1. By DR A K SINGH
LECTURER
PG DEPT OF MEDICINE
BASICS OF
NEUROIMAGING
2. 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
3. Normal CT of brain
• Ventricles are normal sized,
the grey versus white distinction
is clear.
• Midline is straight.
• Sulci are symmetrical on
bothsides.
• Skull is intact with no
scalp edema.
4. 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
33. • 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
34. • 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.
35. 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
40. 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 Magna
2. Cervical Cord
3. Nasopharynx
4. Mandible
5. Maxillary Sinus
41. 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
medulla
Answers
6. Medulla
7. Sigmoid Sinus
42. Fig. 1.3 Post Contrast Axial
MR Image of the brain
15
8
9
10
11
12
13
14
16
17
Post Contrast sagittal
T1 Wtd M.R.I.
Section at the level of
PonsAnswers
8. Cerebellar
Hemisphere
9. Vermis
10. IV Ventricle
11. Pons
12. Basilar
Artery
13. Internal Carotid
Artery
14. Cavernous Sinus
15. Middle Cerebellar
Peduncle
16. Internal Auditory
Canal
17. Temporal Lobe
43. 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
Answers
18. Aqueduct of Sylvius
19. Midbrain
20. Orbits
21. Posterior Cerebral
Artery
22. Middle Cerebral Artery
44. 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 the
III Ventricle
Answers
23. Occipital Lobe
24. III Ventricle
25. Frontal Lobe
26. Temporal Lobe
27. Sylvian Fissure
45. 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
Answers
28. Superior Sagittal
Sinus
29. Occipital Lobe
30. Choroid Plexus
within the occipital
horn
31. Internal Cerebral
Vein
32. Frontal Horn
33. Thalamus
34. Temporal Lobe
35. Internal Capsule
36. Putamen
37. Caudate Nucleus
38. Frontal Lobe
46. 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
Answers
39. Splenium of corpus callosum
40. Choroid plexus within the
body of lateral ventricle
41. Genu of corpus callosum
47. 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
Callosum
Answers
42. Parietal Lobe
43. Body of the Corpus Callosum
44. Frontal Lobe
51. 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.
