Foundations of Medical Imaging and Signal Recording - Biomedical Signal Analysis: Contemporary Methods and Applications - page 4

Tabl e 1 . 1
Most common biosignals [56].

Event Signal

Heart electrical conduction Electrocardiogram (ECG)

at limb surfaces
Surface CNS electrical activity Electroencephalogram (EEG)

Magnetic fields of neural activity Magnetoencephalogram (MEG)

Muscle electrical activity Electromyogram (EMG)

ral and muscle cells. Signal transmission between cells takes place as
each cell becomes depolarized relative to its resting membrane poten-
tial. These changes are recorded by electrodes in contact with the physi-
ological tissue that conducts electricity. While surface electrodes capture
bioelectric signals of groups of correlated nerve or muscle cell potentials,
intracellular electrodes show the difference in electric potential across an
individual cell membrane.

• Biomechanical signals: They are produced by tissue motion or force

with highly correlated time-series from sample to sample, enabling an
accurate modeling of the signal over long time periods.
•

Biomagnetic signals: Body organs produce weak magnetic fields as
they undergo electrical changes, and these biosignals can be used to
produce three-dimensional images.

• Biochemical signals: They provide functional physiological informa-

tion and show the levels and changes of various biochemicals. Chemicals
such as glucose and metabolites can be also measured.

Electroencephalogram (EEG)
The basis of this method lies in the recording over time of the electric
field generated by neural activity through electrodes attached to the
scalp. The electrode at each position records the difference in potential
between this electrode and a reference one. EEG is employed for spon-
taneous brain activity, as well as after averaging several presentations of
the stimulus. These responses are processed either in the time or in the
frequency domain.