6/23/2009

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Inversion Recovery (IR) Techniques and Applications

Chen Lin, PhD

Indiana University School of Medicine & Clarian Health Partners

Chen Lin PhD 6/23

The Anatomy of Basic MR Pulse SequencesMagnetization Preparation Section• Chemical Shift Selective Saturation & Excitation• Spatial Selective Saturation• Magnetization Transfer (MT)• Inversion Recovery (IR)

Data Acquisition Section• Slice/Slab Selective Excitation• Phase Encoding(s)• Echo Generation

• Spin Echo (SE), Fast/Turbo SE (TSE), Single-shot FSE (HASTE)• Gradient Recalled Echo (GRE), Single-shot GRE (EPI)

• Diffusion Weighting (DWI/DTI) and Gradient Moment Nulling (GMN)• Frequency Encoding• Filling of K-space

Magnetization Recovery Section• End of Sequence Spoiling• Driven Equilibrium

Increment Phase

Encoding

Chen Lin PhD 6/23

RF

GS

ADC

GR

GP

180°

M0

Inversion Recovery

Tissue magnetization

Magnetization Preparation by IR

90° 180° 180° 180° 180° 180° 180°

Acquisition

Chen Lin PhD 6/23

Variations of IR Technique

Inversion Options:

• Non-selective

• Slice-selective

• Spectral selective

• Adiabatic

• Flow-induced Adiabatic

• Combination of multiple inversions

Acquisition Options:

• Unlimited (TSE and TFL are common)

• 2D and 3D

• View ordering and correction of k-space modulation can be important.

Chen Lin PhD 6/23

Applications of IR• Selectively suppress tissue / background signal

based on T1 differences– STIR– FLAIR– SPAIR

• Improve T1 contrast (Phase Sensitive Recon)– MP-RAGE, IR-SPGR, IR-TFE– T1 FLAIR– T1 IR

• T1 Measurement / T1 Mapping• Tagging / Labeling

– Non-CE perfusion with Arterial Spin Labeling (ASL)

Chen Lin PhD 6/23

STIR, FLAIR, TI and TINull

STIR: Short Tau Inversion Recovery, TRIM

FLAIR: FLuid Attenuated Inversion Recovery, “Dark Fluid”

TInull (Water)

Fat signal

Fluid signal

Inversion RF Pulse

Signal

TInull(Fat)

Time

Chen Lin PhD 6/23

6/23/2009

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T1 of Various Tissue Types

Tissue T1 @ 1.5T (msec)

T1 @ 3.0T (msec)

CSF 4400 4500

WM 780 850

GM 920 1330

Blood 1200 1500

Muscle 870 1160

Fat 220 260

TInull = 0.69 x T1

Chen Lin PhD 6/23

Dependence on Inversion Flip Angle and TR

As the inversion flip angle or TR decreases:

• TINull also decreases.

• Suppression becomes less selective.

0

0.05

0.1

0.15

200 250 300

T1 (ms)

Rel

ativ

e |M

z(t)

|

180150120

Chen Lin PhD 6/23

Interleave of Inversion & Acquisition

ACQ4

IR1

ACQ5

IR2

ACQ1

IR3

ACQ2

IR4

ACQ3

IR5

TI

ACQ1

IR1

TI

ACQ1

IR1

ACQ2

IR2

ACQ3

IR3

ACQ4

IR4

ACQ5

IR5

TI

IR2 IR3 IR4 IR5

ACQ2 ACQ3 ACQ4 ACQ5

STIR

FLAIR

T1IR

Chen Lin PhD 6/23

More about STIR

• In-sensitive to B0

inhomogeneity

– More reliable than FATSAT for large FOV and off-center

– works at lower field strengths

• High visibility for fluid

– long T1 bright on STIR

– long T2 bright on STIR, given long enough TE

• Lower SNR

– improved with shorter TE (17-48 msec )

• Bad idea with Gd

– shorter post-contrast tumor T1

• Red marrow signal can obscure subtle edema

– use TE=45-48+ to suppress marrow

Chen Lin PhD 6/23

STIR versus FATSAT in the Presence of Metal “Hardware”

STIR T1 TSE with FATSAT

Chen Lin PhD 6/23

Cor FSE T2 with

FATSAT

Cor STIR

81 year old female, right hip prosthesis

Cor CT

Chen Lin PhD 6/23

6/23/2009

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Kijo

wsk

i, R

. et

al.

