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Continuous SWIFT: Fast and Quiet MRI Using Swept Radiofrequency

This presentation discusses the use of Swept Radiofrequency (SWIFT) for fast and quiet MRI imaging. It explores the applications of SWIFT in molecular imaging, dental imaging, lung imaging, breast cancer, MSK, and brain calcification. The advantages of SWIFT in continuous mode with Varian/Agilent DirectDrive system and digital receiver are also discussed.

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Continuous SWIFT: Fast and Quiet MRI Using Swept Radiofrequency

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

  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

  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. 1 f G acq The goal of the project 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. 4T, Breast coil, water phantom 15 cm 1 mm Could we acquire a signal when transmitter is “on”? 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. 0 90 90 0 Transmitter-receiver isolation Quad coil Tune/Match Hybrid Preamplifier Transmitter Self-duplexing radar technique using circular polarization, ~30- 40 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! Regular SWIFT Continuous SWIFT 4 Tesla bw= 62 kHz FOV=40 cm 4 minutes 10 Watt amplifier 0.8Watt 31Watt

  12. Continuous SWIFT Regular SWIFT Continuous SWIFT imaging 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.

  13. Conclusions • 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. 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

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