1. Introductory Neuroimaging: What you need to know at 3 am And some cool stuff. . .
Kathleen Tozer, MD

2. Outline Choosing a study Normal anatomy Trauma Ischemic stroke
Aneurysm

3. Outline Choosing a study Normal anatomy Trauma Ischemic stroke
Aneurysm

4. Which study? Acute change
For acute mental status change, first study is ALWAYS noncontrast head CT
Brain MR:
Stroke protocol (noncontrast)
ICH protocol (with contrast)
Tumor protocol (with contrast)

5. Which study? Vascular CTA: MRA:
Neck: Aortic arch through Circle of Willis.
Head: Circle of Willis only
MRA:
Brain: noncontrast
Neck: without and with contrast.

6. Regarding contrast: Iodinated contrast: GFR > 60: GFR < 60:
in the clear
GFR < 60:
If acute, tread cautiously, especially if <30
Hydration, mucomyst, Sodium bicarb protocol
Decrease dose, Visipaque
ESRD:
Coordinate with hemodialysis

7. Regarding contrast: Gadolinium contrast: GFR > 60: GFR 30-60:
in the clear
GFR 30-60:
weigh risks.
Consider noncontrast study first.
Multihance
GFR < 30:
CONTRAINDICATED due to risk of NSF (nephrogenic systemic fibrosis).
Try noncontrast.
Consult radiology for alternative studies.

8. Hounsfield Units (HU) CT density scale: Air = -1000 Fat = -120
Water = 0
Muscle = +40
Blood clot = +65
Bone = +1000
Metal >> +1000

9. Outline Choosing a study Normal anatomy Trauma Ischemic stroke
Aneurysm

10. Normal Anatomy
Note utility of CT scout view--much easier to comprehend, in this instance

11. Normal Anatomy
Note utility of CT scout view--much easier to comprehend, in this instance

12. Normal Anatomy
Note utility of CT scout view--much easier to comprehend, in this instance

13. Normal Anatomy
Note utility of CT scout view--much easier to comprehend, in this instance

14. Acute Head CT Checklist
Midline Shift
Mass Effect
Density
CSF Spaces
Vascular Territories
Intra-/Extra-axial
Herniation
Checklist of pathological changes

15. Outline Choosing a study Normal anatomy Trauma Ischemic stroke
Aneurysm

17. Epidural Hematoma Injury to epidural vessel Lentiform shape
Arterial bleeding
Lentiform shape
Does not cross sutures
May cross falx or tentorium
Look for:
FRACTURE
RAPID EXPANSION

19. Acute Subdural Hematoma
Injury to bridging vessel
Venous
Crescent shaped
May cross sutures
Does not cross falx or tentorium
Does not enter sulci
Watch for:
MASS EFFECT
SLOW EXPANSION

21. Chronic Subdural Hematoma
HYPODENSE
(blood degradation)
MIXED
(Acute-on-chronic)

22. Note midline shift to the left!

23. Isodense Subdural Hematoma
Coagulopathy
Anemia
Evolution of blood products
Note midline shift to the left!
Look for:
Sulcal Effacement
Subtle Mass Effect

25. Subarachnoid Hemorrhage
Sulci
Cisterns
Ventricles
Trauma
lateral convexities
Aneurysm
basal cisterns
Interpeduncular Cistern
most sensitive

27. Cerebral Contusion Intraparenchymal “Coup-Contrecoup” Look for:
Blow to head
Sudden deceleration
Brain impacts inner table (contralateral side)
Look for:
Scalp contusion
Halo of edema

29. Subcortical Injury Shear-Strain forces “Tip of the iceberg”
Penetrating vessels
Axonal injury
“Tip of the iceberg”
Consider MRI
Neurological deficits may be out of proportion to degree of injury visible on CT

30. MRI: Diffuse Axonal Injury
GRE sequence is useful for CT-occult blood degradation products, although other substances can mimic hemosiderin

33. Diffuse Cerebral Edema
Grey-white interface often obscured
Sulcal effacement
Focal subtypes:
Vasogenic
Extracellular
White matter > GM
Cytotoxic
Intracellular
Grey matter > WM

34. Outline Choosing a study Normal anatomy Trauma Ischemic stroke
Aneurysm

35. Stroke

37. Acute Ischemia-Infarction
Subtle HYPODENSITY
Vascular distribution
Loss of grey-white margin
CT often NEGATIVE
Early CT signs
“Hyperdense MCA”
“Insular ribbon”
Role of CT: EXCLUDE BLEED
MRA or CTA useful
DSA for intervention
Early treatment may improve outcome

38. Diffusion-MRI: Acute Infarct
Note abnormality conforms to a vascular distribution within the brain--right MCA territory

39. Case 1

40. Acute facial droop, hemiparesis

41. Case 1

42. Case 1
CTA

43. Angio

44. Post intervention

45. Watershed Infarction
End

48. 15 hours
later

49. Anoxic brain injury Loss of Gray-White Progresses with worsening edema
PseudoSAH
Hydrocephalus
Cisterns compressed

50. Subacute Infarction 2-14 days out Hypodensity ENHANCEMENT
Hemorrhagic transformation

51. MRI: Enhancing Subacute Infarct

52. Chronic Infarction VOLUME LOSS Hypodensity Ex vacuo dilatation
encephalomalacia

53. Dural Sinus Thrombosis
Occlusive thrombosis
Subtle early signs
Bilateral infarcts
Hemorrhages
CTV or DSA
Filling defect
MRI/MRV

55. Outline Choosing a study Normal anatomy Trauma Ischemic stroke
Aneurysm

57. Aneurysmal SAH Sudden severe headache HYPERDENSE CSF spaces Location
Interhemispheric: ACoA
Sylvian: MCA
HYDROCEPHALUS, VASOSPASM and ISCHEMIA
MUST find the aneurysm!
DSA, CTA and/or MRA

58. Saccular Aneurysm

59. Fusiform Aneurysm

60. Active Re-bleeding

61. Ruptured Aneurysm

63. Intracerebral Hemorrhage
Hypertension
Most common
Characteristic Locations
IF LOBAR BLEED:
SEARCH for underlying cause!
MRI/MRA/MRV
DSA or CTA
Repeat imaging if negative initially
Look for:
EXPANSION
UNDERLYING LESION

64. MRI: Blood Products
GRE “blooming” effect

65. MRI: Hemorrhagic Tumor
Note enhancement

67. Parenchymal Hemorrhage with Ventricular Extension

68. MRI Flow Voids: AVM