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21.05.14 |
StefanDelorme
Division ofRadiology
Slice selection
•
Concept
•
z gradient and HF puls simultaneous
•
Only spins in one slice will be excited
B
(z)
HF
21.05.14 |
StefanDelorme
Division ofRadiology
Fourier
Trans-
formation
k-space
Image
k-space
21.05.14 |
StefanDelorme
Division ofRadiology
T2-weighted images
Bright:
Long T2:
Fat (moderately)
Blood
Fluid
Many pathologies
Dark:
Short T2:
After Gd-DTPA (slightly)
Bone, calcium
Blood (Hämosiderine)
Flow: Signal void
Lack of protons: Air
CSF
Brain
Bone
Vessels
Edema
Tumor
21.05.14 |
StefanDelorme
Division ofRadiology
Contrast medium: Gd-DTPA
•
GD3+ is paramagnetic
•
Reduces relaxation times in tissue
•
Affects mainly T1
•
Toxic if liberated, inert as a DTPA chelate
•
Other chelates: DOTA, DTPA-BMA, etc.
•
Excreted in urine
•
Administration i.v., oral possible
21.05.14 |
StefanDelorme
Division ofRadiology
T1-weighting
Bright
:
Short T1:
Fat
Blood (age !)
After Gd-DTPA:
disturbed BBB
Fluid with high protein
content
Dark
:
Long T1:
Free water
Bone, calcium
Flow: signal void
Lack of protons: air
Fat
Gd-DTPA
Brain
CSF
Bone
Tumor
21.05.14 |
StefanDelorme
Division ofRadiology
Outline
•
Computed tomography
•
How it works
•
Strengths
•
Weaknesses
•
Magnetic resonance imaging
•
How it works
•
Strengths
•
Weaknesses
•
Ultrasound
•
How it works
•
Strengths
•
Weaknesses