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Optimization of acoustic radiation force imaging: Influence of timing parameters on sensitivity
Author(s) -
Dadakova Tetiana,
Krafft Axel Joachim,
Özen Ali Caglar,
Bock Michael
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26734
Subject(s) - imaging phantom , sensitivity (control systems) , residual , biomedical engineering , energy (signal processing) , displacement (psychology) , offset (computer science) , signal to noise ratio (imaging) , materials science , nuclear magnetic resonance , computer science , physics , acoustics , optics , algorithm , electronic engineering , medicine , psychology , psychotherapist , engineering , quantum mechanics , programming language
Purpose Optimization of timing parameters for MR‐guided ARFI to achieve the highest displacement signal‐to‐noise ratio ( SNR d ). Theory and Methods In MR‐guided ARFI the phase change induced by motion encoding gradients (MEGs) is measured to assess tissue displacement. The sensitivity of this encoding procedure depends on several timing parameters, such as the MEG duration and the offset time between ultrasound (US) and MEG. Furthermore, mechanical and MR tissue constants and MEG schemes (bipolar or three‐lobed) influence SNR d . Optimal timing parameters were determined in simulations for bipolar and three‐lobed MEGs, and the results were compared with measurements. To provide clinically usable timing parameters, physiologically relevant ranges of tissue constants were considered. Results For the considered ranges of tissue constants, optimal timing parameters provide only 6% higher SNR d for bipolar than for three‐lobed MEG. Three‐lobed MEG is less sensitive to motion as confirmed in phantom experiments. Bipolar MEG can use approximately 1.5‐fold shorter MEG durations. Conclusion Both bipolar and three‐lobed MEGs can yield approximately the same SNR d if the optimal timing parameters are chosen. Bipolar MEG allows for shorter durations, which is preferable if deposition of US energy needs to be minimized, and three‐lobed MEG is more suitable when residual motion compensation is necessary. Magn Reson Med 79:981–986, 2018. © 2017 International Society for Magnetic Resonance in Medicine.