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Spin Density, T1, T2, T2* Relaxation and Bloch Equations

This unit discusses the four primary sources of signal variation in a standard MRI sequence. T1 and T2/T2* relaxation reveal the time dependence of the longitudinal and transverse component of the magnetization, respectively. When imaging is performed, the effective spin density is considered as the number of spins per voxel. The variation of signal with voxel size is discussed. Modification of Bloch equations that govern the motion of the magnetization is discussed for all four cases.