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Basics of ct mri
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By DR A K SINGH LECTURER PG DEPT OF MEDICINE
BASICS OF NEUROIMAGING
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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
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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.
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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
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Lateral View of Brain
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Cross-sectional Anatomy
• Grey/White interface, Subcortical white matter
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Cross-sectional Anatomy
• Paired of crescent-shape = Twin bananas
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Cross-sectional Anatomy
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Basal ganglia
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Cross-sectional Anatomy
• Third ventricle, Basal ganglia, Superior cerebellar cistern
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Physiologic Calcification
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Cross-sectional Anatomy
• Third ventricle, Smiley face
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Cross-sectional Anatomy
• Midbrain, Interpeduncular cistern
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Cross-sectional Anatomy
• Star shape ~ Circle of Willis, • Fourth ventricle, Temporal horn ~ slit
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Cross-sectional Anatomy
• Base of skull, Midline bony prominence, • Prepontine cistern, Pretrous bone, Frontal
sinus
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Cross-sectional Anatomy
• Orbits, Ethmoid air cell
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GREEN IS TEMPORAL LOBE
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RED DENOTES FRONTAL LOBE
GREEN DENOTES TEMPORAL LOBE
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RED DENOTES FRONTAL LOBE
GREEN-TEMPORAL LOBE
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RED- FRONTAL LOBE
GREEN-TEMPORAL LOBE
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RED-FRONTAL LOBEGREEN-TEMPORAL LOBEYELLOW-OCCIPITAL LOBE
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RED- FRONTAL LOBEGREEN- TEMPORAL LOBEYELLOW-OCCIPITAL LOBE
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RED-FRONTAL LOBEGREEN-TEMPORAL LOBEYELLOW-OCCIPITAL LOBE
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RED –FRONTAL LOBEBLUE-PARIETAL LOBEGREEN-TEMPORAL LOBEYELLOW-OCCIPITAL LOBE
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RED-FRONTAL LOBEBLUE-PARIETAL LOBEYELLOW- OCCIPITAL LOBE
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RED –FRONTAL LOBEBLUE- PARIETAL LOBEYELLOW- OCCIPITAL LOBE
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RED –FRONTAL LOBEBLUE-PARIETAL LOBEYELLOW-OCCIPITAL LOBE
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FRONTAL LOBE –RED
PARIETAL LOBE - BLUE
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RED – FRONTAL LOBE
BLUE-TEMPORAL LOBE
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RED – FRONTAL LOBE
BLUE – TEMPORAL LOBE
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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
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MRI
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• 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
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• 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.
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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
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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
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Fluid-Attenuated Inversion Recovery
FLAIR
• Basically T2 without CSF brightness
• TE>80 and TR>10,000
• Edema and Gliosis are hyperintense
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T1W / T2W / FLAIR
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T1W T2W FLAIR
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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
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Fig. 1.2 Post Contrast Axial MR Image of the brain
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6
Post Contrast sagittal T1 Wtd M.R.I.
Section at the level of medullaAnswers
6. Medulla7. Sigmoid Sinus
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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
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Fig. 1.4 Post Contrast Axial MR Image of the brain
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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
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Fig. 1.5 Post Contrast Axial MR Image of the brain
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24
25
26
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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
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Fig. 1.6 Post Contrast Axial MR Image of the brain
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31
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38
33
34
36
35
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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
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Fig. 1.7 Post Contrast Axial MR Image of the brain
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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
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Fig. 1.8 Post Contrast Axial MR Image of the brain
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43
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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
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T1W T2W FLAIR
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acute/subacute hemorrhage
acute
SUBACUTE T2WI T1WI
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Strokes show up faster on MRI than CT
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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.
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MR:44396
MRI appearances of acute cerebral infarction
T2WI T1WI Flair
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The End…