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with Dr. David Milbauer



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Answer to May's MRI Corner.

T1 Weighted                        T2 Weighted
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What image plane was selected?

What is the difference between these images?

Discussion

These are sagittal images which best depict the relationship of the vertebral bodies and intervertebral discs to the spinal canal and to each other.

The capacity to image in any plane is unique to MRI. The difference between these images is that one is T1 weighted and the other is T2 weighted.

On T1 weighted images, fluid such as CSF appears dark and fat appears bright. This is reversed on T2 weighted images where fluid is rendered bright and the signal intensity from fat diminishes. T2 weighted images, therefore, provide a myelographic images where bright CSF outlines the supra-arachnoid space, surrounds the spinal cord and makes encroachment upon the spinal canal more obvious.

This is of value when imaging osteophytic encroachment upon the canal, which can be poorly depicted on T1 weighted images. This is because both osteophytes and spinal fluid appear dark, obscuring their interface. Intramedullary lesions of the spinal cord, such as multiple sclerosis plaques and spinal cord tumors are also typically better visualized on T2 weighted images.

Such abnormalities of the spinal cord are also an indication to use gadolinium contrast, which can highlite spinal cord lesions on T1 weighted images.

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