1. Montreal Neurological Hospital
Neuroradiology
Dr. Grant J. Linnell
Fellow
Montreal Neurological Hospital
McGill University

2. CT Basics Neuroradiology The BASICS of CT CT History Protocol
Terminology
Contrast
Radiation Safety
Cases

3. CT Basics Neuroradiology The BASICS of CT CT History Protocol
Terminology
Contrast
Radiation Safety
Cases

4. CT Basics
No disclosures

5. Neuroradiologist
A consultant in imaging and disease of the brain, spinal cord, head, neck, face and peripheral nerves

6. Neuroradiology Plain Film CT US MRI Interventional Nuclear Medicine
Angiography
Myelography
Biopsy
Nuclear Medicine

7. Neuroradiology A request for an exam is a consultation
History
Pertinent physical exam findings
Lab results
Creatinine
PT/INR
What is the question?

8. CT Basics Computed tomography (CT)
Computed axial tomography or computer –assisted tomography (CAT)

9. CT Basics

10. CT Basics Neuroradiology The BASICS of CT CT History Protocol
Terminology
Contrast
Radiation Safety
Cases

11. CT History
Electro-Musical Instruments

12. CT History SIR GODFREY N. HOUNSFIELD
1979 Nobel Laureate in Medicine

13. CT History 1972 – First clinical CT scanner Used for head examinations
Water bath required
80 x 80 matrix
4 minutes per revolution
1 image per revolution
8 levels of grey
Overnight image reconstruction

14. CT History 2004 – 64 slice scanner 1024 x 1024 matrix
0.33s per revolution
64 images per revolution
0.4mm slice thickness
20 images reconstructed/second

15. CT Basics Neuroradiology The BASICS of CT CT History Protocol
Terminology
Contrast
Radiation Safety
Cases

16. CT Protocolling What happens when an exam is requested?
A requisiton is completed.
The requested exam is protocolled according to history, physical exam and previous exams.
The patient information is confirmed.
The exam is then performed.
Images are ready to be interpreted in …
Uncomplicated exam – 5-10 minutes after completion
Complicated exams with reconstructions take at least 1 hour but usually 1-2 hours.

17. CT Protocolling CT head protocols With or Without contrast CT Brain
CT Brain with posterior fossa images
CT Angiogram/Venogram
CT Perfusion
CT of Sinuses
CT of Orbit
CT of Temporal bones
CT of Mastoid bones
CT of Skull
CT of Face

18. CT Protocolling Variables Plain or contrast enhanced Slice positioning
Slice thickness
Slice orientation
Slice spacing and overlap
Timing of imaging and contrast administration
Reconstruction algorhithm
Radiation dosimetry

19. CT Protocolling Patient Information Is the patient pregnant?
Radiation safety
Can the patient cooperate for the exam?

20. CT Basics Neuroradiology The BASICS of CT CT History Protocol
Terminology
Contrast
Radiation Safety
Cases (Stroke)

21. CT Terminology Exams using Ionizing radiation Plain film CT
1/10 of all exams
2/3 OF RADIATION EXPOSURE
Fluoroscopy
Angiography, barium studies
Nuclear medicine
V/Q scan, bone scan

22. CT Terminology Attenuation Attenuation is measured in Hounsfield units
Hyperattenuating (hyperdense)
Hypoattenuating (hypodense)
Isoattenuating (isodense)
Attenuation is measured in Hounsfield units
Scale to 1000
-1000 is air
0 is water
1000 is cortical bone

23. CT Terminology What we can see The brain is grey
White matter is usually dark grey (40)
Grey matter is usually light grey (45)
CSF is black (0)
Things that are brite on CT
Bone or calcification (>300)
Contrast
Hemorrhage (Acute ~ 70)
Hypercellular masses
Metallic foreign bodies

24. CT Terminology Voxel Volume element Partial volume averaging
A voxel is the 2 dimensional representation of a 3 dimensional pixel (picture element).
Partial volume averaging

25. CT Terminology

26. CT Terminology Window Width Level or Center
Number of Hounsfield units from black to white
Level or Center
Hounsfield unit approximating mid-gray

27. CT Terminology

28. CT Artifacts

29. CT Terminology
Digital reading stations are the standard of care in interpretation of CT and MRI.
Why?
Volume of images
Ability to manipulate and reconstruct images
Cost

30. CT Terminology DICOM Digital Imaging and Communications in Medicine
DICOM provides standardized formats for images, a common information model, application service definitions, and protocols for communication.

31. CT Basics Neuroradiology The BASICS of CT CT History Protocol
Terminology
Contrast
Radiation Safety
Cases

32. Contrast
Barium
Iodinated
vascular
Biliary, Urinary
CSF
Gadolinium

33. Contrast

34. Contrast Types of iodinated contrast
Ionic
Nonionic - standard of care
No change in death rate from reaction but number of reactions is decreased by factor of 4.
If an enhanced study is needed, patient needs to be NPO at least 4 hours and have no contraindication to contrast, ie allergy or renal insufficiency.

