Montreal Neurological Hospital 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 Terminology Contrast Radiation Safety Cases

CT Basics No disclosures

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

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

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

CT Basics Computed tomography (CT) Computed axial tomography or computer –assisted tomography (CAT)

CT Basics

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

CT History Electro-Musical Instruments

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

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 Attenuation is measured in Hounsfield units 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 Partial volume averaging A voxel is the 2 dimensional representation of a 3 dimensional pixel (picture element). Partial volume averaging

CT Terminology

CT Terminology Window Width Level or Center 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

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 Stochastic 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 study BMJ, 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 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 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 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 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 Hypertensive hemorrhage Clinically looks like a large MCA stroke Generally younger than amyloid angiopathy patients

Chronic Ischemic change = Encephalomalacia

Thrombolysis: Intravenous Intra-arterial 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

Case 11 24 yo male with siezures

Case 11

Case 11 Heterotopia

Case 12 34 y.o. female Severe H/A,nausea Taking oral contraceptives

Case 12

Case 12

Case 12 Transverse sinus thrombosis