Focused ultrasound treatments of the spinal cord may be facilitated using a phased array transducer and beamforming to correct spine-induced focal aberrations. Simulations can non-invasively calculate aberration corrections using x-ray computed tomography (CT) data that are correlated to density (ρ) and longitudinal sound speed (cL). We aimed to optimize vertebral lamina-specific functions at a physiological temperature (37 °C) to maximize time domain simulation accuracy. Odd-numbered ex vivo human thoracic vertebrae were imaged with a clinical CT-scanner (0.511 × 0.511 × 0.5 mm), then sonicated with a transducer (514 kHz) focused on the canal via the vertebral lamina. Vertebra-induced signal time shifts were extracted from pressure waveforms recorded within the canals. Measurements were repeated 5× per vertebra, with 2.5 mm vertical vertebra shifts between measurements. Linear functions relating cL with CT-derived density were optimized. The optimized function was m/s, where w denotes water, giving the tested laminae a mean bulk density of 1600 ± 30 kg/m3 and a mean bulk cL of 1670 ± 60 m/s. The optimized lamina function was accurate to when implemented in a multi-layered ray acoustics model. This modelling accuracy will improve trans-spine ultrasound beamforming.
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Establishing density-dependent longitudinal sound speed in the vertebral lamina
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March 2022
March 07 2022
Establishing density-dependent longitudinal sound speed in the vertebral lamina
Rui Xu
;
Rui Xu
a)
1
Department of Medical Biophysics, University of Toronto
, 101 College Street, Suite 15-701, Toronto, Ontario, M5G 1L7, Canada
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Meaghan A. O'Reilly
Meaghan A. O'Reilly
b)
2
Physical Sciences Platform, Sunnybrook Research Institute
, 2075 Bayview Avenue, Toronto, Ontario, M4N 3M5, Canada
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a)
Electronic mail: [email protected], ORCID: 0000-0003-1606-0932.
b)
ORCID: 0000-0003-2889-6614.
J. Acoust. Soc. Am. 151, 1516–1531 (2022)
Article history
Received:
August 18 2021
Accepted:
December 26 2021
Citation
Rui Xu, Meaghan A. O'Reilly; Establishing density-dependent longitudinal sound speed in the vertebral lamina. J. Acoust. Soc. Am. 1 March 2022; 151 (3): 1516–1531. https://doi.org/10.1121/10.0009316
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