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Basic operations of the MRI scanner. A. The static magnetic field (Bo). The protons align parallel or antiparallel to the static magnetic field, creating a small
net magnetization vector. While aligned to the magnetic field, the protons precess at the Larmor frequency. B. Transmission of radiofrequency energy
(RF). Energy is transmitted to the rotating protons by a radiofrequency pulse at the Larmor frequency. RF pulses that result in a flip angle of 90 and 180
degrees are shown (top and bottom, respectively). The figures are presented in the rotating frame of reference, where the x-y axes are rotating at the
Larmor frequency and thus appear stationary. C. Generation of the MR signal. Rotation of the net magnetization vector into the transverse plane results in
the creation of a time-varying magnetic field, which in turn induces an alternating current in the receiver coil array, which is the MR signal.
Source: Chapter 23. Magnetic Resonance Imaging of the Heart, Hurst's The Heart, 13e
Citation: Fuster V, Walsh RA, Harrington RA. Hurst's The Heart, 13e; 2011 Available at: http://mhmedical.com/ Accessed: June 10, 2017
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