(MSI) The combination of biomagnetic field detection and
MR imaging into a merged data set. Most applications of MSI involve the combined use of
MRI and measurement of magnetic fields created by electric currents in the
brain, so-called magnetoencephalography MEG.
MEG allows calculation of the source of the measured biomagnetic fields, and thereby localization of many regional
brain functions, such as mapping of the sensorimotor, auditory and visual cortex and also localization of epileptogenic foci.
The MEG coordinate system is defined by anatomical landmarks, which are easily identified also with
MRI, making it possible to align the 3D MEG data with the 3D MR image data. The resulting magnetic source images show the spatial relationships between the functional area provided by MEG and the neighboring anato
my and pathology, both provided by
MRI.
Cardiac applications of MSI are also being explored. The electric currents in the
myocardium create extrathoracic magnetic fields and the source of these fields may be calculated by the same principles as those used in MEG. Possible
cardiac applications include mapping of arrhythmogenic sites prior to ablation therapy.