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

Declaration of Relevant Financial Interests or Relationships 2 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

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

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

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).

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

Transmitter-receiver isolation Quad coil Tune/Match Hybrid 90 Preamplifier Transmitter Self-duplexing radar technique using circular polarization, ~30- 40 db.

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

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

MRI signal reconstruction Frequency sweep & time Re 62.5kHz Im

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

Continuous SWIFT imaging Regular SWIFT bone cartilage 0.02Watt 2Watt Human total knee arthroplasty sample, 9.4 Tesla, bw=71 kHz, 128000 views, 7 minutes, without a transmitter’s amplifier.

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

Thanks Acknowledgement This research was supported by NIH P41 RR008079, S10 RR023730, S10 RR027290 RR008079, R21 CA139688 grants and WM Keck Foundation. We also thank Jutta Ellermann and Elizabeth Arendt for opportunity to use TKA sample at this study. Thanks