how to read a head ct, ct brain
TRANSCRIPT
Basics and Anatomy of a brain CT
Dr Gauhar Mahmood Azeem
House Officer, New Radiology Dept. SHL
CT scan machine
CT Head: Extremely important investigation
• CT head is an extremely important investigation used routinely in indoor as well as ER patients.
• A quality physician needs to be able to accurately interpret and act upon certain findings without specialist advise, because these disease processes are time dependant and demand immediate action.
History of the CT
• Sir Godfrey Hounsefield- an electrical engineer-1972
• Nobel Prize for Physiology or Medicine 1979
• Hounsfield units named after him
• Through the years CT’s have come from 1 rotation in 6 minutes to one in under 0.33 seconds
Principle
• X rays are passed through the patient in a circular path
• The absorption data is used in a computer to reconstruct high definition images
• The images are seen on a computer output device or films and be interpreted
• 3D reconstruction is also possible
Slice them up! Usually 5 to 10mm
Basics
• Always describe CT findings as densities, isodense/hypodense/hyperdense
• Higher the density the whiter it is (towards bone)
• Lower the density the darker it is (towards air)
• Brain here is the reference density and thus isodense
Indications for Brain CT
• Acute stroke
• Transient Ischemic Attack
• Acute headache with focal neurological signs
• Acute head injury
• Suspected hydrocephalus
• Mental status change
• Secondary indications when MRI not available including diplopia, CN problems, seizures, syncope etc
Indications for CT brain with IV contrast
• To look for
• Tumours
• Infections (meningial enhancement, abscess)
• Inflammation (MS, granulomatous diseases etc)
Hounsfield again
Hounsfield Units
• Related to the composition and nature of tissue
• Represent the density of the tissue
• Also called CT number
An HFU table
Brain Anatomy as seen by House Officer
Brain anatomy as seen by Professors
Axial Sections of CT brain
• Axial sections are most important in a head CT
• We must have for a complete view posterior fossa and supratentorial(above tentoriumcerebelli) cuts
Axial Sections of CT brain
• Posterior Fossa Cuts
• Above Foramen Magnum, Level of 4th
ventricle, Above 4th ventricle, Tentorial
• Supra Tentorial Cuts
• Third Ventricle Level, Lateral Ventricle Level, Above Ventricular level
Normal Anatomy
A. Orbit B. Sphenoid SinusC. Temporal Lobe D. External Auditory CanalE. Mastoid Air Cells F. Cerebellar Hemisphere
Normal Anatomy
A. Frontal Lobe B. Frontal Bone (Superior Surface of Orbital Part)C. Dorsum Sellae D. Basilar ArteryE. Temporal Lobe F. Mastoid Air CellsG. Cerebellar Hemisphere
Of Cisterns, Sulci and Fissures
• A cistern is any opening in the subarachnoid space of the brain created by a separation of the arachnoid and pia matter. These spaces are filled with cerebrospinal fluid.
• A sulcus is a depression in the cerebral cortex
• A fissure is a large furrow that divides the brain into lobes, and also into the two hemispheres
Normal Anatomy
A. Frontal Lobe B. Sylvian Fissure (divides frontal, parietal from temporal)
C. Temporal Lobe D. Suprasellar CisternE. Midbrain F. Fourth VentricleG. Cerebellar Hemisphere
Normal Anatomy
A. Falx Cerebri B. Frontal LobeC. Anterior Horn of Lateral Ventricle D. Third VentricleE. Quadrigeminal Plate Cistern F. Cerebellum
Normal Anatomy
A. Anterior Horn of the Lateral Ventricle B. Caudate Nucleus (BG)C. Anterior Limb of the Internal Capsule D. Putamen and Globus Pallidus (BG)E. Posterior Limb of the Internal Capsule F. Third VentricleG. Quadrigeminal Plate Cistern H. Cerebellar Vermis
Admit it you’ve percussed your relatives too!
Normal Anatomy
A. Genu of the Corpus Callosum B. Anterior Horn of the Lateral VentricleC. Internal Capsule D. ThalamusE. Pineal Gland F. Choroid PlexusG. Straight Sinus
Normal Calcifications in the brain
• Pineal Gland
– seen in 2/3 of the adult population and increases with age
– calcification over 1cm in diameter or under 9 years of age may be suggestive of a neoplasm
• Hebenula
– it has a central role in the regulation of the limbic system and is often calcified with a curvilinear pattern a few millimeters anterior to the pineal body in 15% of the adult population
• Choroid Plexus
– a very common finding, usually in the atrial portions of the lateral ventricles
– calcification in the third or fourth ventricle or in patients less than 9 years of age is uncommon
Normal Calcifications in the brain
• Basal Ganglia Calcification
– are usually idiopathic incidental findings that have an incidence of ~1% (range 0.3-1.5%) and increases with age
– usually demonstrate a faint punctuate or a coarse conglomerated symmetrical calcification pattern
• Falx, Dura Matter, Tentorium Cerebelli
– occur in ~10% of the elderly population
– dural and tentorial calcifications are usually seen in a laminar pattern and can occur anywhere within the cranium
• Superior Saggital Sinus
– common age-related degeneration sites and usually have laminar or mildly nodular patterns
Choroid Plexus and Pineal Gland Calcifications
Calcification of Falx Cerebri
Normal Anatomy
A. Falx Cerebri B. Frontal LobeC. Body of the Lateral Ventricle D. Splenium of the Corpus CallosumE. Parietal Lobe F. Occipital LobeG. Superior Sagittal Sinus
Ventricular system
Normal Anatomy
A. Falx Cerebri B. SulcusC. Gyrus D. Superior Sagittal Sinus
Thank You!