1. Neuroimaging in Neuropsychiatry
Qurat Khan

2. Basics of reading MRIs

3. Planes

4. Viewed in three planes
Axial, coronal, and sagittal

10. Shades of Gray Matter

11. Routine MRI is presented as black and white images
Shades of gray are described in terms of “signal intensity”
“Low signal intensity” means “dark,” and “high signal intensity” means “bright”
This is different from CT, where lesions are described in terms of “density”. A dark lesion on CT is called “hypodense,” and a bright lesion is “hyperdense”
How to remember this? “den – SITY” rhymes with “C-T”

12. Weights

13. The most commonly used techniques are T1-weighted, T2-weighted, Flair, and Diffusion-weighted

14. T1 weighted images Useful for brain parenchyma
Brain appears dark gray, CSF is black
Tumor- hypointense
Fat- hyperintense
Abscess- hypointense
MS- hypointense foci
Gadolinium contrast on T1 may “light up” a tumor or abscess
If a lesion has dark signal on T1, and bright signal with gadolinium, it is a “contrast enhancing” lesion
T1 weighted images

16. T2 weighted images CSF appears bright white Brain appears light gray
Used to check the size/symmetry of ventricles, edema, sub acute stroke or hemorrhage, MS
T2 weighted images

17. T2 Changes Periventricular ischemic foci
Acute/subacute ischemic stroke- hyperintense- detect 80% of infarctions before 24 hours. May be negative up to 2-4 hours post-ictus; hyperintensity reaches its maximum between 7 and 30 days. After this it starts to fade
Hemorrhagic stroke, acute and sub acute- hyperintense on T2
Edema (Inflammation, vasculitis, infection)- poorly differentiated hyperintense foci
Abscess- hyperintense foci
MS: hyperintense foci, periventricular and subcortical white matter, infratentorial structures, corpus callosum
Tumor- hyperintense foci
PML- asymmetrical, hyperintense foci with predilection for parietal and occipital lobes
Central pontine myelinolysis- hyperintense lesion in the central part of the pons
Migraine- hyperintense foci on T2
Virchow-Robin space-hyperintense on T2
Fat- hypo intense
T2 Changes

18. Multiple Sclerosis

19. FLAIR Is “a T2 with dark CSF,”
Very sensitive to edema and to parenchymal abnormalities like a low grade glioma
FLAIR

20. Purpose: to visualize acute ischemia- positive in the acute phase and then becomes more bright with a maximum at 7 days. Will be positive for approximately for 3 weeks after onset
A person has new onset of stroke symptoms. CT shows no blood, proving that stroke is not hemorrhagic. Stroke will appear as bright signal on DWI images, and dark on diffusion ADC sequence
ADC will be of low signal intensity with a max at 24 hours, then will increase in signal intensity and finally becomes bright in the chronic stage
DWI

21. L MCA stroke

22. CT

23. Bone
Air- Jet black
CSF
Brain

24. Hyperdense: acute intraparenchymal hemorrhage, calcification, tumor, implant
Hypodensity: ischemic stroke BUT changes may not appear upto 24 hours after the stroke
Brain

26. For tumor or infection (abscess)
Contrast

27. MCA infarction