Program Information
Evaluation of a 4D MRI Method Using a MRI Compatible Motion Stage
S Hadley1*, J Balter1 , L Pan2 , H Bhat2 , S Bauer2 , R Kroeker2 , R Grimm2 , (1) The University of Michigan, Ann Arbor, MI, (2)Siemens Healthcare & Medical Solutions, Boston, Baltimore, Erlangen
Presentations
TU-D-FS4-3 (Tuesday, August 1, 2017) 11:00 AM - 12:15 PM Room: Four Seasons 4
Purpose: A study was performed to evaluate the performance of a 4D MRI scanning technique that sorts radial k-space spokes acquired using a golden angle “stack of stars”. The robustness of this technique is evlauted under different scan parameters and motions, non-ideal respiratory patterns seen clinically and random motion patterns.
Methods: A MR-compatible motion stage was used to move a phantom comprised of fresh fruit. 4D MRIs were acquired with different numbers of spokes and respiratory bins. Sinusoidal motions were imaged with respiratory rates from 2 to 40 cycles/minute and motion amplitudes from 0 to 4cm. A baseline shift was simulated with a sinusoid of 15mm and a 20mm shift after 2.5 minutes. Other profiles simulated a breathing cycle which started with a large amplitude and then decayed to stable breathing of 1cm. Random phantom movement was used to determine the robustness of the sorting algorithm. The range of motion in the 4D MRI was estimated from measurements of fiducials in the phantom and compared to the programmed motions. Tradeoffs between numbers of scanning spokes versus spatial resolution and reconstructed image artifacts were explored.
Results: 4D scans using 1000 radial spokes provided a good balance between scan time, ~5 minutes, and sampling artifacts. For clinically relevant patterns and 5 to 10 respiratory bins the errors ranged from 0 to 2.3mm on scans with 2.4mm slice thickness. The “constant velocity” and random patterns presented the most difficulty with significant errors in measured amplitude of motion. There was no motion blurring in any phase image while some did display streak artifacts consistent with undersampled data.
Conclusion: The use of a motion phantom with a range of programmed patterns demonstrated the behavior of a 4D MRI algorithm. Such tests can prove crucial to safe and effective adoption of 4D MRI in the clinic.
Funding Support, Disclosures, and Conflict of Interest: This work supported by NIH R01 EB016079 and Siemens Medical Systems
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