Common MRI Sequences - Basic MRI Brain Interpretation • T1 Sequence - T1 is for anatomy. Since it’s anatomic, brain structures will reflect the same color as real life. So gray matter is gray on T1 & white matter is white on T1. So if you see an image where gray is gray & white is white—you know it’s a T1. • T1 with Contrast - T1 is also for contrast. Contrast material helps us to see masses. Contrast can’t get into normal brain & spine bc of the blood brain barrier- but masses don’t have a blood brain barrier, so when you give contrast, masses will take it up & light up, making them easier to see. • T2 Sequence - T2 sequences are water sensitive sequences. What is pathologic water in the brain? Edema! But this edema can be from many things. • Diffusion Sequence (DWI) - Diffusion is primarily to detect stroke. Acute strokes are bright on diffusion. Not all that is bright on DWI is an acute stroke. This is because all diffusion does is detect how difficult it is for water to move. Anything that makes the space around water crowded and difficult to move will be bright on diffusion imaging. Classically from a stroke - When cells run out of ATP, the Na/K pump stops working & immediately water rushes in from osmotic pressure & the cells swell. These swollen cells fill the interstitium & restrict the movement of water. This is why strokes are bright on DWI! But other things can make it crowded and difficult for water to move. Tumors, hematomas and pus are also bright on diffusion. • Gradient Sequence - Gradient imaging is sensitive to metals. And what’s the most important metal in body? Iron—bc iron is in blood. So gradient is our blood sensitive sequence. Blood is black on gradient. I remember this bc gradient is for metal—and when I think of metal, I think of blacksmiths forging metal products. So BLACKsmith=metal is BLACK on gradient. But other metals will be black too. Notably, calcium, which is in our bones and in many other lesions. By Lea Alhilali, MD @teachplaygrub #MRI #Sequences #Radiology #Neuroradiology #diagnosis #Brain #Interpretation
