Resting-State functional magnetic resonance imaging (rs-fMRI) provides the assessment of some brain functions without tasks. Through rs-fMRI, it is possible to discover that the brain is organized in spatially distributed and interconnected brain regions. Studies suggest that aging and certain neurological or neuropsychiatric diseases affect brain connectivity, such as Alzheimer's disease (AD) and mild cognitive impairment (MCI). The general objective of this work is to investigate the evolution of the brain connectivity of individuals with healthy aging who convert to MCI, and individuals with MCI who convert to AD, using rs-fMRI and analysis based on graph theory (GT). The processing was implemented in SPM12-MATLAB, and the analysis was performed in the CONN Toolbox. The GT metrics chosen to describe the main topological characteristics of the networks were: characteristic path length, global efficiency, local efficiency, clustering coefficient, and degree. Two main findings emerged from this study. When using GT metrics and analyzing healthy subjects converting to MCI, it was possible to observe a decrease in all GT metrics. Second, changes in GT metrics indicated a rupture in the functional connectivity when the cognitive decline occurs from healthy aging to MCI, and from MCI to AD.

O avanço da radiologia digital proporcionou uma melhoria significativa à qualidade das imagens radiológicas. Essa evolução trouxe muitos benefícios para o diagnóstico por imagem como a agilidade do processo, a melhoria da resolução espacial, a diminuição do tempo necessário de exposição, entre outros. Os últimos trabalhos publicados mostraram que a função de transferência de modulação ou MTF (Modulation Transfer Function) é a técnica mais adequada para avaliar a resolução espacial das imagens digitais, pois apresenta um resultado quantitativo mais preciso. O objetivo deste trabalho é avaliar o impacto do uso de diferentes materiais para a determinação da resolução espacial através da MTF. Foram utilizadas diferentes espessuras de placas de alumínio (Al) e cobre (Cu) para a aquisição da imagem de uma borda. A MTF foi avaliada pela técnica da função de propagação de borda ou ESF (Edge Spread Function) usando o plug-in COQ do ImageJ. Foi possível concluir que uma variedade de espessuras de alumínio são aplicáveis para a determinação da resolução espacial através da MTF, assim como uma placa de teste de colimação.

High-resolution structural magnetic resonance imaging (MRI) allows neurological investigation, especially when brain volumes must be carefully delineated to monitor neurodegeneration, such as in multiple sclerosis (MS). This study compares different segmentation techniques applied to brain MRI to measure the white matter (WM) and grey matter (GM) in healthy and MS brains. We propose to evaluate the reliability and how each segmentation method could potentially affect clinical trials in MS. Four segmentation software were evaluated: Statistical Parametric Mapping (SPM), Lesion Segmentation Tool (LST), Freesurfer, and Siena/X. We simulated healthy and MS brain MRI and compared the segmentation volumes with the ground truth. Our results showed that LST provides overall good segmentation with low variability. When SienaX spatially normalizes the images, the WM and GM volumes are overestimated. On the other hand, Freesurfer underestimates volumes. We conclude that the use of different segmentation software produces variability in GM and WM volumes, especially in challenging situations, such as small lesions and in the presence of noise. The best method was the automatic region growth algorithm implemented using the LST, which uses T1-weighted and T2-FLAIR MRI.

Background:The Centiloid scale (CL) represents an attempt to standardize amyloid imaging to create a measure of global cortical β-amyloid deposition using positron emission tomography (PET). The CL approach transforms standard uptake value ratio (SUVR) into values ranging from 0 to 100. This study aims to investigate the brain amyloid load in SuperAgers (SA), healthy age-matched controls (ACs), and healthy middleaged controls (MCs).Method: Thirty cognitively healthy individuals were evaluated with a cognitive screening and the Rey Auditory-Verbal Learning Test (A7 list). They underwent an amyloid PET image with PIB were acquired in 3D mode from 40 to 60 minutes after injection using a PET/CT scanner (Discovery 600, GE Healthcare). Image analysis was performed using the PMOD software -PNEURO tool (PMOD Technologies). SUVR was transformed to CTX (Global Cortical Target region) using the whole cerebellum (WC) as reference. The equation used to convert SUVR to CL is CL=100 (SUVR-0.987)/1.019 and fits the parameters described previously.