Basics of ct mri

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Information about Basics of ct mri
Health & Medicine

Published on March 10, 2014

Author: DrOmkarSingh

Source: slideshare.net

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BASICS OF CT AND MRI

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 distinction is 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

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 LOBE GREEN- TEMPORAL LOBE YELLOW- OCCIPITAL LOBE

RED- FRONTAL LOBE GREEN- TEMPORAL LOBE YELLOW- OCCIPITAL LOBE

RED- FRONTAL LOBE GREEN- TEMPORAL LOBE YELLOW- OCCIPITAL LOBE

RED –FRONTAL LOBE BLUE-PARIETAL LOBE GREEN- TEMPORAL LOBE YELLOW- OCCIPITAL LOBE

RED- FRONTAL LOBE BLUE- PARIETAL LOBE YELLOW- OCCIPITAL LOBE

RED – FRONTAL LOBE BLUE- PARIETAL LOBE YELLOW- OCCIPITAL LOBE

RED – FRONTAL LOBE BLUE- PARIETAL LOBE YELLOW- OCCIPITAL LOBE

FRONTAL LOBE –RED PARIETAL LOBE - BLUE

RED – FRONTAL LOBE BLUE- TEMPORAL LOBE

RED – FRONTAL LOBE BLUE – TEMPORAL LOBE

Thalmus Aqueduct of sylviusS Cerebellum Fourth ventricle Corpus callosum Midbrain Pons Medulla Corpus callosum Thalamus Aqueduct of Sylvius Fourth 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 Magna 2. Cervical Cord 3. Nasopharynx 4. Mandible 5. 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 medulla Answers 6. Medulla 7. Sigmoid Sinus

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

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

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

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

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

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

T1W T2W FLAIR

acute/subacute hemorrhage acu te 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…

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