Atomic nuclei that contain the same number of protons, but differ in the number of neutrons in the nucleus of the atom for the element concerned. For example, 1H, 2H, and 3H are the three isotopes of hydrogen, otherwise known as proton, deuterium, and tritium. Various isotopes have different nuclear magnetic moments and different resonant frequencies. Many isotopes have no magnetic moment and are therefore not observable by MR.

See also Isomer.

The Larmor equation is important because it is the frequency at which the nucleus will absorb energy. The absorption of that energy will cause the proton to alter its alignment and ranges from 1-100 MHz in MRI. The equation states that the frequency of precession of the nuclear magnetic moment is directly proportional to the product of the magnetic field strength (B0) and the gyromagnetic ratio (g). This is stated mathematically as w = g B0.

Return of longitudinal magnetization to its equilibrium value after excitation;; requires exchange of energy between the nuclear spins and the lattice. See also T1 Time.

From Siemens Medical Systems;
the 3 T MAGNETOM Allegra is a dedicated MR headscanner, perfect as a research system in cognitive and neuroscience with MRS and fMRI. MAGNETOM Allegra is a full member of the MAGNETOM product family. It uses many common components, i.e. electronics, computer system, software and pulse sequence concepts.

From Siemens Medical Systems;
The Magnetom Trio™, a 3T whole body MRI system with Tim (total imaging matrix technology), targets clinical applications such as abdominal, cardiac, spine, whole body and orthopedics. TIM enables flexible coil combinations for high resolution imaging of large anatomical areas without the need to change coils.