Radiology Department, Faculty of Medicine

CT Basic & Neuroradiology

Sianny Suryawati

Radiology Department, Faculty of Medicine Wijaya Kusuma University Surabaya

CT Basics

•

Neuroradiology

•

The

BASICS

of CT

– _{CT History}

– _Protocol

– Terminology

– _Contrast

– _{Radiation Safety}

CT Basics

•

Neuroradiology

•

The

BASICS

of CT

– _{CT History}

– _Protocol

– Terminology

– _Contrast

– _{Radiation Safety}

Neuroradiology

• Plain Film

• _CT

CT Basics

•

Neuroradiology

•

The

BASICS

of CT

– _{CT History}

– _Protocol

– Terminology

– _Contrast

– _{Radiation Safety}

CT History

SIR GODFREY N. HOUNSFIELD

•

_{1979 Nobel Laureate}

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}

CT History

•

_{2004 – 64 slice scanner}

– _{1024 x 1024 matrix}

– _{0.33s per revolution}

– _{64 images per revolution}

– _{0.4mm slice thickness}

CT Basics

•

Neuroradiology

•

The

BASICS

of CT

– _{CT History}

– _Protocol

– Terminology

– _Contrast

– _{Radiation Safety}

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}

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}

CT Basics

•

_{Neuroradiology}

•

_The

_BASICS

_{of CT}

– _{CT History}

– _Protocol

– _Terminology

– _Contrast

– _{Radiation Safety}

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}

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}

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

CT Terminology

•

_Voxel

– _{Volume element}

• _{A voxel is the 2 dimensional representation of a 3}

dimensional pixel (picture element).

CT Terminology

•

_{Window Width}

– _{Number of Hounsfield units from black to}

white

•

_{Level or Center}

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}

CT Terminology

•

_DICOM

– _{Digital Imaging and Communications in}

Medicine

– _{DICOM provides standardized formats for}

images, a common information model,

CT Basics

•

Neuroradiology

•

The

BASICS

of CT

– _{CT History}

– _Protocol

– Terminology

– _Contrast

– _{Radiation Safety}

Contrast

•

_Barium

•

_Iodinated

– _vascular

– _{Biliary, Urinary}

– _CSF

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}

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

•

_{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}

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?

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.

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}

Radiation Safety

•

_{Diagnostic CT Scans: Assessment of}

Patient, Physician, and Radiologist

Awareness of Radiation Dose and Possible

Risks

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}

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)}

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}

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}

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.

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

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.

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.

Radiation Safety

•

_{Hiroshima and Nagasaki}

– _{Most victims with high doses died}

– _{Victims with low doses despite their large}

Radiation Safety

Comparison of Image Quality Between Conventional and Low-Dose Nonenhanced Head CT Mark E. Mullinsa, et al.

AJNR April 2004.

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

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

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}

Case 1

•

_{55 yo female with sudden onset of worst}

Case 1

Case 1

•

_{Subarachnoid Hemorrhage}

– _{Most common cause is trauma}

– _Aneurysm

– _{Vascular malformation}

– _Tumor

– _Meningitis

Case 2

•

_{82 yo male with mental status change after}

Case 2

•

_{Subdural hematoma}

•

_{Venous bleeding from bridging veins}

•

_{General presentation}

– _{Older age group}

– _{Mental status change after fall}

Case 3

•

_{44 yo female with right sided weakness and}

Case 3

Case 4

•

_{50 yo male post head trauma.}

•

_{Pt was initially conscious but now 3 hours}

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}

Case 5

•

_{71 yo male who initially complained of}

Case 5

•

_{Intraparenchymal hemorrhage}

– _Hypertensive

– _{Amyloid angiopathy}

– _Tumor

Case 6

•

_{62 yo female acute onset headache}

Case 6

Case 6

•

_{Hypertensive hemorrhage}

– _{Clinically looks like a large MCA stroke}

– _{Generally younger than amyloid angiopathy}

Thrombolysis:

•

_Intravenous

– _{3 hours}

•

_{Intra-arterial}

– _{6 hours ICA territory}

– _{24 hours basilar territory}

•

_{CT head plain shows no established stroke}

nor hemorrhage

Case 7

•

_{53 y.o. male}

•

_{Sudden onset of ataxia loss of}

Case 7

•

_{Probable basilar occlusion with cerebellar}

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}

Case 9

•

_{59 yo female with multiple falls over last}

Case 9

•

_{Stroke involving caudate head, anterior}

limb internal capsule and anterior putamen.

•

_{What is the artery?}

Case 10

Case 10