Download Computed tomography

Mid Term Revision
Imaging Procedure 3
Dr Mohamed El Safwany, MD.
GOALS OF CT
• MINIMAL SUPERIMPOSITION
• IMAGE CONTRAST IMPROVEMENT
• SMALL TISSUE DIFFERENCE
RECORDING
CT MAIN SYSTEMS
• IMAGING SYSTEM
• COMPUTER SYSTEM
• DISPLAY, RECORDING, STORAGE
SYSTEM
• DATA ACQUISITION SYSTEM
COORDINATE SYSTEM IN
CT
X
COORDINATE SYSTEM IN
CT
Y
COORDINATE SYSTEM IN
CT
Z
COORDINATE SYSTEM IN
CT
ISO-CENTER
PATIENT ORIENTATION
• HEAD FIRST
• FEET FIRST
Computed tomography
Softtissue
Computed tomography
Bone
window
Computed tomography
• Unit controls:
–
–
–
–
–
Scanogram AP
Gantry tilt 0º
Slice thickness 7mm
Slice gap 9mm
Soft-tissue (Mediastinal)
window
– Lung window
Computed tomography
Mediastinal
window
Lung
window
Computed tomography
Computed tomography
• Positioning:
– Supine and feet first
– Arms above the head
– The knees flexed 30º
• Parameters:
– Starting at xiphoid
process
– Ending at the level of hip
joint
– Respiration suspended
in expiration
Computed tomography
Unit controls
•
•
•
•
Gantry tilt: 0º.
Lateral scout view.
Gantry tilt:
parallel to the disc
space
• Slice thickness:
– 3mm
air
--- 1000
fat
Pure water
Csf
White matter
Gray matter
blood
Bone/cacification
---70
0
+8
+30
+45
+70
+1000
MCA INFARCT
ACA INFARCT
Old infarct
H’gic infarct
CSF Production
• Produced in choroid plexus in the lateral
ventricles  Foramen of Monroe  IIIrd
Ventricle  Acqueduct of Sylvius  IVth
Ventricle  Lushka/Magendie
• 0.5-1 cc/min
• Adult CSF volume is approx. 150 cc’s.
• Adult CSF production is approx. 500-700 cc’s
per day.
25
B is for Blood
• 1st decision: Is blood present?
• 2nd decision: If so, where is it?
• 3rd decision: If so, what effect is it
having?
26
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.
27
CT Scan
28
Andrew D. Perron, MD, FACEP
Intraventricular/
Intraparenchymal Hemorrhage
29
CT Scan
30
Andrew D. Perron, MD, FACEP
CT SINUS
AXIAL
FRONTAL SINUS
31
CT SINUS
LENS OF EYE
MEDIAL RECTUS
MUSCLE
ETHMOID
SINUS
AXIAL
LATERAL RECTUS
MUSCLE
RETRO ORBITAL
FAT
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CT SINUS
CORONAL VIEW
MAXILLARY SINUS
NASAL
SEPTUM
33
ORBIT
AXIAL CT
RETRORBITAL
FAT
MEDIAL
RECTUS
LENS OF EYE
LATERAL
RECTUS
OPTIC
NERVE
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OR CEREBRAL
ARTERY
MIDDLE CEREBRAL
ARTERY
CAROTID
SYPHON
MAXILLARY
ARTERY
FACIAL
ARTERY
ARTERIOGRAM
OCCIPITAL
ARTERY
INTERNAL CAROTID
ARTERY
EXTERNAL CAROTID
ARTERY
COMMON CAROTID
ARTERY
35
ANATOMY
The pulmonary arteries carry blood from the heart to the lungs.
They are the only arteries that carry deoxygenated blood.
INDICATION
 Pulmonary embolism
 Aortic dissection
 Aortic overloading
 Left ventricular stress
 Teratology of Fallot
CONTRAST DOSAGE
 1.2ml /kg (body weight) of non-ionic iodinated contrast
medium is injected intravenously into the patient using a
pressure injector.
 Rate of injection being 4-5 ml /sec
 Pressure 325 ppm
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
SMART PREP TECHNIQUE
It is a software, that allows real-time monitoring of IV 
Contrast enhancement in the area of interest.
Good Luck