angular momentum - spin, amount of rotation considering speed, volume,mass, shape., precession - change of rotational axis when external magnetic field produces a secondary spin or wobble of the nucleus around the main/static field, magnetic moment - otherwise called torque. measures the tendency of an object to interact with external magnetic field. Determines the toque that a magnetic field will exert on a proton and the force proton can exert on electric current, nuclear magnetic resonance - this property is only present if a nucleus has both magnetic moment and angular momentum= spin, Larmor frequency - also called precessional frequency or resonance frequency which is proportional to the strength of the magnetic field.Frequency at which H absorbs energy and resonates- RF coil needs to be fine-tuned to this frequency for MRI to work. , gyromagnetic ratio - ratio of a particle's magnetic moment to angular momentum. different for each nucleus , high energy state - when the nucleus aligns itself in the opposite direction from B0 with reversed spin axis taking energy from applied RF field. , frequency of precession depends on - magnetic field, nature of the nucleus, Excitation/Radiation - process of sending electromagnetic energy to a sample at its resonant frequency. some spins go from low to high energy state. , Reception/Detection - process of receiving EM energy emitted by a sample at its resonant frequency- as spins return to low energy state/relax they emit energy (free induction decay at T2) measured by receiving RF coil, Net magnetization - sum of magnetic moments of all spins within a spin system. In the absence of strong MF, spins of H+ are oriented randomly, cancel out (small net m.) B0= increases m.f, Echo time (TE) - the amount of time necessary for energy coming back from the sample to be received (usually within 30ms). It can be selected to receive a specific type of signal, TR - repitition time when the signal returns to equilibrium along B0 and RF is reapplied to once again excite the nucleus,

Key definitions

Drucken
Einbetten

Bestenliste

Visueller Stil

Einstellungen

Vorlage ändern

Soll die automatisch gespeicherte Aktivität wiederhergestellt werden?