By DR A K SINGH LECTURER PG DEPT OF MEDICINE

BASICS OF NEUROIMAGING

What We Need to Know

• Air is very black (less than -300 HU)• Water/CSF is black (near 0 HU)• Bone is very dense/white (500-3000 HU)• Blood is white (60-80 HU)• Brain is gray 35-50 HU

Normal CT of brain

• Ventricles are normal sized, the grey versus white distinctionis clear.

• Midline is straight.• Sulci are symmetrical on

bothsides.• Skull is intact with no

scalp edema.

Systemic Approach to Head CT Interpretation

• Symmetry – Compare left and right side of the cranium

• Midline – Look for midline shift• Cross-sectional anatomy – Review anatomical landmark for

each slide– Brain tissue : gray matter, white matter , intracerebral lesions– CSF space : ventricle, basal cistern, cortical sulci, fissure– Skull and soft tissue : scalp swelling, fractures, sinuses, orbit

• Subdural windows : Look for blood collection adjacent to the skull

• Bone windows : Skull, orbit and sinuses, intracranial air

Lateral View of Brain

Cross-sectional Anatomy

• Grey/White interface, Subcortical white matter

Cross-sectional Anatomy

• Paired of crescent-shape = Twin bananas

Cross-sectional Anatomy

Basal ganglia

Cross-sectional Anatomy

• Third ventricle, Basal ganglia, Superior cerebellar cistern

Physiologic Calcification

Cross-sectional Anatomy

• Third ventricle, Smiley face

Cross-sectional Anatomy

• Midbrain, Interpeduncular cistern

Cross-sectional Anatomy

• Star shape ~ Circle of Willis, • Fourth ventricle, Temporal horn ~ slit

Cross-sectional Anatomy

• Base of skull, Midline bony prominence, • Prepontine cistern, Pretrous bone, Frontal

sinus

Cross-sectional Anatomy

• Orbits, Ethmoid air cell

GREEN IS TEMPORAL LOBE

RED DENOTES FRONTAL LOBE

GREEN DENOTES TEMPORAL LOBE

RED DENOTES FRONTAL LOBE

GREEN-TEMPORAL LOBE

RED- FRONTAL LOBE

GREEN-TEMPORAL LOBE

RED-FRONTAL LOBEGREEN-TEMPORAL LOBEYELLOW-OCCIPITAL LOBE

RED- FRONTAL LOBEGREEN- TEMPORAL LOBEYELLOW-OCCIPITAL LOBE

RED-FRONTAL LOBEGREEN-TEMPORAL LOBEYELLOW-OCCIPITAL LOBE

RED –FRONTAL LOBEBLUE-PARIETAL LOBEGREEN-TEMPORAL LOBEYELLOW-OCCIPITAL LOBE

RED-FRONTAL LOBEBLUE-PARIETAL LOBEYELLOW- OCCIPITAL LOBE

RED –FRONTAL LOBEBLUE- PARIETAL LOBEYELLOW- OCCIPITAL LOBE

RED –FRONTAL LOBEBLUE-PARIETAL LOBEYELLOW-OCCIPITAL LOBE

FRONTAL LOBE –RED

PARIETAL LOBE - BLUE

RED – FRONTAL LOBE

BLUE-TEMPORAL LOBE

RED – FRONTAL LOBE

BLUE – TEMPORAL LOBE

ThalmusAqueduct of sylviusS

Cerebellum

Fourth ventricle

Corpus callosum

Midbrain

Pons

Medulla

Corpus callosum Thalamus Aqueduct of SylviusFourth Ven. Mid-brain Pons  Cerebellum Medulla oblongata

SECTION AT MID-SAGITTAL PLANE

MRI

• Based on the absorption and emission of radiofrequency energy – so there is NO ionizing radiation.

• Uses magnets ranging in strength from 0.3 to 1.5 Tesla to create a magnetic field around the patient.

• Magnetic field causes protons in the body to align and then pulsed radiowaves are directed at the patient causing a disturbance of the proton alignment.

• Atoms then realign and in doing so, emit the absorbed radiofrequency

• The time it takes the protons to regain their equilibrium state = • RELAXATION TIME. �• 2 types of relaxation time: T1 – Longitudinal (parallel to the magnetic

field) and T2 –transverse (perpendicular to the mag field). �• Relaxation Time and Proton Density are the main determinants of

signal strength. �• The main determinants of contrast or the weighting are: � 1)Repetition Time (TR) – the time between successive RF pulses

2)Echo Time (TE) – time between the arrival of the RF pulse that excites

and the arrival of the return signal at the detector.

