بسم هللا الرحمن الرحيم

وأفوض أمري الى هللا و هللا لطيف بالعباد

صدق هللا العظيم

Zagazig UniversityFaculty of Medicine

Radiology Department

imaging for medical students

ByDr. Samar Shehata

lecturer of Diagnostic Radiology

•CNS imaging

(CT scanner)

Principle of CT

• Computed tomography scanning anx-ray source and detector, situated180o across from each other, move360o around the patient,continuously sending and detectinginformation on the attenuation of x-rays as they pass through the body.Finally, a computer manipulates andintegrates the acquired data andassigns numerical values based onthe subtle differences in x-rayattenuation

A CT scan is essentially a computerized assembly of several x-ray images taken from a series of different angles

Technique of CT

- Head CTs are performed at an angle parallel to the base of the skull,Orbito-meatal line (Reid’s line).

- Slice thickness is generally between 5 and 10 mm.- The patient is placed in a supine position on the table.- Evaluation of tumors, infections and some stroke cases may benefit

from the use of contrast, but contrast is not used in the routine head CT.

CT Terminology

AttenuationHyperattenuating (hyperdense)Hypoattenuating (hypodense)Isoattenuating (isodense)

Attenuation is measured in Hounsfield unitsScale -1000 to +1000 H.U

-1000 is air, Fat is -100 HU.0 is water , Fluids is 20:40 H.U+1000 is cortical bone & calcificationHg. 60:70 HU.

Cerebral lobes

Sulci and Gyri

• Sulcus– Fissure in the brain tissue.

– Interhemispheric fissure –divides the brain into left and right hemispheres.

• Gyrus– Elevated “hill” areas

between sulci.

Gyrus

Sulcus

Atamai

Meninges Outer dura mater (Latin for “tough

mother”), beneath which is the subdural space;

Arachnoid (Latin for “spider,” because it resembles a cobweb), beneath which is the subarachnoid space, which is accessed during a spinal tap

Pia mater (“soft mother”), which is attached to the brain and dips down into sulci

A subarachnoid hemorrhage will extend down into cerebral sulci, while a subdural hematoma will not.

Pia and dura are vascular while arachnoid is avascular

Ventricular system & CSF

Lateral ventricles – cerebral hemispheres

Third ventricle, aqueduct and 4th

ventricle are in midline and in continuity with the central canal

All are symmetrical and are lined by ependyma

150 ml produced daily by choroid plexus( mostly in lateral ventricles)

Flows cephalad from basal cisterns

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Cerebral Arterial Territory

MCA

ACA

PCA

Normal Enhanced CT

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Here’’’ Just Remember

Imaging of

INTRACRANIAL HEMORRHAGE

What items should be included?

• Site(intracerebral-subarachnoid-dubdural-extradural)

• Distribution

• Stage

• Association (Mass effect)

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B is for Blood

• Blood becomes hypodense at approximately 2 weeks.

• Blood becomes isodense at approximately 1 week.

• Acute blood is bright white on CT (once it clots).

Well defined hyperdense intracerebral hematoma seenin the Rt basal ganglia>>>> Acute Rt basal gangliaintracerebral hematomabasal

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Subdural Hematoma

• Typically falx or sickle-shaped.

• Crosses sutures, but does not cross midline.

• Acute subdural is a marker for severe head injury. (Mortality approaches 80%)

• Chronic subdural usually slow venous bleed and well tolerated.

Axial CT scan of the brain,, demonstrates hyperdense subdural hematomawith concave inner margin and mass effect >>>acute sub dural Lt. parietalhematoma

Axial CT scan of the brain,,demonstrates isodensesubdural hematoma in the LTfrontal region with midline shift>>>Subacute subdural LT frontalhematoma

Axial CT scan of the brain,,demonstrates right fronto-parieto-occipital subdural with layering>>>acute on top of chronichematoma

Axial CT scan of the brain,,demonstrates hyperdense epiduralhematoma with convex inner marginand mass effect in the LT temporo-occipital region >>>acute epidural LTtemporo-occipital hematoma

Extradural hematoma

SDH Vs EDH

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Subarachnoid Hemorrhage• Blood in the

cisterns/cortical gyral surface– Aneurysms

responsible for 75-80% of SAH

– AVM’s responsible for 4-5%

– Vasculitis accounts for small proportion (<1%)

– No cause is found in 10-15%

Axial CT scan of the brain,, demonstrates hyperdensehematoma in the basal cisterns and both Sylvian fissures>>>acute subarachnoid hemorrhage

Axial CT scan of the brain,, demonstrateshyperdense hematoma in the basalcisterns,falx and both Sylvian fissures aswell as intraventricularextension>>>acute subarachnoidhemorrhage

Cerebral contusion

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Here’’’ Just Remember……

Imaging of

BRAIN INFARCTION

What items should be included?

• Site and Distribution ((cortical-subcortical-basal ganglia-lobe-lacunar))

• Stage(Recent –old-hemorrhagic)

• Mass effect or evacudilatation

Infarction• When a scan looks nearly normal , always

consider infarction

Sequential images of infarction

Acute infarction

Axial CT of the brainshows hypoattenuatedarea in the cortical andsubcortical Rt temporalregion …..Rt temporalrecent infarction

MCA Infarction

MCA (inferior devision) Infarction

MCA (main stem) Infarction

Bilateral MCA infarction

PCA INFARCT

Axial CT of the brain shows hypoattenuated area in the cortical andsubcortical Lt occipital region >>> Lt occipital recent infarction

ACA INFARCT

Old infarction

Axial CT of the brain shows hypodense(CSF like) area in the cortical and subcorticalRt Fronto-temporal region with evacudilatation>>>Cortical and subcortical Rtfronto-temporal old infarction

BRAIN SOL

Pre-contrast Post-contrast

Convexicty or bifalcine meningioma

medulloblastoma

Metastatic

Abscess

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What is this

animal ?

Case 1 :32 y F presented to the EDwith a sudden acute onset headachethat radiated down her neck.

Case 2 :54 y F developed right sidedweakness , language deficits with hereyes deviated towards the left.

Case 3 : 82 yo male with mental statuschange after a fall.

Case 4: 62 yo female acute onset headache Hemiplegic on the right and unable to

speak

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