CT History 1972 – First clinical CT scanner Used for head examination Water bath required 4 minutes per revolution 1 image per revolution Overnight image reconstruction

CT History 2004 – 64 slice scanner 0.33s per revolution 64 images per revolution 0.4mm slice thickness 20 images reconstructed/second

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 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 bright on CT Bone or calcification (>300) Contrast Hemorrhage (Acute ~ 70) Hypercellular masses Metallic foreign bodies

CT Artifacts

streak and beam hardening artifact Beam hardening and scatter are different mechanisms that both produce dark streaks between two high attenuation objects, such as metal, bone, iodinated, or contrast. They can also produce dark streaks along the long axis of a single high attenuation object. Bright streaks are seen adjacent to the dark streaks. These artifacts are a particular problem in the posterior cranial fossa, and with metal implants.

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 an enhanced study is needed, patient have no contraindication to contrast, ie allergy or renal insufficiency.

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

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 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 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

Normal CT

Normal CT Older person

Normal Enhanced CT

A. Orbit B. Sphenoid Sinus C. Temporal Lobe D A. Orbit B. Sphenoid Sinus C. Temporal Lobe D. External Auditory Canal E. Mastoid Air Cells F. Cerebellar Hemisphere A. Orbit B. Sphenoid Sinus C. Temporal Lobe D. External Auditory Canal E. Mastoid Air Cells F. Cerebellar Hemisphere

A. Frontal Lobe B. Frontal Bone (Superior Surface of Orbital Part) C A. Frontal Lobe B. Frontal Bone (Superior Surface of Orbital Part) C. Dorsum Sellae D. Basilar Artery E. Temporal Lobe F. Mastoid Air Cells G. Cerebellar Hemisphere A. Frontal Lobe B. Frontal Bone (Superior Surface of Orbital Part) C. Dorsum Sellae D. Basilar Artery E. Temporal Lobe F. Mastoid Air Cells G. Cerebellar Hemisphere

A. Frontal Lobe B. Sylvian Fissure C. Temporal Lobe D A. Frontal Lobe B. Sylvian Fissure C. Temporal Lobe D. Suprasellar Cistern E. Midbrain F. Fourth Ventricle G. Cerebellar Hemisphere A. Frontal Lobe B. Sylvian Fissure C. Temporal Lobe D. Suprasellar Cistern E. Midbrain F. Fourth Ventricle G. Cerebellar Hemisphere

A. Falx Cerebri B. Frontal Lobe C. Anterior Horn of Lateral Ventricle D. Third Ventricle E. Quadrigeminal Plate Cistern F. Cerebellum A. Falx Cerebri B. Frontal Lobe C. Anterior Horn of Lateral Ventricle D. Third Ventricle E. Quadrigeminal Plate Cistern F. Cerebellum

A. Anterior Horn of the Lateral Ventricle B. Caudate Nucleus C A. Anterior Horn of the Lateral Ventricle B. Caudate Nucleus C. Anterior Limb of the Internal Capsule D. Putamen and Globus Pallidus E. Posterior Limb of the Internal Capsule F. Third Ventricle G. Quadrigeminal Plate Cistern H. Cerebellar Vermis I. Occipital Lobe A. Anterior Horn of the Lateral Ventricle B. Caudate Nucleus C. Anterior Limb of the Internal Capsule D. Putamen and Globus Pallidus E. Posterior Limb of the Internal Capsule F. Third Ventricle G. Quadrigeminal Plate Cistern H. Cerebellar Vermis I. Occipital Lobe

A. Genu of the Corpus Callosum B A. Genu of the Corpus Callosum B. Anterior Horn of the Lateral Ventricle C. Internal Capsule D. Thalamus E. Pineal Gland F. Choroid Plexus G. Straight Sinus A. Genu of the Corpus Callosum B. Anterior Horn of the Lateral Ventricle C. Internal Capsule D. Thalamus E. Pineal Gland F. Choroid Plexus G. Straight Sinus

A. Falx Cerebri B. Frontal Lobe C. Body of the Lateral Ventricle D A. Falx Cerebri B. Frontal Lobe C. Body of the Lateral Ventricle D. Splenium of the Corpus Callosum E. Parietal Lobe F. Occipital Lobe G. Superior Sagittal Sinus A. Falx Cerebri B. Frontal Lobe C. Body of the Lateral Ventricle D. Splenium of the Corpus Callosum E. Parietal Lobe F. Occipital Lobe G. Superior Sagittal Sinus

A. Falx Cerebri B. Sulcus C. Gyrus D. Superior Sagittal Sinus

CT Density 68.6 HU (Hounsfield Units) 60 year-old patient with melanoma. Hemorrhage is from metastatic tumor bleed. E Non-contrast CT Brain CT Density 68.6 HU (Hounsfield Units) Acute Intracerebral hematoma: Acute hematoma is seen by non-contrast imaging as an area of high density with density numbers ranging from 50 to 90HU. CT can detect acute intracerebral blood as small as 2mm, due to contrast between high-density of blood and low-density of surrounding brain (arrows).

