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The BOLD (Blood Oxygenation Level Dependent) signal, is the most used contrast mechanism of the so called functional Magnetic Resonance Imaging (fMRI). Although it indirectly measures neuronal activity, its response is directly related to cerebral blood flow (CBF), Cerebral Metabolic Rate of Oxygen (CMRO2) and Cerebral Blood Volume (CBV) and can be, in principle, used to map cerebral perfusion. Thus, the main purpose of this study was to investigate, quantitatively, some aspects of perfusional alterations in the human brain. These changes were mapped by changes in the BOLD signal as a result of a global and uniform stimulation: hypercapnia induced by breath holding paradigms. Magnetic resonance images were acquired in a 1.5 T scanner (Siemens, Magneton Vision) with EPI-BOLD fMRI sequences. It was analyzed the BOLD dependency on breath holding duration and differences on the BOLD signal due the employed breath holding techniques: breath holding after expiration or after inspiration. The regional variability of the BOLD signal propagation was also studied. Moreover, the signal was used to construct maps based on CBV information. It was possible to gain information about the BOLD signal behavior that respond to PaO2 and PaCO2 alterations. Besides, it was demonstrated its regional variations sensibility, which can be correlated with arterial reactivity or the rest CBV of this arteries. It was also possible acquire information about the temporal characteristics of CBF changes induced by hypercapnia across brain regions as well as the identification of cortical areas that were responsible to the voluntary breathing. Finally, the B-CBV maps that used the BOLD contrast were able to reflect CBV information, although, it is necessary the study of other parameters that can influence the signal. LISTA DE ABREVIATURAS AB Area de Brodmann ACA Arteria Cerebral Anterior ACM Arteria Cerebral Media ACP Arteria Cerebral Posterior ACV Linha vertical da comissura anterior AIF Acronimo do idioma ingles que representa: Arterial Input Function ASL Acronimo do idioma ingles que representa: Arterial Spin Labelling BBB Acronimo do idioma ingles que representa: Blood Brain Barrier BOLD Acronimo do idioma ingles que representa: Blood Oxygen Level Dependent CBF Acronimo do idioma ingles que representa: Cerebral Blood Flux CBV Acronimo do idioma ingles que representa: Cerebral Blood Volume CMRO2 Acronimo do idioma ingles que representa: Cerebral Metabolic Rate of Oxygen CSF Acronimo do idioma ingles que representa: Cerebral Spinal Fluid dHb Hemoglobina deoxigenada DSP Diagramas de sequencias de pulso EPI Acronimo do idioma ingles que representa: Eco-Planar Imaging FID Free Induction Decay fMRI Acronimo do idioma ingles que representa: Functional Magnetic Resnoance Imaging FOV Acronimo do idioma ingles que representa: , field of view GLM Acronimo do idioma ingles que representa: General Linear Model Glut-1 Acronimo do idioma ingles que representa: glucose transporter, isotype 1 Hb Hemoglobina oxigenada HRF Acronimo do idioma ingles que representa: hemodinamic response function JPO2 Pressao na jugular de O2 JSO2 Saturacao de O2 na jugular MRI Acronimo do idioma ingles que representa: Magnetic Resonance Imaging MTT Acronimo do idioma ingles que representa: Mean Transit Time NMR Acronimo do idioma ingles que representa: Nuclear Magnetic Resonance PaCO2 Pressao arterial de CO2 PCSFO2 Pressao de oxigenio no CSF PET Acronimo do idioma ingles que representa: Positron Emission Tomography PaO2 Pressao arterial de O2 RF Radiofrequencia ROI Acronimo do idioma ingles que representa: Region of Interest SNC Sistema Nervoso Central SPECT Acronimo do idioma ingles que representa: Single Photon Emission Computer Tomography TE Tempo ao Eco TI Tempo de inversao TMS Acronimo do idioma ingles que representa: Transcranial Magnetic Stimulation TR Tempo de Repeticao VASO Acronimo do idioma ingles que representa: vascular space occupancy VOI Acronimo do idioma ingles que representa: Volume of Interest

Dinâmica da alteração perfusional induzida por estado de apnéia utilizando fMRI