basics of ct mri

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BASICS OF CT AND MRI

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  • 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