T2 weighted image
Characteristic of a T2 weighted image is the high signal intensity of water. Pathology is often associated with edema/fluid and therefore a T2 sequence is very suitable to detect pathology (fig. 15).
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Figure 15. Brain tumor with surrounding (reactive) edema frontoparietal left. Both the tumor and the edema have high signal intensity on T2. PA diagnosis: lymphoma.
As in a T1 weighted image, air and calcifications have very low signal intensity.
Tip: you are unsure whether you are seeing air or calcifications? Try to find the structure on an X-ray/CT scan!
Figure 16. Signal intensities in T2 weighted image. Liver, pancreas and adrenals may have low or intermediate signal intensity (SI) caused by variation in individual fluid contents.
Tip: always look for fluid-filled structures (CSF, gallbladder, bladder) to decide whether you are looking at a T1 or T2 weighted image. Fluid has a high signal intensity on T2 weighted images. Note: fat is a less reliable marker to distinguish between T1 and T2 (especially in view of the development of new types of MRI sequences).
