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MR Imaging of the Brain. Radiology 401. John R. Hesselink, M.D. MR System Components. Transmitter. Gradient Amplifier. RF Coil. Gradient. Computer. Gradient. RF Coil. Magnet. Receiver. Digitizer. Source of Signal and Contrast. Proton density T1 relaxation time T2 relaxation time - PowerPoint PPT Presentation
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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
236
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