Am

. J. R

oen

tgen

ol.

20

05

;18

5:3

71-

37

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Modified STIR for MSK

• TE=50-100; TI=110-120 @ 1.5T

• Improved SNR and excellent fluid sensitivity in soft tissues

STIR Modified STIR

Chen Lin PhD 6/23

Water Saturation plus STIR for Imaging Silicone Implant

WaterFat

220HzSilicone Implant

320Hz

Freq

Chen Lin PhD 6/23

Co

urt

esy

of

Drs

. Gaa

, Bin

k

FLAIR (Dark Fluid) for Brain

2D FLAIR

3D SPACE FLAIR

Chen Lin PhD 6/23

T1 FLAIR (Modified FLAIR)

High Res T1 FLAIR with 3D SPACE @ 3.0T

• Used short TR and TI than conventional FLAIR• Suppress CSF and provides T1 contrast

Chen Lin PhD 6/23

SPAIR – SPectrally Adiabatic Inversion Recovery

• SPAIR uses an adiabatic frequency selective inversion pulse.

• Insensitivity to B1 inhomogeneity (better for 3.0T)

• Takes longer time and generates higher SAR than conventional ChemSat

Null

Fat signal

Water signalAdiabatic Spectral

Selective IR

Chen Lin PhD 6/23

Conventional vs Adiabatic InversionZ

Y

X

M

B1

Z

Y

X

M

B1

Z

Y

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M

B1

Z

Y

X

MB1

Z

Y

X

MB1

Z

Y

X

M

B1

Z

Y

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M

B1

Z

Y

X

M

B1

Z

Y

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MB1

Z

Y

X

MB1

Chen Lin PhD 6/23

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B1 SensitivityZ

Y

X

M

B1

Z

Y

X

M

B1

Z

X

M

B1

Y

Z

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X

M

B1

Z

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M

B1

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B1

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B1

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B1

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MB1

Z

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X

MB1

Chen Lin PhD 6/23 Chen Lin PhD 6/23

C-Spine with SPAIR

TSE w. SPAIR

Breast DCE with SPAIR

VIBE with SPAIR VIBE with FATSAT

Chen Lin PhD 6/23

Breast T2 with SPAIR at 3.0T

T2 SPC w. FatSat T2 SPC w. SPAIR

Chen Lin PhD 6/23

Abdominal Applications

DW SS-EPI @ b=50 w. SPAIR HASTE w. SPAIR

Chen Lin PhD 6/23

Null

Blood signal

Myocardium signal

Data acquisition1 segment = 7 lines

Non-selective

IR

Double IR (DIR), “Dark Blood”

Slice Selective IR

Chen Lin PhD 6/23

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With DBW/O DB With DBW/O DB

Dark Blood for Cardiac Applications

Chen Lin PhD 6/23

T2 with Dark BloodT1 with Dark Blood

Cardiac Morphology with DIR

Chen Lin PhD 6/23

DIR for Brain

Dark Fluid Dark Fluid & Dark WM

Chen Lin PhD 6/23

Inversion-Recovery for ON-resonant water suppression (IRON)

DIR to suppress fat & on-resonance 1H

MR-Lymphography using IRON & SPIO

Koro

soglo

uG

, et al. J

MR

I 2008 M

ay;2

7(5

):1175

Chen Lin PhD 6/23

Data acquisition1 segment = 7 lines

Non-selective

IR Freq Selective

IR

Null

Null

Blood

Myocardium

Fat

Slice Selective

IR

Triple IR (TIR) or DB STIR

Chen Lin PhD 6/23

DIR versus TIR

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TR optimizedTR too short :systolic motion

reduces myocardial signal

TR too long :blood signal

beginsto recover

DIR Optimization for Cardiac

Chen Lin PhD 6/23

Faster HR→ Shorter RR→ Less Recovery → Shorter TI

TI

TI

Heart RateBPM

RRmsec

TRmsec

TImsec

100 600 1200 420

80 750 1500 550

60 1000 2000 630

Adjust TI according to Heart Rate or TR (Lock Contrast)