35. Contrast What are the risks of iodinated contrast? Contrast reaction
1 in 10,000 have true anaphylactic reaction
1 in 100,000 to 1 in 1,000,000 will die
Medical Issues
Acute renal failure
Lactic acidosis in diabetics
If on Glucophage, patient must stop Glucophage for 48 hours after exam to prevent serious lactic acidosis
Cardiac
Extravasation

36. Contrast Who is at risk for an anaphylactic reaction?
Patients with a prior history of contrast reaction
Patients with a history asthma react at a rate of 1 in 2,000
Patients with multiple environmental allergies, ie foods, hay fever, medications
Amin MM, et al. Ionic and nonionic contrast media: Current status and controversies.
Appl Radiol 1993; 22:

37. Contrast Pretreatment for anaphylaxis
50 mg Oral Prednisone 13, 7 and 1 hour prior to exam
50 mg oral Benedryl 1 hour prior to exam
In emergency, 200 mg iv hydrocortisone 2-4 hours prior to exam

38. Contrast
What are the risk factors for contrast induced acute renal failure?
Pre-existing renal insufficiency
Contrast volume
Dehydration
Advanced age
Drugs
Multiple myeloma
Cardiac failure

39. Contrast Considerations in patients with renal insufficiency
Is the exam necessary?
Is there an alternative exam that can answer the question?
Decrease contrast dose

40. Contrast Pretreatment for renal insufficiency Hydration Mucomyst
600 mg po BID the day before and day of study
Prevention of radiographic-contrast-agent-induced reductions in renal function by acetylcysteine.
Tepel M, et al. N Engl J Med 2000 Jul 20;343(3):180-4

41. Contrast Contrast induced renal failure
Elevated creatinine hours after contrast which resolves over 7-21 days.
Can require dialysis
Mehran, R. et al. Radiocontrast induced renal failure:Allocations and outcomes.
Reviews in Cardiovascular Medicine Vol. 2 Supp

42. CT Basics Neuroradiology The BASICS of CT CT History Protocol
Terminology
Contrast
Radiation Safety
Cases

43. Radiation Safety
Diagnostic CT Scans: Assessment of Patient, Physician, and Radiologist Awareness of Radiation Dose and Possible Risks
Lee, C. et al. Radiology 2004;231:393

44. Radiation Safety Deterministic Effects Stochastic Effects
Have a threshold below which no effect will be seen.
Stochastic Effects
Have no threshold and the effects are based on the dose x quality factor.

45. Radiation Safety Terminology Gy = Gray is the absorbed dose (SI unit)
The equivalent of 1 joule/kg of tissue
Rad = radiation absorbed dose
Sv = Sievert is the dose equivalent (SI unit)
Absorbed dose multiplied by a quality factor
Rem = radiation equivalent man

46. Radiation Safety Relative values of CT exam exposure
Background radiation is 3 mSv/year
Water, food, air, solar
In Denver (altitude 5280 ft.) 10 mSv/year
CXR = 0.1 mSv
CT head = 2 mSv
CT Chest = 8 mSv
CT Abdomen and Pelvis = 20 mSv
-The equivalent of 200 CXR

47. Radiation Safety Effects of X rays.
Absorption of photons by biological material leads to breakage of chemical bonds.
The principal biological effect results from damage to DNA caused by either the direct or indirect action of radiation.

48. Radiation Safety Tissue/Organ radiosensitivity Fetal cells
Lymphoid and hematopoietic tissues; intestinal epithelium
Epidermal, esophageal, oropharyngeal epithelia
Interstitial connective tissue, fine vasculature
Renal, hepatic, and pancreatic tissue
Muscle and neuronal tissue

49. Radiation Safety
Estimated Risks of Radiation-Induced Fatal Cancer from Pediatric CT
David J. Brenner, et al. AJR 2001; 176:
Additional 170 cancer deaths for each year of head CT in the US.
140,000 total cancer deaths, therefore ~ 0.12% increase
1 in 1500 will die from radiologically induced cancer

50. Radiation Safety 3094 men received radiation for hemangioma
Those receiving >100 mGy
Decreased high school attendance
Lower cognitive test scores
Per Hall, et al. Effect of low doses of ionising radiation in infancy on cognitive function in adulthood: Swedish population based cohort study BMJ, Jan 2004; 328:

51. Radiation Safety Hiroshima and Nagasaki
There has been no detectable increase in genetic defects related to radiation in a large sample (80,000) of survivor offspring, including: congenital abnormalities, mortality (including childhood cancers), chromosome aberrations, or mutations in biochemically identifiable genes.
William J Schull, Effects of Atomic Radiation: A Half-Century of Studies from Hiroshima and Nagasaki, 1995.

