대구가톨릭대학병원 영상의학과 이 영 환 M M R R Basic Physics. MR Signal T1-,...

대구가톨릭대학병원 영상의학과이 영 환이 영 환

MMRRBasic PhysicsBasic Physics

MR SignalMR Signal

T1-, T2-weightedT1-, T2-weighted

TR, TETR, TE

MR SignalMR Signal

T1-, T2-weightedT1-, T2-weighted

TR, TETR, TE

Radiography, CTRadiography, CT

X-ray

Penetration

UltrasonographyUltrasonography

Ultrasound

Reflection

MRIMRI?RF Pulse

H1

1

RF Pulse

Resonance

Surface Coil

N

S

++

H1

1

Magnetic DipoleMagnetic Dipole

N

S

MagnetizationMagnetization

Magnetic Strength

GaussTesla1 Tesla = 10,000 Gauss

N

S

PrecessionPrecession

PrecessionPrecessionN

S

Resonance

Precession frequencyLarmor frequency

BB00 BB00

Frequency(MHz)

10-4

102

108

1014

1020

RadioVisible

light

X-raysGamma rays

Cosmic rays

MRMR

Electromagnetic WaveElectromagnetic Wave

Microwave

Surface Coil

N

S

N

S

Z

Y

X

N

S

N

S

Z

Y

X

N

S

N

S

Z

Y

X

N

S

Y

X

Z

N

S

LongitudinalMagnetization

TransverseMagnetization

Z

Y

X

N

S

Y

X

Z

N

S

LongitudinalMagnetization

TransverseMagnetization

Effect of RF Pulse

Loss of longitudinal M.Creation of transverse M.

– In Phase

Z

Y

X

Y

X

Z

MR SignalMR Signal

MR SignalMR Signal

T1-, T2-weightedT1-, T2-weighted

TR, TETR, TE

MR SignalMR Signal

T1-, T2-weightedT1-, T2-weighted

TR, TETR, TE

Resonance

E2

E1

; Induction of transition between two energy states

N

S

N

S

N

S

N

S

RelaxationRelaxation

Y

X

Z

Y

X

Z

RelaxationRelaxation

Relaxation

T1 Relaxation T2 Relaxation

; Process determining return to equilibrium of both longitudinal & transverse magnetization

T1 RelaxationT1 Relaxation

N

S

N

S

N

S

N

S

Z

Y

X

T1 RelaxationT1 Relaxation

T1 RelaxationT1 RelaxationLongitudinal

Magnetization

Time

N

S

T2 RelaxationT2 RelaxationN

S

BB00

Transversemagnetization

T2 RelaxationT2 Relaxation

Time

N

S

N

S

RelaxationRelaxation

Y

X

Z

Y

X

Z

RelaxationRelaxation

Transversemagnetization

T2 RelaxationT2 Relaxation

Time

Transversemagnetization

T2 RelaxationT2 Relaxation

Time

TE

T2 ContrastT2 Contrast

Time

Short T2 TissueLong T2 Tissue

T2-weightedT2-weighted

Time

Short T2 TissueLong T2 Tissue

Long TE

TE ; 28 msec TE ; 90 msec TE ; 230 msec

TR ; 3000 msec

Spatial LocalizationSpatial Localization

TE

TR

T1 RelaxationT1 RelaxationLongitudinal

Magnetization

Time

T1 ContrastT1 Contrast

Time

Short T1 Tissue

Long T1 Tissue

T1-weightedT1-weighted

Time

Short T1 Tissue

Long T1 Tissue

Short TR

TR ; 150 msec TR ; 500 msec TR ; 1500 msec

120 - 60

40 - 10

300 - 800 1500 - 4000TR (msec)

TE (msec)

Spin EchoSpin Echo

Poor contrastPoor S/N

Poor contrastPoor S/N T2

?T1

TR 3000 msec, TR 28 msec

120 - 60

40 - 10

300 - 800 1500 - 4000TR (msec)

TE (msec)

Spin EchoSpin Echo

Poor contrastPoor S/N

Poor contrastPoor S/N T2

ProtonT1 ?

Normal Tissue

Proton DensityT1T2

Lesion

Proton DensityT1T2

Normal Tissue

LesionLesion

IntrinsicIntrinsicTissueTissue

ContrastContrast

TRTRTETE

NEXNEXMatrixMatrixFOVFOV

Slice ThicknessSlice ThicknessMagnetic StrengthMagnetic Strength

Pulse SequencePulse Sequence........

TRTRTETE

NEXNEXMatrixMatrixFOVFOV

Slice ThicknessSlice ThicknessMagnetic StrengthMagnetic Strength

Pulse SequencePulse Sequence........

ExtrinsicExtrinsicImagingImaging

ParametersParametersImageImage

ContrastContrast

MR SignalMR Signal

T1-, T2-weightedT1-, T2-weighted

TR, TETR, TE

BB00

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