MRIrelaxációs

MRIrelaxációs, also known as relaxation in Magnetic Resonance Imaging, refers to the processes by which excited atomic nuclei return to their equilibrium state after being subjected to a radiofrequency pulse in an MRI scanner. This relaxation is fundamental to how MRI generates images. There are two primary types of relaxation: T1 relaxation and T2 relaxation.

T1 relaxation, also known as spin-lattice relaxation, describes the recovery of longitudinal magnetization along the main magnetic field. When a radiofrequency pulse is applied, it tips the net magnetization vector away from its equilibrium alignment. T1 relaxation is the process by which the protons release energy to their surrounding molecular environment (the "lattice") and realign with the main magnetic field. The time constant associated with this process is called the T1 time, and it varies depending on the tissue type. Tissues with short T1 times, like fat, recover magnetization quickly.

T2 relaxation, also known as spin-spin relaxation, describes the decay of transverse magnetization, which is the component of magnetization perpendicular to the main magnetic field. This decay occurs due to interactions between neighboring protons. As protons dephase in the transverse plane, the overall transverse magnetization decreases. The time constant for this process is called the T2 time. Tissues with longer T2 times, like water, maintain their transverse magnetization for a longer period. MRI sequences are designed to exploit the differences in T1 and T2 times between various tissues to create contrast in the resulting images.