Interpretation of brain CT lecture one

بسم الله الرحمن الرحيم

Interpretation

Interpretation

Something that serves to explain or clarify: Clarification, Explanation, Illumination, Illustration. The act or process of explaining the meaning of something.

Interpretation

Interpretation
1=Normal Radiological Anatomy 2= How to look at the images? (a) Where to look? Systematic approach (b) what look for: (i) abnomal opacty (ii) abnorma radiolucency (iii) distotion or displacement of a normal structure 3= How to interpret the abnormality? (a) Recognizing the abnormality, (b) Describing it in generic terms, (C) Giving a specific diagnosis

Normal radiological image of certain age and sex is a mental image that must be developed

Normal Radiological Anatomy


By developing a systematic approch to examine the radiological image Advantages: Minimizes the chance of missing an abnormality Makes complex images easier to read with practice Builds up a mental databank of what is normal
How to build up a normal mental image

Normal VS, Abnormal

It is not possible to call an image abnormal if the normal appearance is not known!!

Bone is white Calcium is white; Acute hemorrhage is usually white Brain parenchyma is light grey; White matter is darker than grey matter CSF is very dark grey; Sulci, cisterns and ventricles Air is black; Nasal cavity, sinuses, mastoid air cells
White
Light Grey
Charcoal Grey
Black
In order to recognize the abnormal, you first need to know the appearance of the normal. On non-contrast head CT:

T1 Characteristics

DarkCSFIncreased Water – edema, tumor, infarct, inflammation, infection, hemorrhage (hyperacute or chronic)Low proton density, calcificationFlow Void Bright Fat Subacute hemorrhage Melanin Protein-rich Fluid Slowly flowing blood Gadolinium Laminar necrosis of an infarct
White matter brighter than Gray
Johnson,KA and Becker, JA. The Whole Brain Atlas. 1995-1999

T2 Characteristics

Dark Low Proton Density, calcification, fibrous tissue Paramagnetic substances - deoxyhemoglobin, methemoglobin (intracellular), iron, hemosiderin, melanin Protein-rich fluid Flow Void
BrightIncreased Water – edema, tumor, infarct, inflammation, infection, subdural collectionMethemoglobin (extracellular) in subacute hemorrhage Gray matter brighter than white
Johnson,KA and Becker, JA. The Whole Brain Atlas. 1995-1999


Interpretation
Learn Normal Radiological Anatomy How to look at the images? How to interpret the abnormality?

How to look at the images?

Where to look? Systematic approach What to look for? The documentary evidence of name and age Technical factors Areas of interest (Normal anatomical structures)

Patient Name

What to look for? 3.Areas of interest (Normal anatomical structures)

Systematic Approach to reading a Head CT

I. Check Brain ParenchymaCheck grey/white differentiationGyriLook for bloodSurgeons need to know . . . (size of hematoma, extent of midline shift, herniation)II. Check CSF spaces: Ventricles, Cisterns and SulciCSF spaces (ventricles and cisterns)size, symmetry, midline shiftherniation Subfalcine – cingulate gyrus crosses falxTranstentorial – temporal lobe into tentorial notch Cerebellar – cerebellum into foramen magnum

Systematic Approach to reading a Head CT (cont’d 2) III. Check face and skull bones on bone windowsDo not confuse sutures with fracture especially in pediatric patientsIV. Check “air spaces”SinusesNasal airwayEar Canals and Mastoid air cells


What to look for? In CT HeadBrain tissue (windows) Pre contrast Post contrast Bone detail (window)
Frontal lobe
Midbrain
Cerebellum
RIGHT
LEFT
Pre contrast Post contrast
Bone detail
Brain tissue



what look for: (i) abnomal opacty (ii) abnorma radiolucency (iii) distotion or displacement of a normal structure
Frontal lobe
Midbrain
Cerebellum
RIGHT
LEFT
Normal
abnomal opacty
abnorma radiolucency
distotion or displacement of a normal structure


3= How to interpret the abnormality? (a) Recognizing the abnormality, (b) Describing it in generic terms, (C) Giving a specific diagnosis

Patient’s A Head CT R frontoparietal subdural hematoma (6 mm) Midline marker R temperoparietal epidural hematoma (1.8 cm) 6 mm leftward shift of lateral ventricles Right lateral ventricle Left lateral ventricle Effacement of R sulci
BIDMC
Film findings:

Parenchymal Hemorrhage

Subarachnoid Hemorrhage
Subdural Hematoma
Epidural

Patient B

57yr old woman History of migraines Presents with persistent headache several months duration different from her usual headache
Need to rule out intracranial abnormality

