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Parametric Mapping is a way to measure relaxation time for longitudinal and transverse relaxation time along with extracellular volume. The longitudinal (T1) relaxation time is the time constant which determines the rate at which excited protons return to equilibrium. It is a measure of the time taken for spinning protons to realign with the external magnetic field. The transverse (T2) relaxation time constant which determines the rate at which excited protons reach equilibrium or go out of phase with each other. It is a measure of the time taken for spinning protons to lose phase coherence among the nuclei spinning perpendicular to the main field.
"T1 mapping stands for registering the course of recovery of longitudinal magnetism", this means the relaxation time after either the preparation step (saturation or inversion prepulse) followed by the acquisition of images at several time points during the T1 recover/relaxation. T1 value represents the time when recovery of magnetism has reached a percentage of its original state (63%). The recovery rate relates to the myocardial tissue properties that may be altered by pathological tissue presence (https://www.ahajournals.org/doi/10.1161/circresaha.116.307974). T1 mapping values increase with disease, and decrease post contrast.
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