Spin-lock imaging of intrinsic susceptibility gradients in tumors.

Previous studies have shown that diffusion of water through intrinsic susceptibility gradients produces a dispersion of the spin-lattice relaxation rate in the rotating frame (R ) over a low range of spin-locking amplitudes (0 ω 100 Hz), whereas at higher ω and high magnetic fields, a second dispersion arises due to chemical exchange. Here, we separated these different effects and evaluated their contributions in tumors.