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 console Gantry 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 fat---70 Pure water 0 Csf+8 White matter+30 Gray matter+45 blood+70 Bone/cacification+1000

CT /MRI CT PICTURE I. WHITE MATTER IS DARKER THAN GREY MATTER SINCE LIPID CONTAINING MATERIAL IS RADIOLUCENT I. CSF IS BLACK MR PICTURE GREY MATTER T1WI DARK T2WI BRIGHT WHITE MATTR BRIGHTDARK CSF GREY TO DARK WHITE

LOW VENTRICULAR

CT Scan Basics The denser the object, the whiter it is on CT –Bone is most dense = Hounsfield U. –Air is the least dense = H Hounsfield U. 17

CT Scan Basics: Windowing 18 Focuses the spectrum of gray-scale used on a particular image.

CT SINUS CORONAL VIEW MAXILLARY SINUS 19 NASAL SEPTUM

ANATOMY The 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

l Diffusion gradients sensitize MR Image to motion of water molecules l More motion = Darker image Freely Diffusing Water = Dark Restricted Diffusion = Bright Restricted Diffusion = Bright - Diffusion contrast -

27 - 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*

28 Perfusion imaging DefinitionsDefinitions PrinciplesPrinciples Some more definitionsSome more definitions Perfusion techniquePerfusion technique ApplicationsApplications FutureFuture

29 Definitions Perfusion is refer to the delivery of oxygen and nutrients to the cells via capillaries Perfusion is refer to the delivery of oxygen and nutrients to the cells via capillaries Perfusion is identified with blood flow which is measured in milliliters per minute per 100 g of tissue Perfusion is identified with blood flow which is measured in milliliters per minute per 100 g of tissue

Good Luck