Homework-4: Imaging Principles

  1. A sample contains water at two locations, y = 1.0 cm and y = -2.0 cm. A one-dimensional magnetic field gradient is applied along the y-axis during the acquisition of an FID. The frequency encoding gradient is 1 G/cm. What frequencies (relative to the isocenter frequency) are contained in the Fourier transformed spectrum?

  2. An NMR spectrum is recorded from a sample containing two water locations. The frequency encoding gradient is 0.5 G/cm along the z-axis. The spectrum contains frequencies of -1000 Hz and +500 Hz relative to the isocenter frequency. What are the locations of the water?

  3. You want to excite spins in an xy-plane located at z = -2.0 cm. The resonance frequency at the isocenter is 63.85 MHz and your slice selection gradient is 2 G/cm. Describe in detail the RF pulse which should be used.