Radiology Department, Faculty of Medicine

  CT Basic & Neuroradiology

Sianny Suryawati

  Radiology Department, Faculty of Medicine Wijaya Kusuma University Surabaya 2014

  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

• – Terminology –

  Contrast

• – Radiation Safety –

  Cases

Neuroradiology

• Plain Film •

  CT

• US
• MRI
• Interventional
• – Angiography – Myelography – Biopsy
• Nuclear Medicine

  CT Basics

  CT Basics

• Neuroradiology • The BASICS of CT
• – CT History
• – Protocol –

  Terminology

• – Contrast –

  Radiation Safety

• – Cases

  CT History SIR GODFREY N. HOUNSFIELD 1979 Nobel Laureate

• in Medicine

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 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 Basics

• Neuroradiology • The BASICS of CT
• – CT History
• – Protocol
• – Terminology –

  Contrast

• – Radiation Safety –

  Cases

  Uncomplicated exam – 5-10 minutes after completion _• Complicated exams with reconstructions take at least 1 hour but usually 1-2 hours.

  

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 … _•

  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 Protocolling

• Variables
• – Plain or contrast enhanced
• – Slice positioning
• – Slice thickness
• – Slice orientation
• – Slice spacing and overlap
• – Timing of imaging and contrast administration
• – Reconstruction algorhithm

  CT Protocolling

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

  CT Basics

• Neuroradiology • The BASICS of CT
• – CT History –

  Protocol

• – Terminology
• – Contrast –

  Radiation Safety

• – Cases (Stroke)

  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 Terminology

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

  White matter is usually dark grey (40) _• Grey matter is usually light grey (45)

• _• CSF is black (0) _• Things that are brite on CT _–

  CT Terminology

• What we can see
• – The brain is grey _•

  Bone or calcification (>300) _– Contrast

• _–

  Hemorrhage (Acute ~ 70)

  _– Hypercellular masses _– Metallic foreign bodies

  CT Terminology

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

  CT Terminology

  CT Terminology Window Width

• Number of Hounsfield units from black to
• – white
• Hounsfield unit approximating mid-gray

  Level or Center

• –

  CT Terminology

  CT Artifacts 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 Terminology

• Digital Imaging and Communications in

DICOM

• – Medicine DICOM provides standardized formats for
• – images, a common information model, application service definitions, and protocols for communication.

  CT Basics

• Neuroradiology • The BASICS of CT
• – CT History –

  Protocol

• – Terminology
• – Contrast
• – Radiation Safety –

  Cases

  Contrast

• Barium • Iodinated
• – vascular
• – Biliary, Urinary –

  CSF

• Gadolinium

  

Contrast

Types of iodinated contrast
• Ionic –
• – No change in death rate from reaction but number of

  Nonionic - standard of care

• 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.

  

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
• –

  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.

  Contrast

• 50 mg Oral Prednisone 13, 7 and 1 hour prior

Pretreatment for anaphylaxis

• – to exam 50 mg oral Benedryl 1 hour prior to exam
• – In emergency, 200 mg iv hydrocortisone 2-4
• – hours prior to exam

  Contrast

• What are the risk factors for contrast induced acute renal failure?
• – Pre-existing renal insufficiency
• – Contrast volume
• – Dehydration –

  Advanced age

• – Drugs –

  Multiple myeloma

  

Contrast

Considerations in patients with renal
• insufficiency

  Is the exam necessary?

• – Is there an alternative exam that can answer the
>– question? Decrease contrast dose
• –

  Contrast Pretreatment for renal insufficiency

• Hydration –
• – 600 mg po BID the day before and day of study

  Mucomyst

• Prevention of radiographic-contrast-agent-induced reductions in renal function by

  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.

  CT Basics

• Neuroradiology • The BASICS of CT
• – CT History –

  Protocol

• – Terminology –

  Contrast

• – Radiation Safety
• – Cases

  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 Safety

Deterministic Effects
• Have a threshold below which no effect will be
• – seen.
• Have no threshold and the effects are based on

Stochastic Effects

• – the dose x quality factor.