BIDMC PACS system

Frontal lobe
Midbrain
Cerebellum
RIGHT
LEFT

Patient’s B Head CT (no contrast) BIDMC PACS system

Frontal lobe
Midbrain
Cerebellum
RIGHT
LEFT
Film Findings: Spherical mass Smooth margined High attenuation Slight mass effect Located just anterior to the Circle of Willis No acute hemorrhage, edema, infarct


Frontal lobe
Midbrain
Cerebellum
RIGHT
LEFT

DDx: Cerebral mass

Tumor Hematoma Abscess Arterio-venous malformation (AVM) Aneurysm

Patient’s B Head CT (with contrast) BIDMC PACS system

RIGHT
LEFT
BIDMC PACS system
Frontal lobe
cerebellum
Frontal lobe
cerebellum
RIGHT
LEFT
2 brightly enhancing round lesions suggestive of cerebral aneurysms

Lets review the anatomy of the Circle of Willis

http://www.strokecenter.org/education/ais_vessels/ais048.html
Communicating system of vessels that supplies blood to the brain Anterior portion fed by the internal carotid arteries Posterior portion fed by the vertebral arteries

Patients B Axial MR (T2 sequence)

BIDMC PACS system
BIDMC PACS system
RIGHT
LEFT
RIGHT
LEFT
T2 sequence: CSF is bright (“high signal”) Round lesions with flow void confirmed

Menu of tests for evaluating suspected: Cerebral aneurysm

Computed tomography (CT) + contrast Magnetic resonance imaging (MRI) Magnetic resonance angiograpy (MRA) Cerebral angiography

MRA - Circle of Willis

BIDMC PACS system
http://www.strokecenter.org/education/ais_vessels/ais048.html
b
Internal carotid artery aneurysms
a
s
i
l
a
r
vertebral arteries
internal carotid
internal carotid
ACA
MCA
PCA
RIGHT
LEFT
Our Patient
Anatomic Diagram

Patient C

Patient’s C Normal

Patient’s C Normal

Patient’s C

Interpretation

Features of several diseases, trauma and non-trauma

CNS Trauma Imaging

SELLA TURCICA
CORONAL SUTURE
GROOVE FOR MCA
EXT.AUD MEATUS
ORBITAL GROOVE
Normal
Linear fracture
Epidural H
Depressed fracture

Orbital Fracturesblow-out

NORMAL WATERS VIEW
Medial/Inferior orbital wall blow-out

Orbital Fracturesblow-out

NORMAL WATERS VIEW
Medial/Inferior orbital wall blow-out
Axial CT
Coronal CT


Medial/Inferior orbital wall blow-outDepressed right orbital floorOpacification of right maxillary sinusOpacification of right ethmoid sinus“Hanging tear drop”: herniation of orbital fat into maxillary sinus (not seen here) Orbital Fracturesblow-out

Interpretation

Non-trauma

Extra-axial vs Intra-axial

Meningioma Glioma
(external to pia)
(beneath pia)

Supra-tentorial vs Infra-tentorial

Glioma Medulloblastoma


Nonenhanced computed tomography scan shows a hyperdense mass resulted in midline shift to the right aspect in the left frontal lobe 
CECT shows a homogeneous enhancing mass located in the left frontal lobe.
DSA, Left external carotid artery injection shows early stain of the mass 
DSA: Left external carotid artery shows delayed stain of the mass

Hydrocephalus versus Cerebral Atrophy

Definition :Hydrocephalus is abnormal accumulation of intracranial fluid resulting from structural or functional block to normal flow of CSF, cerebral atrophy is parenchymal volume loss

Hydrocephalus is abnormal accumulation of intracranial fluid resulting from structural or functional block to normal flow of CSF,

cerebral atrophy is parenchymal volume loss

Agenesis of the corpus callosum

Patterns of edema

Edema: Increase in tissue water CT - decreased density MR - T1W - decreased signal MR - T2W - increased signal

Patterns of edema

Vasogenic (intertitial) white matter only neoplasm abscess
Cytogenic (intracellular) both gray and white matter infarction
Normal
Vaogenic oedema (tumor &inflamation) Cytotoxic oedema ( infarction) White matter
White&gray matter

CONCLUSION

KNOW YOUR Normal Radiological Anatomy look for: (i) abnormal opacity (ii) abnormal radiolucency (iii) distortion or displacement of a normal structure Interpret the abnormality: (a) Recognizing the abnormality, (b) Describing it in generic terms, (C) Giving a differential diagnosis

Give a specific diagnosis KNOW your radiological terminology

BEST LUCK
HOPE THIS WAS HELPFUL