Chen Lin PhD 6/23

T1 In-sensitive DB with Quad IR

QIR DIR

Yarnykh VL, Yuan C. MRM 2002 Nov;48(5):899

Pre

Post

Chen Lin PhD 6/23

Small FOV with Quad IR

Yarnykh VL, Yuan C. 2006 May;55(5):1083

Chen Lin PhD 6/23

Background Suppression with IR in Renal MRA

Inversion Imaging

J. Carr. Northwestern University

Inflow

Chen Lin PhD 6/23

Improve Tissue Contrast with IR

MP-RAGE T1 @ 3T; 0.9x0.9x0.9 mm3; TA: 4:31

Chen Lin PhD 6/23

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MP-RAGE, IR-SPGR, IR-TFE

MP-RAGE SequentialIR-SPGR CentricMP-EFGRE Recessed EC

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

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0150

300450

600750

9001050

12001350

15001650

18001950

21002250

2400

|Mz(WM)|

|Mz(GM)|

Contrast

TI TDCentral Views

IR IR

Chen Lin PhD 6/23

MP-RAGE versus MP-EFGRE at 3.0T

MP-RAGE 9:14 MP-EFGRE 6:30

Chen Lin PhD 6/23

T1-weighted FLuid-Attenuated Inversion Recovery (T1FLAIR)

• Axial T1 FLAIR @ 3T with TR/TE/TI/ETL = 2100/9.5/900/3

• Improves T1 contrast at 3.0T

• High SAR limits number of slices and coverage

Chen Lin PhD 6/23

T1-weighted Imaging for Brain @ 3.0T

2D SE 60 2D T1 FLAIR 2D FLASH 3D FLASH 3D MPRAGE

IQ=4 IQ=6 IQ=4 IQ=5 IQ=5

IQ: The median perceived overall image quality

Lin C et al ISMRM2008 Poster2003 Chen Lin PhD 6/23

Myocardial Viability (Delay Enhancement)

• Increased distribution volume of contrast within necrotic myocardium.

• Necrotic tissue has faster T1 recovery than normal tissue following an IR pulse.

• Adjusting the TI to null normal myocardium gives maximum image contrast between necrotic and normal myocardium tissues.

Necrotic

Normal

Chen Lin PhD 6/23

R

ECG

Trigger

R R

Non-selective180o inversion

n

...

TI 200 - 300 ms

Non-selective180o inversion

. . .

Necrotic

Normaldata

Suppress Normal Myocardium with IR

Chen Lin PhD 6/23

6/23/2009

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Finn, J. P. et al. Radiology 2006;241:338-354

IR FLASH/TruFISP/EPI for Delayed Enhancement

Suppress the signal from normal myocardium

Chen Lin PhD 6/23

T1 Scout

Inversion

Signal

Time

Blood

Myocardium

Contrast Reversal

Chen Lin PhD 6/23

IR with Phase Sensitive (PS) Recon

Inversion

Signal

Time

Blood

Myocardium

Chen Lin PhD 6/23

True IR (Real IR) for Brain

Chen Lin PhD 6/23

PS T1IR

PS T1IR T1SE T2 FLAIR

Hou et al. AJNR 2005 26 (6): 1432Chen Lin PhD 6/23

Phase Sensitive Reconstruction

• An image reconstruction option, no additional scan time

• Improve contrast

• May produce artifact.

Ask for both magnitude recon and PS recon images.

Chen Lin PhD 6/23

6/23/2009

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Look-Locker IR for T1 mapping

Kimelman T et al. Invest Radiol. 2006 Feb;41(2):198 Chen Lin PhD 6/23

Summary

• Inversion Recovery (IR) is a useful technique to improve tissue contrast based on their T1 differences.

• The improvement typically come with a cost of lower SNR and longer time.

• Multiple IRs targeting different species can be combined in a single acquisition.

Chen Lin PhD 6/23

Thank you!

www.indiana.edu/~mri

Chen Lin PhD 6/23