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Thomas M. Grist, MD, FACR

ICRU Gray Symposium

AAPM 2017

Denver, CO

Development and Clinical Applications of Time-

Resolved Magnetic Resonance Angiography

Objectives and Outline

• Objectives:

– Share some key developments in MRA conceived by Chuck

Mistretta, PhD

– Describe the clinical impact of the innovations

• Part 1: Time-resolved MRA during passage of contrast

• Part 2: Time-resolved MRA during cardiac cycle

Development of the MRA version of DSA

Gd-DTPA invention

Weinmann

Gd MRA Prince

X-ray

DSA Mistretta

Clinical Needs Grist

CFR research Polzin

MRI PSD Korosec

UW MRA Research Group

1982 1994 1980

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kx

ky

k-Space Signal Image

Detail

Contrast

Pitfalls: Timing

-5

0

5

10

15

20

0 20 40 60 80 100 120 140

Sig

nal

Time (s)

Arterial

Venous

Tissue

Timing Artifacts……..

………..Needed 3D MRA with method for optimal timing

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Mistretta and Crummy:

Digital Subtraction Angiography (DSA)

IV DSA IA DSA

Coronary Flow and Flow Reserve by 2D PC

Grist TM, Polzin JA, Bianco JA, Foo TKF, Bernstein MA, Mistretta CM

Measurement of Coronary Blood Flow and Flow Reserve Using Magnetic Resonance Imaging

Cardiology 1997 88, (1),

k-space Image

space k-space Image space

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k-space Image

space k-space Image space UW - Star Trek Transform

3D Time Resolved Imaging of Contrast Kinetics (TRICKS) aka: TREAT, DIRKS

A D C C B B D k y

k z

Korosec et al.,

Magn. Reson. Med. 1996

ky

kz

3D TRICKS: Technique

C(I) D(I)

B(I)

A

... ... D A C A B A D A C A B A D

10 11 12 13 14 15 16 17 18 19 20 21 22 Time frame

FFT

Image at

time frame 15

Contrast curve Artery Vein

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TRICKs – Time-Resolved CE 3D MRA

Frame 4 (17s) Frame 6 (28s) Frame 8 (39s)

Frame Time 5.6 s TR = 10.8 (1996)

3D TRICKS

Korosec et al

Mag Res Med

1996

512 x 128 x16

Reconstruction: 6 hours + 1 graduate student

Time resolved digital vascular imaging

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Benefits of time-resolved imaging

Left Popliteal Occlusion

Benefits of time-resolved imaging

Improved Peripheral MRA

• Significantly more arteries diagnostic

with TRICKS

• Significantly more venous

contamination with moving

SmartStep in lower station

•n=20, p < 0.05

Smartstep TRICKS

Hany TF, et al

Radiology 2001;221:266-272.

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TRICKS: Peripheral MRA

Accuracy:

SN = 93%

SP = 86%

n = 68

Swan JS, et al

Radiology 2002

225; 435-52

70 y/o had fainting spell while welding overhead

“Subclavian Steal” Syndrome

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Type II endoleak

→ k-space sampling and image reconstruction strategies help to

achieve high spatial resolution time-resolved MR angiograms.

MRA Remains A Balancing Act

Innovating at the UW Fishing Meeting

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k-space Image

space k-space Image space

Undersampled Cartesian Imaging

½ encodes ¼ encodes

kx

ky

Undersampled Radial Imaging

kx

ky ¼ encodes ½ encodes

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Time-resolved 3-dimensional 3-directional

Velocity-encoded MRI Acquisition:

• Volumetric coverage with conventional cartesian encoding

• 3-directional flow encoding

• ECG gating

• Respiratory correction

• Clinically Impractical – Acquisition times 40 min – 4 hours

Flo

w A

/P

Flo

w R

/L

Flo

w S

/I

Mag

nitu

de

Animation courtesy of M. Markl, Chicago, IL

x

y z

Flow, z

Flow, x

Flow, y

Ky

Kx

Radial -

SOS

kx

kz

ky

3D RADIAL ACQUISITIONS

Cartesian

3D VIPR

Barger AV et al. Time-resolved contrast-enhanced imaging with isotropic resolution and

broad coverage using an undersampled 3D projection trajectory. Magn Reson Med, 2002; 48: 297–305.

PC VIPR vs 3D Cartesian PC Acceleration Factor 30 With Contrast

PC VIPR

Time: 7:30

S/I Coverage: 18 cm

Isotropic resolution

0.63 x 0.63 x 0.63mm

Cartesian 3D PC

Time: 7:22

S/I Coverage: 4 cm

Through-plane resolution 2mm

0.94 x 0.94mm

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4D Flow: Visualization

Too much data?

