T2WI

T2-weighted imaging (T2WI) is an MRI sequence that emphasizes differences in the transverse relaxation time (T2) of tissues. In T2-weighted images, tissues with higher water content, such as edema, inflammation, or fluid-filled structures, tend to appear bright, while fat may appear less bright or intermediate depending on the sequence. Tissues with low water content, such as fibrous structures, generally appear darker. T2WI is commonly used to assess pathology because many disease processes increase tissue water content.

Acquisition and technical aspects: T2WI is typically acquired with long repetition time (TR) and long echo time (TE). In practice, fast spin-echo or turbo spin-echo techniques are used to shorten scan times while preserving T2 contrast. Fat suppression or short-tau inversion recovery (STIR) methods may be applied to improve lesion conspicuity by reducing fat signal. In many protocols, dedicated T2 sequences are obtained in brain, spine, joints, and other regions as part of a multiparametric MRI study.

Interpretation and clinical use: T2WI is particularly sensitive to edema, gliosis, demyelination, inflammatory processes, and cystic or fluid-filled lesions. In the brain, cerebrospinal fluid is bright on T2, providing high contrast with surrounding tissue. T2WI complements T1-weighted imaging and diffusion-weighted imaging, aiding in lesion characterization, monitoring of disease progression, and planning of treatment.

Advantages and limitations: Advantages include high sensitivity to water-related pathology and good anatomical detail. Limitations include lower spatial resolution compared with some T1-weighted sequences, potential for motion artifacts, and longer scan times. Fat signal and flow-related artifacts can affect interpretation if not properly managed.