Which of the following refer to the relaxation mechanism in the transverse direction? (Choose all that apply)
T2 relaxation
Spin-lattice relaxation
Spin-spin relaxation
T1 relaxation
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Which of the following refer to the relaxation mechanism in the longitudinal direction? (Choose all that apply)
T2 relaxation
Spin-lattice relaxation
Spin-spin relaxation
T1 relaxation
To determine which of the options refer to relaxation mechanisms in the transverse and longitudinal directions, we need to understand the concepts of T1 and T2 relaxation, as well as spin-lattice and spin-spin relaxation.
1. Transverse Relaxation:
In magnetic resonance imaging (MRI), transverse relaxation refers to the process of decay of the magnetization vector in the transverse (XY) plane. It involves the loss of phase coherence between the individual magnetic moments of the nuclear spins.
The two relaxation mechanisms associated with transverse relaxation are:
- T2 Relaxation (also called spin-spin relaxation or transverse magnetization relaxation): T2 relaxation refers to the decay of the transverse magnetization caused by spin-spin interactions. It is characterized by the loss of phase coherence due to differences in precession frequencies of spins within a sample.
- Spin-Spin Relaxation (also called T2 relaxation): Spin-spin relaxation describes the interactions between individual nuclear spins within a sample. It is responsible for the loss of coherence of the transverse magnetization.
Therefore, T2 relaxation and spin-spin relaxation both refer to the relaxation mechanism in the transverse direction.
2. Longitudinal Relaxation:
In MRI, longitudinal relaxation refers to the process of recovery of the magnetization vector along the longitudinal (Z) axis. It involves the return of the nuclear spins to their equilibrium state.
The two relaxation mechanisms associated with longitudinal relaxation are:
- T1 Relaxation (also called spin-lattice relaxation or longitudinal magnetization relaxation): T1 relaxation describes the process of energy transfer between the nuclear spins and their surrounding lattice or environment. It is characterized by the re-alignment of nuclear spins back to their equilibrium state.
- Spin-Lattice Relaxation (also called T1 relaxation): Spin-lattice relaxation refers to the process by which nuclear spins transfer energy to their surrounding lattice or environment, resulting in the recovery of longitudinal magnetization.
Therefore, T1 relaxation and spin-lattice relaxation both refer to the relaxation mechanism in the longitudinal direction.
To summarize:
Transverse Relaxation Mechanism:
- T2 relaxation
- Spin-spin relaxation
Longitudinal Relaxation Mechanism:
- T1 relaxation
- Spin-lattice relaxation