CT scanning provides images of brain tissue based on density differences detected by x-rays. The images produced use Hounsfield units to represent densities on a scale where air is -1000 and bone is +1000. On CT, white matter appears darker than gray matter and CSF appears black. Common sequences seen on CT include axial, coronal, and sagittal cuts at various anatomical levels. CT is used to identify acute ischemic strokes within 12 hours by detecting hyperdense arteries, and in subsequent days can identify low density infarcts and hemorrhagic transformations. Chronic infarcts appear as well-defined low attenuation areas.

1. CT BRAIN - BASICS D.SUBBURAJ PROF.G .ELANGOVAN’S UNIT

2. CT Principle RING OF XRAY DETECTORS

3. Frankfurt plan e

4. HOUNSFIELD UNITS Numeric information in each pixel of ct image Related to composition & nature of tissue Represent the density of tissue Also called as CT NUMBER

5. air --- 1000 fat ---70 Pure water 0 Csf +8 White matter +30 Gray matter +45 blood +70 Bone/cacification +1000

6. CT /MRI CT PICTURE WHITE MATTER IS DARKER THAN GREY MATTER SINCE LIPID CONTAINING MATERIAL IS RADIOLUCENT CSF IS BLACK MR PICTURE GREY MATTER T1WI DARK T2WI BRIGHT WHITE MATTR BRIGHT DARK CSF GREY TO DARK WHITE

7. Step wise approach Ventricles/ cisterns Cortex Deep gray matter Focal lesions Bone Extracranial soft tissue Para nasal sinuses

8. LV FRONTAL HORN TEMBORAL HORN OCCIPITAL HORN FORAMEN OF MONRO 4 V AQUEDUCT OF SYLVIUS 3V trigone

9. COMMON SECTIONS AXIAL SECTIONS CORONAL SECTIONS SAGITTAL SECTIONS POSTERIOR FOSSA CUTS - ABOVE THE FORAMEN MAGNUM LEVEL -LEVEL OF THE FOURTH VENTRICLE -ABOVE THE FOURTH VENTRICULAR LEVEL - TENTORIAL SUPRATENTORIAL CUTS - THIRD VENTRICULAR LEVEL -LOW VENTRICULAR LEVEL -ABOVE THE VENTRICULAR LEVEL -FRONTAL HORN LEVEL -THIRD VENTRICULAR LEVEL -MID VENTRICULAR LEVEL -OCCIPITAL HORN LEVEL -MID SAGITTAL LEVEL -PARASAGITTAL LEVEL THROUGH THE LATERAL VENTRICULAR BODY -LATERAL ORBITAL LEVEL

10. ABOVE THE LEVEL OF FORAMEN MAGNUM VA MEDULLA TONSIL 4 V CM INT OCC PROT

11. LEVEL OF FOURTH VENTRICLE MCP CPCISTERN PONS 4V TEM HORN Optic nerve

12. LEVEL ABOVE FOURTH VENTRICLE SUPRA SELLAR CISTERN MB AMB CIST SYLV FISSURE 4V OLF SULCUS vermis

13. THIRD VENTRICULAR LEVEL

14. LOW VENTRICULAR

15. Above ventricle level

16. Cerebral Arterial Territory MCA -most of lateral hemisphere , Basal ganglia, insula, ACA- Inferomedial basal ganglia,ventromedial frontal lobes, anterior 2/3rd medial cerebral hemispheres , 1 cm supero medial brain convexity PCA -Thalami, midbrain, posterior 1/3of medial hemisphere , occipital lobe, postero medial temporal lobe

17. Anterior Choroidal artery branch of ICA supply part of the hippocampus, the posterior limb of the internal capsule Medial lenticulostriate arteries Branches of the A1-segment of the anterior cerebral artery. They supply the anterior inferior parts of the basal nuclei and the anterior limb of the internal capsule . Lateral lenticulostriate arteries Branches of the horizontal M1-segment of the middle cerebral artery . They supply the superior part of the head and the body of the caudate nucleus , lentiform nucleus and the posterior limb of the internal capsule

