revision imaging procedure 3 dr mohamed el safwany, md
TRANSCRIPT
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