Need for advanced visualization.

Animation courtesy of M. Markl PhD,

Freiburg, and Chicago, IL

Acute aortic syndrome: dissection

Cases –

Thora

cic

• Patient presents with

persistent pain despite HTN

treatment

• MRA Flow analysis for

further evaluation

PC VIPR acute aortic dissection Pre-repair

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• No flow in MPV - ? thrombus

• Reversed flow in LPV

66 yo F with portal HTN

• Stomal varices draining

from SMV

• Patent portal vein

(no thrombus)

66 yo F with portal HTN

66 yo F with portal HTN

PC-VIPR Magnitude PC-VIPR Flow Visualization

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PAPVR: Value of MRI with 4D flow

• Chest pain, dizziness.

• Right sided cardiac enlargement

• History of palpitations.

• Patient had TEE which showed possible shunt.

PAPVR: Value of MRI with 4D flow

PAPVR: Value of MRI with 4D flow

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Vessel Selective Seeding

Patient with AVM: Nidus seeding + Reverse

tracking

Animal model of renal artery stenosis1 1Bley TA, et al. Radiology 2011

Pearson Correlation

r = 0.977; p < 0.001

95% CI: 0.939- 0.991

4D Flow: Quantitative Hemodynamics

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Quantitative flow analysis: Measuring pressure gradient

18 month old with aortic coarctation

P = pressure V = velocity

μ = viscosity g = gravitation

ρ = density

P = pressure V = velocity

μ = 4 cP (centipoise) g = 9.8 m/s

ρ = 1066 kg/m3

Summary: Time-resolved MRA • Time-resolved MRA during contrast passage

– “Can’t miss” approach to timing

– Window into functional significance of stenosis

• Time-resolved during cardiac cycle

– Clinically practical using under-sampling

– Demonstrates complex flow patterns

– Provides quantitative hemodynamics

1. Michael Ort, M.D., Ph.D. – 1975

2. Frederick Kelcz, M.D., Ph.D. – 1976

3. Robert Kruger, Ph.D. – 1978

4.Willi Kalendar, Ph.D. – 1979

5. Stephen Riederer, Ph.D. – 1979

6. ChorngGang Shaw, Ph.D. - 1981

7. David Ergun, Ph.D. - 1982

8. Michael Van Lysel, Ph.D. - 1983

9. Bruce Hasegawa, Ph.D. – 1984

10. James Dobbins III, Ph.D. - 1985

11. Ching-Shan Lee, Ph.D. - 1986

12. Shaikh Naimuddin, Ph.D. – 1986

13. Sabee Molloi, Ph.D. - 1987

14. Nick Hangiandreou, Ph.D. - 1990

15. David Weber, Ph.D. - 1990

16. Cynthia Mc Collough, Ph.D. - 1991

17. Frank Korosec, Ph.D. – 1991

18. Frank Zink, Ph.D. - 1992

19. Yi Wang, Ph.D. - 1994

20. David Kruger, Ph.D. – 1995

21. Jason Polzin, Ph.D. – 1995

22. Kris Wedding

23. Dana Peters

24. Yousef Mazaheri

25. Karl Vigen,

26. Andrew Barger

27. Oliver Wieben

28. Jiang Du

29 Tianliang Gu

30 Yan Wu

31 Kang Wang

32 John Floberg

33 Tim Szczykutowicz1.

1. Orhan Nalcioglu - 1975-76

2. Theodore Houk - 1976-78

3. Robert Kruger* - 1978-79

4. Walter Peppler - 1981-83

5. Michael Van Lysel* - 1983-85

6. Jack Cusma - 1983-86

7. Shaikh Naimuddin* - 1986-87

8. David Weber* - 1990-92

9. Frank Korosec* - 1991-92

10. Marc Alley - 1991-94

11. Richard Frayne - 1994 -1999

12. Orhan Unal 1995 - present

13. Tim Carroll 1997--2002

14. Emilio Esparza Coss 1998-2001

15. Sean Fain 2000-200

16. Fred Browning 2001-2003

17. Mark Quigley 2001-2004

18. Ross Boutchko 2002-2004

19. Guang-Hong Chen 2002-2004

20. Yijing Wu 2002-2004

20. Jiang Du 2003-2005

21. Julia Velikina 2003-2005

22.Tianliang Gu 2004-2005

23. Kevin Johnson 2008-…

24. Tim Szczykutowicz*

25. Martin Wagner

26. Marc Buehler

Mistretta’s

Impact

Trainees!

What impact have they had, and

what will they do in the future?

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k-space Image

space k-space Image space UW - Star Trek Transform

“The greatest danger facing us

is the fear of the unknown. But

there’s no such thing as the

unknown – only things

temporarily not understood”