fMRI Specialty Lexicon

Capillary bed: The system of fine vessels connecting arties and veins which facilitates the exchange of materials from the blood to cells.

Diamagnetic Materials:  These materials are everything else ... plants, water, soil, wood, your skin ... all other substances. Diamagnetic substances show no visible reaction to the presence of a magnetic field, because the electrons in their atoms are spinning in equal numbers in opposite directions.

fMRI: Functional Magnetic Resonance Imaging or FMRI is a non-invasive technique for imaging the activation of brain areas by different types of physical sensation (sight, sound, touch, taste, smell) or activity such as problem solving and/or movement (limited by the machine).

MRI: MRI is a non-invasive imaging technique used to create highly detailed anatomic images in medicine.

Paramagnetic Materials: These are metals that are weakly attracted to magnets. They include aluminum, gold, and copper. The atoms of these substances contain electrons most of which spin in the same direction ... but not all . This gives the atoms some polarity. They are only weakly influenced by a magnetic field, (you couldn't pick up even a tiny piece of gold with a magnet) and since some of the atoms can be turned to point their poles in the same direction, these metals can become very weak magnets. Their attractive force can only be measured with sensitive instruments.

T1 or Spin Lattice Relaxation Time: In MRI and fMRI, the amount of time it takes for for the atoms in MRI-induced, high energy resonation to return to their equilibrium value, i.e., the time it takes for Z dimension equilibrium magnetization value to return from zero after a radio frequency pulse.  Typical T1 values are around 1s.

T2 or Spin-Spin Relaxation Time: In MRI and fMRI, the measure of the rate of change of spin phases from MRI-induced, high energy resonation to their normal low energy; typical values are around 100ms.

T2* or BOLD or Blood-oxygen Level Dependent Signal: The measure of signal variation due to spatial and temporal variation in local concentrations of deoxygenated hemoglobin in capillary beds as a result fo radio frequency pulse in fMRI.

Telsa: A telsa is a unit measure of magnetic force.  A single telsa is defined as enough magnetic force to induce 1 volt of electricity in a single-coil circuit during 1 second of time for every square meter.

Voxel: A contraction for volume element, which is the basic unit of CT or MR reconstruction; represented as a pixel in the display of the CT or MR image.  There are approximately 60,000 brains cells in a given voxel.