T1weighted

T1-weighted imaging refers to magnetic resonance imaging (MRI) sequences in which the image contrast is primarily determined by the T1 relaxation times of tissues. These images are typically acquired with short repetition times (TR) and short echo times (TE), often using spoiled gradient-echo or fast spin-echo techniques. The result is an image where differences in how quickly protons realign with the magnetic field after excitation produce the contrast between tissues.

In standard T1-weighted images, tissues with shorter T1 relaxation times appear bright, while those with longer T1 times appear darker. Fat tends to be bright, while water-containing tissues such as CSF are relatively dark. Gray matter has intermediate signal, and white matter is somewhat brighter than gray matter. The appearance of a tissue can be influenced by field strength, pulse sequence, and pulse timing.

Gadolinium-based contrast agents shorten T1 relaxation times in the extracellular space, leading to increased signal on T1-weighted images. Post-contrast T1-weighted imaging is commonly used to detect areas of disruption of the blood-brain barrier or neovascularity in tumors, inflammation, and some infections. T1-weighted images are also useful for delineating anatomy and guiding surgical planning, as well as in body imaging to evaluate fat, marrow, and certain lesions.

Limitations include sensitivity to magnetic field inhomogeneities, which can affect image quality in certain regions, and relatively lower sensitivity to edema or tissue water content compared with T2-weighted or FLAIR sequences. T1 weighting provides high-resolution anatomical detail and complementary contrast when used with other MRI sequences.