Magnetic source imaging
(MSI) refers to studies where the distribution of sources (or source current distributions) of magnetic fields are determined on the basis of external measurements.
Magnetic field tomography (MFT)
is a near-synonym of MSI.
The intent here is to produce
tomographic images displaying neural electrical activity
estimated on the basis of measured magnetic fields.
Gradiometer is a kind of magnetometer coils. The spontaneous or evoked magnetic fields emanating from the brain
induce a current in these coils, which in turn produce a magnetic field in
a special device called a superconducting quantum interference device
(Superconducting QUantum Interference Device) acts as a low-noise, high-gain current-to-voltage converter that provides the system with sufficient sensitive to detect neuromagnetic signals of only a few femto Tesla in magnitude. It is a superconducting ring that includes one or two Josephson junctions
[Drawing of a dc SQUID]
A Josephson junction - quantum tunneling device essential to SQUID operation -
is a barrier for current flow between two superconductors.
It is usually made of an insulator, but could also be a thin
vacuum gap or a very narrow constriction in the superconductor.
Drawing of a Josephson junction]
DC SQUID - Superconducting Quantum Interference Device with 2 Josephson Junctions
1 fo -- 1 quantum of flux = 2.06875 E-15 Weber
Flux Transformer - Superconducting inductive loops which sense local fields and gradients and coupling the resulting current to the DC SQUID sensor.
1st Gradiometer - sensor consisting of a flux transformer + a (DC) SQUID where the flux transformer consists of 2 oppositely wound equal area coils, spaced by a baseline. This provides a measure of one component of the 1st spatial gradient tensor of the local field. There are 5 independent components.
HD MEG - Horizontal (adjustable) Dewar MEG system
LHe - Liquid Helium, B.P. = 4.22 K at 1 atm pressure.
LHe BOR - Liquid Helium Boil-off Rate
LN2 -Liquid Nitrogen B.P. = 77.3 K at 1 atm pressure.
Magnetometer - sensor consisting of a flux transformer + a (DC) SQUID where the flux transformer consists of a single coil. This provides a measure of the projection of the local field along the coil normal. There are 3 independent components.
MSR-magnetically shielded room
Pascal - unit of pressure = 1N/m2.
Psi - unit of pressure = 1 lbf/in2 = 6894.8 Pa
SQUID transmission line - wire set connecting DC SQUID at ﾅ 4.2 K to 300 K preamplifier.
Torr - unit of pressure = 1mm Hg at 0C = 133.32 Pa
1 degree Celsius = 1 C = 1 degree Kelvin = 1 K in magnitude
0 C = 273.15 K
4.21 K = -268.94 C = Boiling point of LHe at 1 std. atm. pressure
77.36 K = - 195.79 K = Boiling point of LN2 at 1 std. atm. pressure
or Low Resolution Electromagnetic Tomography is a term introduced
by Pasqual-Marqui and Michel for their method of solving
the bioelectromagnetic inverse problem.
Around 40-Hz magnetic oscillation in the human brain is probably
relative to attention and cognition, around 40-Hz in humans is continuously
generated by the central nervous system and is reset or modified by sensory
is a non-invasive instrument used for the treatment of arteriovenous
malformations (AVMs), benign and malignant tumours and functional
disorders of the brain.
presurgical localization of critical brain regions
non-invasive or minimally invasive neurosurgery
frame-based stereotactic neurosurgery
evaluation of fetal neurological status
environment magnetic noise cancellation
motor cortex -- signals descending from the motor cortex can
be integtated with signals arriving from the muscles that produced the
voluntary-movement patterns. After this integration occurs, signals are
sent back up to the place in the motor cortex where the signal originated.
(named for a neurologist, Juhn A. Wada)
consists of behavioral
testing after the injection of sodium amobarbital (an anesthetic) into the
right or left internal carotid artery.