Navegando por Palavras-chave "mri"

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    AUTOMATIC SUBCORTICAL TISSUE SEGMENTATION OF MR IMAGES USING OPTIMUM-PATH FOREST CLUSTERING
    (Ieee, 2011-01-01) Cappabianco, Fabio Augusto Menocci [UNIFESP]; Ide, Jaime Shinsuke [UNIFESP]; Falcao, Alexandre; Li, Chiang-shan R.; Universidade Federal de São Paulo (UNIFESP)
    Automatic MR-image segmentation of brain tissues is an important issue in neuroimaging. For instance, it is a key methodological component of a popular technique denominated voxel-based morphometry (VBM), which quantifies gray-matter (GM) volumes from MR images. However, segmentation accuracy in some subcortical regions on the basis of extant methods is not satisfactory, compromising VBM results. We combine a probabilistic atlas and a fast clustering approach based on optimum connectivity between voxels in their feature space. The algorithm exploits local image properties and global information from the atlas as features to group GM and white-matter (WM) voxels in distinct clusters, and uses the total probability values inside the clusters to label them as GM or WM. This new method is validated in the region of the thalamus and outperformed two widely used methods packaged in SPM and FSL.
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    Magnetofecção mediada por nanopartículas de óxido de ferro em tumores de glioblastoma para posterior aplicação terapêutica da magneto hipertermia: estudos in vitro e in vivo
    (Universidade Federal de São Paulo (UNIFESP), 2015-12-18) Aguiar, Marina Fontes de Paula [UNIFESP]; Contreras, Lionel Fernel Gamarra Contreras [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Objective: Elucidate the in vitro and in vivo magnetofection process in glioblastoma tumors induced by C6 cells, with future perspective for therapeutic application of magneto hyperthermia. Therefore, superparamagnetic iron oxide nanoparticles conjugated with fluorescent Rhodamine-B molecules were used along with an external magnetic field for active tumor targeting. Methods: For magnetofection process, a resistive electromagnet capable of generating a variable magnetic field and pole geometry able to create a magnetic field gradient, was built. Previous in vitro tests with 50 nm hydrodynamic size NOFRhod were made to verify the transport and specific local accumulation. For in vivo targeting, the magnetic field of the poles was adjusted to 0 T (control) or 1,3 T (experimental value) and the nanoparticles were administrated by three different routes: tumor local, tail vein or carotid artery. Results: At first, we demonstrated that nanoparticles in this study are stable in DMEM culture medium and when dispersed in saline or PBS at a concentration of 50 µgFe/mL. The cell labeling analysis by prussian blue and fluorescent microscopy showed that NOF-Rhod are efficient for this purpose in all used concentrations (1, 10, 30 e 50 ug/mL), being enhanced by external magnetic field application. Besides that, cytotoxicity assay showed that cell death caused by these nanoparticles was barely evident. The volumetry study by MRI and histology demonstrated that in all used concentrations the tumor growth was evident and proportional both according to the day and the C6 cell concentration (104 , 105 ou 106 ). The in vitro tests showed that nanoparticle aggregation was efficient in all magnetic field gradients used. Moreover, the oblique steel pole addition created a punctual nanoparticle accumulation in one hose?s side, being this artifice selected for subsequent in vivo studies. The MRI monitoring was effective for NOF-Rhod identification in tumor region after local administration, showed an important signal reduction. The MRI sensibility, moreover, was not able to detect NOF-Rhod in tumor region after tail vein or carotid administration, further studies for these administration parameters are required. The in vivo magnetofection process analysis by histology, however, demonstrated more sensibility than MRI, evidencing iron concentration in tumor after the three NOFRhod administration routes. Furthermore, targeting intravenous administration with an external magnetic field was capable to increasing nanoparticle accumulation in tumor region. Conclusion: Taken together, our in vitro and in vivo results showed the NOF-Rhod magnetic targeting efficience, being this strategy a promisse tool for further applications of magneto hyperthermia technique.
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    Técnicas lúdicas de dessensibilização e ambientação para aquisição de exame de ressonância magnética de crânio
    (Universidade Federal de São Paulo (UNIFESP), 2015-06-10) Miranda, Walter Alves de [UNIFESP]; Jackowski, Andrea Parolin Jackowski [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Scanning children is a challenge for clinical and research purposes since movement artifact affects severely the quality of the exam. Although clinical protocols have been optimized to reduce movement on acquiring a high quality pediatric brain scan without sedation, the success is limited. Moreover, for research purposes, alternative methods to sedation have been proposed with positive outcome but with intensive training and time consuming. Aims: In this study, we evaluated the use of a thirty-minute playful technique for preparing children and adolescents for a brain MRI research protocol. Methods: A total of 781 subjects (430M/351F) from 6-14 years-old were invited to perform a brain MRI protocol in two centers. In one center the intervention was individual and in the other was in group. Prior to the scan, subjects underwent a playful technique which included dance, relaxation, music, and recreational and interactive games. Results: Overall, 96% of the children (749/781) submitted to the playful intervention performed an MRI scan. All scans had diagnostic quality. Older children had a higher change of performing a scan without movement (OR= 1.16, p= 0.004), and overtime the chance of delivering a MRI sequence without movement decreases (OR= 0,43; p<0,001). The success rate of acquiring a scan without movement varied from 98,5-70 % overtime. Children who received individual intervention had 3.53 chances (p<0.001) of a successful imaging (i.e., without movement) compared to those who were exposed to group intervention. No gender effect was observed on images quality (OR=- 0,72; p=0,081). Conclusion: Our results suggest that our therapeutic protocol is effective in preparing children and adolescents for a research MRI scan and should be considered as a potential alternative technique to be used in medical diagnostic imaging centers.