Search results
Results from the WOW.Com Content Network
Zero line and star artifacts are due to system noise or any cause of RF pollution within the room (Faraday cage). If this pattern persists, check for sources of system noise such as bad electronics or alternating current line noise, loose connections to surface coils, or any source of RF pollution.
Head movements cause the voxel-to-neurons mapping to change while scanning is in progress. Noise due to head movement is a particular issue when working with children, although there are measures that can be taken to reduce head motion when scanning children, such as changes in experimental design and training prior to the scanning session. [58]
Resting state fMRI (rs-fMRI or R-fMRI) is a method of functional magnetic resonance imaging (fMRI) that is used in brain mapping to evaluate regional interactions that occur in a resting or task-negative state, when an explicit task is not being performed.
This is most marked with high-field machines, [40] and rapid-imaging techniques in which sound pressure levels may reach 120 dB(A) (equivalent to a jet engine at take-off), [41] and therefore, appropriate ear protection is essential for anyone inside the MRI scanner room during the examination. [42]
Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) show that musical hallucinations activate a wide variety of areas in the brain including the following: auditory areas, motor cortex, visual areas, basal ganglia, brainstem, pons, tegmentum, cerebellum, hippocampi, amygdala, and peripheral auditory system.
Typically in MRS a single spectrum is acquired by averaging enough spectra over a long acquisition time. [8] Averaging is necessary because of the complex spectral structures and relatively low concentrations of many brain metabolites, which result in a low signal-to-noise ratio (SNR) in MRS of a living brain.
EEG-fMRI (short for EEG-correlated fMRI or electroencephalography-correlated functional magnetic resonance imaging) is a multimodal neuroimaging technique whereby EEG and fMRI data are recorded synchronously for the study of electrical brain activity in correlation with haemodynamic changes in brain during the electrical activity, be it normal function or associated with disorders.
However, fMRI also suffers limitations. First, the cost and size of MRI machines can be prohibitive. Second, for fMRI to achieve a high spatial resolution necessarily decreases its time resolution and/or signal-noise ratio. As a result, it is hard to image fine spatial details of transient events such as epilepsy.