Problem 1

Assume that the figure above shows the timing of a readout gradient in an MR sequence, scaled to unit amplitude at TE, which occurs at the time 6t in the center of the readout period, and that the dashed line represents zero gradient amplitude. The period indicated in blue is the readout. Find the amplitude 'A' such that the sequence produces zero net phase shift for stationary, constant velocity, and accelerating spins. See Motion artifacts in MRI for help.

Which of the following are reasons that spectroscopy is best done at higher magnetic fields (check as many as are correct)?

The chemical shift (ppm) between molecules is increased	The larger magnetization results in improved SNR
The 'J' coupling results in broader splitting	Chemical shifts are larger compared to local field distortions
The acquisition times are shorter for constant SNR	High field instruments are easier to shim
The increased shift (in Hz) results in a lower readout bandwidth and improved SNR	The increased RF power results in better excitation homogeneity

True or False: in vivo MR Spectroscopy can provide reliable absolute measures of solute concentrations.

SNR decreases with the 1/square root of the total readout duration	Required Gradient Power decreases
Chemical Shift artifact decreases	Motion artifact is decreased
Achievable Spatial Resolution Decreases	Specific Absorptoin Rate (SAR) is reduced
Magneto-Stimulation becomes more likely	Shape Distortions Increase

Is Quantitative for flow velocity	Time-of-flight (saturation)	Phase Contrast
Uses spatial presaturation to detect flow direction	Time-of-flight (saturation)	Phase Contrast
Is more effective at short TR	Time-of-flight (saturation)	Phase Contrast
Requires six excitations to measure 3D flow	Time-of-flight (saturation)	Phase Contrast