Neuroradiology

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Neuroradiology

• Dr. Grant J. Linnell
• Fellow
• Montreal Neurological Hospital
• McGill University

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CT Basics

• Neuroradiology
• The BASICS of CT
• CT History
• Protocol
• Terminology
• Contrast
• Radiation Safety
• Cases

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CT Basics

• Neuroradiology
• The BASICS of CT
• CT History
• Protocol
• Terminology
• Contrast
• Radiation Safety
• Cases

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CT Basics

• No disclosures

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Neuroradiologist

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

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Neuroradiology

• Plain Film
• CT
• US
• MRI
• Interventional
• Angiography
• Myelography
• Biopsy
• Nuclear Medicine

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Neuroradiology

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

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CT Basics

• Computed tomography (CT)
• Computed axial tomography or computer assisted
  tomography (CAT)

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CT Basics
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CT Basics

• Neuroradiology
• The BASICS of CT
• CT History
• Protocol
• Terminology
• Contrast
• Radiation Safety
• Cases

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CT History

• Electro-Musical Instruments

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CT HistorySIR GODFREY N. HOUNSFIELD

• 1979 Nobel Laureate in Medicine

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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

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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

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CT Basics

• Neuroradiology
• The BASICS of CT
• CT History
• Protocol
• Terminology
• Contrast
• Radiation Safety
• Cases

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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.

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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

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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

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CT Protocolling

• Patient Information
• Is the patient pregnant?
• Radiation safety
• Can the patient cooperate for the exam?

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CT Basics

• Neuroradiology
• The BASICS of CT
• CT History
• Protocol
• Terminology
• Contrast
• Radiation Safety
• Cases (Stroke)

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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

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CT Terminology

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

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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 (gt300)
• Contrast
• Hemorrhage (Acute 70)
• Hypercellular masses
• Metallic foreign bodies

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CT Terminology

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

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CT Terminology
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CT Terminology

• Window Width
• Number of Hounsfield units from black to white
• Level or Center
• Hounsfield unit approximating mid-gray

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CT Terminology
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CT Artifacts
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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

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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.

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CT Basics

• Neuroradiology
• The BASICS of CT
• CT History
• Protocol
• Terminology
• Contrast
• Radiation Safety
• Cases

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Contrast

• Barium
• Iodinated
• vascular
• Biliary, Urinary
• CSF
• Gadolinium

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Contrast
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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.

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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

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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 41-54.
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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

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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

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Contrast

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

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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 20343(3)180-4
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Contrast

• Contrast induced renal failure
• Elevated creatinine 24-48 hours after contrast
  which resolves over 7-21 days.
• Can require dialysis

Mehran, R. et al. Radiocontrast induced renal
failureAllocations and outcomes. Reviews in
Cardiovascular Medicine Vol. 2 Supp. 1 2001
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CT Basics

• Neuroradiology
• The BASICS of CT
• CT History
• Protocol
• Terminology
• Contrast
• Radiation Safety
• Cases

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Radiation Safety

• Diagnostic CT Scans Assessment of Patient,
  Physician, and Radiologist Awareness of Radiation
  Dose and Possible Risks
• Lee, C. et al. Radiology 2004231393

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Radiation Safety

• Deterministic 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.

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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

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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
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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.

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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

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Radiation Safety

• Estimated Risks of Radiation-Induced Fatal Cancer
  from Pediatric CT
• David J. Brenner, et al. AJR 2001 176289-296
• 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

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Radiation Safety

• 3094 men received radiation for hemangioma
• Those receiving gt100 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
studyBMJ, Jan 2004 328 19 - 0.
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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.
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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.
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Radiation Safety

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

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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
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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--http//hps.org
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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 mothers health is the primary concern.

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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

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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

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CT Basics

• Neuroradiology
• The BASICS of CT
• CT History
• Protocol
• Terminology
• Contrast
• Radiation Safety
• Cases

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Normal CT
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1 day 1 year 2 years
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Normal CTOlder person
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Normal Enhanced CT
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Case 1

• 55 yo female with sudden onset of worst headache
  of life

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Case 1
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Case 1
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Case 1

• What do I do now?

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CTA
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Normal Angiography
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Diagnostic Angiography
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Case 1

• Subarachnoid Hemorrhage
• Most common cause is trauma
• Aneurysm
• Vascular malformation
• Tumor
• Meningitis
• Generally a younger age group

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Case 2

• 82 yo male with mental status change after a fall

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Case 2
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Case 2

• Subdural hematoma
• Venous bleeding from bridging veins
• General presentation
• Older age group
• Mental status change after fall
• 50 have no trauma history

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Subdural Hematoma
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Case 3

• 44 yo female with right sided weakness and
  inability to speak

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Case 3
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Case 3

• Acute ischemic left MCA stroke

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MCA StrokeDense MCA
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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.

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Case 4
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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.

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Case 5

• 71 yo male who initially complained of
  incoordination of his left hand and subsequently
  collapsed

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Case 5
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Case 5

• Intraparenchymal hemorrhage
• Hypertensive
• Amyloid angiopathy
• Tumor
• Trauma

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Case 6

• 62 yo female acute onset headache
• Hemiplegic on the right and unable to speak

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Case 6

• Add htn image here

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Case 6

• Hypertensive hemorrhage
• Clinically looks like a large MCA stroke
• Generally younger than amyloid angiopathy patients

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Chronic Ischemic change Encephalomalacia
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Thrombolysis

• Intravenous
• 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

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Case 7

• 53 y.o. male
• Sudden onset of ataxia loss of consciousness
  proceeding rapidly to coma

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(No Transcript)
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Case 7

• Probable basilar occlusion with cerebellar and
  brainstem infarction

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Case 8

• 52 yo male with right sided weakness

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Case 8
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Case 8
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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

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Chronic Small Vessel Disease
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Case 9

• 59 yo female with multiple falls over last weekend

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Case 9
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Case 9

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

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Case 10

• 42 yo male found in coma

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Case 10
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Case 10

• Global ischemia

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Angiographic Brain Death
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Case 11

• 24 yo male with siezures

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Case 11
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Case 11

• Heterotopia

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Case 12

• 34 y.o. female
• Severe H/A,nausea
• Taking oral contraceptives

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Case 12
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Case 12
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Case 12

• Transverse sinus thrombosis