analyze 7.5. DICOM es un estándar para imágenes digitales y comunicaciones en medicina y Analyze es un formato propietario diseñado para el mismo propósito. Sin embargo, es difícil intercambiar e integrar la información DICOM o Analyze fuera del ámbito del equipamiento médico específico. Este inconveniente dificulta su uso e integración en un ámbito más amplio como es la Web. Por un lado, XML es el estándar para el intercambio de información y transporte de datos entre múltiples aplicaciones y, por otro, las bases de datos XML surgen como la mejor alternativa para almacenar y gestionar la información XML. En este trabajo presentamos un sistema de información Web para almacenar, de forma integrada, ficheros DICOM y Analyze en una base de datos XML. Para este desarrollo se han obtenido los esquemas XML de los formatos DICOM y Analyze y se ha definido la arquitectura para la integración de documentos XML en la base de datos.In recent years, the use of digital imaging for medical diagnostics and research has increased considerably. Because of this, it is necessary to develop new and better applications to manage large amounts of medical information efficiently. The The most widely used formats for encoding medical images are DICOM and Analyze 7.5. DICOM is a standard for digital imaging and communications in medicine and Analyze is a proprietary format designed for the same purpose. However, it is difficult to exchange and integrate DICOM or Analyze information outside the scope of specific medical equipment. This inconvenience hinders its use and integration in a broader environment such as the Web. For On the one hand, XML is the standard for the exchange of information and transport of data between multiple applications and, on the other hand, XML databases emerge as the best alternative for store and manage XML information. In this work we present a system of Web information to store, in an integrated way, DICOM and Analyze files in a database of XML data. For this development, the XML schemas of the DICOM formats have been obtained. and Analyze, and the architecture for the integration of XML documents in the database has been defined. data

Gestión de imágenes médicas a través de la Web

En los ultimos años, el uso de imágenes digitales para investigación y diagnóstico médico ha aumentado considerablemente. Debido a esto, es necesario desarrollar nuevas y mejores aplicaciones para gestionar grandes cantidades de información médica de forma eficiente.Palabras clave: Imágenes médicas, XML, DICOM, Sistemas de información Web

Resting state functional MRI reveals abnormal network connectivity in orthostatic tremor.

Very little is known about the pathogenesis of orthostatic tremor (OT). We have observed that OT patientsmight have deficits in specific aspects of neuropsychological function, particularly those thought to rely on the integrity of the prefrontal cortex, which suggests a possible involvement of frontocerebellar circuits. We examined whether resting-state functional magnetic resonance imaging (fMRI) might provide further insights into the pathogenesis on OT. Resting-state fMRI data in 13 OT patients (11 women and 2 men) and 13 matched healthy controls were analyzed using independent component analysis, in combination with a “dual-regression” technique, to identify group differences in several resting-state networks (RSNs). All participants also underwent neuropsychological testing during the same session. Relative to healthy controls, OT patients showed increased connectivity in RSNs involved in cognitive processes (default mode network [DMN] and frontoparietal networks), and decreased connectivity in the cerebellumand sensorimotor networks.Changes in network integrity were associated not onlywith duration (DMN and medial visual network), but also with cognitive function. Moreover, in at least 2 networks (DMN and medial visual network), increased connectivity was associated with worse performance on different cognitive domains (attention, executive function, visuospatial ability, visual memory, and language). In this exploratory study, we observed selective impairments ofRSNs inOT patients. This and other future resting-state fMRI studiesmight provide a novelmethod to understand the pathophysiological mechanisms of motor and nonmotor features of OT.post-print571 K

Altered brain rhythms and functional network disruptions involved in patients with generalized fixation-off epilepsy

Fixation-off sensitivity (FOS) denotes the forms of epilepsy elicited by elimination of fixation. FOS-IGE patients are rare cases [1]. In a previous work [2] we showed that two FOS-IGE patients had different altered EEG rhythms when closing eyes; only beta band was altered in patient 1 while theta, alpha and beta were altered in patient 2. In the present work, we explain the relationship between the altered brain rhythms in these patients and the disruption in functional brain networks

The Vallecas Project: a cohort to identify early markers and mechanisms of Alzheimer's disease

Alzheimer’s disease (AD) is a major threat for the well-being of an increasingly aged world population. The physiopathological mechanisms of late-onset AD are multiple, possibly heterogeneous, and not well understood. Different combinations of variables from several domains (i.e., clinical, neuropsychological, structural, and biochemical markers) may predict dementia conversion, according to distinct physiopathological pathways, in different groups of subjects

AUTOMATIC CLASSIFICATION OF STRUCTURAL MRI FOR DIAGNOSIS OF NEURODEGENERATIVE DISEASES

This paper presents an automatic approach which classifies structural Magnetic Resonance images into pathological or healthy controls. A classification model was trained to find the boundaries that allow to separate the study groups. The method uses the deformation values from a set of regions, automatically identified as relevant, in a process that selects the statistically significant regions of a t-test under the restriction that this significance must be spatially coherent within a neighborhood of 5 voxels. The proposed method was assessed to distinguish healthy controls from schizophrenia patients. Classification results showed accuracy between 74% and 89%, depending on the stage of the disease and number of training samples