Radiology 401
John R. Hesselink, M.D.
MR Imaging MR Imaging of the Brainof the Brain
MR System Components
Computer
Gradient Amplifier
Receiver
Transmitter
Digitizer
RF Coil
Gra
dien
t
RF CoilG
radient
Magnet
MR Imaging
Proton density
T1 relaxation time
T2 relaxation time
Flow effects
Source of Signal and Contrast
Spin-echo Pulse SequenceSingle Echo T1-weighted
RF
Signal
TR
TE
1st
echo2nd
echo
Spin-echo Pulse SequenceDual Echo T2-weighted
1st
echo2nd
echo
RF
Signal
TR
TETE
T2-Weighted Images
Proton Density Weighted Images
Normal FLAIR ImagesTR = 6000 msec, TI = 2000 msec, TE = 102 msec
T1-Weighted Images
MR Signal ofMR Signal ofBrain LesionsBrain Lesions
SolidBrainLesion PDW
T2W T1W
CysticLesion
T2W
T1W
FLAIR
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SubacuteHemorrhage
PDW
T1W
T2W
AcuteHemorrhage
T2W
FLAIR
T1WGRE
History: 9 y/o boy with prior head trauma
466
Hemorrhage SequenceGradient-echo
PDW
Fator
Lipoma
T2W
T1W
MR Signal Intensities
T2WI PD/FLAIR T1WI
Solid mass Bright Bright Dark
Cyst Bright Dark Dark
Subacute blood Bright Bright Bright
Acute & chronic blood Dark Dark Gray
Fat Dark Bright Bright
Acute Stroke SequenceDiffusion Weighted Imaging
MR Angiography
Dx: Anaplastic astrocytoma > GBM
MR Spectroscopy
Brain Screening Protocol
Axial T2-weighted images Axial FLAIR images If normal:
Stop If abnormal:
T1-weighted images Gd-DTPA enhancement
History: 46 y.o. manwith headaches & increasing confusion
21
T2W PDW
{Page 2}
5
34
T1W
T1W / Gd
T1W
Dx: Meningioma & right MCA infarct
Increasing confusion {Page 3}
76
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