Understanding MRI Brain Sequences: T1, T2, Flair, and DWI

MRI brain sequences are important for neurologists and medical students.

A pulse sequence in MRI consists of a radio frequency component and an acquisition phase.

Contrast in MRI images is obtained from the different rates of relaxation of protons in different tissues.

⚡️ T1 and T2 are MRI sequences with different signal intensities for water, fat, and contrast.

🧠 T1 images show bright fat, dark water, and are useful for anatomic details and vascular changes.

💡 T2 images show bright water, dark fat, and are useful for identifying pathology and lesions.

🧠 MRI sequences like T1, T2, Flair, and DWI have distinct characteristics and applications.

🖼️ T1 sequence shows fat as bright and CSF as dark, while T2 sequence shows fat as dark and CSF as bright.

💡 Flair sequence is similar to T2, but with flipped CSF spaces.

🔍 Flair does a better job of delineating lesions near the ventricles and can distinguish edema from CSF.

🧠 Flair is useful for gray-white differentiation, especially in structures like the putamen and the head of the caudate.

💡 Flair and T2 images are similar, but the CSF spaces are inverted in Flair.

🔍 Susceptibility weighted imaging or T2 star can detect metals like blood and calcium in the brain.

🩸 GRE is useful for detecting early and old hemorrhages, including hemosiderin deposition.

🧠 T1 sequence can be used to identify myelin, while CSF appears dark.

⚡️ DWI, or diffusion-weighted imaging, is crucial for detecting strokes.

🔍 DWI is a fast MRI sequence that measures the movement of water molecules in the extracellular space.

⚡️ Cytotoxic edema causes fluid restriction in the affected area, leading to hyperintensity on DWI images.

🧠 The presence of hyperintensity on DWI images may indicate an ischemic stroke.

🧠 The T2 image can sometimes create false ischemia due to high intensity areas.

💡 ADC fluid restriction can be used to rule out certain conditions.

🔍 DWI and ADC sequences provide different brightness levels for imaging.