1. Continuous SWIFT Djaudat Idiyatullin. , Steven Suddarth+, Curt Corum
Continuous SWIFT Djaudat Idiyatullin*, Steven Suddarth+, Curt Corum*, Gregor Adriany*, Michael Garwood*
*Center for Magnetic Resonance Research and Department of Radiology University of Minnesota Medical School, Minneapolis, Minnesota, USA +Agilent Technologies Santa Clara, California, USA
ISMRM, 2011

2. Declaration of Relevant Financial Interests or Relationships2
Declaration of Relevant Financial Interests or Relationships
Speaker Name: Idiyatullin Djaudat
I have the following conflict of interest to disclose with regard to the subject matter of this presentation:
Company name: Steady State Imaging
Type of relationship: sales royalty and consulting fee

3. SWeep Imaging with Fourier Transform (SWIFT)
Fast and quiet MRI using a swept radiofrequency,
D. Idiyatullin, C. Corum, J.-Y. Park, M. Garwood,
JMR (2006).
Applications:
Molecular imaging,
Dental imaging,
Lung imaging,
Breast cancer,
MSK,
Brain calcification. 1 f G
Sensitive to fast relaxing spins
Projection method
No “echo time”
Time shared excitation and acquisition
acq

4. Time shared acquisition, limitations
- excitation duty cycle
- acquisition duty cycle
bw - acquisition bandwidth
trd - coil ring-down time

5. The goal of the project f Expected advantages1 G f
acq
To test SWIFT in continuous mode
with Varian/Agilent DirectDrive system & digital receiver.
Expected advantages
acquisition duty cycle =1 -> higher S/N;
excitation duty cycle =1 -> lower power & SAR,
absence of sidebands;
absence of coil ringing -> SWIFT efficiency at higher bandwidth,
with low Larmor frequency (low field, X-nuclear).

6. Could we acquire a signal when transmitter is “on”?
15 cm
1 mm
4T, Breast coil, water phantom
cSWIFT, R=256
cSWIFT, R=4096
40 db
Receiver threshold
MRI signal level
Peak power needed for excitation calculated for: θ = Ernst angle, T1= 1 s with TR=Tacq, bw=50 kHz, R = bwTp

7. Transmitter-receiver isolation
Quad coil
Tune/Match
Hybrid 90
Preamplifier
Transmitter
Self-duplexing radar technique using circular polarization, ~ db.

8. Continuous SWIFT spectroscopy
Ethanol-water mixture, 4T, bw= 6kHz, 4096 points
Chirp
Transmitter leakage
cSWIFT signal
Smooth function

9. Continuous SWIFT spectroscopy
Ethanol-water mixture, 4T, bw= 6kHz, 4096 points

10. MRI signal reconstruction
Frequency sweep & time Re
62.5kHz Im

11. Wow, it is working! 4 Tesla bw= 62 kHz FOV=40 cm 4 minutes
Regular SWIFT
Continuous SWIFT
4 Tesla
bw= 62 kHz
FOV=40 cm
4 minutes
10 Watt amplifier
0.8Watt
31Watt

12. Continuous SWIFT imaging
Regular SWIFT
bone
cartilage
0.02Watt
2Watt
Human total knee arthroplasty sample,
9.4 Tesla, bw=71 kHz, views, 7 minutes,
without a transmitter’s amplifier.

13. Conclusions Future development: 1. Probe and connection
Continuous SWIFT up to 70kHz bandwidth can run in modern
MRI scanners without hardware modification.
Challenges: Sensitive to transmitter instability, coil deformations,
subject motion, vibrations.
Future development:
1. Probe and connection
Crossed coils, Hybrids, Circulators
2. Hardware
Modulation technique: ωacq =ω0 +ωmod
3. Software
Digital Receivers: signal reconstruction, filtering

14. Thanks Acknowledgement
This research was supported by NIH P41 RR008079, S10 RR023730, S10 RR RR008079, R21 CA grants and WM Keck Foundation. We also thank Jutta Ellermann and Elizabeth Arendt for opportunity to use TKA sample at this study.
Thanks