الفهرس 
TitleOnly 14 pages are availabe for public view
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Abstract
unctional imaging of brain with magnetic resonance imaging (MRI) has become a popular modality in neuroscience, but the exact relationship between the measured blood-oxygenation level dependent (BOLD) signal and the underlying neurophysiological parameters remains unclear.(145)
The BOLD functional MRI (fMRI) method allows detection of changes in blood oxygenation during a physiological stimulation with gradient-echo. The BOLD image-contrast relies on physiologically induced changes in the magnetic properties of blood (oxyhemoglobin is diamagnetic and deoxyhemoglobin is paramagnetic), where an increase in the fractional BOLD fMRI signal-change consistent with a DROP in venous deoxyhemoglobin concentration.
Higher resolution is also desirable for practical reasons such as the reduction in signal dropout due to less macroscopic, susceptibility related intra-voxel dephasing and for the purposes of brain segmentation.(146,147)
By collecting functional data from 60 healthy participants (30 male and 30 female) included in the study. Their age ranging from 18-33 years old an average age of 25years. Using 1.5T closed MRI instrument and a head coil with 8 channels.
The equation (SNR= V M (T)1/2 ) describe the direct relationship between signal to noise ratio, voxel size (FOV), field strength and time. The most sensitive parameter was the voxel (V) since it controls the image field of view as we notice 0.3mm was enough to detect different signal. Also the best image and signal accepted by the radiologist was SNR0.8 pixel area=2.7×2.7mm2. Finally, there is different in hemodynamic response between males and females.