T1-weighted image

A T1-weighted image is a type of magnetic resonance imaging (MRI) that emphasizes the differences in the relaxation times of tissues. In T1-weighted imaging, the signal intensity is weighted more towards the recovery of longitudinal magnetization, which is influenced by the T1 relaxation time of the tissues being imaged.

T1-weighted images are commonly used in clinical practice and research for anatomical imaging of structures in the body, including the brain, spine, joints, and abdomen. They are particularly useful for visualizing detailed anatomical structures with high contrast between different types of tissues, such as distinguishing between gray matter and white matter in the brain.

see Axial T1-weighted image.

(also referred to as T1WI) is one of the basic pulse sequences in MRI and demonstrates the differences in the T1 relaxation time of tissues.

The T1WI relies upon the longitudinal relaxation of the net magnetization vector (NMV). T1 weighting tends to have short TE and TR times.

Fat has a large longitudinal and transverse magnetization and appears bright on a T1-weighted image. Conversely, water has less longitudinal magnetization before a RF pulse, and therefore has less transverse magnetization after an RF pulse. Thus, water has a low signal and appears dark.

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T1-weighted anatomical brain scans are routinely used in neuroimaging studies, for example, as anatomical reference for functional data and in brain morphometry studies. Subject motion can degrade the quality of these images. An additional problem is the occurrence of signal dropouts in the case of long echo times and low receiver bandwidths. These problems are addressed in two different studies. In the first study, it is shown that the high scalp signal, which results from the low T1 value of fat, may cause a typical ringing artefact in the presence of head motion. This problem may be enhanced if phased array coils are used for signal reception due to their increased sensitivity in the peripheral head regions. It is shown that this artefact can be avoided by combining certain fat suppression techniques that reduce the scalp signal. In the second study, it is shown that signal dropout affects mainly the orbitofrontal cortex and the temporal lobes, and that a bandwidth of 100 Hz/pixel should be chosen for the investigation of these areas to avoid signal losses while maintaining an acceptable signal-to-noise ratio. Experimental results are based on the MDEFT sequence but can be applied to other T1-weighted sequences like FLASH and MP-RAGE. Furthermore, the presented methods for improving the image quality can be combined with other artefact reduction techniques ¹⁾

Results did not show usefulness of the Diffusion-weighted magnetic resonance imaging and T1-weighted images for assessing the consistency of pituitary macroadenomas, nor as a predictor of the degree of surgical resection ²⁾