CT density of blood is 74HU consistent with acute blood. Acute Subdural Hematoma: Acute subdural hematoma is recognized by CT as an area of peripheral zone of crecentic shaped increased density, outside the surface of the brain (arrows). Most subdural hematoma is caused by tear of bridging cortical veins. Acute Subdural Hematoma: Up to 7 day old High CT density (50-90HU) Subacute Subdural Hematoma (7 to 21 days old) The CT density of acute blood gradually decreases and becomes isodense with adjacent brain, thus less readily visible and can be easily overlooked. Acute subdural hematoma covering the right cerebral hemisphere (arrows), more prominent posteriorly. CT density of blood is 74HU consistent with acute blood.

CT Density 25.0 HU 3 weeks later Non-contrast CT Brain 09/21/2003 09/02/2003

Chronic Subdural Hematoma: Over 21 days old: Acute blood as it evolves, it undergoes liquefaction, and also mixes with cerebrospinal fluid from adjacent subarachnoid space, thus converting into a serosanguineous fluid. This fluid has low CT density reaching close or similar to cerebrospinal fluid. Slow movement of subarachnoid fluid into the subdural hematoma can give rise to gradual expansion of subdural hematoma that can exert mass effect upon the adjacent brain with or without brain edema. This can produce herniation of the brain resulting in sudden decompensation of the patient leading to coma. Thus even a chronic subdural hematoma might need an emergent neurosurgical intervention. 09/21/2003

Subarachnoid Hemorrhage: Subarachnoid blood is recognized by visualizing the high-density of acute blood outlining the cerebral sulci and subarachnoid cisterns.

Shunt-induced (arrow), intraventricular blood (v) Shunt-induced (arrow), intraventricular blood (v). Intraventricular blood is recognized by replacement of normal CSF density by high-density of blood. v

Common cause of intracranial hemorrhage in a hospital emergency room. a) Rupture of arterio-venous malformation b) Rupture of cerebral aneurysm c) Trauma d) Hypertension e) Stroke C

a) Rupture of arterio-venous malformation Likely cause of nontraumatic intracranial hemorrhage in an 8 year-old girl. a) Rupture of arterio-venous malformation b) Rupture of cerebral aneurysm c) Hypertension d) Stroke A

a) Rupture of arterio-venous malformation 35 year-old man developed severe headache and drowsiness while having sex. The patient was taken to the emergency room and a CT scan showed subarachnoid hemorrhage. Most likely cause for subarachnoid hemorrhage to be considered is: a) Rupture of arterio-venous malformation b) Rupture of small vessel within the brain from excitement, nothing to worry about. c) Rupture of cerebral aneurysm d) Acute migraine e) Stroke C

Common Etiology for Nontraumatic intracranial Hemorrhage Congenital: Arterio-venous malformations Cerebral berry aneurysms Tumors: Primary: Glioblastoma Metastasis: Melanoma Thyroid Carcinoma Mets Renal Cell Carcinoma Chorio Carcinoma Vascular: Embolic Infarction Venous Sinus Thrombosis Hypertension Coagulopathy

Patient had documented hemoglobin of 16. 9 GM/dl and hematocrit of 49 Patient had documented hemoglobin of 16.9 GM/dl and hematocrit of 49.7%, is awake and moves all limbs

Hemoconcentration and polycythemia Polycythemia and hemoconcentration can produce hyperattenuation of cerebral arteries, veins, and venous sinuses. This can mimic hyperdense artery sign and dural venous sinus thrombosis. Hyperattenuation in multiple vascular distributions suggests hemoconcentration. Care must be taken when evaluating imaging of patients with polycythemia as intravascular hyper density may coexist with dural venous sinus thrombosis. 

C: Prominent subdural/subarachnoid space A 30-year-old man with alcoholic cirrhosis presents with a large chest wall hematoma secondary to trauma. Head CT was obtained to evaluate for traumatic injury. Which one of the following should be included in the differential diagnosis? a A: Anemia B: Subdural empyema C: Prominent subdural/subarachnoid space D: Dural venous sinus thrombosis E: Metastatic carcinoma

B: Evaluate noncontrast CT attenuation of the aorta If global hypoattenuation in the dural venous sinuses is seen and laboratory results are not readily available, determination of whether a patient has profound anemia can be made by which of the following imaging methods?   A: Carotid Doppler B: Evaluate noncontrast CT attenuation of the aorta b C: Cardiac MRI D: Cardiac nuclear thallium perfusion scan

Global hypoattenuation of the dural venous sinuses secondary to systemic anemia Knowledge of the effect of hemoglobin/hematocrit levels on CT attenuation can be useful in evaluating a patient’s underlying blood concentration status. Hypodense venous sinuses are a possible sign of anemia. Hyperdense venous sinuses may be a sign of thrombosis versus hemoconcentration. Superior sagittal sinus attenuation of less than 35 HU can be suggestive of anemia. Hounsfield attenuation values of the aorta on noncontrast CT can be a reliable indicator of anemia. HU values greater than 45 in women and 50 in men, respectively, can reliably exclude the presence of anemia.

Case 1 55 yo female with sudden onset of worst headache of life

Case 1

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

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

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