18. MCA ACA PCA

19. AICA- inferolateral part of pons, middle cerebellar peduncle, floccular region, anterior petrosal surface of cerebellar hemisphere PICA- posteroinferior surface of cerebellar hemisphere , ipsilateral part of inferior vermis, Superior cerebellar artery -superior aspect of cerebellar hemisphere (tentorial surface), ipsilateral superior vermis, largest part of deep white matter including dentate nucleus, pons

21. Water shed infarct

22. CEREBRAL ISCHEMIA

23. Cerebral ischemia Significantly diminished blood supply to all parts(global ischemia) or selected areas(regional or focal ischemia) of the brain Focal ischemia - cerebral infarction Global ischemia -hypoxic ischemic encephalopathy(HIE),hypotensive cerebral infarction

24. Goal of imaging Exclude hemorrhage Identify the presence of an underlying structural lesion such as tumour , vascular malformation ,subdual hematoma that can mimic stroke Identify stenosis or occlusion of major extra- and intracranial arteries Differentiate between irreversibly affected brain tissue and reversibly impaired tissue (dead tissue versus tissue at risk)

25. Infarct vs pneumbra In the central core of the infarct, the severity of hypoperfusion results in irreversible cellular damage . Around this core, there is a region of decreased flow in which either: The critical flow threshold for cell death has not reached Or the duration of ischemia has been insufficient to cause irreversible damage.

27. Hyper acute infarct(<12 hours) Acute infarct(12 - 48 hours) Subacute infarct(2 - 14 days) Chronic infarct(>2 weeks) Old infarct(>2 months )

28. CT-Hyperacute infarct Hyperdense MCA sign -acute intraluminal thrombus Attenuation of lentiform nulei Dot sign -occluded MCA branch in sylvian fissure Insular ribbon sign –grey white interface loss along the lateral insula

29. Dense mca sign

30. ‘ loss of insular ribbon’

31. M C A DOT SIGN

32. ATTENUATION OF LENTICULAR NUCLEUS

33. CT- Acute infarct Low density basal ganglia Sulcal effacement Wedge shaphed parenchymal hypo density area that involves both grey and white matter Increasing mass effect Hemorrhagic transformation may occur -15 to 45% ( basal ganglia and cortex common site ) in 24 to 48 hours

34. CT – sub acute infarct PLAIN CT Wedge-shaped area of decreased attenuation involving gray/white matter in typical vascular distribution Mass effect initially increases, then begins to diminish by 7-10 days H’gic transformation occurs in 15-20% of MCA occlusions, usually by 48-72 hrs CECT Enhancement patterns typically patchy May appear as early as 2-3 days , persisting up to 8-10 weeks &quot;2-2-2&quot; rule = enhancement begins at 2 days, peaks at 2 weeks, disappears by 2 months

35. CT-chronic infarct Plain ct Focal, well-delineated low-attenuation areas in affected vascular distribution sulci become prominent; ipsilateral ventricle enlarges Dystrophic Ca++ may occur in infarcted brain but is very rare CECT : No enhancement

36. INFARCT / TUMOUR CLINICAL HISTROY DISTRIBUTION SHAPES GRAY / WHITE INVOLVEMENT ADVANCED IMAGING

37. VENOUS INFARCT HISTROY BEYOND VASCULAR DISTRIBUTION HAEMORRHAGIC INFARCT THORMBUS IN VENOUS SINUSES SYMMETRICAL LOW ATTENUATION IN DEEP GRAY MATTER - DEEP CEREBRAL VEIN THORMBUS

38. EDEMA/ INFARCT INFARCT TYPICAL VASCULAR DISTRIBUTION GRAY MATTER INVOLVEMENT EDEMA NOT CONFINED TO VASCULAR DISTRIBUTION MOSTLY INVOLVES WHITE MATTER

39. PCA INFARCT

40. MCA INFARCT

41. ACA INFARCT

42. WATERSHED INFARCT

43. Old infarct

44. H’gic infarct

45. Thank u