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. Author manuscript; available in PMC: 2013 Jan 1.
Published in final edited form as: Anal Cell Pathol (Amst). 2012;35(4):205–227. doi: 10.3233/ACP-2011-0050

Figure 1.

Figure 1

(a) The source of signal in MR is the proton magnetization, which precesses around the static magnetic field at the Larmor frequency. (b) In a reference frame rotating at this Larmor frequency M0 appears to be stationary. In the 90-FID pulse sequence, the net magnetization is rotated down into the x′y′ plane with a 90° RF pulse. (c) A changing magnetic flux induces a current in the receiver coil. (d) The signal recorded in the laboratory frame following the RF pulse constitutes the FID.