T2weighted

T2-weighted imaging (T2W or T2WI) is an MRI sequence designed to emphasize differences in transverse relaxation time (T2) among tissues. Tissues with higher water content tend to have longer T2 relaxation times and therefore appear bright on T2-weighted images, while tissues with shorter T2 times appear relatively darker. This contrast makes T2-weighted images particularly sensitive to fluid and edema.

Technically, T2 weighting is achieved with long repetition times (TR) and long echo times (TE), using spin-echo or fast spin-echo (turbo spin-echo) techniques. The sequence can be performed with or without fat suppression. In non-fat-suppressed T2 images, fat may appear intermediate to bright, whereas applying fat suppression or using related sequences can enhance the visibility of pathology by reducing fat signal and emphasizing fluids and edema.

Appearance and interpretation. In the brain, cerebrospinal fluid is typically very bright on T2 images, with gray matter generally lighter than white matter; lesions containing water, such as edema, cysts, or demyelinating plaques, often appear hyperintense. In the musculoskeletal system, joint effusions, edema, and certain tumors may also be conspicuous. T2 weighting is commonly used alongside T1-weighted imaging to characterize lesions, differentiate cystic from solid components, and assess inflammatory or infectious processes.

Applications and limitations. T2-weighted imaging is widely used for evaluation of the central nervous system, spine, joints, liver, and pelvis. It is particularly sensitive to edema and fluid-containing abnormalities but can be less specific than T1-weighted imaging for tissue composition. Artifacts from motion, susceptibility, or fluid flow can affect image quality, and fat suppression techniques are sometimes employed to improve contrast.