Questions: 1. In MRI, what is a bulk magnetization vector? How is it formed? 2. What does it mean that a bulk magnetization vector is "tipped 90 degrees"? How is this done? 3. A patient is laying in an off MRI machine. There is no external magnetic eld applied. a) The bulk magnetization vector is O. b) The magnetic dipole moments will align in a parallel direction. c) The magnetic dipole moments will align in an anti-parallel direction. d) The magnetic dipole moments will align in parallel or anti-parallel directions. e) The bulk magnetization vector is pointing up. 4. Which of the following would increase the bulk magnetization vector the greatest? a) Doubling the external magnetic field. b) Sending an RF pulse at double the Larmorfrequency. c) Tripling the temperature. d) Doubling the gyromagnetic ratio of the nucleus. e) Tripling the number of protons present. 5. Tipping the bulk magnetization vector away from its equilibrium requires: a) A radiofrequency (RF) at the Larmor frequency for a preset time. b) A continuous radiofrequency (RF) pulse at the resonant frequency. c) Any radiofrequency (RF) pulse for a preset time d) Any photon with energy E=hf. e) A radiofrequency (RF) pulse at the resonant frequency for a Bo field of 1 Tesla. 6. Protons subjected to an external magnetic eld will align their magnetic dipole moments in which of the following ways? a) High energy and low energy with a majority in the high energy state. b) Randomly orientated c) High energy and low energy with a majority in the low energy state and remain stationary. d) Parallel high energy and W at the Lamor frequency e) High energy and low energy with a majority in the low energy state and megess at the Lamor frequency 7. In MRI, right after a 90 degree pulse has been applied and then turned off: a) Both 2 and xy are at a minimum b) 2 is at a minimum, xy is at a maximum 0) z is at a maximum, xy is at a minimum d) z and xy are equal e) Both 2 and xy are at a maximum 8. An external magnetic eld has been applied. Which of the following is true? a) Protons aregess about the z axis at varying frequencies. b) Protons W about the z axis at the Larmor frequency. c) The bulk magnetization vector (Mo) precesses about the z axis at the Larmor frequency d) Both Aand C. e) Both B and C. 9. Mxy= MoeA-t/T 2* Three minutes after turning off an F pulse, you measure that the x-y component of your signal has decreased by 63% of the maximum signal. What is the T2* relaxation time of the tissue you are measuring? a) 0.21 minutes b) 3 minutes 0) 0 0.15 minutes d) 0.33 minutes e) 0.12 minutes