  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 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

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 Safety

• Fetal cells

Tissue/Organ radiosensitivity

• – Lymphoid and hematopoietic tissues;
• – intestinal epithelium Epidermal, esophageal, oropharyngeal
• – epithelia Interstitial connective tissue, fine vasculature
• – Renal, hepatic, and pancreatic tissue
>– Muscle and neuronal tissue
• –

  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 Safety

• Estimated Risks of Radiation-Induced Fatal

  Cancer from Pediatric CT
• – David J. Brenner, et al. AJR 2001; 176:289-296 _•

  Radiation Safety 3094 men received radiation for

• hemangioma

  Those receiving >100 mGy

• – Decreased high school attendance
>– Lower cognitive test scores
• –

  Radiation Safety

• There has been no detectable increase in

Hiroshima and Nagasaki

• – 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.

  

Radiation Safety

• However, exposed individuals who survived the

Hiroshima and Nagasaki

• – acute effects were later found to suffer increased incidence of cancer of essentially all organs.

  Radiation Safety

• Most victims with high doses died

Hiroshima and Nagasaki

• – Victims with low doses despite their large
• – numbers are still statistically insignificant.

Radiation Safety

  Comparison of Image Quality

Between Conventional and Low-

Dose Nonenhanced Head CT _a Mark E. Mullins , et al.

  AJNR April 2004.

  

Reduction of mAs from 170 to 90 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

  

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 Safety

"No single diagnostic procedure results in a radiation dose
• that threatens the well-being of the developing embryo and
• American College of Radiology

  fetus."

"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
• American College of Obstetricians and Gynecologists

  pregnancy loss."

  Radiation exposure

  Conclusion

• CT Terminology
• – Attenuation (density) in Hounsfield units
• – Digital interpretation is standard of care
• CT has risks
• – Contrast –

  CT Basics

• Neuroradiology • The BASICS of CT
• – CT History –

  Protocol

• – Terminology –

  Contrast

• – Radiation Safety
• – Cases

  Normal CT

  1 day 1 year 2 years

  

Normal CT

Older person Normal Enhanced CT

Case 1

  55 yo female with sudden onset of worst

• headache of life

  Case 1

  Case 1

  Case 1

• What do I do now?

  CTA Normal Angiography

Diagnostic Angiography

  Case 1

• Subarachnoid Hemorrhage

• – Most common cause is trauma
• – Aneurysm –

  Vascular malformation

• – Tumor –

  Meningitis

• – Generally a younger age group

Case 2

  82 yo male with mental status change after

• a fall

  Case 2

  Case 2

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

  Subdural Hematoma

Case 3

  44 yo female with right sided weakness and

• inability to speak

  Case 3

  Case 3

• Acute ischemic left MCA stroke

  

MCA Stroke

“Dense MCA”

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 4

  Case 4

• Typical history is a patient with head trauma

Epidural hematoma

• – 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

  71 yo male who initially complained of

• incoordination of his left hand and subsequently collapsed

  Case 5

  Case 5

• Intraparenchymal hemorrhage
• – Hypertensive –

  Amyloid angiopathy

• – Tumor –

  Trauma

  Case 6

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

  Case 6

• Add htn image here

  Case 6

• Clinically looks like a large MCA stroke

Hypertensive hemorrhage

• – Generally younger than amyloid angiopathy
• – patients

  Chronic Ischemic change = Encephalomalacia

  

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

  53 y.o. male

• Sudden onset of ataxia loss of
• consciousness proceeding rapidly to coma

Case 7

  Probable basilar occlusion with cerebellar

• and brainstem infarction

  Case 8

• 52 yo male with right sided weakness

  Case 8

  Case 8

  

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
• –

  Chronic Small Vessel Disease

Case 9

  59 yo female with multiple falls over last

• weekend

  Case 9

Case 9

  Stroke involving caudate head, anterior

• limb internal capsule and anterior putamen. What is the artery?
• Recurrent artery of Heubner •

  Case 10

• 42 yo male found in coma

  Case 10

  Case 10

• Global ischemia

  Angiographic Brain Death