T2 Weighted image---high signal o Fluid Edema o Fat Blood (extracellular methemoglobin
T2 weighted image---high signal • Fluid • Edema • Fat • Blood (extracellular methemoglobin)
T2 Weighted image---low signal Air Calcification 月 owing blood o Very high concentration of protein Fungus o Metal
T2 weighted image---low signal • Air • Calcification • Flowing blood • Very high concentration of protein • Fungus • Metal
Tissue Contrast parameter on MR Imaging TI relaxation time 丁2 relaxation time Proton density Diffusion of water
Tissue Contrast Parameter on MR Imaging • T1 relaxation time • T2 relaxation time • Proton density • Diffusion of water
FLAIr IMAGING A heavily T2 weighted image with suppression of CSF signal intensity A 180 degree pulse with an inversion time of 2500 ms tailored to null CSF signal o Greater conspicuity of lesions at the csf-brain interface
FLAIR IMAGING • A heavily T2 weighted image with suppression of CSF signal intensity • A 180 degree pulse with an inversion time of 2500 ms tailored to null CSF signal • Greater conspicuity of lesions at the CSF-brain interface
Diffusion Weighted Imaging Diffusion of water is random---isotropic White matter tracts---anisoptropic, or directional Highly sensitive to motion o Intracellular water(restricted water)is not susceptible to the diffusion gradients Mobile water loses signal intensity due to dephasing
Diffusion Weighted Imaging • Diffusion of water is random---isotropic • White matter tracts---anisoptropic, or directional • Highly sensitive to motion • Intracellular water (restricted water) is not susceptible to the diffusion gradients • Mobile water loses signal intensity due to dephasing