Functions of MRI

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Introduction

Since the early 90s, in addition to the established procedures (PET, SPECT, MEG, EEG), a new method to measure functional parameters of the cortex are available. Using functional magnetic resonance imaging, it is possible to measure cortical responses to external stimuli with a superior spatial resolution the previous methods. Furthermore, can the activated areas identified easily assign the appropriate anatomical structures. While the initial results were achieved even with the help of exogenous contrast agents, functional studies can now be performed without the application. In these measurements, the local oxygenation of the blood of the decisive influences the signal intensity parameters.

The Functional magnetic resonance imaging (fMRI) is a fascinating method by which we can "watch the work" our brains. Here, the FMRI is harmless to health process: there is no radiation exposure and contrast medium is not required.

In a magnetic resonance imaging (other names for magnetic resonance imaging, or MRI) are the magnetic properties of the hydrogen particles measured in our bodies. From this information may be an accurate picture of the internal body of a measurement beechen.

The response of the hydrogen particles in the body to this magnetic field is measured with a type of "antenna". In a few minutes you can therefore create a fairly accurate picture of the brain. Magnetic resonance imaging is safe and has been used for many years for the study of disease. Because these strong magnetic waves are used, are people with metal parts in the body (or similar pacemakers, bone screws, shrapnel) but could not be investigated (Radiology Info. Org, 2012).

In the functional magnetic resonance imaging (FMRI), the measurement takes a little longer than normal tests (e.g., 30 - 45 minutes). The subject during the measurement leads repeatedly from certain tasks, such as a gesture. The parts of the brain that need to work on this task, during which more oxygen and blood, and thus you can see it on the calculated images. 

The conditions necessary for fMRI experiments computer calculations are very complicated. The evaluation of a single measurement can take many hours or even days (Psych Central, 2012).

Discussion

The BOLD Effect

This known as the BOLD effect phenomenon was published in 1990 by Ogawa et al described. It makes use of the different magnetic properties of oxygenated and deoxygenated blood to use. Responsible for this is bound to hemoglobin iron. This is oxygenated for oxygen transport and there is oxy-hemoglobin, a molecule in which the magnetic property of the iron is largely masked. Therefore, it is diamagnetic. In contrast, the deoxyhemoglobin, the iron atoms have their full magnetic property and thus paramagnetic. The paramagnetic deoxyhemoglobin caused in its immediate environment, and induces magnetic field in homogeneity in the vicinity of a local magnetic field gradients vessels.

In the stimulation of cortex, there is an increase in the cortical metabolism rate (CMRO 2) and the activated complex reacts with an increased regional cerebral blood flow (rCBF). Thereby more oxygen is transported to the site than can be consumed by the ...