Download basic neuroradiology

Sianny Suryawati
Radiology Department, Faculty of Medicine
Wijaya Kusuma University, Surabaya
2015
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Normal Imaging Anatomy of Brain
Basic Features of Brain Lesions
Brain Tumor
Cerebrovascular Disease
Traumatic Brain Injury
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Skull and Meninges (Dura, Pia)
Vasculature: Veins and Arteries
Surface Anatomy-Lobes, gyri, Sulci
Histologic-Broadman’s
Functional-motor, sensory, speech
White Matter
Cross sectional imaging
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Plain Film
CT
US
MRI
Interventional
Angiography
Myelography
Biopsy
Nuclear Medicine
• Neuroradiology
• The BASICS of CT
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CT History
Protocol
Terminology
Contrast
Radiation Safety
Cases
• 1979 Nobel Laureate in
Medicine
• 1972 – First clinical CT scanner
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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
• 2004 – 64 slice scanner
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1024 x 1024 matrix
0.33s per revolution
64 images per revolution
0.4mm slice thickness
20 images reconstructed/second
• Neuroradiology
• The BASICS of CT
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CT History
Protocol
Terminology
Contrast
Radiation Safety
Cases
• 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 head protocols
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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
• Variables
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Plain or contrast enhanced
Slice positioning
Slice thickness
Slice orientation
Slice spacing and overlap
Timing of imaging and contrast administration
Reconstruction algorhithm
Radiation dosimetry
• Patient Information
• Is the patient pregnant?
• Radiation safety
• Can the patient cooperate for the exam?
• Neuroradiology
• The BASICS of CT
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CT History
Protocol
Terminology
Contrast
Radiation Safety
Cases (Stroke)
• 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
• 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
• What we can see
• The brain is grey
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White matter is usually dark grey (40)
Grey matter is usually light grey (45)
CSF is black (0)
Things that are brite on CT
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Bone or calcification (>300)
Contrast
Hemorrhage (Acute ~ 70)
Hypercellular masses
Metallic foreign bodies
• Voxel
• Volume element
• A voxel is the 2 dimensional representation of a 3 dimensional pixel
(picture element).
• Partial volume averaging
• Window Width
• Number of Hounsfield units from black to white
• Level or Center
• Hounsfield unit approximating mid-gray
• 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
• DICOM
• Digital Imaging and Communications in Medicine
• DICOM provides standardized formats for images, a common information
model, application service definitions, and protocols for communication.
• Neuroradiology
• The BASICS of CT
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CT History
Protocol
Terminology
Contrast
Radiation Safety
Cases
• Barium
• Iodinated
• vascular
• Biliary, Urinary
• CSF
• Gadolinium
• 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.
• 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
• 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.
• 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
• What are the risk factors for contrast induced acute renal
failure?
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Pre-existing renal insufficiency
Contrast volume
Dehydration
Advanced age
Drugs
Multiple myeloma
Cardiac failure
• Considerations in patients with renal insufficiency
• Is the exam necessary?
• Is there an alternative exam that can answer the question?
• Decrease contrast dose
• 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
• 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
• Neuroradiology
• The BASICS of CT
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CT History
Protocol
Terminology
Contrast
Radiation Safety
Cases
• Diagnostic CT Scans: Assessment of Patient, Physician, and
Radiologist Awareness of Radiation Dose and Possible Risks
• Lee, C. et al. Radiology 2004;231:393
• 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.
• 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
• 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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Effects of X rays.
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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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Tissue/Organ radiosensitivity
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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
• 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
• 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: 19 - 0.
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Hiroshima and Nagasaki
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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.
• 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.
• Hiroshima and Nagasaki
• Most victims with high doses died
• Victims with low doses despite their large numbers are still statistically
insignificant.
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
• 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
• 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.
• "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
• CT Terminology
• Attenuation (density) in Hounsfield units
• Digital interpretation is standard of care
• CT has risks
• Contrast
• Radiation exposure
• Neuroradiology
• The BASICS of CT
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CT History
Protocol
Terminology
Contrast
Radiation Safety
Cases
Normal CT
Older Person