Der Radiologe
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Measurements of blood flow velocity in the basal cerebral arteries during functional testing by means of transcranial Doppler sonography are reviewed. Special emphasis is placed on cerebrovascular reserve capacity, which we determined in two groups of patients with obstructive cerebrovascular disease and in normal persons. We discuss the value of functional testing during endovascular neuroradiological procedures.
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Magnetencephalography (MEG) is a new diagnostic tool for the exact localization of the biomagnetic sources of the electrical activity of the brain. The extremely weak magnetic fields are generated by the postsynaptic activity of the neurons, acting like current dipoles. They are measured with a SQUID (superconducting quantum interference device). ⋯ The effect of background activity can be eliminated by alpha wave filtering and the dipole-density plot (DDP), which also increases the signal/noise ratio. MEG seems to be useful in purely functional lesions of the brain. A final decision on the value of MEG for routine diagnosis is not yet possible, however.