MRI chapter 1: Basic Principles Questions and Answers 2023

MRI chapter 1: Basic Principles Questions and Answers 2023 atom a tiny element that is the basis for all things molecule 2 or more atoms arranged together hydrogen the most abundant atom in the body electron negatively charged particles that spin around the nucleus nucleons particles in the nucleus proton positively charged element of the atomic nucleus neutron neutral charged element of the atomic nucleus atomic number sum of protons in the nucleus mass number sum of protons and neutrons isotopes same number of protons but different number of neutrons ions atoms with excess or deficit of electrons angular momentum the spin of MR active nuclei, which depends on the balance of the number of protons and neutrons in the nucleus MR active nuclei nuclei that possess an odd mass number magnetic moment denotes the direction of the north/south axis of a magnet and the amplitude of the magnetic field protium isotope of hydrogen used in MRI. nucleus contains a single proton spin-up the population of low-energy hydrogen nuclei that align their magnetic moments parallel to B0 spin down the population of high-energy hydrogen nuclei that align their magnetic moments anti-parallel to B0 B0 the main magnetic field measured in Tesla thermal equilibrium assumes that patient's temperature is constant and therefore does not influence the thermal energy of hydrogen during the MR experiment Net Magnetization Vector (NMV) the magnetic vector produced as a result of the alignment of excess hydrogen nuclei with B0 precession the secondary spin of magnetic moments around B0 precessional path the circular pathway of magnetic moments as they precess around B0 precessional (larmor) frequency the speed of precession resonance a phenomenon that occurs when an oscillating object is exposed to a frequency having the same or similar oscillating frequency to the object radio frequency (RF) low energy, low frequency electromagnetic radiation radio frequency (RF) What is used to excite hydrogen nuclei in MRI? excitation application of an RF pulse that causes resonance to occur flip angle the angle of the NMV to B0 longitudinal plane the axis parallel to B0 transverse plane the plane at 90 degrees to B0 phase the position of a magnetic moment on its precessional path at any given time in phase (coherent) magnetic moments that are in the same place on the precessional path around B0 at any given time out of phase (incoherent) when the magnetic moments are not in the same place on the precessional path frequency the speed of a rotating object or the rate of change of phase per second MR signal the voltage induced in the receiver coil relaxation process by which the NMV loses energy decay loss of the transverse magnetization recovery growth of longitudinal magnetization T1 recovery growth of the longitudinal magnetization as a result of spin-lattice relaxation T2 decay loss of transverse magnetization as a result of spin-spin relaxation spin-lattice relaxation process by which energy is given up to the surrounding lattice T1 relaxation time time taken for 63% of the longitudinal magnetization to recover spin-spin relaxation process by which interactions between the magnetic fields of adjacent nuclei causes dephasing T2 relaxation time time taken for 63% of the transverse magnetization to decay