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Combining Two-dimensional Spatially Selective RF Excitation, Parallel Imaging, and UNFOLD for Accelerated MR Thermometry Imaging

Department of Physics, Boston College, Chestnut Hill, MA, USA.
John Wiley & Sons, Inc.
Publication Date:
Magn Reson Med
Volume Number:
Issue Number:
Magn Reson Med. 2011 Jul;66(1):112-22.
PubMed ID:
2DRF Excitations, UNFOLD, parallel imaging, fast imaging, MR thermometry
Appears in Collections:
P01 CA067165/CA/NCI NIH HHS/United States
R01 HL073319/HL/NHLBI NIH HHS/United States
R21 EB009503/EB/NIBIB NIH HHS/United States
P41 RR019703/RR/NCRR NIH HHS/United States
Generated Citation:
Mei C-S., Panych L.P., Yuan J., McDannold N., Treat L.H., Jing Y., Madore B. Combining Two-dimensional Spatially Selective RF Excitation, Parallel Imaging, and UNFOLD for Accelerated MR Thermometry Imaging. Magn Reson Med. 2011 Jul;66(1):112-22. PMID: 21337421. PMCID: PMC3120911.
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MR thermometry can be a very challenging application, as good resolution may be needed along spatial, temporal, and temperature axes. Given that the heated foci produced during thermal therapies are typically much smaller than the anatomy being imaged, much of the imaged field-of-view is not actually being heated and may not require temperature monitoring. In this work, many-fold improvements were obtained in terms of temporal resolution and/or 3D spatial coverage by sacrificing some of the in-plane spatial coverage. To do so, three fast-imaging approaches were jointly implemented with a spoiled gradient echo sequence: (1) two-dimensional spatially selective RF excitation, (2) unaliasing by Fourier encoding the overlaps using the temporal dimension (UNFOLD), and (3) parallel imaging. The sequence was tested during experiments with focused ultrasound heating in ex vivo tissue and a tissue-mimicking phantom. Temperature maps were estimated from phase-difference images based on the water proton resonance frequency shift. Results were compared to those obtained from a spoiled gradient echo sequence sequence, using a t-test. Temporal resolution was increased by 24-fold, with temperature uncertainty less than 1°C, while maintaining accurate temperature measurements (mean difference between measurements, as observed in gel = 0.1°C ± 0.6; R = 0.98; P > 0.05).

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