T2* combines two sources of signal loss: true spin-spin relaxation and extra dephasing caused by magnetic susceptibility or magnetic-field inhomogeneity. Consequently, its value is sensitive not only to intrinsic tissue behavior but also to local variations in the magnetic environment. This combined sensitivity makes the metric informative for tissue composition and local magnetic-field variation.
Multiple echo times provide several points along the gradient-echo signal-decay curve. Fitting those measurements estimates the rate at which transverse magnetization loses phase coherence and produces a T2* value or map. Using a range of echo times therefore turns a sequence of MRI measurements into a quantitative image rather than relying on a single qualitative contrast.
Magnetic susceptibility and field inhomogeneity are central determinants of the measured value because they add dephasing to true spin-spin relaxation. Tissue composition can therefore influence T2* through its effect on the local magnetic environment. This relationship is especially relevant when interpreting signal patterns associated with blood oxygenation, hemorrhage, calcification, or tissue iron.
An examination generally acquires gradient-echo MRI data at multiple echo times, models the resulting signal decay, and converts the fitted estimate into a spatial T2* map. The key output is not merely the source images but a quantitative representation of relaxation behavior across tissue. Investigators can use the map for tissue characterization or monitoring disease-related changes.
Medical applications include evaluating blood oxygenation and identifying imaging patterns associated with hemorrhage, calcification, and tissue iron. The method is used in both cardiac and brain imaging, where these targets can provide information about tissue composition and local magnetic conditions. Its value is broad because the same measurement framework supports several medically relevant sources of contrast.
Within clinical research, T2* maps can improve tissue characterization, monitor disease-related changes, and complement conventional MRI biomarkers. Rather than replacing other MRI information, the maps add a measurement that is sensitive to both spin-spin relaxation and local magnetic effects. This complementary role supports studies seeking quantitative markers of tissue status in the heart or brain.