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Neuroradiology. Dr. Grant J. Linnell Fellow Montreal Neurological Hospital McGill University. CT Basics. Neuroradiology The BASICS of CT CT History Protocol Terminology Contrast Radiation Safety Cases . CT Basics. Neuroradiology The BASICS of CT CT History Protocol

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neuroradiology

Neuroradiology

Dr. Grant J. Linnell

Fellow

Montreal Neurological Hospital

McGill University

ct basics
CT Basics
  • Neuroradiology
  • The BASICS of CT
    • CT History
    • Protocol
    • Terminology
    • Contrast
    • Radiation Safety
    • Cases
ct basics3
CT Basics
  • Neuroradiology
  • The BASICS of CT
    • CT History
    • Protocol
    • Terminology
    • Contrast
    • Radiation Safety
    • Cases
ct basics4
CT Basics
  • No disclosures
neuroradiologist
Neuroradiologist
  • A consultant in imaging and disease of the brain, spinal cord, head, neck, face and peripheral nerves
neuroradiology6
Neuroradiology
  • Plain Film
  • CT
  • US
  • MRI
  • Interventional
    • Angiography
    • Myelography
    • Biopsy
  • Nuclear Medicine
neuroradiology7
Neuroradiology
  • A request for an exam is a consultation
    • History
    • Pertinent physical exam findings
      • Lab results
        • Creatinine
        • PT/INR
    • What is the question?
ct basics8
CT Basics
  • Computed tomography (CT)
  • Computed axial tomography or computer –assisted tomography (CAT)
ct basics10
CT Basics
  • Neuroradiology
  • The BASICS of CT
    • CT History
    • Protocol
    • Terminology
    • Contrast
    • Radiation Safety
    • Cases
ct history
CT History
  • Electro-Musical Instruments
ct history sir godfrey n hounsfield
CT HistorySIR GODFREY N. HOUNSFIELD
  • 1979 Nobel Laureate in Medicine
ct history13
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
ct history14
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
ct basics15
CT Basics
  • Neuroradiology
  • The BASICS of CT
    • CT History
    • Protocol
    • Terminology
    • Contrast
    • Radiation Safety
    • Cases
ct protocolling
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.
ct protocolling17
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
ct protocolling18
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
ct protocolling19
CT Protocolling
  • Patient Information
    • Is the patient pregnant?
      • Radiation safety
    • Can the patient cooperate for the exam?
ct basics20
CT Basics
  • Neuroradiology
  • The BASICS of CT
    • CT History
    • Protocol
    • Terminology
    • Contrast
    • Radiation Safety
    • Cases (Stroke)
ct terminology
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
ct terminology22
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
ct terminology23
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
ct terminology24
CT Terminology
  • Voxel
    • Volume element
      • A voxel is the 2 dimensional representation of a 3 dimensional pixel (picture element).
    • Partial volume averaging
ct terminology26
CT Terminology
  • Window Width
    • Number of Hounsfield units from black to white
  • Level or Center
    • Hounsfield unit approximating mid-gray
ct terminology29
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
ct terminology30
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.
ct basics31
CT Basics
  • Neuroradiology
  • The BASICS of CT
    • CT History
    • Protocol
    • Terminology
    • Contrast
    • Radiation Safety
    • Cases
contrast
Contrast
  • Barium
  • Iodinated
    • vascular
    • Biliary, Urinary
    • CSF
  • Gadolinium
contrast34
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.
contrast35
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
contrast36
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.

contrast37
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
contrast38
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
contrast39
Contrast
  • Considerations in patients with renal insufficiency
    • Is the exam necessary?
    • Is there an alternative exam that can answer the question?
    • Decrease contrast dose
contrast40
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

contrast41
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 failure:Allocations and outcomes.

Reviews in Cardiovascular Medicine Vol. 2 Supp. 1 2001

ct basics42
CT Basics
  • Neuroradiology
  • The BASICS of CT
    • CT History
    • Protocol
    • Terminology
    • Contrast
    • Radiation Safety
    • Cases
radiation safety
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
radiation safety44
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.
radiation safety45
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
radiation safety46
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

radiation safety47
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.
radiation safety48
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
radiation safety49
Radiation Safety
  • Estimated Risks of Radiation-Induced Fatal Cancer from Pediatric CT
    • David J. Brenner, et al. AJR 2001; 176:289-296
      • 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
radiation safety50
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 studyBMJ, Jan 2004; 328: 19 - 0.

radiation safety51
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.

radiation safety52
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.

radiation safety53
Radiation Safety
  • Hiroshima and Nagasaki
    • Most victims with high doses died
    • Victims with low doses despite their large numbers are still statistically insignificant.
radiation safety54
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

radiation safety55
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

radiation safety56
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.
radiation safety57
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
conclusion
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
ct basics59
CT Basics
  • Neuroradiology
  • The BASICS of CT
    • CT History
    • Protocol
    • Terminology
    • Contrast
    • Radiation Safety
    • Cases
case 1
Case 1
  • 55 yo female with sudden onset of worst headache of life
case 167
Case 1
  • What do I do now?
case 171
Case 1
  • Subarachnoid Hemorrhage
    • Most common cause is trauma
    • Aneurysm
    • Vascular malformation
    • Tumor
    • Meningitis
    • Generally a younger age group
case 2
Case 2
  • 82 yo male with mental status change after a fall
case 274
Case 2
  • Subdural hematoma
  • Venous bleeding from bridging veins
  • General presentation
    • Older age group
    • Mental status change after fall
    • 50% have no trauma history
case 3
Case 3
  • 44 yo female with right sided weakness and inability to speak
case 378
Case 3
  • Acute ischemic left MCA stroke
case 4
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.
case 482
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.
case 5
Case 5
  • 71 yo male who initially complained of incoordination of his left hand and subsequently collapsed
case 585
Case 5
  • Intraparenchymal hemorrhage
    • Hypertensive
    • Amyloid angiopathy
    • Tumor
    • Trauma
case 6
Case 6
  • 62 yo female acute onset headache
    • Hemiplegic on the right and unable to speak
case 687
Case 6
  • Add htn image here
case 688
Case 6
  • Hypertensive hemorrhage
    • Clinically looks like a large MCA stroke
    • Generally younger than amyloid angiopathy patients
thrombolysis
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
case 7
Case 7
  • 53 y.o. male
  • Sudden onset of ataxia loss of consciousness proceeding rapidly to coma
case 793
Case 7
  • Probable basilar occlusion with cerebellar and brainstem infarction
case 8
Case 8
  • 52 yo male with right sided weakness
case 897
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
case 9
Case 9
  • 59 yo female with multiple falls over last weekend
case 9101
Case 9
  • Stroke involving caudate head, anterior limb internal capsule and anterior putamen.
  • What is the artery?
  • Recurrent artery of Heubner
case 10
Case 10
  • 42 yo male found in coma
case 10104
Case 10
  • Global ischemia
case 11
Case 11
  • 24 yo male with siezures
case 11108
Case 11
  • Heterotopia
case 12
Case 12
  • 34 y.o. female
  • Severe H/A,nausea
  • Taking oral contraceptives
case 12112
Case 12
  • Transverse sinus thrombosis