Revision Imaging Procedure 3

Dr Mohamed El Safwany, MD

SCANNER

GANTRY

TABLE/COUCH

DFOV – DISPLAYED FIELD OF VIEW

• SIZE DISPLAYED ON THE MONITOR

PIXEL SIZE

PIXEL SIZE= DFOV (mm)/ MATRIX SIZE

PIXEL vs VOXEL

PIXEL VOXEL

VOXEL SIZE DEPENDS

• FOV• MATRIX SIZE• SLICE THICKNESS

SCANNING

TECHNIQUE

• kVp

• mA

• TIME

• SLICE THICKNESS

• SLICE INCREMENTATION

Operation consoleGantry and Table

Computed tomography

Before the Procedure

• explain the procedure to the patient.

• If the procedure involves the use of contrast dye, consent should be signed form the patient.

• Ask the patient if he has ever had a reaction to any contrast media.

• Generally, there is no fasting requirement prior to a CT scan, unless a contrast media is to be used. (abdomen and pelvis need fasting and cleaning the colon – iv contrast need fasting 4 hours before the examination).

CT Scan of the Brain

• An imaging technique of the brain that reveal tumors, blood clots, hemorrhages, or other abnormal anatomy. A series of computerized images of the brain at various levels are taken to reveal normal anatomy or any abnormality.

Computed tomography

HOUNSFIELD UNITS

• Numeric information in each pixel of ct image

• Related to composition & nature of tissue

• Represent the density of tissue

• Also called as CT NUMBER

air --- 1000

fat ---70

Pure water 0

Csf +8

White matter +30

Gray matter +45

blood +70

Bone/cacification +1000

CT /MRI

• CT PICTUREI. WHITE MATTER IS

DARKER THAN GREY MATTER SINCE LIPID CONTAINING MATERIAL IS RADIOLUCENT

I. CSF IS BLACK

• MR PICTURE GREY GREY

MATTERMATTERT1WIDARK

T2WI

BRIGHT

WHITE WHITE MATTRMATTR

BRIGHT DARK

CSFCSF GREY TO DARK

WHITE

LOW VENTRICULAR

CT Scan Basics• The denser the object, the whiter it is on CT

– Bone is most dense = + 1000 Hounsfield U.

– Air is the least dense = - 1000H Hounsfield U.

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CT Scan Basics: Windowing

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Focuses the spectrum of gray-scale used on a particular image.

CT SINUS CORONAL VIEW

MAXILLARY SINUS

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NASAL SEPTUM

ANATOMYThe pulmonary arteries carry blood from the heart to the lungs.

They are the only arteries that carry deoxygenated blood.

PATIENT POSITIONING

Proper breath hold instructions should be given

Ensure the patient connected IV lines, are long enough to

allow full travel of the couch without being pulled or entangled

while undergoing a CT

Cervical Spine 3 – Trauma

• • Indications– Trauma

• • Sequences– Sag T1 FSE/TSE– Sag T2 FSE/TSE– Sag IR T2 FSE/TSE– Ax IR T2 FSE/TSE– Ax T2 FSE/TSE

• Can add sag T2 GRE to r/o hemorrhage

Diffusion gradients sensitize MR Image to Diffusion gradients sensitize MR Image to motion of water moleculesmotion of water molecules

More motion = Darker image More motion = Darker image

Freely Diffusing Water = DarkFreely Diffusing Water = Dark Restricted Diffusion = BrightRestricted Diffusion = Bright

- Diffusion contrast -

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- Principles -Isotropic and Anisotropic diffusion• Diffusion is a three dimensional process, but

molecular mobility may not be the same in all directions

• In brain white matter, diffusion’s value depends on the orientation of the myelin fiber tracts and on the gradient direction*

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Perfusion imagingPerfusion imaging

• DefinitionsDefinitions

• PrinciplesPrinciples

• Some more definitionsSome more definitions

• Perfusion techniquePerfusion technique

• ApplicationsApplications

• FutureFuture

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DefinitionsDefinitions

• Perfusion is refer to the delivery of oxygen Perfusion is refer to the delivery of oxygen and nutrients to the cells via capillaries and nutrients to the cells via capillaries

• Perfusion is identified with blood flowPerfusion is identified with blood flow which is measured in milliliters per minute which is measured in milliliters per minute per 100 g of tissue per 100 g of tissue

• Good Luck