Magnetization Transfer

59 Magnetization Transfer

Fig. 59.1

As illustrated in Fig. 59.1, the magnetic moment of a single hydrogen nucleus, if aligned parallel to the magnetic field, superimposes its own intrinsic field on its neighbor. Depending on the orientation of the water molecule (which contains two hydrogen nuclei) within the main magnetic field, the field strength at that location will be increased or decreased. Because the number of possible orientations is large, there is also a large range of different resonance frequencies. The latter causes the sum of all magnetizations, the transverse magnetization, to dephase rapidly. The T2 relaxation time can be as short as 10 μsec. Water molecules that are frozen in their orientation are not visible due to the very short T2. Ice cubes within the iced tea thus appear hypointense (Fig. 59.1

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