BASIC NEURORADIOLOGYSianny SuryawatiRadiology Department, Faculty of MedicineWijaya Kusuma University, Surabaya2015

Outline• Normal Imaging Anatomy of Brain • Basic Features of Brain Lesions• Brain Tumor• Cerebrovascular Disease• Traumatic Brain Injury

Normal Imaging Anatomy of Brain • 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

Anterior circulation Internal Carotid ArteriesPosterior Circulation Vertebral arteries

Superficial and Deep Arterial Supply to the Cerebral Hemispheres

Neuroradiology Modalities : • 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

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

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 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 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 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• 1000 is cortical bone

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 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

• Level or Center• Hounsfield unit approximating mid-gray

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• 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 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 • 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.

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

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.

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

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

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• 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• 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 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.

• Stochastic Effects• Have no threshold and the effects are based on 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

-The equivalent of 200 CXR

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

• 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 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 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 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 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 Safety• Hiroshima and Nagasaki• Most victims with high doses died• 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

Mark E. Mullinsa, 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

Health Physics Society on the web--http://hps.org

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

• CT has risks• Contrast• Radiation exposure

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

Normal CT

1 day 1 year 2 years

Normal CTOlder personNormal CT

Older Person

Normal Enhanced CT