52. Radiation Safety Hiroshima and Nagasaki
However, exposed individuals who survived the acute effects were later found to suffer increased incidence of cancer of essentially all organs.
William J Schull, Effects of Atomic Radiation: A Half-Century of Studies from Hiroshima and Nagasaki, 1995.

53. Radiation Safety Hiroshima and Nagasaki
Most victims with high doses died
Victims with low doses despite their large numbers are still statistically insignificant.

54. Radiation Safety
Comparison of Image Quality Between Conventional and Low-Dose Nonenhanced Head CT
Mark E. Mullinsa, et al.
AJNR April 2004.
Reduction of mAs from 170 to 90

55. Radiation Safety What does all this mean?
1 CXR approximates the same risk as:
1 year watching TV (CRT)
1 coast to coast airplane flight
3 puffs on a cigarette
2 days living in Denver
1 Head CT is approximately 20 CXR
Health Physics Society on the web--

56. Radiation Safety The pregnant patient
Can another exam answer the question?
What is the gestational age?
Counsel the patient
3% of all deliveries have some type of spontaneous abnormality
The mother’s health is the primary concern.

57. Radiation Safety
"No single diagnostic procedure results in a radiation dose that threatens the well-being of the developing embryo and fetus." -- American College of Radiology
"Women should be counseled that x-ray exposure from a single diagnostic procedure does not result in harmful fetal effects. Specifically, exposure to less than 5 rad has not been associated with an increase in fetal anomalies or pregnancy loss." -- American College of Obstetricians and Gynecologists

58. Conclusion Neuroradiologists are consultants
Garbage in Garbage out
CT Terminology
Attenuation (density) in Hounsfield units
Digital interpretation is standard of care
CT has risks
Contrast
Radiation exposure

59. CT Basics Neuroradiology The BASICS of CT CT History Protocol
Terminology
Contrast
Radiation Safety
Cases

60. Normal CT

61. 1 day year years

62. Normal CT Older person

63. Normal Enhanced CT

64. Case 1
55 yo female with sudden onset of worst headache of life

65. Case 1

66. Case 1

67. Case 1
What do I do now?

68. CTA

69. Normal Angiography

70. Diagnostic Angiography

71. Case 1 Subarachnoid Hemorrhage Most common cause is trauma Aneurysm
Vascular malformation
Tumor
Meningitis
Generally a younger age group

72. Case 2
82 yo male with mental status change after a fall

73. Case 2

74. Case 2 Subdural hematoma Venous bleeding from bridging veins
General presentation
Older age group
Mental status change after fall
50% have no trauma history

75. Subdural Hematoma

76. Case 3
44 yo female with right sided weakness and inability to speak

77. Case 3

78. Case 3
Acute ischemic left MCA stroke

79. MCA Stroke “Dense MCA”

80. Case 4 50 yo male post head trauma.
Pt was initially conscious but now 3 hours post trauma has had a sudden decrease in his neurological function.

81. Case 4

82. Case 4 Epidural hematoma
Typical history is a patient with head trauma who has a period of lucidity after trauma but then deteriorates rapidly.
Hemorrhage is a result of a tear through a meningeal artery.

83. Case 5
71 yo male who initially complained of incoordination of his left hand and subsequently collapsed

84. Case 5

85. Case 5 Intraparenchymal hemorrhage Hypertensive Amyloid angiopathy
Tumor
Trauma

86. Case 6 62 yo female acute onset headache
Hemiplegic on the right and unable to speak

87. Case 6
Add htn image here

88. Case 6 Hypertensive hemorrhage
Clinically looks like a large MCA stroke
Generally younger than amyloid angiopathy patients

89. Chronic Ischemic change = Encephalomalacia

90. Thrombolysis: Intravenous Intra-arterial
3 hours
Intra-arterial
6 hours ICA territory
24 hours basilar territory
CT head plain shows no established stroke nor hemorrhage
CT perfusion shows a salvagable penumbra

91. Case 7
53 y.o. male
Sudden onset of ataxia loss of consciousness proceeding rapidly to coma

93. Case 7
Probable basilar occlusion with cerebellar and brainstem infarction

94. Case 8
52 yo male with right sided weakness

95. Case 8

96. Case 8

97. Case 8 Acute lacunar infarction
Cannot reliably differentiate this finding on CT from remote lacune without clinical correlation.
MRI with diffusion is the GOLD STANDARD
A word on TIA

98. Chronic Small Vessel Disease

99. Case 9
59 yo female with multiple falls over last weekend

100. Case 9

101. Case 9
Stroke involving caudate head, anterior limb internal capsule and anterior putamen.
What is the artery?
Recurrent artery of Heubner

102. Case 10
42 yo male found in coma

103. Case 10

104. Case 10
Global ischemia

105. Angiographic Brain Death

106. Case 11
24 yo male with siezures

107. Case 11

108. Case 11
Heterotopia

109. Case 12
34 y.o. female
Severe H/A,nausea
Taking oral contraceptives

110. Case 12

111. Case 12

112. Case 12
Transverse sinus thrombosis