Short TR + Short TE = T1 weighted

•Dark– CSF– Increased Water –

edema, – tumor, infarct,

inflammation, – infection, hemorrhage (hyperacute or

chronic)– Low proton density, calcification– Flow Void

•Bright– Fat– Subacute hemorrhage– Melanin– Protein-rich Fluid– Slowly flowing blood– Gadolinium– Laminar necrosis of

an infarct

Long TR + Long TE= T2 weighted

• Dark– Low Proton Density, – calcification, fibrous

tissue– Paramagnetic

substances - • deoxyhemoglobin, • methemoglobin

(intracellular), • iron, hemosiderin,

melanin – Protein-rich fluid– Flow Void

• Bright– CSF– Increased Water –

edema, – tumor, infarct,

inflammation, – infection, subdural

collection– Methemoglobin – (extracellular) in

subacute – hemorrhage

Fluid-Attenuated Inversion Recovery

FLAIR

• Basically T2 without CSF brightness

• TE>80 and TR>10,000

• Edema and Gliosis are hyperintense

T1W / T2W / FLAIR

T1W T2W FLAIR

Fig. 1.1 Post Contrast Axial MR Image of the brain

1

2

3

4

5

Post Contrast sagittal T1 Weighted M.R.I.

Section at the level of Foramen MagnumAnswers

1. Cisterna Magna2. Cervical Cord3. Nasopharynx4. Mandible5. Maxillary Sinus

Fig. 1.2 Post Contrast Axial MR Image of the brain

7

6

Post Contrast sagittal T1 Wtd M.R.I.

Section at the level of medullaAnswers

6. Medulla7. Sigmoid Sinus

Fig. 1.3 Post Contrast Axial MR Image of the brain

15

8

9

10

11

1213

14

16

17Post Contrast sagittal

T1 Wtd M.R.I. Section at the level of

PonsAnswers8. Cerebellar Hemisphere9. Vermis10. IV Ventricle11. Pons12. Basilar Artery

13. Internal Carotid Artery14. Cavernous Sinus15. Middle Cerebellar Peduncle16. Internal Auditory Canal17. Temporal Lobe

Fig. 1.4 Post Contrast Axial MR Image of the brain

18

19

20

21

22

Post Contrast sagittal T1 Wtd M.R.I.

Section at the level of Mid Brain

Answers18. Aqueduct of Sylvius19. Midbrain20. Orbits21. Posterior Cerebral Artery22. Middle Cerebral Artery

Fig. 1.5 Post Contrast Axial MR Image of the brain

23

24

25

26

27

Post Contrast sagital T1 Wtd M.R.I.

Section at the level of theIII Ventricle

Answers23. Occipital Lobe24. III Ventricle25. Frontal Lobe26. Temporal Lobe27. Sylvian Fissure

Fig. 1.6 Post Contrast Axial MR Image of the brain

28

29

30

31

32

38

33

34

36

35

37

Post Contrast sagittal T1 Wtd M.R.I.

Section at the level of Thalamus

Answers28. Superior Sagittal Sinus29. Occipital Lobe30. Choroid Plexus within the occipital horn31. Internal Cerebral Vein32. Frontal Horn

33. Thalamus34. Temporal Lobe35. Internal Capsule36. Putamen37. Caudate Nucleus38. Frontal Lobe

Fig. 1.7 Post Contrast Axial MR Image of the brain

39

40

41

Post Contrast sagittal T1 Wtd M.R.I.

Section at the level of Corpus Callosum

Answers39. Splenium of corpus callosum40. Choroid plexus within the body of lateral ventricle41. Genu of corpus callosum

Fig. 1.8 Post Contrast Axial MR Image of the brain

42

43

44

Post Contrast sagittal T1 Wtd M.R.I.

Section at the level of Body of Corpus

CallosumAnswers42. Parietal Lobe43. Body of the Corpus Callosum44. Frontal Lobe

T1W T2W FLAIR

acute/subacute hemorrhage

acute

SUBACUTE T2WI T1WI

Strokes show up faster on MRI than CT

MRI and CAT views of the same whole R. hemispherical infarct

Some very big strokes settle down and don’t require surgical decompression. This man opens his eyes to verbal on nasal cannula and follows on the right side 10 days post stroke.

MR:44396

MRI appearances of acute cerebral infarction

T2WI T1WI Flair

The End…